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1929 6 cyl master carburator transformation


Roland Kirpach

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Hello,

I want to modify my inlet manifold from my master engine:

- take away the Marvel Carburetor with all the preheating stuff

- close the Marvel inlet

- put 2 new flanges for horizontal carbs on the existing manifold, one between cyl. 2 & 3 and one between cyl 4 & 5

I think that the gas-distribution between all the cylinders will be more equal than in the original configuration, that the power will increase a little bit UP and the consumption a little bit Down...

Do somebody have experience with a similar transformation and which carburators can be used?

modified-buick-inlet-manifold.jpg

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On my '31 straight 8 they flipped the intake manifold, installed an adapter plate and put an early 50's Rochester carb. Runs great and only problem I have is the linkage for the manual choke(binds up).A short length was added to the exhaust where the old intake heater was.

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Without pre heating the power will get up but also the gas consumption. Dual carbs does not save gas but can give more power at high rpm. At the low rpm your engine use, I think the longer inlet to the outer cylinders has no influence on the gas consumption.

Jan

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that's a nice drawing, but a lot of over kill for a low rpm & compression engine.

If you want to get rid of your marvel, which I don't see a need for, just flip the intake over and mount a 1950's carter on it.

Below is a free '30 buick group you can join.

do you want to drive a 1929 buick, or one then runs like a 1950?

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Hi to all,

Thanks for your replies.

First I want to say that I'm living in Luxembourg, Europe, and from here it's not so easy to get spare parts for my American car...

My initial idea was to fix 2(big) English SU Carburetors where I can get all the parts easily, even here in Luxembourg.

Personally I prefer to let the car in the (perhaps restored) original configuration ...but I would mention that we don't have so much straight and flat roads then in the USA, instead we have a lot of hills....last Sunday I participated on a local Rally and I can say that more than 70% was up- or downhill...and that's not so fine with the 3 gears, where the second is often to short and the third to long!Ok, it was one of the "faster" cars, but ....I don't have other excuses.

Below is an evolution from my idea....

modified-buick-inlet-manifold1.jpg

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Roland - if you are serious about this (and anything is better than a Marvel, even hiring a 15-year old lad to stand on the running board and pour petrol into the engine out of an old boot! wink.gif); you will have much better results by using three SU's instead of two, and locating the flange for each directly outside the ports (three individual manifold runners). Make sure you have a small pulse equalization tube joining the three.

Running a hot water pipe along side the manifold may/may not be useful. Only experimentation will tell. Icing might occur without the heat.

I don't envy you trying to pick the proper metering needles.

If you go ahead with the project, please post some pictures.

Jon.

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Rowland,

Here in the states we can easily find a single downdraft carburator from another GM engine with about the same displacement and adapt it to fit the upside-down-mounted Buick manifold as mentioned in a previous post. This is the kind of modification that can easily be reversed by the next owner of your car. However, I detect that you may really want to increase the power from your old Buick while eliminating the problematic Marvel carburator.

Significantly increasing power (more than 10-15%) will most probably involve additional changes in exhaust diameter, re-grinding the cam to change the duration of the valve openings, increasing compression by shaving the head, etc.... Once done, you or the next owner can never go back to original.

But, one of the most cost effective ways to increase power from these old engines (without making modifications that show) is to simply change to aluminum pistons. You can realize at least a 10% power increase by eliminating much the weight your engine is pushing up and down with each revolution.

I suggest you switch to a single downdraft carburator to eliminate the Marvel and swap out your heavy cast iron pistons to increase power. Give it a try and preserve that old engine for the next guy.

Mark Shaw

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Contrary to many people I have never had any trouble with my original Marvel Carb. It took a little fiddling to get the float set right but in 46 years as a daily driver and 380,000 miles I have had no trouble. When I had my engine apart I shaved .020" off of both the head and the block and put in aluminum pistons with three modern rings rather than the original four. I found that this did wonders for the power. Also one size smaller tires in the rear will give you more power but with a slight loss in top speed. I appreciate that a Pontiac is not nor ever will compare to a Buick but I thought this info might be of some help as we are talking about the same vintage.

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My Marvel carb in my Buick 32-87 has always worked fine and efficient. I think the weak points are the cork float and no separate adjustments for idling. The cork float was originally coated with shellac that dissolves in modern gas alcohole). The float may also be a little to small to efficiently close the valve when using an electric gas pump. The absent of idle adjusters makes it difficult to both have good economy and good idling.

Jan

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How fast do you want to go with this car? At 60 MPH you will have so much engine noise that it will sould like the engine is going to come apart. I have driven my 1928 Master that fast and it is not a comfortable ride.

If you want a hot rod, the problems that I see are that if you put more torque and the drive line, you may lose axel keys or pop a ball out of the pinion bearing. I had the pinion bearing fail on an extremely step hill. I tried to pull it in 2nd and had to stop and down shift. I reved the engine and let the clutch out a little fast an heard the pop in the rear end.

Also, too high revolutions will wear out your babit in the rods.

A single down draft from an early 6 cyl chevy will probably work best with very little work.

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Roland,

I have heard that the down draft will give you more miles per gallon. I think that I have a single barrel down draft carburetor with an adaptor plate on it to fit on the flipped over intake manifold. If you can not find anything close to you, let me know and I will dig it out and send you the throat measurements. It came with a lot of 1928 parts so I am not positive that it is the dame diameter as 1929.

fredrawling@verizon.net

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If the carburetor is correctly adjusted, you can not do much for reducing the gas consumption. By making the engine to breath better will not save gas as long as you have the same rear gears. It will increase the power but may hurt your babbit so you will better change to insert bearings.

You can save some gas by giving the engine a leaner mixture but then the power will be less and you may burn the valves. More pre-heating at the intake will also save some gas but with reduced power.

