valk

1941 Roadmaster coupe

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Posted (edited)
On 4/28/2019 at 9:07 PM, Buicknutty said:

 I hate to disagree with Matt, as I have great respect for him, but the info I have indicates that the rear carb has an idle circuit. I did not realize that when I first got mine on the road, and had a terrible idle, till I realized that a previous owner had blocked the fuel off to it with a small screw jammed into a passage. I guess to try to save fuel. Then I had a more acceptable idle. This tends to confirm my belief that the rear carb aids in idle. I have had consistent trouble with the butterfly which is under the base of the rear sticking in one position, or the other. When its' closed you don't get the extra performance of the rear carb, but honestly, its' like icing on the cake, the car still performs good without it working. But if its' stuck open, then more air is fed through the rear one, and that will upset the idle quality. I am seriously considering taking it off and machining it for small ball bearings during the winter, in the hope that it will work more reliably.

 I can't agree MORE with Matt on this, it is tough to get that silky smooth idle that I have in other Buicks with the '41's. I have mine set so that it idles decently, and it goes great when I put my foot in it. Driving dymanics is great as well, and when one considers the age of these cars.

 It is possible that there is some internal issue with the rear one that is causing the problem, but hopefully it can be solved with tuning.

 Keith

I've been refurbishing my dampers that sit under rear carb trying to find a pat solution that would solve it every time. Different issues showed up while disassembling. Consistant was a slightly bent/tweaked shaft, possibly from being dropped and hitting on the round weight causing the bend. The bushings, at least in the early production units, are steel with brass shaft. All the steel bushings had surface rust inside on the ones I disassembled making them tighter with less clearance. I found some small diameter round steel brushes to put in my drill and the inside of the bushings cleaned up nicely. Most were also "coked up" from carbon, also restricting movement. I soaked them in Evapo-Rust for 24 hrs and more and that took surface rust from butterfly parts and cleaned the diecast/pot metal base as well. I used Scotchbrite on the brass shafts and steel wool on the steel shafts, but it's readily apparent with the undercutting on some of the shafts where they contacted bushing surfaces that some had seen long service and had been working. I've contacted someone who says they have a couple NOS shafts,and so I'm hopeful I can get those with worn shafts from high mileage use and bent shafts to "flop" loosely, which is, IMHO, the only way to have consistently good operation from this valve. I also posted under prewar other info that might be of interest. Other solutions/input on this part solicited please.20190511_123049.thumb.jpg.f781fc008e260cf3333877420cb4d703.jpg20190510_162549.thumb.jpg.2cbc8cef0ceccda9c9259fb9db1d815c.jpg

Edited by 2carb40 (see edit history)
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For those of us with '41s, we greatly appreciate your efforts Greg. Regarding my '41, I am withholding a final report until my resolution plan has been finalized and implemented. 

Peter

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As the suspense builds ...  I hope you get your Roadie running as good as it looks.  I'm pretty confident you will.

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Thanks, Neil, for your confidence! I owe you guys an update. After some further figitting, I come to find I have 2 broken/bent pushrods  - inlet on number 7 and exhaust on number 6 -  so the plan is to replace them, adjust the valves and take it from there. My hope is that somehow this is related to the rear plugs fouling. If not, I'll have both carbs rebuilt, which I kinda want to do anyway. 

 

I can see no evidence of any valves sticking, the valve train looks pristine. I'm going to take the pushrod cover off and check the other rods and lifters.  Neither I or the previous owner can explain how this happened.  If no valves were stuck, the only scenario I can come up with is that the engine was over-reved as unlikely as that sounds.  

 

I should add that the seller and his representative,  previous owner and fellow member John Sobers, have been absolutely first-class in working with me to resolve all this.  Both have dealt with this  more than honorably and this level of accountability is rare these days. Can't say enough about how grateful I am for their understanding and help.  Another update soon!

Peter

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So I see 2 options, beat it straight enough to lift out of the top or cut it in half. Any opinions?

pushrod1.JPG

pushrod2.JPG

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Is it bent too much to come out the top? It's a bit more disassembly, but you'll have to do it anyway. Pull the valve cover, loosen the rocker arm shaft and pull them out the top. No cutting (which will put metal shavings down the hole) and no hammering (which will surely bend or break something adjacent).


While I am often a fan of blunt force trauma and showing a car who's boss, discretion is always the better part of valor. I do the destructive stuff after the car has bested me, not before or during.

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Hi Matt

The rod is bent at the bottom so it will not pass up through the tunnel even when the rocker arm is pulled out of the way.  I did get it out by carefully tapping it back into shape enough to allow me to remove it from the top. I really didn't have any options but to smack it back into shape or saw through it and create metal shavings. I opted for the Fred Flintstone method and I think I'm ok.  I'm hoping the valves didn't get damaged. 

