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Converting to down draft carb on 28 Buick sport roadster?


Rod L
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1 hour ago, loftbed said:

As to the last two responses, Edinmass & dibarlo, I didn't ask for a critique! Neither of you gentlemen have driven the vehicle in question and have no idea as to the nature of its power, I am not trying to hot rod or even make a "1958" out of it. I have retained the complete Marvel system for the next owner should they chose to use it. The poster prior to my last post, suggested a possible adjustment to the carb I am using, I was merely seeking clarification for his suggestion and NOT someone else's opinion  as to the merits of what I decided to do. If you don't have a directly related answer to the question asked, you are just making noise.

Rod

 

Rod,  I'm sure you don't want another opinion,  but the two guys who are are gently (Jon) and more directly (Ed) pointing out the folly of what you are trying to do should be listened to.    At this point it is too late,  but you are jumping through a lot of hoops to end up no better than where you started.

 

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12 minutes ago, alsancle said:

 

Rod,  I'm sure you don't want another opinion,  but the two guys who are are gently (Jon) and more directly (Ed) pointing out the folly of what you are trying to do should be listened to.    At this point it is too late,  but you are jumping through a lot of hoops to end up no better than where you started.

 

I guess I just don't understand a statement like that. When you have no idea as to how the car was running at the time that I decided to go down draft.

If there was a carburetor shop capable of rebuilding my existing Marvel then why wasn't it recommended? Being it wasn't, that left me with two choices: park the car or go down draft. Now that I  have gone down draft, I  am accused of not listening to the offered advice and if you look closely you will note that STILL no where has anyone pointed to a capable Marvel carb re-builder.

 I have completed what appears to have been a successful conversion (so far). The engine (with the Carter w1) starts, idles and accelerates just fine (with no load). It does not like accelerating under load, and that is the issue. I am certain it is something to ,do with the carburetor, i just don't know what! I guess maybe I need to go to a Carter forum to find my answer.

Sorry to have troubled the "experts".

Rod

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I consider Jon......aka .......Carbking as one of the top carburetor people in the world.......period. No, he is not GOD but he is the most experienced fuel guy I have ever met in fifty years......and I have been around a lot. The solution to the problem is simple. Diagnose the running problem, is it fuel? Is it ignition? Is it mechanical. Some of the top people in the world of antique cars come here and offer advice. Trying to convert that Buick is a waste of time, money, and energy. Put it back to stock, and get a good correct carb, or a correct replacement carb. Engineers with a lifetime of experience designed, built, and tuned the system back when it was new. No one today will come up with anything better. Buick built great cars.....and they were trouble free when new. Put it back to new condition, and it will be trouble free for you also. Modifying a car from that era, while being reversible, just tells potential future buyers the fuel system has been hacked.....the next logical question for the buyer is.....what else has been hacked. You will hurt the value of the car, Make it harder to sell, and still have a mess on your hands that probably won’t run right. I have often installed different carburetors on vehicles for assorted reasons......but we had correct tools and facilities to do so........a chassis dyno, a five or seven gas exhaust analyzer, an ignition scope, and fuel monitoring system. Shady tree mechanics and inverting an intake manifold is just poor workmanship, plain and simple. You stated your 78..........you should have enough life experience to understand good advice when you get it. People who have been making their living doing this for half a century are chiming in............now, the question is what you choose to do after getting advice that many people pay a lot of money to get. Your fortunate that you got it for free...........

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With a new fuel system, you have either a new problem, of and existing one. That’s why basic diagnostic procedures need to be followed. Sure sounds like ignition to me......and you state you “don’t know what”......your words. Following a proper diagnostic routine and fixing issues prevents things like flipping manifolds upside down and incorrect replacement carburetors from getting you to the point of running well. You probably had the ignition problem before you went to the carburetor. As Jon and many others say.....99 percent of carburetor problems are ignition. I wish you good luck with your repair.......

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7 minutes ago, edinmass said:

With a new fuel system, you have either a new problem, of and existing one. That’s why basic diagnostic procedures need to be followed. Sure sounds like ignition to me......and you state you “don’t know what”......your words. Following a proper diagnostic routine and fixing issues prevents things like flipping manifolds upside down and incorrect replacement carburetors from getting you to the point of running well. You probably had the ignition problem before you went to the carburetor. As Jon and many others say.....99 percent of carburetor problems are ignition. I wish you good luck with your repair.......

And still no Marvel carburetor re-builder recommendation.

