Jump to content

Converting to down draft carb on 28 Buick sport roadster?


Rod L
 Share

Recommended Posts

Rod - I have no idea why the search function did not find this thread after my initial post. It just turned up today with the post by TriumphDude. I am sorry you had an issue with a rebuilt Carter W-1. Someone missed something when it was rebuilt. I consider this one of the very best single barrel downdraft carburetors. We have sold hundreds of them. Specifications, parts, and technical assistance are readily available. And properly rebuilt, the later ones are bullet-proof. 

 

I am reading that you returned the W-1, as you should have. 

 

Should you acquire another, here is a link to factory service data:

 

Carter W-1 service data

 

TriumphDude - beautiful cars. You mentioned owners converting to downdraft carbs right after they came out in the 1930's. Someone may have, but most conversions to downdraft are relatively recent, occurring in the last 15 years or so. The Marvel carbs DID work, never well, but they did work. In fact, the standard mechanics joke that I heard in the 1950's "you have a Marvel? It will be a marvel if it works!" (the same mechanic used to refer to "cough", "cough" Holley carburetors ;) )

 

But today, one has to consider the zinc alloy of the 1920's and early 1930's. Not just Marvel, but every company using zinc alloy had issues. Think about door handles, and generator back plates. Some of the more popular (Stromberg U-2 as an example) carburetors have been recast in aluminum. Unfortunately, Marvel believed in proprietary everything, and each of their carburetors are so different there is not sufficient demand to reproduce the castings. The same proprietary design means special adapters have to be fabricated (we actually DID produce adapters to allow the Carter BB-1 to replace the Marvels some 40 years ago, but are sold out, and the shop that molded them had a fire, and the mold was destroyed) to put other updraft carbs on the Buick.

 

As to your cars having the electric fuel pumps fitted, Marvel used a cork float. These were problematic in 1915!!! And still are today. But the real issue is that the design was specifically for low pressure. The mechanical advantage of the float, because of the relationship of the pontoon, fulcrum, and fuel valve just will not permit more than about 3/4 psi. We have brass floats for the older Marvels, which improve reliability, but do nothing for improving the amount of pressure than may be used.

 

My comment above were quick, but basically if you do decide to convert to a downdraft, I personally think one that is made in the USA, has specifications and parts readily available, and is familiar to at least a few enthusiasts for tech support if needed. Plus, a single carburetor that will work correctly on engines from 200 CID to 300 plus CID??? Maybe they also sell bridges in Brooklyn? If you wanted to utilize a Marvel on your 1928, the 1926 version (brass) is a bolt-on swap for the zinc alloy version. I am unaware of a bolt-on brass Marvel for the 1930.

 

Jon.

  • Like 1
Link to comment
Share on other sites

Just saw this recent post, Jon, thanks for the comment.

TriumphDude, good luck with your conversion. I can tell you that I have been very happy with converting, except for the initial carburetor issues I have been quite happy with the conversion, the car runs spectacular wth the generic carb on it, no issues what so ever, Starts instantly, idle is as it should and accelerates smoothly. I couldn't be happier. If and when I should sell the car, all the stock parts will go with the car.

Rod

  • Like 1
Link to comment
Share on other sites

Hello Carbking, Rod L and maok and many thanks for the replies of which i am grateful. I have done a bit of research myself and looking at feedback of people who have fitted the replica Zenith carb, it seems that most people are happy with the fitment. As you say Engines from 200 to 300 cubic inch, one size fits all. The carb has a variable jet which shouldn't be over difficult to dial in. If The engines are gasping a bit on tickover, it should be a straight forward approach to put bigger jets in the idle circuit. I do alot with older motorcycles like BSA Norton and Triumph and have quite a bit of mechanical knowledge and sorting out the carb issues on both Buick's does not phase me at all. Suck, Squeeze, Bang, Blow is the normal sequence of normal aspirated Engines and these motors are not hi tech. I just realized that as i am a Amal Dealer which are common fitted to most British bikes, the parent company which is Burlen also own SU and Zenith   https://burlen.co.uk/  I might give them a call.  Also i don't think many people on this forum know of an English guy called Phil, who bought a rater dilapidated 1928 Buick sedan which is right hand drive and apparently the right hand drive models were shipped as chassis and engine units from Canada and bodied in Hendon in London as General Motors had a factory there back in the day and Phil did some research to discover a fascinating history of the car from it being owned by a rather wealthy family to it being converted into a machine that pulled a grass cutter on a golf course and it also being shot at by the German Luftwaffe in the war to it being put away in the 1950's and forgotten about till the late 1980's. Phil flipped the manifold on his Buick, then made an adapter and fitted a SU carb and it run's really well. Check out his journey and have a couple of hours spare as it a fascinating read and he keeps doing an update right to the present day  https://1928buick.com/  Start at chapter number 1 and keep going to chapter 57 plus 00 is the latest update. Comments are welcome.  As tonybuick said on this thread putting the car on a rolling road to set it up is a good idea and i think i will go down that route. I will keep you all updated. Cheers.

Edited by TriumphDude (see edit history)
Link to comment
Share on other sites

Calibrating a carburator correctly requires expensive equipment. A DVOM and a five gas exhaust analyzer are a must. Tossing some carb on it because others have done it is far from doing it correctly. Burning gasoline in an engine requires a knowledge of stoichiometry. There are few people today who can do a proper conversion. Guess wrong and burn valves, melt pistons, and have hard starting and running issues. It should be done with engineering and scientific methods. It almost never is. Moe above is correct. A generic one carb fits all is folly. 

Edited by edinmass (see edit history)
  • Like 2
Link to comment
Share on other sites

TriumphDude - it is not the jet size that is concerning, rather the venturi air velocity; but more so the lack of documentation, parts, and tech.

 

There is a difference in "running" and "running well".

 

Check the 4th line in my signature block! ;)

 

Jon.

Edited by carbking (see edit history)
  • Like 2
Link to comment
Share on other sites

On 4/28/2021 at 2:00 PM, maok said:

I think some have vested interest in not supporting these generic carbs.

Moe - you are absolutely correct, but not for the reason you might think!

 

How would you like to be called names that would make a sailor blush, when you get a call from someone that just bought an old car that had sat a couple of months, needs carburetor parts for an unknown generic carburetor; and you are forced to tell him he has a doorstop?

 

Jon

Link to comment
Share on other sites

59 minutes ago, carbking said:

 

 

, when you get a call from someone that just bought an old car that had sat a couple of months, needs carburetor parts for an unknown generic carburetor; and you are forced to tell him he has a doorstop?

 

Jon

 

 

I'm fine with that...........been there, done that. Always hair an expert before you buy the car. 😎

  • Like 2
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...