Setup is in the sig. Ok, well occassionally the car will backfire through the intake when I come off idle, and I never really thought of it as an issue (I figure it needs a bigger accelerator pump nozzle). I've noticed now that when I floor it from a dead stop, the car will pull fine all the way through 1st and 2nd gear no problem, but as soon as I shift into 3rd, it backfires through the intake a couple times in a row. As soon as I let off the gas, it's fine. My jetting is the stock 76 and 82. Timing is set at 15 degrees initial, and 36 degrees total. Normally I would guess that an intake backfire is caused by a lean condition, but I'm boggled because it only happens consistantly in 3rd gear. Any ideas??? Thanks in advance.

 

hmmmm dist 180 out? thats my only guess.........

 

this probably isn't the problem, but a problem you could have if you haven't already.


Your power valve blew out in your carb. One backfire and it could blow it out, but it would backfire alot. but worth checking into.

 

Thanks for the replies. It's a demon carb, and don't they have power valve blowout protection??? Thanks.

 

Forgot to put this in my last reply...Now it seems to do it everytime I floor it. And today after a 10 minute drive, I shut off the engine, and it "dieseled" on my. The engine was dead for a second, then ran for a second on it's own with the key in the off position!!! Any more ideas?? Thanks for the replies.

 

I would go up 2 sizes on your shooters and see if that helps the backfire. As for the dieseling, how far open are your throttle plates at idle? What is your idle speed? I find it odd that the car was running fine and just started to do this, but those two things are where I'd start.

 

Well, I hooked up a vacuum gauge today....it's only pulling 7 inches in park!! It was pulling around 12 before in park. The car won't even run now in drive unless I double foot it and have the throttle open a little. So I'm definitely guessing a vacuum leak is causing all this mayhem. Thanks for all the replies.

 

Just found out it's no vacuum leak. The timing was way off. It was sitting at about 2 degrees retarded. I knocked it back up to 15, and the car runs fine now. The distributor bolt came loose. Anyone have any tricks to keeping that bolt tight? I know it was snug when I put it in. Thanks again for the help.

 

are you using a chrome dist hold down? I had one and it just bent when I tightened it down. I went to a orginal gm.

I am having the same problem, I have checked everything. I just cant find the problem.