Flathead V8 Problem

W

wolfords

Member
I have a flathead V8 8BA engine with two Holly AA94s.

If you let off full throttle then it's okay (like at quarter throttle), but when you accelerate beyond that it acts like it's starving for fuel or the advance isn't working (but the advance is working). I've had both carburetors rebuilt, messed with the timing, put a new blue streak coil on it, messed with the jets and I'm running the factory distributor. It also smells rich at idle and acts lean on top end.

Any ideas?
 
Start by putting a vacuum gauge on it.
This will tell you what powervalves to aim for.
To big number powervalve and you have rich condition on idle/cruise.
Real hard to tune an engine on distance.
Get an Air/Fuel gauge and install it in the car takes a lot of the guesswork away.
Fuelpressure gauge is also in my setup when tuning an engine.
 
You said "factory distributor"...if you mean the stock Load a matic, there is your problem.
Lots of threads on this by people much smarter than me.
Try bubba, charlie new york, & tubman....they have solutions! m
 
mfirth said:
You said "factory distributor"...if you mean the stock Load a matic, there is your problem.
Lots of threads on this by people much smarter than me.
Try bubba, charlie new york, & tubman....they have solutions! m
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He says the advance is working but I wonder how he knows. If it is advancing the curve may not be right.
 
as others said, the distributor is not able to advance correctly with multiple carbs. you need a single ported vacuum signal for it to work as it should.

to test, disconnect and plug the vaccum, manually set the timing to 14-18 degrees and take it around the block. timing will be locked with no advance when you disconnect the vacuum. if it runs better, get a distributor that doesn't use ported vacuum. bubba makes electronic conversions, and many others sell mechanical advance units.
 
Just FYI: I am running an 8BA with two 94's, a Howard M6 cam and with Bubba's converted GM distributor. Also along the way Charlie NY advised me to block both Power Valves. I balanced them using a Uni-Sync and I experience no stumble or studder. This worked for me. Chap
 
Try Bubba's ignition for distributor and info. The GM conversion distributor I am running is mechanical.
Great guy to work with (Jim Linder) and always willing to answer your questions.
 
Check the gasket under the top cover of the fuel pump and at the bolt. If they aren't sealing properly, the pump will not generate enough vacuum to pull fuel through the pump essentially starving the carburetors on acceleration or under load.

I chased carburetor, distributor, advance and coil problems and vacuum leak problems at the carbs for a year before change the fuel pump upper gaskets. The engine now starts better and runs fine.

I'm still using a cork gasket under the cover. Does anyone make a fuel resistant rubber gasket for the fuel pump upper cover??
 
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wolfords said:
I have a flathead V8 8BA engine with two Holly AA94s.

If you let off full throttle then it's okay (like at quarter throttle), but when you accelerate beyond that it acts like it's starving for fuel or the advance isn't working (but the advance is working). I've had both carburetors rebuilt, messed with the timing, put a new blue streak coil on it, messed with the jets and I'm running the factory distributor. It also smells rich at idle and acts lean on top end.

Any ideas?
Click to expand...

Like others have said, stock distributor is a "no go" with multi-carbs. It doesn't receive the correct vacuum signal to function properly. Bubba's, Pertronix or maybe find a Mallory dual point mechanical advance. Bubba's will steer you right as he is very knowledgeable about early distributors.

Once you get that sorted out, then you can figure out what your fuel pressure, PV's or plugs, etc. and go from there!

Good luck!

3blap.
 
Are you running power valves in both carbs.? As posted earlier check manifold vacuum divide that number by 2 and go with that power valve. (15 in vacuum would = a 7.5 power valve etc. Also only run one power valve. Second power valve should be plugged. Also on the second carb. idle screws should be turned all the way in and throttle blades should be completely closed. The second carb is only a (dumper) Vintage Speed in Daytona Beach Fl. has base plates designed for this omitting the idle screws and and throttle closes completely. You also need to watch some power valves that come in the kits as the tip at the end is too large and interferes with the housing. Late Holley power valves do not work on Holley 94'S. Hope this helps.
 
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On a two carb 8ba I'd lose the vacuum distributor for sure. Not sure how you would make it work well otherwise. Charlie can handle it, no issue, or get a chevy conversion from bubba.


Then work out your 94? 97? carb issue. They make vacuum carb sync equipment available if you need.
 
I would avoid an electronic distributor, especially with a 6 volt system. A points distributor doesn't care about voltage; the coil does. Also, beware of new Mallory flathead distributors. They have been known to come with SBC advance curves that are too aggressive. My personal opinion is that if you want to go with a Mallory dual point, get the best older unit you can find, either an original flathead unit or one for an SBC which can be converted for use in an 8BA.
 
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Sid said:
Are you running power valves in both carbs.? As posted earlier check manifold vacuum divide that number by 2 and go with that power valve. (15 in vacuum would = a 7.5 power valve etc. Also only run one power valve. Second power valve should be plugged. Also on the second carb. idle screws should be turned all the way in and throttle blades should be completely closed. The second carb is only a (dumper) Vintage Speed in Daytona Beach Fl. has base plates designed for this omitting the idle screws and and throttle closes completely. You also need to watch some power valves that come in the kits as the tip at the end is too large and interferes with the housing. Late Holley power valves do not work on Holley 94'S. Hope this helps.
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This is fine if you are using progressive linkage. However I do not recommend this kind of setup. Run both carbs with straight linkage.
 
Thanks for all the suggestions. It sounds like it's power valves and distributor. Both carburetors have 7.5 power valves. I ordered smaller ones to put in this week. Everyone says I need a mechanical distributor. This is an original 6 volt. I don't want to put electronic on it. I need an old Mowery. I'll keep checking. Thanks again!
 
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