 

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 Wow, that's some bend! Bothers me as to what happened, something must of seriously jammed it. Yes, hopefully there is other damage. I once had a pushrod break on me, a few hundred miles on the rebuild. An old time defective part, not recent manufacture.

 Thanks for the update, Peter.

 Keith

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Ok technical question,  I want to make damn sure I have TDC on the two pistons with the new pushrods so I can set the valve lash and it's kinda awkward on this car 'cause you have to bump the engine with the starter as opposed to hand turning the crank. I'm doing this by 1) bumping the engine until the distributor rotor is aligned with the plug wire servicing the cylinder in question and 2) then checking to make sure the piston is at the top of the cylinder. Am I good to go??

Peter

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45 minutes ago, valk said:

bump the engine with the starter as opposed to hand turning the crank.

 

Oh god no. That's enough to drive any sane person to the brink.

 

For valve adjustment you only need to be close. I would remove all the plugs and push the car by hand while watching the rotor. It is probably easier to put the car in reverse and roll it backwards.  There are two TDC points (firing and overlap), but if this was a running engine and you have the rotor pointing to the correct cylinder, you will have the right one.

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Thanks Bloo...and just to make sure, aside from the bump-starter routine, you sayin' I'm good to go and I can be confident the piston is on the right stroke? 

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Posted (edited)

Assuming the car ran recently, and the rotor is pointing to the cylinder in question, yes.

 

The only thing that could screw you up is if the distributor was somehow inserted 180 degrees out, or just plain wrong, and the engine will not run like that.

 

One more thing if there is any doubt, or if the car didn't run, or if the distributor has been out, etc. etc.

 

The cylinder you are working on will not have, or have had any pushrod motion for a while as you cross TDC. Meanwhile the OPPOSITE cylinder, the one the rotor is pointed farthest away from, will have one valve closing and the other opening as you cross TDC.

Edited by Bloo (see edit history)

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Thanks Bloo, very much appreciated. The car ran, distributor not moved, etc., so no complicating factors.  So the new pushrods have been installed, I'll adjust the valves, do a compression check and either die laughing or crying depending on the results....

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In regards to a smooth idle. Since I replaced my rear carb with a matching front carb removed the rear carb intake flap and converted to parallel linkage the idle is now quite smooth steady and at times imperceptible. Before this modification I could never get it balanced enough to be happy and it always shook and hunted a bit. I do not think there is enough lift to the cam profile to be an issue. The stock setup is a poor design and will never work correctly. It will always be a compromise and the vacuum operated rear flap is a crude device at best. In regards to stuck heat risers never leave them stuck closed. I keep mine pinned open at all times. Tapping the shaft on alternate sides with some WD or equivalent will free it up. Grip the circular counterweight with a vice grip and work it loose moving back and forth until full range is achieved/ Takes a while but it will work itself free. Both of mine were stuck with zero movement but loosened. I use aviation  hose clamps around the counterweights with adjusters set against manifold to hold them open. Heating the intakes is really unnecessary except for winter driving. when its cold it just means a couple more minutes to warm up the motor. 

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FYI,  Another issue seldom mentioned in carburetor performance is the amount of vacuum your engine has and a good indication of that will be the performance of your windshield wipers. If they are moving slowly or not at all after engine reach's operating temperature then its likely you have vacuum loss at the intake manifold. If it has never been serviced with new gaskets or re tightening then its likely that its losing vacuum. This will greatly affect carburetor performance especially with twin carb intake. Its a job made considerably easier if you have a chain hoist as its heavy and unwieldy  but with a hoist its a simple job. I used a thick copper gasket and a slurry of oil and graphite on both sides for expansion and contraction which is important to avoid cracking the manifold in the cool down part of the heat cycle. Use Jeep wrangler dished spring washers that allow for movement while retaining tension. I use 18 lbs torque a bit less then factory spec.  Engine advance carburetion  wiper speed and power are all improved. 

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23 hours ago, valk said:

either die laughing or crying depending on the results....

I've got my fingers crossed for you!

Keith

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Thanks Keith! So the rods are installed, compression is good (no valve damage!)  and it runs great with one exception, it still smokes too much (blue smoke)  So I did another compression check expecting to see low compression somewhere indicating ring wear but no, all cylinders have great compression. My hope is that the  2 cylinders that had busted rods  have oil build up  and just need blowing out.  The rear plugs also look MUCH better so maybe my carbs are ok afterall. The engine really does run nice and I'd claim victory if it weren't for the smoke.  

 

One BIG take away from all this is the major mistake I made not testing all cylinders from the get-go. This thread would be just 3 pages instead of 6 had I zeroed in on the problem sooner. Lesson learned.  So I'm not all the way out of the woods yet. I'll drive it around the neighborhood and hope the smoke gets better. If it doesn't, I afraid I'm at or near the end of my abilities so I'll punt and let a pro look at it . Thank you all for your support and help. I'll keep you informed. 