 

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25 minutes ago, loftbed said:

The engine (with the Carter w1) starts, idles and accelerates just fine (with no load). It does not like accelerating under load,

This is a long shot, and I'm just trying to help:  Did you have the same "runs well at idle, goes to hell under load" condition before the carb swap?  If so, consider this:  Fully 25 years ago I had that condition with a Pierce Series 80 (the junior varsity model) with a nearly identical-to-yours Delco 6-cyl distributor.  Two of us well-experienced guys finally noticed that the specified points gap would not hold--that is, set to 0.018, idle 5 minutes, begin to slip the clutch and it sputtered, then find the gap to have changed to 0.008.  Turned out there was a problem in the distributor plate's vertical post on which the points are mounted.  On that specific distributor, the vertical post was NOT a press fit into the plate as on everything else I've ever seen, but was fastened with a nut (maybe #8-32 thread) on the underside of the plate.  The nut had loosened, allowing the post to wobble under pressure from the spring in the points set.  We added a lock washer, tightened the nut, and the problem was solved!  Drove the car another 20 years without recurrence.  I don't know whether that fastening was factory, or someone had modified it over the years.  The key indicator was that the points gap changed within minutes.  So please check your point adjustment.

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3 minutes ago, Grimy said:

This is a long shot, and I'm just trying to help:  Did you have the same "runs well at idle, goes to hell under load" condition before the carb swap?  If so, consider this:  Fully 25 years ago I had that condition with a Pierce Series 80 (the junior varsity model) with a nearly identical-to-yours Delco 6-cyl distributor.  Two of us well-experienced guys finally noticed that the specified points gap would not hold--that is, set to 0.018, idle 5 minutes, begin to slip the clutch and it sputtered, then find the gap to have changed to 0.008.  Turned out there was a problem in the distributor plate's vertical post on which the points are mounted.  On that specific distributor, the vertical post was NOT a press fit into the plate as on everything else I've ever seen, but was fastened with a nut (maybe #8-32 thread) on the underside of the plate.  The nut had loosened, allowing the post to wobble under pressure from the spring in the points set.  We added a lock washer, tightened the nut, and the problem was solved!  Drove the car another 20 years without recurrence.  I don't know whether that fastening was factory, or someone had modified it over the years.  The key indicator was that the points gap changed within minutes.  So please check your point adjustment.

Grimy, Finally someone with some actual help, thank you so much, it is much appreciated. No the stumbling, miss and backfire that is occurring with the Carter down draft, did not occur with the Marvel. The Marvel equipped engine just had very low power and as

I mentioned in another post, the model A's I have are much more peppy. I hope to get it out this weekend to see if my changing the intake manifold gaskets made a difference.

Again thanks for the help and for staying on topic.

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@loftbedTwo other off-the-wall suggestions that are relatively easy and non-invasive:

1. If you have a vacuum takeoff for the wipers, put a vacuum gauge on that while you are spraying carb cleaner or light oil looking for vacuum leaks.  First, what is the vacuum reading before you look for leaks?  Second, how much --if any--does it improve with a carb cleaner or other fluid sparyed on mating surfaces?  I'd start with the reused gasket surface.

2. For grins, add another (modern) condenser (I've had to do this on the road as a quick fix), attaching the pigtail to the coil primary terminal that leads to the distributor but you must ground the case with a jumper wire to something on the engine or firewall.  For the Pierce 80 with near-identical Delco distributor, a condenser for a 1962 Ford full-size 6 (223 cid) has the correct capacitance.  If that's not the problem, still carry the condenser and the jumper for a roadside fix for a gone-bad distributor-mounted condenser.  Besides, it keeps the tigers away!

 

Other than checking for vacuum leaks, I don't have knowledge to help you with the WA-1 modification.  I have no objections to the mod you made, and we all share your frustration!

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39 minutes ago, Ben P. said:

This won’t help, but there was an excellent one (check out Terry W’s ‘And Then There Were Three’ thread early on) and he died about the time I got my Buick. Don’t know of another one - and that Marvel is still waiting for me too I just know it. Though we’re pretty sure all the problems were electrical. Just won’t know for sure till the engine is back from the rebuild shop.

I really don't want to push this Marvel switch controversy too far, but here is something to contemplate for the future (maybe sooner than expected). If no one steps up or is qualified down the road to work on and adequately repair the Marvel carburetors, then what will be the answer. It would seem to me that without a means of repair everyone including the "purest" will be forced to go with something other than the Marvel or maybe it is their intention to create a knock-off "Marvel"? Can you imagine the cost of that item, I should think pretty cheap considering the huge demand.

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Instead of guessing.......I recommend diagnosing the problem. Fixing a vacuum leak that may or may not exist? It’s about as helpful as letting air out of the tires. You could put the ignition on a scope and check for KV’s. Or you can use an exhaust analyzer to check for a lean burn misfire. You could use an alternative source of HC’s during the stumble to check stoichiometry. But all of these diagnostic techniques are not nearly as fun as guessing, turning the manifold up side down, and dumping a carb on it. 
 

