The Stovebolt Site Forums The Shop Area Engine Shop Dual carb Setup

I'm currently going to install a dual fenton header and split maniflods in my 1955 2-series inline 235 engine.
I have read various articles that have said it is better to go with 2 Carter YF's of a 216 engine application rather than 2 Roch carbs for a 235 engine.

I guess because the 235 carb's, especially for street driving would be an "overload" for the engine??? I do have a couple of Roch B & BC's and 2 Carter YF 2101S (auto choke). Is it not feasible to LEAN the main jets several sizes in either the Roch or Cart carb's and lighten the load on the engine?

My experience with this kind of set up is limited so I would appreciate any and all help/input. Thanks.

If you use the 235 carbs they will be far too lean already due to having throttle bores too big to get the right venturi velocity. Big carbs provide LOTS of AIR, and very little fuel. It's almost impossible to richen the jets enough to get sufficient fuel flow. Using small-bore carbs and possibly leaning out the jets a little will get close to the right mixture, but it's still a fool's mission to try to outsmart the engineers who designed the fuel system. If a stovebolt needed two carbs, it would have been born that way!
Jerry

[quote=Hotrod Lincoln]If you use the 235 carbs they will be far too lean already due to having throttle bores too big to get the right venturi velocity. Big carbs provide LOTS of AIR, and very little fuel. It's almost impossible to richen the jets enough to get sufficient fuel flow. Using small-bore carbs and possibly leaning out the jets a little will get close to the right mixture, but it's still a fool's mission to try to outsmart the engineers who designed the fuel system. If a stovebolt needed two carbs, it would have been born that way!
Jerry

Well I happen to know this daul setup has been tried by more than ONE FOOL & sucessefully I might add. Maybe the design engineer's back in the day didn't have performance as their priority. You should try talking to Tom Langdon or Patrick's in AZ. You might learn something!

I do have another option. And that is to use 2 smaller bore carb's. I happen to have a couple of Carter YF 964's for a 216 engine. Maybe this is a better place to start.

My stovebolt My Pride & Joy

Talk to Tom. He fixed me up with two Holley Webers and the truck never ran better. Maybe not original but way better.

One day the owners of the following companies (there’s more but this is all I remember off hand) said ”We are going to make a pattern and cast multi carburetor intake manifolds for the stovebolt 6 engine”. Some made numerous versions.


Cyclone
Edelbrock
Edmunds
Ellis
Fenton
Harper
McGurk
Nicson
Offenhauser
Sharp
Tattersfield
Thickstun
Weiand


Hard to believe they were all fools trying to improve what could not be improved.

well180 bucks for two carbs it sure is whort a shot
at being the town fool around here

pizza40 check the link

http://stoveboltengineco.com/catalog/store/#ecwid:category=361512&mode=product&product=1222026

woops i reread your post and see you have several carbs already

It IS possible to SLIGHTLY improve performance on a stock 235 by going to 2 carburetors IF ONE DOES IT PERFECT!!!!!

It is also quite possible to significantly LOSE PERFORMANCE if one does NOT do it perfectly!

On a stock 235 (no other modifications) the change could be from a minus 25 percent to a plus 10 percent, depending on ones homework and skill. Is it worth it? Each will have their own answer.

The following link will explain further:

http://www.thecarburetorshop.com/Dual1barrelcarbs.htm

And just because some company offers something for sale is absolutely NO guarantee that the product is beneficial to anyone other than the investors in the selling company!

And just to expand slightly on a comment by Jerry (HRL): we find that we virtually ALWAYS have to RICHEN the jets when going to multiple carbs. This is because of the reduced air velocity in the carbs. The novice will not account for the action of the power valve (which will need adjustment), and mistakenly thinks the carbs are too rich.

Jon.

I have a 261 in my '55 1st series. I installed a set of Carter Weber carburetors from Tom Langdon. I also have hot water heat to the intake manifold. Powerful engine runs great. I planning to convert my '54 Belair using the same setup. Talk with Tom concerning the carburetor issue.
Larry

I'm no carb man but here is my take on the dual carbs from Langdon. Looks really cool and that is the best part of it. Probably is also the the "why" part of it. You must remember that what he sells is the two bbl Ford Escort carbs that have progressive linkage so they are running on one very small primary of the carb as Escorts were 4 cylinder engines. I've got this setup and I wouldn't do it again or necessarily recommend it unless you like the look. Mine runs fine but it would run fine with only one of these carbs and perhaps even better.

As for those 4 bbl manifolds that is pure bovine droppings. But COOL as Hell. But not to frett...Tom Langdon will do a selling job on you and you'll come away convinced it is the perfect setup. Ask me how I know..
Bottom line: it's your truck/car and your money.

I have two Carter-Webers from Langdons on a 1960 261 in my Suburban. They are very well-behaved (to say the least) carbs but they are way "under rated" for my dual-exhaust .060-over-bored cylinders. They have good acceleration - better than one original Rochester. At high RPMs they are sluggish. They are very economical unless I really push them.

The dual original 261 Rochesters (different from 235 Rochesters) provide much more performance, not so much at the low end but considerably more power at high RPMs in each gear (and at higher speeds). These are a little more work to get and keep tuned but they are more fun to drive with.

I am no pro but I have friends who are pros (including race car mechanics). They feel the extra performance from the dual carb set ups.

Nonetheless, I have been looking for a good single carburetor, something like a Rochester 2GC for a 265 (probably too small) or for an early 283. I am ignorant about what to look for (and how to adapt the intake manual) but I am accumulating 2GC manuals and spec sheets and I interested in hearing any opinions.

Dave, sending you a PM

Tim, I'm starting on a 261. Would like to know more about your rebuild/modifications to your's. Is that info on your site?

I have a Roch 2-bbl 2GV up for auction just today on eBay. Do a search for "Rochester 2-bbl 7031714" and it'll come up. If your interested.

Great input! I do appreciate it. Thanks.

Thanks Carb King. I was hoping you would chime in. Great article. I read and printed it out. I'm thinking now I might go with the 2 Carter 216 types. I have 2 YF 964S that I may use. I'll have to weld and redrill the bases, though. I'm guessing in your reply you meaan the pwr valve spring in a Roch B/BC will need a some of the turns clipped off. Do you have a starting point or is it trail & error?

I would suggest building whatever carbs you decide on perfectly stock. This way you have a repeatable baseline.

As for cutting coils on springs, I don't. Of course we have lots of different springs to choose from, so not really a problem.

However, if you use the Carter YF's that you suggest you have; AFB spring kits (readily available) may be used in the the YF.

Jon.

If I use the Carter's (for 216), what would I ask for to order spring kits from you. And are the Carter 964's a good choice or is there a better one to pair up? I know you won't give me a straight up answer but maybe a hint of sorts.

We don't sell the AFB spring kits, but thank you for asking.

As to carburetors, since you asked; I highly recommend the Carter W-1 series. For your application, probably the 574s (1946~1948 Chevrolet 216). These have a mechanical power system (no need to retune for vacuum changes) plus they have leather accelerator pumps which are total impervious to ethanol based fuels.

The YF's will also work well, but require more tuning. Call if you need more assistance.

Jon.