The Stovebolt Site Forums The Shop Area Engine Shop 235 dual carb selection help

Hello All,


I dumped my 216 in favor for a 61' 235 that is just about done getting a fresh rebuild. In the process I opted for a fenton dual intake setup. My question is can I double up on the carter YF 756 unit that I pulled off my 216 (freshly overhauled) or move on to another matched set with higher flow? Any suggestions? If I must change I have been reading about Carter/webber 2bbl pairs working well. not quite sure where to pick those up as of yet however I would prefer to keep the YF if that will work.

216 carbs- - - -and Carter- - - - -you're starting out right. You'll still have far more carburetion than the 235 can ever use, but at least you won't encounter the misery of running two Rochesters for a 235 like some people attempt. Now all you need to do is figure out a way to bore and stroke that 235 so it has 432 cubic inches, and open up the ports in the head so you can get that much mixture in and out. You'll have to modify the intake to accept the narrow bolt spacing of the 216 throttle bodies, however. Good luck!
Jerry

This link might help:

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

Jon

The early 216 carters will work prety well on a 235 chevy. I ran that very set up for quite a few years on a couple of my 235 motors. The alternaive is not Rochesters in the event you cant get a matching pair of YFs. Some years ago I swapped over to the Holley/Weber 5200 carb as installed on the Ford Pinto. You can run a pair of them on adapters. They will also run really well. The pinto carbs are progressive two bbls with a small primary and a larger secondary that opens only after a cerain amount of throttle, like a quadrajet. They can easily be converted to electric choke. I prefer the 1974 versions as the fuel inlet is threaded. One thing you have to be careful of when running these carbs. You want to pull the top off and confirm the position of the main jets. They are in one end of the bowl and when you set them up you want the jets to be positioned so that they are rearward. In other words, so the fuel is pushing toward the jets on acceleration as opposed away fornj teh jets. If the jets are set up to be in the forward position, hard acceleration may uncover the jets and leave you with a stumble. other then that, they are good carbs to use in a two carb set up.

With both operating at all times, engine vacuum is reduced by about 29% in each (1 ÷ 2^.5 = .707). This may cause a power system to open earlier than desired, killing mileage.

Exactly why I have been suggesting carburetors with MECHANICAL power circuits (like the Carter W-1) for decades.

From the article referenced in the link a few posts above:

"The second criteria for selecting carburetors is that the EASIEST AND LEAST EXPENSIVE good results will be obtained by selecting either (A) carburetors which were originally designed for used in a multicarb environment (example: Carter WA-1’s used on the Twin-H Hudson) or (B) carburetors with a mechanical (as opposed to vacuum) power system. Carburetors with a vacuum power system may be used, but the tuning MAY be more difficult. If you have a spring winding kit and feel comfortable hand winding small precision springs, you may ignore this paragraph."

Jon.

I don’t necessarily disagree with the W-1 recommendation. The issue is finding a nice matched pair and being able to easily have them rebuilt professionally. That is the hard part. I gave up rebuilding my own carbs a long time ago. I just did not have access to all the things a good rebuilder has access to. Good carb cleaner, ultra sonic cleaners, chromate baths, ability to rebush throttle shafts, galley plugs, wet and dry flow benches, proper tools and specifications for setting them up. Truth be told, I just installed a pair of Holley 2300 carbs on one of my 261 motors primarily because I could get my hands on brand new carbs and did not have to deal with used cores needing a rebuild.

OP - to attempt your question about the 756s YF:

Yes, it MAY be used, IF you don't mind some difficult tuning, and some expensive parts.

The YF uses a vacuum power system, so the vacuum springs will require changing. Sometimes AFB springs may be used in the YF, but there are maybe a dozen different, and to my knowledge, difficult to purchase ala carte. The metering rods will need replacing. Finding donor carbs with the correct profile rods may be difficult, although metering rods MAY be purchased individually (with some restrictions).

And you still have the issue of the YF having a neoprene diaphragm accelerator pump, which also drives the power circuit. The neoprene CAN be an issue in a vehicle that is not started regularly.