Actually the first thing that needs to be done is a compression test. And yes, I could fix this car in under an hour......as could a bunch of other technicians. Nothing special about a running problem. They are easy to fix. But the fact is, you need to know what your doing. Primary voltage to the coil through the ignition switch should also be checked. But all of the above have not been done..........just keep guessing and tossing parts at it.

 

And, if you can’t rebuild a Marvel carburetor yourself without help, what makes you think you can diagnose or fix the running problem. Yup...it’s a smart ass remark. But I know what I am doing. 
 

And , yes......one could make a carburetor. But costs are prohibitive. The last special run of carbs I saw was about 70k for five carbs. That’s kind of expensive.......but it went on a blown Duesenberg.

 

And for the record, we(meaning my brother in law and I) make about 175 parts for Stromberg up and down draft carbs.

Edited by edinmass (see edit history)
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57 minutes ago, edinmass said:

Instead of guessing.......I recommend diagnosing the problem. Fixing a vacuum leak that may or may not exist? It’s about as helpful as letting air out of the tires. You could put the ignition on a scope and check for KV’s. Or you can use an exhaust analyzer to check for a lean burn misfire. You could use an alternative source of HC’s during the stumble to check stoichiometry. But all of these diagnostic techniques are not nearly as fun as guessing, turning the manifold up side down, and dumping a carb on it. 
 

Actually the first thing that needs to be done is a compression test. And yes, I could fix this car in under an hour......as could a bunch of other technicians. Nothing special about a running problem. They are easy to fix. But the fact is, you need to know what your doing. Primary voltage to the coil through the ignition switch should also be checked. But all of the above have not been done..........just keep guessing and tossing parts at it.

 

And, if you can’t rebuild a Marvel carburetor yourself without help, what makes you think you can diagnose or fix the running problem. Yup...it’s a smart ass remark. But I know what I am doing. 
 

And , yes......one could make a carburetor. But costs are prohibitive. The last special run of carbs I saw was about 70k for five carbs. That’s kind of expensive.......but it went on a blown Duesenberg.

 

And for the record, we(meaning my brother in law and I) make about 175 parts for Stromberg up and down draft carbs.

Well, unfortunately myself and a good number of the rest of us don't think so highly of ourselves and just keep stumbling along hoping that a question we might ask might be reasonably answered without being  dissed as ignorant fools.

I'm sorry I started this thread.

 

Rod

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I don't have a 5-gas analyzer but do have an oscilloscope as part of a Sun 820 tuneup machine.  My recommendations above have *assumed* (with all the limitations therein) that you don't have either, and I seek to rule out, using only simple shop equipment, that which can indeed be ruled out at home. For me, a vacuum leak can result in a lean condition (on the Marvel as well as the Carter) and thus I recommended capping off the vac feed to the wiper (which may be a fitting on top of the vacuum tank) before doing anything else.  Many of us have learned the Hard Way the old adage that 90% of presumed carb problems are electrical.  Ed is right to suggest measuring voltage input into the coil, comparing it against battery voltage, as there can be significant losses in the ignition switch.  Are you getting a fat blue spark at each plug when shorting out each plug with a screwdriver?  What do the plugs look like?  Sorry if you've provided this info before, I haven't read the whole thread.

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After reading all the posts in this thread I think i need to reiterate what exactly has been the issues with this engine and

i'm going to do it numerically in the order in which they occurred:

1. Bought the car in March of this year.

2. Noticed on the 1st drive that there was a noticeable lack of power in all gears at all rpms. There was NO missing or back firing at this time!! It did run really rich.

3. Read of the possibility of reversing the manifold and using a down draft carburetor because multiple people were reporting issues with the Marvel. (at this time i knew nothing about this type of carb).

4. drove it  through the summer.

5. Asked on this forum for a recommended carb rebuilder. NOBODY recommended.

6. Based on that recommendation I decided to proceed with the downdraft.

7. Using the recommended carb (Carter W1) I completed the install

 

Now here is the pertinent information

 

Remember item 2 in parentheses "There was NO missing or back firing at this time!!"

Now with the new carb installed I am getting missing and occasional back firing.

In my backward and ignorant way of reasoning I would and am assuming that if there was no missing etc before the carb was changed and there is after, then the missing and back firing has something to do with the new carb. It didn't happen before only after.

 

I'll bet if I put the marvel back on, the missing and backfiring goes away?

 

 

Rod

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2 hours ago, loftbed said:

Now here is the pertinent information

 

Remember item 2 in parentheses "There was NO missing or back firing at this time!!"

Now with the new carb installed I am getting missing and occasional back firing.

