Edelbrock backfires

[buscemishark]

I recently put in the Edelbrock performer series cam, intake and carb on my 1980. Everything seems to be working fine....idles nice, choke seems to be working properly. It even revs out nice and smooth. The only problem is that I get a big backfire through the carb when ever I stomp on the throttle. I can hit it hard and it's ok but when I do one of those intantaneous "mash it to the floor" revs, it sputters, backfires and the rpms never move.

Afterwards the car runs fine again with no obvious effects.

I've checked the plugs and wires and all are installed correctly, timing is good (I set initial at 14 deg BTDC). The only thing I don't know about are the valves (intake sticking, not closing, etc.).

Any help would be appreciated.

Dave

 

[Robin7TFour]

Dave try adjusting the accelerator pump lever on hole richer. also you may have to change the springs for the secondary needles. http://www.edelbrock.com/automotive/eps_intro.html

this should help also

Robin

 

[buscemishark]

Thanks.

I've played with the accelerator pump a little bit. Not much changes. The bigger the pump shot I give it, the longer it takes to get it to backfire, but it still does it. I have also tried running a richer mixture but that doesn't seem to help...maybe I should go even richer. The only thing i haven't tried is changing the metering rods.

 

[SG4206]

Dave-
Are you actually hearing an explosion (backfire) or is it gulping too much air and bogging down.


Doug

 

[buscemishark]

It's definitely a big backfire...flames and all. Looks cool in the dark garage but I still don't like it. ;-)


Dave

 

[Robin7TFour]

flames? then you have a definate timing problem. the fuel is firing when a valve is open. check timing,advance and even the chain for slack or wear

robin

 

[Bob Chadwick]

I don't know the 80 Vette but the 77 is timed at 8 degree BTDC. Could that be too much. Also did you time with the vacuum disconnected from the advance and the line plugged?

 

[SG4206]

Dave-
Normally too much retard will c
cause backfires; but to maintain a decent idle, you must have the primary butterflies open way to far.

Isn't this real difficult to start?
Doug

 

[buscemishark]

Ok now i'm stumped. I did a compression test and everything seems ok. I got everything buttoned up to recheck the timing and it won't start. It has never given me trouble with starting and now it won't catch. It will sputter and barely hang on no matter how much gas I give it but it dies the instant I take my foot off the gas.

I rechecked the plugs and wires and they are all hooked up right...hmmmm.

Any suggestions?

 

[SG4206]

Dave-
Start fresh. Bump the engine over to TDC #1. Pull the distributor cap and make sure the tip of the rotor is dead center pointing at the #1 wire . Then,grab the rotor and twist it counterclock wise until it stops. This should show you about 15-20 degrees of movement . Make sure it returns when you let go. You might have a phasing problem, or the mechanical advance sticking

Good luck-.

 

[buscemishark]

Yup, that's what I started to do when I jumped on Edelbrock's website to check out some tech tips. Well one of their tips for the Edelbrock cams is to use an Edelbrock timing chain w/o the 4deg retard that typical chevy 350 chains have...figures. Now I have to get into the front end.

Well while I'm at it I might as well pick up some other new stuff like an oil pan, front cover, etc.

Thanks for all your help guys...I will let you know how things end up.

Dave