4bbl carb on flathead?

[38 coupe]

Since I'm not planning to run a four barrel on a flathead I can only speculate on popular carburetor selection (why not a Rochester 4 Jet, why not a Stromberg 4A, why not a Carter WCFB, etc.), but my guess is most people today want a new carburetor instead of searching for a 60 to 70 year old core and rebuilding/tuning it themselves. Personally if I was going to go four barrel I would try the smaller bore Autolite 4100 carburetor, but there may be a good reason other people don't do that too.

[tubman]

The main problem is that all of the available 4-BBL manifolds have the old small "Square Base" mounting pattern. The means you have to run an adapter or use on of the older carburetors (early WCFB, early small base 4G, etc.) with the attendent availability and wear problems. There is someone who has posted on here or the H.A.M.B. that is running an early 4G with great success, but I forget who. I have 3 flathead 4-BBL manifold, an Edmunds, a Sharp, and a Fenton that I plan on using. I also have a small base 4G from a '53 Oldsmbile that I have rebuilt and am planning on using. It is for a 303 ci engine and my flathead is 258 ci, so I hope it's not off to much size-wise.

And "38 coupe" is right; those old carburetors are getting more and more difficult to find and those you do find are usually worn out and missing parts.

[Ol' Ron]

I have an Offy 4bl intake with the small carb intake. I installed and adapter for the modern 4bl carbs anf bores the intake to match the carb.
Gramps

[38convsedan]

41LJH: is this the offy intake you’re using?

[petehoovie]

Originally Posted by 38convsedan

41LJH: is this the offy intake you’re using?

[frnkeore]

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The thing about a Holley and the vacuum secondary's, is that the secondary's will not open, until there is enough air flow through the primary's to warrant it.

It is much like progressive linkage on 2 x 2 manifold and carbs but, it works on demand, instead of forced throttle position.

The 390 carb has 1 1/6 venturi and 1 7/16 throttle bores, similar to the late (2100) 94 type carbs.

In some bigger, high rpm engines, you could probably use the more common 450 cfm Holley, with 1 3/32 x 1 1/2 venturi / throttle. I have one of those, that was on a 327 Rambler.

There is a easy way to find out if your over carbureted and that is to hook up a vacuum gauge, that you can read in side the car and run it at full throttle to the max rpm you use, if the vacuum doesn't go under 1.5" vacuum your good for a street car, you can go as low as .5" for a race engine.

[aussie merc]

a couple that may have been overlooked is the good old carter AFB in 400 cfm[ they differ from the edelbrock which is a copy of the afb comp series so they run a bit richer ] or a WW from stromberg .Yeh its only a 2 barrel but still a good unit.

[olddaze32]

I have a Stromberg 4A Aeroquad that has my interest. Anyone out there had experience running them on a flathead?

[billy’s40]

Hello, Sir!

Do I need to put on a new intake manifold to use the Edelbrock carb? I just inherited my dad‘s 1940 Ford coupe. I’m just trying to make some changes to make it more reliable. I don’t need a new intake manifold, is there a certain adapter I need to use with the Edelbrock to make it fit on my flathead? Thank you.

[tubman]

If your main concern is reliability, your best bet is to have the proper stock original carburetor rebuilt by Charlie Schwedler in New York. There is none better.

If you're really looking for something else (optimal performance, gas mileage, or a "wowser" appearance), decide what it is and get back to us.

[Ol' Ron]

I just ran into a new old caeb. It,s a holley 485 from a chrysler 440 according to the list no. I haven't measured them yet, but the primaries are very small, and the secondaries are very bIG. Should make a nice street carb???
Gramps

[tubman]

Originally Posted by Ol' Ron

I just ran into a new old caeb. It,s a holley 485 from a chrysler 440 according to the list no. I haven't measured them yet, but the primaries are very small, and the secondaries are very bIG. Should make a nice street carb???
Gramps

Sorry Ron, probably not. A couple of years ago, I spent some time trying to get a quadrajet from a 3.8 GM V6 to run on a flathead. I had a Sharp 4 BBL manifold laying around, and I stacked a Quadrajet to Holley adapter on top of a Holley to Square pattern and did a bunch of filling and and blending to hopefully "smooth the airflow out". I had completely rebuilt the carb with a quality kit and to make a long story short, although I got it to start, run, and idle, the results were very disappointing. On the chance that I had screwed up the rebuild, I took the quadrajet off of a '68 Corvette 327 I had at the time that ran perfectly and mounted it on the Sharp with the same unsatisfactory results. (When I re-installed the carb back on the Corvette it ran perfectly again.) I posted a thread on the H.A.M.B at the time, and the general opinion was that I was just changing the flow characteristics way too much. Jon, ("CarbKing" over there) who is very knowledgeable about such things, said that anytime you use an adapter you mess up the airflow and using two such dissimilar adapters would lead to flow reversal, vortexes, and other undesirable effects. I abandoned the project, lesson learned.

So, to the O/P, the Edelbrock on an adapter would only cause problems. As said earlier, send your carb to Charlie Schwendler and have no worries. While you're at it, send the fuel pump, too. If you want to hear about what I consider the best "street" carburation for a flathead, rattle my cage and I'll expound on a small base 2G on a bored out late Merc manifold.

A couple of pics of my failed experiment.