In my backward and ignorant way of reasoning I would and am assuming that if there was no missing etc before the carb was changed and there is after, then the missing and back firing has something to do with the new carb. It didn't happen before only after.

 

I'll bet if I put the marvel back on, the missing and backfiring goes away?

Rod, thanks for this, it helps.  Did you attempt any diagnosis of the ignition system before changing carbs?  Late timing will give lack of power.

 

Lack of power can also be caused by a clogged exhaust.  To check for that, with a warmed engine, attach a vacuum gauge.  Have a helper run the engine to about 1500 rpm on a pre-1933 car and hold it there for 2 minutes.  It will take about 15 seconds for the gauge to settle down.  Note that "settled-down" reading.  At the end of two minutes, note the reading.  If the reading has dropped since it settled down, that's an indication of a clogged exhaust, especially if the drop is continual over two minutes.

 

Did you inspect the tubes in the heat riser for pinholes?

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Rod, 

      I was the first person to respond to this thread.  My first recommendation was to rebuild the Marvel.   I provided a link to the rebuilding instructions.  I do most to the antique work myself because there are too many shops that say they can do things, then they give it to the rookie or break it themselves.  Very few shops know what these antique cars need because they see so few of them.  All of us have been in the same situation.  Sorry that I do not have a name of someone that would do the work for you.  If you want to go thru the instructions I and others can clarify any issues as you go thru the procedure.   

 

My second suggestion was to stay with an updraft.  That would allow you to swap between a working replacement and the Marvel easily if that were needed.   So when the car does not run correctly and you suspect it is the carburetor, you swap them out and if it still does not run correctly, then the problem is likely elsewhere.  

 

Now you are on a down draft.  This complicates things because your car is no longer stock.  Maybe the person who rebuilt your Carter is willing to send you another of like kind if this one is not operating as intended.  Are they a reputable shop?   

 

My suggestion for any antique car owner is that a great spare is an additional functioning carburetor.  An easy swap and it really helps with troubleshooting because it either fixes the problem or you learn the trouble may lie elsewhere.       Hugh   

Edited by Hubert_25-25 (see edit history)
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13 hours ago, loftbed said:

After reading all the posts in this thread I think i need to reiterate what exactly has been the issues with this engine and

i'm going to do it numerically in the order in which they occurred:

1. Bought the car in March of this year.

2. Noticed on the 1st drive that there was a noticeable lack of power in all gears at all rpms. There was NO missing or back firing at this time!! It did run really rich.

3. Read of the possibility of reversing the manifold and using a down draft carburetor because multiple people were reporting issues with the Marvel. (at this time i knew nothing about this type of carb).

4. drove it  through the summer.

5. Asked on this forum for a recommended carb rebuilder. NOBODY recommended.

6. Based on that recommendation I decided to proceed with the downdraft.

7. Using the recommended carb (Carter W1) I completed the install

 

Now here is the pertinent information

 

Remember item 2 in parentheses "There was NO missing or back firing at this time!!"

Now with the new carb installed I am getting missing and occasional back firing.

In my backward and ignorant way of reasoning I would and am assuming that if there was no missing etc before the carb was changed and there is after, then the missing and back firing has something to do with the new carb. It didn't happen before only after.

 

I'll bet if I put the marvel back on, the missing and backfiring goes away?

 

 

Rod


Better information. The problem was just going ahead with a manifold flip and new carb. Running rich and low on power sounds like two issues to me. Since the car is new to you, the following is the best way to fix it, easily and inexpensively. Put it back to the exact condition when you bought it. Start and run the car briefly. If it is back to the same condition, which it should be, then it’s time to start with the basics. Compression test. Quick electrical evaluation. Battery voltage at battery, battery voltage at ignition switch. Battery voltage at coil. Often bad batteries can cause weird ignition issues.........been there, done that. Then, with the initial checks complete, it’s time to look at the entire ignition and fuel system. Without experience........years of it and thousands of cars serviced, it’s usually difficult for most people to figure out of its fuel or ignition. In this case, as the car is a new purchase, I would work through both systems........usually every car had been modified over the years. Your Buick should be on a vacuum tank I’d I am not mistaken. If it has an electric fuel pump, that’s probably the running rich issue. I could go on for hours. If you like, put it back to stock, and I will walk you through it here or on the phone. Understand.......most rebuild kits for carburetors have generic and incorrect parts.......often times using kits made up from many sources will CAUSE problems, and add to your misery. Same thing with vacuum tank rebuild kits......often times the springs supplied are too heavy. Not only do you need to figure out what is wrong......and it’s probably 90 percent certain it’s multiple issues.......you need to know what and where to look for.......on top of the common problems of pot metal causing carb issues. George was right with his possible restriction in the exhaust.....l.its one of the first things that came to my mind. Also, when you service the car.......you need to service the ENTIRE system. Example........having fuel problems?

