Marvel carb.

[Guest Taco]

Hello,

my Buick has a Marvel updraft carb, just like it has to be.

As you can see at the photo above, the inside has some cracks.(seen at the bottom too) <span style="font-weight: bold">Is this a problem for using the carb?</span>

So yes, where can i find a replacement? Is it repairable?

At this photo are two Nuts (screws) at the right. What for??

One is for the 'plunjer'.

At the last photo in the middle there is a 'plunjer' (not seen at the pic). <span style="font-weight: bold">What does it normaly??</span>It wasn't connected to somewhat in the car.

What is step one for adjustment the hole lot?

Forgotten: <span style="font-style: italic">It's a 1928 Opera coupe Master six.(posted somewhere else)</span>

Best Wishes.

Taco.

[Buicksplus]

Taco:

Those cracks in that flapper are probably no problem. You can safely repair them with JB Weld or similar epoxy. What is important is that the flapper valve moves smoothly and fits well to the throttle body when closed -- no sticking or major gaps.

The plunger you talk about is a needle that is lifted by a short linkage to the throttle -- it is sort of a power valve, designed to richen the mixture when the throttle opens. If you don't have this valve, I suggest you plug the jet in the bottom somehow or she may run too rich.

The two nuts are cleanouts below various jets in the bowl. Suggest you remove them and make sure the jets are clean and open. They are probably OK, your carb looks very clean.

The main mixture adjustments is the lower needle with that wheel on it. Begin with it by closing the valve, then opening it until the notch lines up with that post on the carb. The other adjustment is the air valve, controlled by that knurled knob on the throttle body. Open this knob so the end is flush with the brass spring clip that rides in the knurls.

If all the jets are open, close the choke and you can probably get the engine started. Marvels like to run rich, just crank open that lower valve and crank in the air valve if she needs more gas. You really have to get the car on the road to set the mixture right. Don't expect a super smooth idle with these Marvels, they sort of hunt about like a hit or miss tractor. If they are too lean the engine will run hot under load and she'll backfire a lot. If too rich, she won't rev up smartly and you'll get a lot of black smoke in the exhaust.

Hope this helps, Good luck and good Marvelling!

Bill.

[Guest Taco]

<span style="font-style: italic">The plunger you talk about is a needle that is lifted by a short linkage to the throttle -- it is sort of a power valve, designed to richen the mixture when the throttle opens. If you don't have this valve, I suggest you plug the jet in the bottom somehow or she may run too rich.</span>

This is the one:

In my car it wasn't connected.

If i understand you correctly, i must connect it again.

Must the flapper normaly close completely?

In my case the flapper stays open 1/4 inch.

Taco.

[critterpainter]

The flapper must close completly for the engine speed to drop to an idle. If you can, remove the fixed piece and file or sand the face closest to the flapper until it will allow the flapper to close completely.

Bill

[Buicksplus]

Taco:

Here is a picture showing how that linkage on the power valve connects to the throttle. There should be pin on the throttle crank just made for that linkage:

I note you're from the Netherlands. We had a nephew who lived in Eindhoven for several years. Loved it, but he is now back in the States.

Good luck and good driving.

[Guest Taco]

Thanks for the help!

@ Buicksplus: i see that you disconnected the heating?

Does 'overheating' causses backfiring?

Taco.

[Buicksplus]

Taco:

Most folks who drive these cars plug up the manifold heating system, all it does is enhance vapor lock. With today's volatile fuels, it is not needed. I also removed the butterfly valve in the main exhaust outlet on the front of the engine -- even when this valve is open, it restricts the exhaust and reduces power. I saved all the original parts, they can be put back for show if necessary.

If your car is backfiring, the mixture is probably way too lean. Open that needle valve on the bottom a half turn or more to richen the mixture.

Also if your air valve flapper is not closing completely, (as per your earlier post) that will also give you a lean mixture. See if you can get it to seat properly.

Bill, Albuquerque, NM

[Guest Taco]

You are right.

I took another pic from my car, here it is:

In the middle you can see the pin that must be connect to the plunger.

Further i will plug up the heating system i think.

Thanks for the answers.

Taco.

[Fred Rawling]

Regarding the die cast piece in the venturi of the carb:

There should be a .005 to .003 clearance between the die cast piece and the flapper. If you do not have the clearance, the flapper will not close properly and the car will run but not as well if it closes.

The best bet is leave the die cast piece alone. If you try to remove it, it WILL break and there are no replacements available. I have one with cracks in it and it has lasted for over 84,000 miles that I put on the car.

Remove the flapper and with a piece of sand paper glued to a thin flat stick, sand down the face of the die cast piece. Re fit the flapper and check the clearance with the flapper closed. Do this until you have the proper clearance.

I did not go to the trouble of pluging the heat pipe from the manifold to the carburetor. I just set the valve in the exhaust open all the way and left the linkage to it on the shelf in the garage. I am in California with warmer wheather than you probably have and the car runs good.

