After sitting a couple days, I removed the bowl covers on my Ford/Holley 94 carbs ('50 Merc 8CM dual carbs). The front carb had about a half inch fuel in the bowl; the rear carb was almost empty. Is this normal? Reason for removal: to check float height. Spark plugs are black/sooty. Idle mixture screws are turned slightly less than 1 1/2 turns out for each screw. Why are my fuel bowls draining? Leaky power valves? Thanks in advance. Matt
Yes that is common...do you have a radiused power valve...if you do it needs to be machined... Is there a gasket used with the powervalve...there should be and it has to seat correctly It may also be loose...IF it is machined... Check your oil it may have whats missing in it... They are vented (carbs) so there is some evaporation that could be happening...that much...not sure...any wetness at base?
I was talking to an older fella that says he's rebuilt 2000 or so 94's...he says those radiused powervalves are actually not the correct valves for the 94...yes they work IF they are machined but I get what he's saying... He also said another big problem is the base of the carb to the throttle body...3 screws. He says both surfaces must be checked for unevenness and trued if nessesary as they are prone to distortion. That is also true for the carb top plate to carb body...
Pull the carb base off the throttle body and check the power valve. Make sure everything is dry, then fill fuel bowl to float level and keeping carb level let it sit on a paper towel. Checking every hour or so, you will soon see if it is a faulty power valve or gasket. modern fuels over here seem to evaporate enough in 4 - 7 days to empty the bowl. .
The power valve is suspect and my dyno runs have shown my mild hop ups do better with the PV blocked off and have a better AFR https://www.ebay.com/itm/354724419714
Thanks for the tips! If I go the blocked off PV route, what changes will I note in drivability/acceleration? Someone installed a mild cam in the engine. I will never race this vehicle, just want to cruise.
Take a carb off and make sure the fuel level is correct and let it sit on two bits of wood on the bench overnight, maybe put some paper underneath. That should let you know if it is the PV. Or something else.I suspected my PV , but Lo and behold the fuel was actually percolating up the fuel bowl and escaping over the wall , fugitive style. I think I swapped out the convict carb and problem carb was jailed for life. Seriously I saw it happen!,,,! Why ,how ??? Don’t know but the seemingly impossible I watched, voodoo happening. Yes I was sober.
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