Clean the tank, check for a good vent, check for incorrect fitting causing restrictions, check for incorrectly installed electric fuel pump, including the wiring on the pump as it will often cause voltage problems in the primary ignition system, vacuum tank service, carburetor rebuild and inspection for incorrect and missing parts, intake air leaks, and all of this is just a partial list. 100 year old cars WILL have incorrect parts on them, and you need to know if that’s a problem also. Like having the coil wired backwards causing a weak spark at speed. So, now the question is..........do you try and fight the  car the way it is, or do you go back to square one. If the car was in my shop.......it would go back to square one. And then, we would do the step by step process of fixing it. Let me know of you want the help.......I’m happy to give you my best advice. Good luck, Ed.

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Thank you  Ed, Grimy, And everyone else who have offered constructive advise on finding out why this engine is misbehaving. I have made a list of all the suggested items to check. This is going to take some time and I will keep posting findings as I get to them. First off though is the down draft carb. I need to figure out if it is also misbehaving as it only has a 60 day warranty.

This morning I replaced the intake manifold gasket as well as the carb to manifold gasket. I checked (starter fluid spray) at all the suspected areas for a vacuum leak. I didn't detect any. I took the car for a drive and there was some improvement but still some coughing (slight) and a little backfire. Then this interesting thing: while driving, if I advanced the hand throttle the engine hesitation (missing?) evened out. Also note that the hand throttle was no longer connected to the foot throttle. i.e. when moving the hand throttle the foot throttle stayed stationary.

what is the hand throttle connected to at the end of the steerng column?

(SEE PHOTO)

Rod

 

 

throttle.png

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I’m guessing that is timing advance and retard........I haven’t worked on a late 20’s Buick in years. Here is a test to try in the garage. While running the engine and advancing the throttle, when the engine begins to stumble or run rough......introduce some propane into the throat of the carb. Use a torch for soldering pipes and the like. The purpose of this test is to ADD hydro carbons in addition to the carburetor.......IE adding more fuel. If the carburetor is lean, the engine will rev higher and smooth out......if the car is already to rich, it will choke the car and cause it to run worse. Also, you can use the propane to check for vacuum leaks similar to starting fluid......but there is no fire danger. Sounds to me that when you add the hand throttle your advancing the timing. When standing there in person I can eliminate dozens of issues.......Interpretation of what you are seeing is subjective........and not always easy to convey what is occurring. I still think you have multiple issues. Are you running a electric fuel pump? What is the fuel pressure? What is battery voltage exactly? How old is the battery. Do you have a good ground? Lots of things to check......

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I fooled with my 1928 Standard for 6 months before I finally found a tiny paint chip lodged in  the vacuum tank valve.  Yes, it can be extremely frustrating.  You might consider talking to Tony Built [sp] at Old School House Antiques 262 275 6403  He has many of the Marvel carb parts and will run the rebuilt carb on a vehicle to make sure it is functioning correctly prior to shipping it back to you

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The 2 gears on the bottom end of the steering column are independent of each other.   If you move either lever, and the other gear moves, then you have a problem with the parts in the steering column.  On the 1925 model, there is a thin metal plate between the spark and throttle levers to prevent interaction.  Maybe you are missing this piece?  Do you see a thin piece of metal between the 2 levers?

 

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Sounds like you need to check that interaction like Hubert says. also check that the distributor is moving properly with the advance and retard lever. If it's timed right you run with both ears up and perhaps retard slightly on a hard pull.  Lack of power on these engines is often timing related. Buicks manual on timing may just confuse the issue, See other posts on timing. 

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i think you should carry on when you get it running right you will never look back good starting better miles to the gallon and with the new set up and fuel pump you can take on long and high hills and it will keep going like a train

you will need to fit a fuel pump but its also a new carb  with a good float and seat so it will handle the pressure from the fuel pump marvel carb wont 

you can get a low pressure high flow fuel pump we make some in new zealand in 6 and 12 volt

i dont belive you will melt pistons the carb dosent pump fuel in the engine has to suck it and the new carb will be doing a better job of metering the fuel than what the marvel ever did and i dont belive the old carb could limit the revs if so can i come and hold my foot hard down on the accelartor on his buick bet it revs it guts out if the carb is letting to much fuel in it will flood the engine run rough and you will need to clean the spark plugs if you do run for a long time like this you may wash the bores but you should have it sorted before you do any damage 

i put a down draft on my buick would never go back i have stopped many times to help other buick owners out to find vaccuum tank problems fuel running out of the carb not running right i would get in my buick and drive 200 miles any day it just goes so good i fitted the down draft carb 20 years ago and have done about 15000 miles in it 

i would mount the carb so it sits the same as it did on the car it came off i would fit or use a carb with a adjustable main jet and getting it set up on a rolling rd is good 

i would check what size engine the car was and its rpm of the carb you are using 

my buick is 191 cubic inch so i fitted a carb off a 202 cubic inch car (it work but used lots of fuel )but it revered to 6000 rpm the buick will only rev to 3000 so i went to a carb off a 173 cubic inch motor at our lower rpm the air following through it is more correct for the carb im not a expert but this is my 2 cents worth 

i also  fitted a  disturber from a morden car with autmatic advance works well and i can go to the local shop and get parts for the carb and disturber caps points etc good luck tony

