I'm having another issue with my car... It's backfiring perioticly when I'm getting started from a stop or just idling through a parking lot. and when I'm at low RPM's as in stopped or idling it almost feels like it's getting bogged down... to much gas? I've adjusted the idle mixture and I have the timing set about as far advanced as I can before it detonates to much on 91 octane... btw... is octane grade chosen based off of compression or what??? initialy anyway... my engine has between a 9:1 to 9.5:1 compression ratio. any info would be helpful... after 3 years still can't get it tuned right...
If you have a Holley 4bbl carb, check the power valve. A blown power valve will cause this. Also, check the float level and the needle and seat. Also, recheck the points, if you have them. Good luck!
your compression is not that high so you shouldn't be having to worry that much, could be your timing that is causing your back firing problem ?? just a sugestion..
yes with higher compression you need more octane. that is why when you see guys mixing fuels and such.... also if you have to adjust your timing so far off (points)? your points might need looking at or possibly your dwell is off?? i couldn't figure out what was wrong with mine, i did alot of work to it and it didn't get better... people told me dwell wouldn't have any effect..... it was the dwell....i could have saved alot of money if i would have known.....worst case possiblay your chain has skipped a tooth.....
it's electronic ignition, and I've turned down the timing to about 7 or 8 degrees advanced at idle, it's a edlbrock carb 600 cfm
Backfires are rarely happen because of carb problems. so i would go through your ignition system first. also eldlebrocks REALLY dont like junk in them and as our gas tanks are prone to rust this is a possiblity. does your carb look gas stained or when its running especialy at low rpms do you see gas coming from anywhere on the carb if so it will need to be clean on the inside. or rebuilt.
A carbon build-up can also help your engine to idle and sound rough, so you may want to check into that, especially if you haven't driven it in a long time, does it turn off or hesitate to turn off?
First of all.......I would swap the Edelbrock for a Holley, then look closely at the ignition. Even the power and ground supply for the module and pickup.
if he had a holley it would be toast already because it backfired. i agree with checking the ignition as the first source of trouble though. also double check your timing, start at around 5btdc.
I had to disect this one, although I do agree. I also agree with hotrod and young grabba. I prefer the Holly but the power valve will likely suffer in a back fire. My Mav force tells me that it's in the valves/cam lobes. Good luck and let us know
Well really what could a normal carb do to cause a backfire...other then being really really messed up. Also i do agree edlebrocks are junk they make good manifolds but they should have stopped there. HOLLY all the way Check the simple thinks first like did you take the vacuum advace off for the timing.......ive forgot before. Vacuum lines..... any hissing. spark plug wires. dizzy just cuz its new doesnt mean its perfect. electronic ignitions... grounds do funny things.
Take a look at the vacuum source for the vacuum advance. Use ported vacuum with a stock or mild cammed motor. Larger lumpy cams work better sometimes with manifold vac. Been a while since I messed with a Cartter AFB - but I think the port on the bottom that you think would be manifold vac is actually ported vac. This is an example of a carb causing an ignition problem. The edlebrock equivalent to the holley power valve is the metering rod springs. You might try stretching the spring out a little. If it fixes it ...good. If it is worse then you need to pick up a tuning kit which will have lighter weight springs. I'm putting my money on the vacuum source for this. Cleaver
