Ok, after help from LKGTO, Got the car going. Idels fine, and drives fine. Untill I punch it, or try to rev it up in gear to about 3000rpm. Then it backfires out the carb.
I did a vacuum check and it was at 9. I read on Holley's site that with a auto trans, and 9" of vac. I should use a 4.5" power valve. I changed that.
Idel is really really good now. But still backfires out the carb under load.
Timing set at 10. also tryed 12.
I was reading that its going lean under load. Thats what causes the backfire. If thats true. Could the wrong size mechanical fuel pump cause it.
I'm using a fuel pump from a 5.4L.. 6.5psi.
The one for a 5.7L. 9psi.
Maybe under load its not getting enough fuel.
Other then that.
Anything else?
I listened to the sound bite and based on an allowance for poor sound quality I think its time to go back to basics. As stated RV cams should have a higher manifold vacuum at idle. This lower vacuum can result from several conditions;
Your cam is really more radical than you think. Do you have the spec sheet and did the numbers match? And did you install the cam? A cam that is installed one tooth off will still run, but low vacuum and poor response to normal ignition settings are the results. One should always rotate the crank two full turns to check for timing mark alignment. Verifying this is a biggie and not easily checked without the proper tools or removal of the timing chain cover lets check some other things first.
Do the timing mark on the harmonic balancer and the timing indicator match when the #1 piston is at top dead center? This can be checked by removing the #1 plug and inserting a piston stop. Then by hand rotate the engine clockwise until it stops. Mark the balancer at the 0 timing mark. Now rotate the engine counter clockwise until it stops. Again mark the balancer at the ) timing mark. These marks should be equal distance from the factory mark on the balancer if the timing indicator is correctly positioned. These are serious problems and should be addressed after easier solutions have failed.
Properly adjust your valve lifters. This needs to be done on a hot engine and I like the following procedure although it is messy. Remov one rocker cover at a time and with the engine idling back off (turn the retainer nut counter clockwise) on one rocker at a time until the lifter begins to clatter. Then slowly turn the nut clockwise until the clatter stops. For the street continue to turn it down one eighth of a turn. This eliminates the possibility of a tight lifter causing the backfire and excessive cam wear.
Next go over every aspect of the ignition. check the cap and rotor for cracks and carbon tracking. Also check the coil to rotor contact in the center of the cap. Check the centrifical and vacuum advance mechanisms for proper movement. Check the reluctor to pickup gap Also check the plug wires for spark leakage. HEI coils are too powerful for some types of plug wines and spark will jump to from wire to wire. I have seen this problem where metal wire looms are used or where two plug wires touch. This an be checked at night in a dark place. If you are using mechanical and vacuum advance a timing setting at idle with the vacuum advance disconnected of 6 to 10 degrees is sufficient. HEI distributors should be hooked up to a ported vacuum source. Your vacuum advance can be checked by leaving it disconnected and rev the engine to see if this eliminates the backfire. Also check wiring connections to the engine for shorts that might occur from engine vibrations.
A vacuum leak that drops several inches of mercury should be fairly easy to find. Any of the types of liquid stated that are applied to the head to manifold should readily be sucked into the intake port. If the leak is in the valley area under the manifold the spark plugs should show signs of burning oil. Because the amount of oil burned may be small the plugs may only show whitish crystal deposits.
A careful check of the basis will isolate the problem so you an repair it.
Al
EDIT:
oh ya.
350. RV cam, HEI dis. Had rebuilt. all new insides, other the crank.