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Hi, I have gone down this same “Rat Hole”. Five years ago I bought a 1928 Buick 54C country club coupe that had been decently restored in the nineties. It had been driven occasionally as it was part of a small collection of cars.  I had many other projects in various stages of repair and really wanted a well sorted car that I could just drive and not worry about it much (ha ha).  What was so impressive was how it started and ran, hardly any choke to start when it was stone cold and you could push the knob in all the way , put it in gear and go through the gears up to 50 mph without a snort or backfire. Crazy as it sounds it did this with a late  1928 pot metal Marvel.  If I would have done my homework I might still have that reliable dependable driving experience.  You may ask what could I have done to bring down misfortune on myself and that car, I did nothing, meaning I poured in gas and checked the oil and put hundreds of miles on it.  Then it happened on a 105 degree day, driving 52 mph up a hill on highway 101 . I heard a big shotgun blast under the hood, the car lost power and as I coasted to the edge of the highway a flume of black smoke and orange flames shot out of the hood side.  I grabbed my new Chinese fire extinguisher, you know the one that has no words just pictures ( ikea instructions) And could not get it to work.  Luckily I had been in a car tour in Paso Robles a week before ( touring in a friends Pierce) and I heard a first hand account of a model 66 Pierce that caught fire In Altria’s on tour many years ago and it was saved by someone that scooped up dirt and threw it on the flames. Lucky for me it worked.  I brought it home and discovered a melted carb and no compression in  and no6# cylinders.  So what happened is the engine got hot because the cylinder water jackets were full of rust, the engine had a crappy repair done on the head a mechanic from the past welded in a chunk of cast iron between the intake and exhaust valve.  The weld failed and hot flame traveled down the marvel and turned it to a metal sculpture. Found a head, redid the water pump, valve job, radiator and found another marvel, but this time a brass one, so far I have rebuilt it twice. The car pops snorts idles rich and runs poor.  I have now procured another marvel and had it rebuilt we shall see.  The point I am trying to make is that unless you are extremely lucky you are risking your life and fortune unless you systematically start at the bottom and work up.  Another item I would like to share is on my Buick, it seemed to be a little lacking on power, I suspected it was but I did not have anything to compare.  A friend of mine who has a restoration shop suggested that the spark advance might not be set right.  He suggested moving the distributor so that it would advance more with the lever and listen to hear if it either pings or when hot check if engine fights back when you try to start it.  This little trick made a huge difference. I think I have it dialed in, I generally retard the spark when starting it when it’s hot , then advance it.  Someday I will tell the story about what happens when you do not pull the wheels off to inspect all the brakes, I will give you a clue, it involves a fire extinguisher, see some people can be slow learners,

 

3FBD6522-32DF-461F-A907-644C8A5B62B3.jpeg

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Thanks guys for the new comments-suggestions, all are appreciated. I have been tied up with a wet sand/buff project on one of the "A's" and hope to get back to the Buick today - After Voting of course!

 

Rod

PS

Where exactly is the inspection cover to view the timing mark on the flywheel? I'm looking on the distributor side and see nothing.

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16 hours ago, dibarlaw said:

Timing mark cover is on the drivers side under the brake/steering column area on my 1925. I believe it is the same for yours. And yes.. it does not make sense to us now.IMG_4541.thumb.JPG.c32972a3ac6066344cc68749ae318d13.thumb.jpg.48dc83b682d0fce490ac8e75bdf286c4.jpg See highlighted area from Dave Bs image.

Thanks Larry,

Geeez, could they have not have found a more perfect spot!

So far here is what I am finding on the engine.

1. Checked the battery and coil voltage: Battery = 6.09 Coil = 5.91 so some voltage loss there, don't know if that is significant?

2. Advanced timing  ~ 3* (a guess) Engine likes that with power increasing but still requires choke only open about 3/8".

3. used propane in the intake of the carb as per Ed's instruction and the stumbling was somewhat reduced, so there is a vacuum leak somewhere. I had already disconnected all the vacuum connections and plugged the nipples etc; so I'm certain the leak is within the carburetor itself. Directing propane at the base of the carb (gasket) does not influence the engine at all.

