The Stovebolt Site Forums The Shop Area The HiPo Shop Dual carb setup

Would 2 Carter 2100s carbs be a good fit for a dual carb setup on a 54 235 engine, or what is recommended?
Thanks in advance.

I always like W-1's. Great vintage look, especially if you top with oil bath cleaners. Dependable, parts available, and the small base carbs are the perfect CFM match for the engine. Worse thing you can do is over carburete.

Do a search on this one Kevin. Lot's of mileage on this topic. Tim Lederman advises Tom Langdon sells Carter-Webers that work well with the 235. Lot's of folks have had luck with the smaller Rochesters that come on a 216. Others have tried the larger Rochester 1B that comes on the 235, but two of them are too big and very tough to get lined out from idle to WOT (are near it). I plan to do it myself on a 235, like how it looks. Not practical at all. Good luck.

As long as we're being impractical, why not go with a setup that's been proved to work well in the past? The 235 engine is almost exactly 3.8 liters, a displacement it shares with 1950's Jaguar engines. How about adapting a set of triple side-draft S-U carbs from an early Jag XKE and really have some eye candy? With a 3-carb setup and the firing order of an inline six, each carb only has to deal with supplying mixture to one cylinder at a time. That makes the carbs relatively easy to tune and synchronize, and side draft carbs don't have some of the clearance problems a 3-downdraft setup does.
Jerry

The last 1k trip I made I achieved 18.9 mpg with dual C-W's (Tom Langdon's) on a dual period Edelbrock intake. Kevin, glad to see you are going for that period hop-up look.

Would the triple side-draft S-U carbs mount easily on a 235? (not interfere with steering?)
Would the accelerator linkage be easy?

The Holley/Motorcraft 740 Carter-Weber carbs (early 1980s Pinto) can be easily mounted and connected to the accelerator linkage.

Nothing impractical about the 740s on a 235.

Since no commercially-made manifolds exist for the S-U setup, it would be a one-off fabrication job. Anybody handy enough with a milling machine, aluminum billets, and a TIG welder could probably make the clearances work. The engine compartment on the Jag was at least as crowded as under a Stovebolt hood, probably more so. I'm planning something similar if I get around to running a 230 inline six in the Excalibur roadster I'm building, with three Weber DCOE 40 side drafts and enough internal modifications to run a 6500-7K RPM redline.
Jerry

Just do this instead:

http://www.ebay.com/itm/Chevy-235-2...25355743?hash=item25ad8af7df&vxp=mtr

Cosmo,
Can't argue with 18 mpg. Sounds like a plan. Thanks

Hotrod,
I guess I'm not a practical kind of guy, that's why I've got trucks and tractors parked all over the place.

Deve,
That's cool but I refuse to cut my hood.

Thanks Guys

Well it took long enough, we finally got Jerry to advise us impractical folk on multi carb setups. I knew there were some jewels in there....who else is going to come up with a triple jag setup? Now that would be a conversation piece.

Jerry's carbs

mo2cyl,

If you go with the Carter-Webers from Langdon and you want to know how to hook up the electric chokes and the throttle rod, just ask here (or search the forums).

Langdon's carb-to-carb linkage is quite nice, but his illustration/photo is hard to understand.

Make sure your fuel system in clean. I put a filter in the fuel line before the fuel pump. I think I might have also put a filter at the inlet of each carb (or, an in-line, clear-body filter between the fuel pump and the carbs).

In OZ they have triple SU's for the Holden six. To get an idea of how it would look, take a look at the Revheads site. Pretty nice eye candy.
Revheads Triple SU kits

SimS

SimS,

Will the triple set work on a 47-55 Holden truck? Maybe yes, if the steering wheel is on the right?

The double set should work OK on NA american trucks?

Tim;

I don't know on the fit for LH drive applications. I just heard of Revheads when I was visiting Sydney. They have a lot of vintage Utes with hot sixes and some V8s. It might pay to drop Revheads an email and get some dimensions, etc.

Sim

Duals, if properly selected, and tuned; will work:

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

Triples, if properly selected, and tuned; will work:

http://www.thecarburetorshop.com/Triple1barrels.htm

Remember that the SU's are AIRVALVE carburetors!!! So even if the throttle is floored from idle, and the throttle valves are completely open; the airvalve (in this case, the slide) will open only as the engine demands. The SU's are very well suited for multiple carburetor setups because of the airvalve.

Also remember that the SU's have no accelerator pump; so proper selection and adjustment is critical to low RPM driveability.

And, if fabricating your own intake manifold: the following was posted in another thread by "panic" on these forums, and is probably the best article I have seen on intakes in the last 50 plus years:

http://victorylibrary.com/mopar/intake-tech-c.htm

You can do it for eye candy, but if you do your homework, you can actually gain a minimal amount of both power and economy. Don't do your homework, and it can go the other way!

Jon.