[petehoovie]

Originally Posted by tubman

Sorry Ron, probably not. A couple of years ago, I spent some time trying to get a quadrajet from a 3.8 GM V6 to run on a flathead. I had a Sharp 4 BBL manifold laying around, and I stacked a Quadrajet to Holley adapter on top of a Holley to Square pattern and did a bunch of filling and and blending to hopefully "smooth the airflow out". I had completely rebuilt the carb with a quality kit and to make a long story short, although I got it to start, run, and idle, the results were very disappointing. On the chance that I had screwed up the rebuild, I took the quadrajet off of a '68 Corvette 327 I had at the time that ran perfectly and mounted it on the Sharp with the same unsatisfactory results. (When I re-installed the carb back on the Corvette it ran perfectly again.) I posted a thread on the H.A.M.B at the time, and the general opinion was that I was just changing the flow characteristics way too much. Jon, ("CarbKing" over there) who is very knowledgeable about such things, said that anytime you use an adapter you mess up the airflow and using two such dissimilar adapters would lead to flow reversal, vortexes, and other undesirable effects. I abandoned the project, lesson learned.

So, to the O/P, the Edelbrock on an adapter would only cause problems. As said earlier, send your carb to Charlie Schwendler and have no worries. While you're at it, send the fuel pump, too. If you want to hear about what I consider the best "street" carburation for a flathead, rattle my cage and I'll expound on a small base 2G on a bored out late Merc manifold.

A couple of pics of my failed experiment.

[TJ]

Originally Posted by billy’s40

Hello, Sir!

Do I need to put on a new intake manifold to use the Edelbrock carb? I just inherited my dad‘s 1940 Ford coupe. I’m just trying to make some changes to make it more reliable. I don’t need a new intake manifold, is there a certain adapter I need to use with the Edelbrock to make it fit on my flathead? Thank you.

Check with your local speed shop or on e-Bay. Those adapters are still available. I suspect they around $30 or so.

[Ggmac]

I’ve been using a Holley Economaster 4 barrel carb (450 cfm ) with great throttle response and no problems for over a year now . I like it so much I bought 3 more carbs to play with . They can be had for $40 and up on ebay . My manifold is edelbrock with an adapter . The cfm on these carbs varies according to applications, according to the Holley book .

[tubman]

Originally Posted by Ggmac

I’ve been using a Holley Economaster 4 barrel carb (450 cfm ) with great throttle response and no problems for over a year now . I like it so much I bought 3 more carbs to play with . They can be had for $40 and up on ebay . My manifold is edelbrock with an adapter . The cfm on these carbs varies according to applications, according to the Holley book .

Is this a "Spread-Bore" carburetor? If so, what did you use for an adapter? I have not been able to find a "Spread-Bore" to "Square" adapter anywhere.


In case the O/P ("billy's40") is not up to speed, a little information is in order. First, I believe that using a 4BBL to 2BBL adapter on a stock manifold just to mount a 4 BBL carb is a waste of time and money; there's just too much mismatching of airflow. Second, if you can find a 4BBL manifold for a flathead, it will have the old "Square" mounting pattern. The only carburetor that will bolt directly to these manifolds will be an early Buick Stromberg Aeroquad, an early Carter WCFB, or and early ('52 or '53) Olds or Caddy Rochester 4G. Anything else will need an adapter. Adapters for "Square Bore" Holley's and Carter AFB's (Edelbrock's are the same) are available but surprisingly getting harder to find. I've had a Holley 390 on and Offenhauser manifold (with adapter) and it ran fine. (Please note that "Square" and "Square Bore" are two different mounting patterns.)

In my opinion, the best approach for using a 4 BBL on a flathead is to use one of the "Square" carbs on an aftermarket manifolds. On a practical basis, the Aeroquads are out because they are scarce as hen's teeth with parts are even worse. A lot of the WCFB's have been priced into the stratosphere by the Corvette guys and early Mopar muscle folks. This leaves the Rochester. Although I've never run one on a flathead, many here have and speak quite highly of the combination. Charlie Schwendler has contacted me and informed me that he still has rebuildable cores and affirms that they are a perfect fit for a flathead.

[Ggmac]

It fits a spreadbore bolt pattern but the venturies are aprx the same diameter. I just used a spreadbore to holley adapter on one and redrilled the offey adapter plate on the other . Or I redrilled the carb base , can’t remember now .
They aren’t performance carbs and they come in many jetting and apparently cfm ratings , from v6 buicks to big block Chevys .

[flatjack9]

Originally Posted by petehoovie

When using an open adapter like that, you generally need to up the main jets 3 to 4 sizes.

[tubman]

Originally Posted by flatjack9

When using an open adapter like that, you generally need to up the main jets 3 to 4 sizes.

I temporarily shelved this project, mainly because of the lack on initial success and the fact that I realized I was out of my depth for a project like this. Your information will be useful should I ever decide to revive it. One of my rules was this project was that I did not want to modify the Sharp manifold in any way. From some of the posts here, it seems that this can be made to work, although I have strong suspicions that that the carbs are functioning as 2BBL's only. In all actuality, I probably won't get back to this because of the success I have experienced with Rochester 2G's on Merc manifolds.

[deuce_roadster]

I don't care for Quadra jets on anything and can't imagine one would work well on a flathead. I have a small 390 Holley on my 40 coupe and a friend who tunes all the race cars in the area made it run perfect. He changed the jets modified air bleeds, can't remember if he changed the metering blocks. I have the carb on the Offy intake with an adapter to raise it up higher and backwards, so the throttle linkage is easy to deal with.