The best way of increasing the efficiency of the engine is to increase the compression ratio (thin gasket and shaved head). This will both increase economy and power. For a low compression engine as yours, the efficiency is approximately proportional to the compression ratio.

Jan

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Hi to all,

Thanks a lot for all the replies.

Next Sunday will be my last trip with the Buick for this year and then I'll take it in my garage to do all the required work, the heaviest will probably be to change the clutch...

The proposal for rotating the inlet manifold 180 degres is very smart and I think that will be the solution for me. But again I'll help from the community: I 'll need a corresponding carburator - Who have experience with that and can give me carburator data (brand, type, nozzles...) and I need also an address to buy a new one.

Many thanks to all,

Roland

Roland's Buick Site

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Probably the best single barrel downdraft carburetor to use for this purpose would be one of the Carter model YF carburetors AS USED ON THE FORD 300 CID 6 CYLINDER!

Carter made hundreds of different model YF's used on everything from a 134 CID 4 cylinder up to the 300 CID Ford 6. These carburetors differ in internal venturi size.

A good rule of thumb is that when migrating any O.E. carburetor from one engine to another; the donor engine and the receiver engine should be within 3 percent of each other in displacement. This can sometimes be fudged slightly if the RPM potential of the two engines is vastly different. The 1929 Buick Master 6 is 310 CID. 3 percent of 310 CID is about 9 CID. Thus the donor engine should be between 301 and 319 CID. The 300 is close enough, as the 300 will turn somewhat higher RPM. I would suggest as early (yearwise) as possible, as the later carbs are calibrated leaner for smog emission. No, we don't have any.

Jon.

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JC Page wrote me an E-Mail with the following contents:

in response to your question in the SILVRT ANNIVERSARY NEWSLETTER,i have changed my buick from a up draft carburetor system to down draft system. i installed a 1966 ford fairlane 6 cyl.carburetor on my 1929 model 27 buick.

my name is JC PAGE phone # 704-282-9716. i am going to try to send you a seperate email w/pictures. you are welcome to give me a call and i will explain every thing.

HAPPY BUICKING JC PAGE

jcpage2.jpg

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  • 4 weeks later...

I was thinking on SU's....the model from the 3.5 ltr Rover.

This car has a 3500 cc engine with 2 SU's = 3500/2= 1750 cc for 1 SU. The Buick engine is 5100cc/3=1700 cc for 1 SU...I know that this calculations are a little bit "simple" but I think that they can't be totally wrong?

The only thing is that the Rover engine will rotate at around 6000 RPM and the Buick only 2700 RPM...

MANIFOLD-3-SU.jpg

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using triple carbs on an engine like this is only beneficial in an optical way. With the camshaft that is used it not an advantage in any way to use triples. Triples will be very difficult to synchronize (I know because I have an Austin Healey) and will not give a smooth idle. Transforming the updraft by a downdraft will give a significantly better performance and is very easy to tune, even better than the sidedraft SU's. I transformed mine by turning the inletmanifold upside down and installing a single venturi Model 29 Zenith, which was frequently used on military engines. The appearance of this carb is also more period than SU-carbs. I attached a picture of this transformation. But mine is a 1931 Model 54 with 3,7 liter engine so this particular carb is not right for your engine. You could look for something alike from a military engine like the 2,5 ton M135. The advantage of miltary parts is that these are relatively easy to find even in Europe.

post-32963-143137876769_thumb.jpg

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  • 2 weeks later...

Hello all. In my opinion turn the manifold upside down and stick on a down draught carby. A Holley carb from an early Ford V8 flathead should work OK on the master. What do others think ?

I restored my standard '29 tourer here in Australia and one of the first things I did was put on a down draught carby from a later model Ford crossflow engine. Never had any problems , get about 15 mpg.

Also, if it gets hot in your country like here , put in an electric fuel pump.

Here it's mandatory to stop vapour locking.

Cheers Ken.

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The carburetor of the flathead V8 Ford is far too small. The Ford has a displacement of 220 cid where this Buick has 310 cid. I tried the Ford carb and even with my smaller engine it strangled the engine at 45 mph. I put in the right one (see the picture) and it is easely doing 65 mph at half throttle. After running in the engine properly I guess it will run up to 80 mph. The size of the venturi is depending on the displacement. The formula is: the diameter of the venturi in milimeters is the square root of displacement in liters times rpm devided by the number of cylinders. So if you want too run this 309 cid engine at 2800 rpm without strangeling, the venturi should be the square root of 5,063 x 2800 / 6 which is 48,6 mm. The largest Ford carb of the thirties has a venturi of 1,25 inch (32 mm). That means the enginespeed is limited to 1300 rpm! Using one carb for less cilinders, for example the three carb layout, does not mean you can use proportinal smaller ones. If you use three carbs the venturi could be approx 20% smaller, in this case about 38 mm. As written before the problem is synchronisation and a possible instable idle. Allthough the single carb I am using gives a perfect running, it could even do better with a two stage carb (registercarb) where the second stage opens at about 40-50% of full throttle. With such a carb you have a good/better idle, very good torque at low speeds and enough breathing at higher rpm. This talk starts to sound like building a hotrod but it is still a normal conversion for the thirties. Buick experimented a lot with carbs and even the factory itself delivered carbmodifications for older models because there were too many complaints. So for the purists: this is acceptable allthough using a fifties carb is not right. Happy revving in 2006!

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I'm in communication with a German Carburetor Specialist.(http://www.ioz.de/frontframe.html) They told me that it's not necessary to put in a connection between the 3 inlet manifold tubes. It's mainly needed to get enough vacuum for servo-brakes....

When the carburators are mounted on the car they will get it and then they will do the fine tuning on the rolls - dynamometer

What's really unusual: The boss is a girl!!

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