Dragsix - everyone has their own idea of pleasure from the hobby. When I was still working on vehicles for myself; part of the enjoyment was doing my own work. On a couple of vehicles, I rebuilt everything on the vehicle, including an electric overdrive transmission. Not funny then, but funny today. Was smart enough to take the transmission apart inside a 7 x 10 foot metal building with a concrete floor. SPROONG! I picked up ball bearings for hours

The tools you mention are useful, but they are just tools. Yes, I have a milling machine for bushing throttle bodies. Yes, I HAD a chromate bath BEFORE I found out about the side effects of using one without protection (cancer, and dementia). About 7 nanoseconds later, my chromate bath was history. There are metal laundry companies that will do the chromate for you. The engine has always been my flow bench. Yes, I have an exhaust gas analyzer; and tried it a few times AFTER I had tuned various Carter carbs (and found the analyzer could do no better). Yes, I have an ultrasonic cleaner, that I bought early in their development. My made-in-USA unit cost $5500. and paid for itself in about 6 month. Now, they are MUCH cheaper.

A couple of other tools you did not mention are an acetylene torch and a machine lathe.

But all of the above are tools, and millions of carburetors have been rebuilt without these tools.

Jon.

I am with you Jon, I am. I do everything on my old cars and trucks, mechanical, paint, interior, electrical. When I lost my man for rebuilding my distributors, I bought a Sun machine and sorted out how to rebuild them. But there are a couple of thngs I just dont have the room to do, or the tools or the knowledge. Carbs are one, alternators, starters and generators are another. I really enjoy reading your posts. You know so much about carbs and Carter carbs. I have a friend who is a race car builder, fabracator, welder. He thinks nothing about some of what he does, actually thinks its easy, while I am in awe of what he can do. I am in the same boat when it comes to carbs. You are so very good at it, and it sounds easy, but I know, its not so easy, lol.


Any chance I and maybe others here could convience you to take on one more rebuild, say a W-1 in horrendious shape. Maybe some donations to cover the costs. Make a series out of it, step by step how actually rebuild back to specification? A real professional job, not just a clean up and new kit?

Mike - at this time, no. Business is great! I turn down maybe 25 rebuilds each week! Right now, there is a tremendous market for a carburetor rebuilder that will do a good job, and guarantee their work. How long will that market last??? Don't know. Took ESP 101 in college, and dropped the crystal ball on the instructor's big toe. Didn't get a good grade

If we should get completely caught up I would consider doing one. No donations necessary, as I would sell the carb once done.

Jon

Jon, I admire your persistence. After many years of beating one's head against a reinforced concrete wall, the only reward is the fact that it feels so good to stop. "My mind is made up- - - - -don't confuse me with facts!" seems to be the attitude of far too mnay people who know what they're going to do already, so trying to educate them is a fool's mission!
Jerry

I've considered doing that, Jon. But there are 2 problems. One---I'd want to limit what I do to only a few makes/models of carburetors and Two---it would be difficult to do this sort of work living under a bridge. According to my wife, that's where I'd be and it probably wouldn't even be a nice bridge. Plus it isn't (and hasn't been for a while) easy to find parts carburetors, so it might be costly to get started.

Jon G - parts carbs are not a problem, they just gravitate to you.

Lets take an example of the W-1 483s, and 574s.

You shop on Ebay. You pay NO attention to what the vendor writes, you look at the carburetors.

You buy 10 of them. You can expect you can fully restore (assuming you have new parts backup) 3 of them. You can restore less the choke bracket an additional 4. So out of 10, you can retail 3, and semi-retail 4 or a total of 7. And you have 3 parts carburetors.

If you buy 20, the semi percentage will increase to maybe 9 plus the 6 full retail. Again, you have more parts carburetors.

The two limiting parts are the afore-mentioned choke bracket, and the bowl cover (the inlet on some will have been cross-threaded). You should have new part backup for linkage, jets, rods, springs, plugs, etc.

But if you can talk your wife into becoming your helper (pay her!), give me a call !

Jon (the other Jon)

Thanks Jon,
Please look at your email and I'll explain a little further...

Jon G - understand. Check your emails, I sent you two.

Jon.