I have been fighting with my carbs the engine runs great although it has poor throttle response it stumbles when you give a little gas. I am running 2 94s I have changed carbs changed timing also its acts like booster pump is not working any ideas
We'll hard to tell you what to do with out knowing your engine configuration. But on 94 s I always had best luck number 56 jets power valves blocked. That's me I'm sure many will argue that.. Posted using the Full Custom H.A.M.B. App!
Cannot be debugged without information... What flathead? What ignition? Which model carbs...model info is on left of bowl...and do you know what jets? First task, with some information, is to pin it on carbs or ignition...then find prob.
What's a booster pump? Electric fuel pump? I had one with a fuel pressure regulator. It would run good but when you drove it would fall on its face. I thru that crap on the trash and used a stock fuel pump and it ran Lika top. Posted using the Full Custom H.A.M.B. App!
Straight carb linkage? Sounds like the power valves are opening too soon and the engine is bogging. Either block them or run 3.5 valves in both carbs. When you switched carbs did you use a pair that had been run to together and adjusted? Vacuum advance working???
I first look at this as a fuel issue. If the engine runs fine at normal speeds, starts easily and shows no real running issues my first go is the fuel system. The question is are you getting enough fuel or too little? Both will cause the engine to stumble but in most cases its not the excess fuel but the lack of fuel when both carbs open quickly. This produces a super lean mixture and stumble do to lack of fuel. Before you go trying a bunch of stuff as an experiment try this approach. Get the engine up to operating temperatures and go for a test run. At cruising speed quickly accelerate to produce the stumble, now if the engine stumbles slow and repeat, this time pulling the choke 1/4 -1/2 Closed to restrict the air flow and again accelerate to see if the engine stumbles. If the engine stumbles and coughs its too rich meaning that you have too much fuel. If the engine does not stumble and picks up rpm then you have too lean a mixture and you will have to increase the fuel flow. In most cases I find the addition of two carbs jetted for one carb application produce a lean mixture upon WOT and the engine goes lean because of the excessive air pulled in by the two carbs. My backyard mechanics rule is raise the jet sizes 1 point per carb so if you have two carbs you increase the jetting from say .045 to .047 each to richen the mixture and allow more fuel to mix with the additional air. Try the choke method trail and report your findings..
You also might check your accelerator pump rod connector links to see if the holes are worn or loose...check for a worn loose fitting throttle shaft. accl. pump squirter should respond as soon as you touch the throttle. look in the top of the carb and work the linkage.. If that checks out look at the ignition next. Good Luck finding your problem
OK, first things first, replace that distributor with one that will give you adequate spark advance. The one you have was designed to work with a vacuum signal that originates from the carburetor venturi, you no longer have that regardless of where you have attached the vacuum hose. You simply can not use that distributor with anything other than the single, original carb that it was designed to work with. You may still have a carburetion problem but you will have a better chance of trouble shooting that after you get a distributor that supplies an adequate spark advance. Check with GMCBUBBA here on the HAMB, he converts GM distributors with full centrifugal advance that many have used with success.
Well, I guess I lucked out when I installed dual 94s on my stock '51 Ford years ago. I set the carbs up based on advice of 286Merc on the old Ford Barn, who had read from several people dual 94s wouldn't work with '49-'53 Loadomatic distributors, as I had. First thing was to make sure the distributor was working properly, that the dwell was 27 degrees and advance diaphragm was in good condition. I then made sure each carb was built exactly the same, using stock #51 jets and non-stock 5.5 PVs, that they ran the same on the stock intake, with the same vacuum levels, both manifold and distributor. The duals were then installed with straight linkage, carefully adjusted and synced. The distributor vacuum line needs to go only to one carb, along with a choke. The result was a slightly peppier engine with no flat spots and good throttle response, and vacuum levels measuring the same as with each single carb. ( The engine ran no worse than before). My point with this post is not to start a s_ _t storm, but to point out that there's much more to multi carbs than just changing intakes and bolting on two carbs, and that dual 94s can work with stock Loadomatics. Well,... at least mine did. I did eventually install a Chevy point conversion from charlie ny because I'll swap the 94s to 97s in the future. The overall performance is definitely better with the new distributor, fwiw.
Well, one of the biggest analytical problems with the Loadomatic is that it is close to impossible to check on its operation...the stipulated machine tests are run with arbitrary vacuum levels that might or might not match the vac signal on actual car (since the cars at best had pretty feeble full throttle curves) and you cannot static test with timing light on car...what the distributor does revving up in neutral has nothing at all to do with what it will do under any particular load situation. Best you can do is record distributor line vac under some repeatable situation then see what that much vac does with car not moving.
Bruce, The Loadomatic operation can be checked with a hand held external vacuum source (like a Mityvac), while the engine is running, along with using an adjustable timing light, to verify actual timing advance per carb vacuum levels, i.e., 1 Hg, 2 Hg, etc. I then monitored distributor and manifold vacuum while road driving, comparing both single carbs v.s. the dual setup, and saw no appreciable change. I thought these methods produced factual results, but I may be wrong?
I have the fix to your distributor problems. Offenhauser use to sell an item called "Vac-U-Trim" that allows you to adjust the vac diaphram and re-adjust the advance unit. It is a simple install. I have a bunch left from the last production run 35 years ago. Call me at 559-592-2707 for more information. Dan Marvin, Owner Exeter Auto Supply
http://www.jalopyjournal.com/forum/showthread.php?t=267985&showall=1 This is a link to a thread from a happy user of the Vac-u-trim. Dan Marvin, Owner Exeter Auto Supply
Recording and then artificially duplicating vac is about the only way to assess the curve underway, short of duct-taping your wife to the fender with a timing light in hand. A judgement from the history books: I have here somewhere the early edition of California Bills hotrod book, circa 1950. He reported that many new '49 Ford would post better 0-60 numbers at 3/4 throttle than at full (this on a car that is demonstrably under carbureted!)...because the part throttle operation was so much better than full. He suggested a Mallory for even the family chug if post-1948...
Well, that's a big start on debugging. Once you are sure it is running happily, swap the rear carb for the front and see if it runs right or not. If not we have a place to focus to get THAT one running right. Once you know you have two live carbs, the system can be put back together and problems attacked.
The Jalopy Journal