As mentioned above, set the idle wheel with the notch one turn open to the post thatsticks down from the bottom of the carburetor. That spring on it looks like a good idea. I have had my valve stem work out and fortunatly fall on the splash apron where I found it when the smell of raw gas caused me to stop. I wired mine with a strand from stranded copper wire to keep it from unscrewing. Some carburetors had a clamp that attached to the wheel of the idle valve to keep it from working out.

Open the air valve so that the top is even with the end of the spring on the side of it. That lets the car start.

The valve on the bottom is for idle only. Set the carb to run using the air valve. Be sure that the car is well warmed up. Drive is around a bit. Then, I screw the air valve out until the car falters. Screw it back in counting the turns until the car picks up speed. Open the valve half the turns you just counted. From this point pull the accelerator rod back fast to rev up the engine. If it falters, richen the mixture (turn it in one or 2 turns and try it again). When the engine will rev up when you pull back the accelerator rod you have it set for good pick up when you start from a stand still. Also, if, from the middle point between stalling and acelerating, the engine does not falter when you pull back the accelerator rod, try one or 2 turn out on the air valve knob.

Fred

[Guest Taco]

Thanks a lot!

So, the brass pin see here at the bottom is my reference.

The notch has to be at the same spot as the brass post.

After all i was reading, it's the best that i took everything apart, to check if the flapper works alright.

Taco.

[Guest Taco]

I have checked the carb again.

The flapper couldn't move at all. There was a small piece of the die-cast piece broken of, and was between the diecast piece and the flapper.

The hot air intake from the carb war already blocked.(gasket without a hole)

The valve at the junction wasn't there any more. The whole 3-way junction is replaced with a dummy.

I tried the engine, it is running again. (after timing the ignition)

Now i have the plunger connected.

Later i will have a try running the engine with the plunger at work.

Taco.

[Guest Taco]

The plunger does have a small hole in it, but why?

Taco.

[Guest Taco]

At this pic you can see the Air Valve isn't closed at all.

I have also an spare one (carb), and at this carb it's just the same.

BUT............

.....at all drawing (Master Parts Book)the Air Valve is closing completely.

I cannot find any 'adjustments' done later at my carbs.

How on earth is that possible??

Are they 'redone' at the factory?

Taco.

[carbking]

For the marvelous Marvel to work as well as possible (but never well) it is necessary for the airvalve to close. The culprit is normally the low speed venturi (the half-moon zinc-alloy piece) which is visible in your photo at the bottom of the airvalve.

The low speed venturi is constructed of a poor quality zinc alloy. With age, this zinc alloy "grows", wedging against the lower edge of the airvalve and preventing closure.

To repair, remove the two flat-headed screws affixing the low speed venturi in the throttle bore. Now carefully remove the low speed venturi.

Obtain a piece of glass, and some 800 grit emery paper. Place the emery paper on the glass, and "sand" the flat side of the low speed venturi, removing sufficient material to allow the airvalve to close (check often, do not remove too much material). From memory (we no longer work on Marvels), the installed clearance from the lower edge of the airvalve when closed to the low speed venturi should be approximately 0.005 inch.

Jon.

[Fred Rawling]

Jon,

I was always afraid that removing the screws from he die cast piece in the ventri would cause it to break. I always glued a piece of sand paper to a stick and sanded it down while it was still in the venturi.

What was your experience with them breaking?

[Guest Taco]

Fred, i am doing the same as you.

But in my case it's a lot af sanding. There was a gab of 8 mm. as you can see at the pic.

The engine wasn't runnig very well, so i had to remove the carb again.

Still sanding at this time. Did not very much the last few weeks, it was too cold in the barn.....

Taco.

[Guest Taco]

Finaly the work is done. BUT......

when i have the flapper-valve in the good position (just closing) and the engine is running, the mixture is too rich. Black smoke, and a terrible smell in the barn.

To get the engine running in a proper way, i had to turn the brass-piece a lot back.

See pic.

Now what??

Taco.

[Mark Shaw]

You probably have the wrong spring.

Check this eay item

http://cgi.ebay.com/ebaymotors/1924-29-V...1QQcmdZViewItem

[Guest Taco]

I see.

If this is the right spring, then i have a wrong one in my carb.

Thanks for the answer.

I have to buy another one to get everything allright.

Taco.

[carbking]

Fred - we never broke one, but have not rebuilt any Marvels in a few years.

Taco - there are MANY different air valve springs for Marvels, the one pictured by Mark is one of the more common. What year is your Buick? Also, did you try adjusting the fuel adjustment on the bottom of the carburetor as well as the knurled knob? Fuel pressure can also cause the black smoke. The Marvel doesn't like electric fuel pumps. About 1 pound pressure is all the early ones are going to accept.

Jon.

[Guest Taco]

Carbking: my Buick is from 1928. This one:

It's a master. Then this must be the 'T 4' as the reverence book says.

I turned the fuel adjustment 1 1/2 turn open, the mark of the wheel is at the point where the brass pin is.

At this time the engine runs fine.(i think)(no more black smoke)But with the 'old' spring, the knurled knob is turn out a lot.

