Can a fuel pump show good pressure at idle (around 7 psi for a 383 carbed sbc) and still be bad ? I have no mid range torque and no high rpm (4500 to 6000 rpm) horsepower.

I've changed to a race HEI dizzy, new plugs and wires and checked compression which is good (180-190 psi)

Engine used to pull hard from 3500 to 6200 rpm and now, it no longer has that power. And engine is actually breaking up at 6000 rpms and only has about 800 miles on this engine.

 

What kind of carb are you using?

Holley's are bad for having the floats set wrong from the factory, which lets the engine run out of fuel when under heavy acceleration.

If it's a Holley, re-set your floats and see if that helps. Otherwise, you need to do a volume check on your fuel pump.

Is it a mechanical pump or electrical?

If it's a mechanical, check your oil and see if it smells like gas. If it does, the pump is bad.

If it's electrical, look for the pumps GPM rating. Then do a volume check and see how much fuel the thing spits out in a period of time, do the math, and see if it's putting out enough.




And if it isn't fuel related, check the dist. for proper timing and advance. If it's advancing too far, it can cause it to break up at higher RPM's.

Hope that helped
Dan

 

It is a Holley race carb and timing is set for 38 degrees total advance. Has a Carter mechanical fuel pump that has only less than 800 miles on it and the carb has been dynoed about 15 miles ago.

 

Yes, a pump can behave like that, check your fuel lines for kinks as well.

Could be an ignition problem or valvtrain problem (something's floating), as well. Can you check the pressure at full throttle?

And then put a TPI on it, hehe (to keep this TPI related).

 

If something is floating, wouldn't it show up on the dyno sheet that power is falling off at some point in the rpm range? I mean, wouldn't the sheet show that the engine is falling flat on it's face at a given rpm?

 

Can someone explain this to me? Thanx