Peter

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Did you put the flappers back in the damper under the rear carb?  Just curious.

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I wouldn't get too excited about smoke until you have driven it a while. The oil rings might just be sticking a little from disuse. They could be bad, but don't condemn them yet.

 

Also, if you suspect the car is running rich, fix that. I find mild oil burners show more visible oil smoke (blue) when they are running a little rich.

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Hey Peter

       Glad to hear you got some relief from the troubles that happened. Just a thought on the smoking. There is an oil flow restricting fitting in the line leading to the rocker arm shaft, if the fittings have the larger hole it will over supply oil to the rocker arms causing pooling, which can leak around valve stems to cylinders, leading to smoking out the ex pipe. Just a thought that might be worth checking.

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Thanks Boys,

Keith, no flappers in the damper yet because 1) don't have one with valves or couner-weight, and 2) The car ran great for years without this gismo so I am not convinced this is the primary cause of my plug woes. Mr Sobers (previous owner and ex-curator of the Nethercutt Collection in L.A.) suggested I change the oil in the event gas may have diluted it so that's the next step.  Hope Bloo is right and it only needs some miles.  Greg, oil supply to the valve train looks right, good idea though. 

 

I am going to fix this car or die trying...if things go south, please send donations to the Beagle Rescue organization in you area...

Peter

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Peter, the fitting Grege is talking about can be on top, under the valve cover, or on the side of the head. I have found it in either place.  The  passage is rather small, maybe .060. 

 

  For what it is worth, I agree with some of the other folks. If it is not throwing a smoke screen and fouling the plugs, I would drive it a couple thousand miles. Should do no harm.

 

  Good luck.

 

  Ben

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After sitting for more than two or three weeks, Melanie's Chrysler station wagon always smokes for the first 50 miles or so, then it's fine. I stopped worrying about it. Some driving will limber things up and get it all sealed up again. I'm sure it's not related to anything you've done in the valve area beyond some oil getting in where it shouldn't be and needs time to burn off.

 

It's easy to try to second-guess the 1941 engineers and I often see cars in my inventory where someone has "modified" an old car with varying results--usually failure. If the engineers decided that the flapper was necessary, well, I'm going to consider it necessary. The one on my '41 Limited was stuck closed, probably since I've owned it, and I only just noticed that when I took it apart to do my exhaust upgrade. That probably meant my rear carb was never really doing any work, despite the fact that my car is seriously fast. Your car, without any plates, is pulling vacuum through the rear carb all the time. It may or may not have an idle circuit, but even if it does, it's not like the front carb and it's far less precise. The rear carb is designed for all-or-nothing work. Without the blades in that flapper, there's gas flowing through it all the time, but it's unmetered because the throttle plates are closed. It's like the choke is stuck in the on position (if the rear carb had a choke).

 

I'm still putting my money on that missing flapper being the source of your rich rear cylinders. Do we know for certain that it was running great or is that just what the previous owner is saying? Despite his pedigree as a caretaker at the Nethercutt, does he know what "running right" is with that car? I have so many cars come through my shop where the owner thinks it's running great and then I get in and realize that the idle is wrong, it has a stumble, and two exhaust leaks. What one guy thinks is good isn't necessary "right." I've learned that a vast majority of people, even experienced people in the hobby, settle for "good enough" because they simply don't know the difference. Not that this is the case here, but it's always possible that it ran good but not great and the previous owner just didn't recognize it because he had no other car to which it could be compared. I let a fellow 1929 Cadillac owner drive my car a few years ago and he was astounded by how smooth it was, how easily it pulled in high gear, and how smoothly the transmission shifted--he figured his car was typical but now he's tearing his hair out and spending a lot of money to make it work as well as mine. He didn't even know there was a problem with his car until he had something to which he could compare it.

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47 minutes ago, Matt Harwood said:

After sitting for more than two or three weeks, Melanie's Chrysler station wagon always smokes for the first 50 miles or so, then it's fine.

 

What engine do you have? The drains from the head are probably clogged, most likely with crud and pieces of old umbrella seal. This issue affects Wideblock 318s, and probably early Hemi and Spitfire as well (isn't yours a Spitfire?). It happens because when the valve cover does not drain, the oil level has to come up much higher to spill over into the lifter valley. The result is that the exhaust valve stems, guides and springs are underneath oil. The oil slowly drains into the exhaust manifold and makes all the smoke when you fire it up.

 

You don't necessarily need to replace the valve seals if you find pieces, not unless you're just trying to reduce the oil consumption to that of a brand new engine. Just unplugging the drains should get rid of the smoke.

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