I do not know what pressure my electric fuel pump gives.

I removed the top of the float chamber. I could see that the fuel is stopped when the chamber is full. The level of the fuel is not too high i think. (not overfloating)

I have a spare one carb. I had a look at it, and the spring in it is the same as in the pic above. Not seen before.

I will chanche the spring and will see what happens.

Do you think that spring is the right one?

Taco.

[carbking]

Taco - there are several springs that all have much the same shape, but different tension due to different wire size. The spring pictured is of the correct shape for your carburetor. Free length of the spring is 1.5 inches (about 38 mm).

Very pretty car!

The electric pump may be your culprit! But try the spring from the spare carb.

Jon.

[Guest Taco]

I made a pic of the spring that was used in the carb.

It seems to me that someone pulled it out in the middle......

Taco.

[Mark Shaw]

Exactly!

[carbking]

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Taco</div><div class="ubbcode-body">I made a pic of the spring that was used in the carb.

It seems to me that someone pulled it out in the middle......

Taco. </div></div>

Dr. Goodpliers strikes again!!!

[Dave_B]

Taco,

Beautiful car. It looks like it's a model 58. I see that the headlight buckets are painted black. Weren't all 50 series cars headlights plated?

Dave

[Mark Shaw]

The Standards had black headlight buckets & the Masters had plated buckets in 1929. That is how I identified the right parts at swap meets for my car (now my son's car).

My reference book says the 1928 Standard series had new bullet shaped painted headlights except for models 24 & 25 which were nickel plated. It also states that all Master Sixes had chromed headlight shells.

[Guest Taco]

My car is the 128" wheel base type 58, a 5 passenger coupe as fas as a i know.

And why the headlamps are painted black? I don't know. It's how i bought the car. The car is still original, apart from the paint. That's made new, but when? The car isn't restored, but the engine has several new parts.

I have a flat tyre, new tubes are ordered in the USA,and i have to wait for them making the flat tyre.

Later this week or next week i will test the new spring in the carb.

Taco.

[Mark Shaw]

The car looks great either way. My guess is that a previous owner did not want to spend the $$ to nickel plate the headlight buckets & just painted them.

[Guest Taco]

Well,

finally this day i had the chance to impove the engine (carb) with the other spring.

And yes: it's running much better now.

I have driven 20 miles i think, no rare things occured.

So i am satisfied.

Thank you all for the help!

@Mark: i cannot see any 'old' chrome or so on the head light, maybe the paint is original? Just the head light rim was/is chrome / nickle.

Taco.

[Guest Fr Mike]

Regarding the possibility of repair as an option, you might want to check this website out as a source of materials.

http://www.muggyweld.com

Good luck!

Fr. Mike

[Dave_B]

Taco, Re the head lights: I see in the Buick color sales book that the master series 47 and 48 had painted head light buckets. Perhaps Buick used these on export models? On my car, which has the plated lights, the buckets are made of brass. Put a magnet on yours and see if it is steel or not. If it is steel the paint is probably original. It would be interesting to hear from others with export cars if their lights are plated or not.

Great to hear the car is running better. They are a lot more fun that way:)

Dave

[Guest Taco]

This is a little BIT off topic, but....well....

The magnet does not 'stick' to the head light at all.

So it must be made of brass.

In that case the paint is not original? Was it chrome??

BW.

Taco.

[Dave_B]

Yeah, a little off topic but, anyway... a brass headlight bucket means it was plated, which would be as advertized. According to the sales catalog all plated headlights were nickle plated that year. I don't think Buick used chrome till '29.

Dave

[Guest Taco]

In that case i like the head light painted more than plated with nickle.

Because nickle isn't very shiny.

But nickle is much more original.........

Maybe i will nicle again the 'rims' (don't know the right word)around the glas, brass is coming trough the nickle from all the polishing in the past.

Taco.

[Guest Taco]

On topic again.........

can you all tell me about the fuel consumption of this cars?

How many miles can you drive on a gallon?

The engine is running very good, but, i think, a little too rich. Later i will remove a spark plug to examine the state of the plug.

At this time i do not have any back firing.

Taco.

[Mark Shaw]

Taco,

Glad you are making progress. Fuel consumption generally is not very good for any updraft carburetor. The Marvel is worse than others with finer adjustability. Running a little rich is not necessarily a bad thing when you consider the consequences of running lean.

I am guessing my buicks get around 12 mpg overall. Most of my driving has been short trips. Last year, I drove my 24 Master Buick truck 180 miles from Vancouver to Seattle Washington and calculated just over 14 mpg with almost all highway driving.

Some Buick owners use a spare downdraft set up with a Rochester downdraft carburetor from a 50s Chevrolet six cylinder for better economy on the highway. It is a simple conversion to flip the intake manifold & set it up either way.

[Guest Taco]

Hello Mark,

i know the Marvel is not the best of the best.

But i like to drive as original as possible, so any conversion is the second option for me.

[Mark Shaw]

For me too.

[Guest]

Nickel is just as shiny as chrome if you polish it. It is just a slightly different colour.