Just about done collecting parts for a new build. It's going to be another 26 27 roadster body on an A frame. I'm going to keep the mechanical brakes and use as many vintage parts as possible including the model A four banger that I have. The original updraft intake and exhaust are possibly the only thing that will not be original to the A. My question is regarding carburation. I've been wondering what size carbs the banger can handle. I'm not against running one carb but I've been leaning towards dual carbs. What I really am wondering about is side draft carbs. Specifically motorcycle carbs. Let's say I fabricate an intake manifold that would accept two carbs. What size or CFM should I look for. Is there some magic number? Should I go by the CC's of the engine? I don't have a clue. I've been looking at used carbs in the motorcycle parts ads and wondered which, if any, would be the right size for this application. Although I may not go this route, I'm just wondering. Anybody got Ideas? Let us know.
http://www.gtsparkplugs.com/CarbCFMCalc.html A good calculator. Let's you put in Volumetric Efficiency. A flathead is probably only 55-70% efficient. Makes a graph to look at too. No connection. Mike
Look more at the horsepower, but take into account how many cylinders the carb(s) need to feed. A carb feeding a single fourstroke cylinder (as on many high performance motorcycle engines) will only flow air about 1/4 of the time, meaning it could supply enough air for ~4x as much power if it was flowing air all the time = feeding four cylinders or more. The power each carb can handle is very dependant on the intake arrangement.
From what I understand the four banger is about 200 ci. 40 hp. with 4.2 compression. What is a comfortable rpm that it can handle,3000?
http://www.rarecarrelics.com/tests-...tock Model “A” on the,only 35.6 HP @ 2250 RPM! Nice link. Jeesh. Mike
If you bump the compression up to 6-1 use a B cam and go with a good dist. you should have a decent 55 to 60 mph motor. Rpms around 2500. There are a few guys on the monthly banger meet that use SU carbs but I wonder if two stock M74 Harley linkerts would work. One would power a 80 inch Harley.
Lots use 2 81"s (I believe V860 carbs) or a Weber on a manifold designed for it. There's also a manifold (fairly rare)that uses 2 of the original style carbs. FWIW Paul in CT Or a single B carb on a stock manifold that has been enlarged to the B size.
If you are looking at sidedrafts, a pair of matched Carter YH are made in USA, and more reliable than motorcycle carbs. Manifold would have to be fabricated. Jon.
I ran an Ansen manifold and Holley 94 on my 30 pickup, ideally the 81 off a V8 60 is the best fit as far as cfm. The 81's are hard to come by since they made a lot less of them than the 94's and 97's off the standard V8's. I also ran a Winfield 6:5 high compression head, Mallory distributor and a Red's header, ran good but still a 50-55 mph car due to the rpm range. With a 30" tall tire and a stock 3:78 rearend you are turning 2545 rpm at 60 mph, without a counterbalanced crankshaft that's about as high as I would want to spin a basically stock motor for very long.
The M74 is a good carburetor on an old Harley if you don't mind the droolin SOB getting your britches leg wet. It would be a little difficult to keep one tuned on a car where you can't reach down and turn the jet adjuster. If I wanted to run twin pots on an old banger I would consider a pair of the small SUs or a pair of the one barrel carters from an old Chevy 6. The SUs are not period correct but they are very forgiving.
IDK about that. After the war, a huge chunk of all British car production came here. From the 50's on, I'm sure there were plenty of wrecked Jags, MGs and Triumphs in the yards. I watched "Hot Rod Girl"(1956) the other day (I know), the first race was T-Bird vs Jag and when they went to the "Hot Rod" shop, the car in the bay was an MG T. I think they were around. Post war anyhow. BTW, Herbert and Thomas Carl Skinner patented their carb in 1905. I don't have a picture of any on an A though. I guess it must have never happened Mike
by the 50s no one was running a an A banger, well no one with sense enough to pour piss out of a boot. I was thinking about the era that someone building a "hot rod" banger would have been building in. Yes SUs were common here in the '50s and '60s. Just not that common in the '30s and '40s.
FWIW My original plan was to put a v8 60 in it. I was thinking that it just might fit under the T hood. Unfortunately that deal fell through. Then thought about the 81 carb from a v8 60. I've been on the E auction site and su's, yt's and 81's are readily available. Started thinking out of the box and sizing became an issue. Already a great wealth of information has come forth and I praise The Hamb for getting it out. Found an old circa 1901 sidedraft carb but do I want to go there? not. I'll take all the info I can get so keep it coming.
I have those Carters Carb King mentioned if it is of interest '53 Corvette YH carbs | The H.A.M.B. (jalopyjournal.com)
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