Of note on the test drive, is that with the increased timing and adjustment of the choke to get a richer a/f mixture results in what I would describe as what the engine would have been from new.

Also there is no detonation (pinging) that i can hear, though it would take a "knock sensor" to truly know. I have done considerable work with a laptop tuning an engine equiped with sensors for timing, A/F mix (stoichiometric) and knock sensors, so I'm not completely in the dark.

One thing I'm seeing is that movement of the timing lever does not make a significant difference in engine rpm, nothing like my Model a's so maybe a linkage issue as well?

I am sending this carb back and getting a new one with main jet adjustment. Zenith 28/228

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First - CAUTION! Car is running lean and can burn a calve or hole a piston........read that ten times...........

 

Read it ten more times..........

 

OK, now, thats why I said you need a five or seven gas exhaust analyzer  ........you are in DANGER of damaging your engine. Now, that said, its very difficult to help you remotely because your carburetor isn't made for your car, so everything without scientific instrumatation is CONJECTURE.....nothing more. Don't drive the car until you have a better handle on it. I could list 100 things right now for you to check..........bit none of it would be productive. You need to ADD more fuel, now. A phone call would be easier to go over things. If you like, PM me your number. Best, Ed

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6 minutes ago, edinmass said:

First - CAUTION! Car is running lean and can burn a calve or hole a piston........read that ten times...........

 

Read it ten more times..........

 

OK, now, thats why I said you need a five or seven gas exhaust analyzer  ........you are in DANGER of damaging your engine. Now, that said, its very difficult to help you remotely because your carburetor isn't made for your car, so everything without scientific instrumatation is CONJECTURE.....nothing more. Don't drive the car until you have a better handle on it. I could list 100 things right now for you to check..........bit none of it would be productive. You need to ADD more fuel, now. A phone call would be easier to go over things. If you like, PM me your number. Best, Ed

Yes, the lean condition is what I've been talking about for some time now and that is why this carb is going back and another one is on the way. When I ordered the intake manifold gasket, I also got the exhaust manifold gasket, I think the ports are the same, so those exhaust gaskets should work in the intake ports, if so, I might put the marvel back on and see what it is like with the timing advanced. (just for shi.. & giggles). My conversion to the down draft is not set in stone, but i'm a stubborn old fool pretty intent on seeing something through once I start it.

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It's not a bad carburetor......it's an incorrect carburetor. A engine is a fine tuned and engineered machine, that experts designed almost perfectly in the day. They KNEW what they were doing. Flipping a manifold in itself can cause flow and paddling issues.....volumetric efficency on that engine was figured out using an updraft at the time......with fuel changing over time, and a modified manifold, and an obviously replaced exhaust.......the entire thing needs to be recalibrated, and jetted for its new configuration.......dumping any old carb on it isn't going to solve the problem. Each carburetor model usually had four of five different air horns, Venturi sizes, jetting and air bleeds.......the list is endless. I have been doing this a long time, and my stuff runs GREAT not good....ask the guys on the fourm here. I would have not done the swap over at all.........for a bunch of reasons, one of which is what you are dealing with now. That said, I would approach it from an engineering standpoint, and NOT copy something else already done by someone else........as 99.9 percent of the time....what they did was half assed and the cheap and easy way out. Alterations to the fuel supply system, ignition system, should also be considered. There is a lot more going on than just flipping the manifold and running a carburetor that fits. To be honest, I have no clue on Buicks of this era.....first I would study them, and investigate several options, and then figure out how to proceed. Just my two cents. I'm still willing to help to the best of my ability.......the the path chosen is probably much more difficult than most people understand. Ed

 

 

PS- The variable main jet on the above carburator is NOT a correct way to set up a car.......it's a band-aide on a huge wound.........and it's not going to heal. 

Edited by edinmass (see edit history)
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32 minutes ago, edinmass said:

It's not a bad carburetor......it's an incorrect carburetor. 

Ed, I am pretty certain there IS a vacuum leak in this carb. I have totally isolated it from any other source of a vacuum leak. the only connections to it are the fuel line and the throttle linkage. Using your "propane" test I get no reaction at the gasket between the carb and manifold or any where externally, but when the engine starts bogging down and I apply the propane to the inlet, it immediately levels out and runs great. The same reaction as choking it. We are not talking high rpm's or no more load than coming off idle up maybe 50-75 rpm while parked.

it  seams to me that adding this carb would in all likelyhood create a rich condition not a lean one?

just saying.