The triple setup makes much more sense than any dual carb arrangement, since each carburetor can be sized to supply the proper mixture for a single cylinder. Even with siamesed ports, the intake impulse is 360 degrees of crankshaft rotation apart for each port. Basically, with the right size carbs, triples are the equivalent of six one-cylinder engines sharing a common block and crankshaft. Duals, not so much!

The S-U also has a "constant depression" (vacuum) system where the sliding piston effectively minimizes the tendency to over-carburete and maintains sufficient manifold vacuum for good low speed and midrange performance.
Jerry

So, are the "yes" posters stating that the three side-draft SUs will fit on a USA 47-55 truck 6 cylinder with no interference - steering column and/or 3-speed shifter?

Wonder if the Holden triple manifold would be close enough in dimension to provide a starting point for the welding/milling Jerry described?

I only get about 14 mpg with my dual Carter-Webers. With the mechanical secondaries you cant floor it. you have to slowly work your way into it for it to pull nice. Wish there was a easy way to adjust them so you can test other opening options.

I was a Jag mechanic (and several other "foreign" cars)way back in the day and personally think the SU carb is the best ever made.
After seeing this thread, I went out in the shop and looked at the '48 2 ton. There is certainly enough room for 3 SU's with a well made manifold. Might have to be creative with the air filters, but inner fender and steering clearance is there.
This one has currently has twin W-1's on an Offenhauser manifold.

The trick would be finding Jag (or similar-sized S-U) carbs that aren't either worn out or priced higher than the reproductive system on a giraffe! Making the manifold(s) is just a matter of milling and TIG welding something appropriate to adapt the carbs to the cylinder head.
Jerry

Another "trick" might be dialing the S.U. carbs to the Stovebolt engine. Haven't played with S.U.'s for years, so not aware of tuning parts currently available. But they offered many different needle profiles.

Jon.

Back when we were racing Healeys, MG's, Triumphs, Jags, etc., carb tuners kept a handful of needles handy, and a few different piston springs for tweaking the mixture. Another trick was using different weights of oil in the dampers to alter the speed of the piston response to throttle position changes.
Jerry

Thanks Jon for posting that intake manifold tech article.

A quick google of "235 side draft" brought up a couple interesting threads from the HAMB. One guy had a period Nicson side draft intake and was looking for carb options. In another thread, our very own Cosmo had a cool, period side draft intake (Clifford I think).

I'm too lazy tonight to link.

235-261 dual exhaust mated to a 235-261 triple side draft. I should start a new thread to explore the possibilities of SU carbs on this manifold, adapters would have to be made.

That looks suspiciously like the OEM Corvette manifold. Fitting SU's would probably be less expensive than acquiring the original Carter carbs and they might work better due to the air valve setup.
Jerry

Jerry - it looked like the Corvette manifold to me also.

You are probably right that the initial cost of the SU's would be less. I doubt seriously that the final cost would be less. 90 percent of the SU's we worked on 40 years ago needed major machine work. I cannot believe they have magically repaired themselves. And that is just to get them so they would work, NOT recalibrate for the Chevrolet engine!

If I had that manifold, I would be looking for some of the marine YH Carters. While the calibration depended on the application, all of the YH's were designed for lower RPM engines, so the calibrations would be at least acceptable.

The major difference from the Corvette YH's to all other YH's was the Corvette used manual chokes. All others used auto chokes.

The manual choke on the YH was one of the poorer of all Carter ideas. The manual pull cable was attached to a zinc alloy (pot metal housing), and the housing was similar to voting in Chicago (vote early, vote often is replaced by break early, break often)!

The manual choke housing today (never used on any other Carter carb) is worth almost as much as the entire carburetor! Someone once machined them from brass, but even though they were much more reliable, they didn't sell because they could not be chromated. Very few drive the 6 cylinder Corvettes, they just look at them, and every little thing has to look correct.

We have helped several enthusiasts make the marine YH's work on the 235 with the Corvette intake.

And it is said a picture is worth a 1000 words:

Comparison new old stock Corvette carb & Nash carb:

http://www.thecarburetorshop.com/YH_manual_and_auto.jpg

New old stock Corvette carb:

http://www.thecarburetorshop.com/YH_manual.jpg

Mechanical rebuild of Nash carb:

http://www.thecarburetorshop.com/YH_auto.jpg

Jon.

I've got a 196 cubic inch OHV Rambler engine with one of those carbs on it stashed away in the barn. I wish I'd scavenged up a few more of them when they were plentiful and cheap.

The Keihin carb for the 74 and 80 cubic inch Harley engines looks pretty promising- - - -diaphragm-operated slide pistons, and just about the right CFM to supply mixture to one stovebolt cylinder at a time at moderate RPM's. They're also a lot newer and a lot less expensive than the Carter side drafts, and less than half as long- - - -better clearance for shift linkage and steering. If I can scavenge up a few of them in rebuildable condition it might be worthwhile to do some dyno testing.
Jerry

You gonna try it, HRL? I think this is a pretty cool discussion.

That just might give me the incentive to get the dyno back in operation- - - - -behind about half a dozen other projects that have been on hold since my bike wreck!
Jerry