 Rod

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Rod......not being there in person makes things difficult........my guess I’d the carburetor is too small for the application.......but venturi size and jetting can make a carb work from 225 cid to 400 cid........rpm also comes into play along with the efficiency of the design. Please understand my experience is in different platforms than what you are working on. I would isolate the fuel supply from the car to eliminate that whole aspect. Still want a compression reading. It would be great to find a factory horse power and torque graph on the exact application........a Buick overhead valve engine is a much better breathing engine........from most L and F head designs. Currently I’m working on my one car with a unusual factory horizontal barrel throttle......with no accelerator pump.......on a large displacement dual valve T head engine. Still don’t have the car right.......and I’m not sure when I am at 100 percent..........and I’m also dealing with timing issues. It’s three steps forward, two steps back. It can be difficult and frustrating........so I walk away from it sometimes........I’m not in any hurry, and taking time allows me to think things through.........which is much more productive than lots of changes with no control. I’m suspicious you have timing issues......and too much or not enough fuel pressure. I would look into venturi size .......can you change it or is it fixed? Just too many variables to work it over a computer........

Edited by edinmass (see edit history)
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Rod, 

   Before you reinstall that Marvel carburetor, Be sure to file down the pot metal venturi, or replace it so that the air valve works it's full travel.  Tony Bult and now I believe Roger McGinnis have replacement venturi's for these Marvels, and that is usually the biggest failure of these old Marvel Carburetors.   Hugh 

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29 minutes ago, Hubert_25-25 said:

Rod, 

   Before you reinstall that Marvel carburetor, Be sure to file down the pot metal venturi, or replace it so that the air valve works it's full travel.  Tony Bult and now I believe Roger McGinnis have replacement venturi's for these Marvels, and that is usually the biggest failure of these old Marvel Carburetors.   Hugh 

 

Yep, ours was out of shape as well (probably up to a 1/4" in places) 

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Well I received the new carburetor and installed it today https://newcarburetors.com/?product=y200-universal-carburetor

This is a new, not rebuilt unit. Straight out of the box, the car started right up, I adjusted the idle mixture using a vacuum gauge to 60" max it has about a 2" intermittent drop. 58-60-58-60....

The prior issues: intermittent miss, stumble and near closed choke requirement are all gone, so I think I was was right about the Carter w1 being defective was correct after all. Lots more power than originally but some of that increase is probably the result of my adding in a couple degrees of timing. I'm going to go back and reset the timing to stock just to see where that gets me. I'll bet that even with the~2 degrees I added, it will still be  retarded. I don't know at this time if I'm going to keep the down draft or take her back to the Marvel?????

 

unfortunately the rains are about to start out here in Oregon, and I will be storing her for the duration.

 

Thanks to Ed, Hugh, Ben, Tony etc etc for your input on this thread. At some point I'll put up a step/by/step of how i

 did this conversion, maybe if it dries out long enough I'll get some miles on it and some more info.

 

Rod

                                                                                                     

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  • 5 months later...

Hello Everyone, I have been reading this thread regarding fitting a down draft carb to a six cylinder Buick with interest as i have a Brown 1928 Country Club Coupe master six Model 54C 128 Inch Wheelbase and a Blue 1930 Country Club Coupe master six Model 64C 132 Inch Wheelbase and both cars are fitted with the Marvel updraft carburetor. Neither car runs particularly well and rather than rebuild them, i think the way to go is to fit a Zenith Y200 type 28 carb  https://carbkitsource.com/carburetors/y200.html  The fact that the carb will be on an angle due to the bolt hole pattern won't be an issue as i will make an adapter plate and countersink the screws into the plate and drill and put the carb square to the engine.  With a variable jet, it should be straight forward to dial the motor in for the mixture. I just don't rate the marvel carb and as both cars have electric fuel pumps fitted, even set at number one, they still tend to flood. I was told you can overcome this by fitting a SU Float to the bulkhead which will cope with an electric fuel pump and then gravity feed the marvel carb but i feel the downdraft option is the way forward and i am led to believe that in the 1930's when downdraft carbs became available, it was quite a common mod that people used to flip the intake manifold and do the downdraft conversion. I have enclosed a couple of photo's of the cars that i intend to convert to downdraft. Also i wish to fit an air filter, does anyone have any recommendation on those. I am thinking of something like this.     https://www.amazon.com/RA-045V-Universal-Clamp-Air-Filter/dp/B00062YNJG  Any input on this is welcome. Cheers.

1930 Buick with Trunk.jpg

1928 Buick country club coupe 1.jpg

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That unit appears to NOT be a genuine Zenith, rather a "knock-off", made somewhere.

 

Good luck if you need either tech support or parts, ever.

 

Personally, I believe this would be a downgrade from the Marvel, not an upgrade.

 

Banned from our shop, permanently.

 

Jon.

Edited by carbking (see edit history)
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