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Ok so it is actually not on fire, but I have a problem with my Chevy 350 engine and you all seem very knowledgable so I hope someone can help me out. The engine has an HEI ignition and I recently timed it and well now it backfires through the carb. I have tried, according to NAPA, retarding the timing back to about 12 BTC, and the manual said it should be set at 8 BTC. I still have the same problem at 12 I had at 8 but not quite as severe. I have tried adjusting the carb by richening the mixture but i still get the same thing with it backfiring through the carb. It is an Edelbrock 600CFM with electric choke if that helps anyone. And now it has trouble starting. It is not the starter because it turns over easily it just takes a while to start and when it does it coughs and sputters and then finally after several tries it will start. Any ideas you have would be helpful since i am clean out. I don't know if it needs to be more than 12 or there may be some other problem completely. Thanks

John

Man it sounds like timing to me. Have you put it top dead center and checked where the rotor is on the dist.?

I have had the same problem and if I remember correctley the distributor was 180 degrees off.

Well the truck ran great when i first put the engine in. Then i bought a timing light and timed it and it was off. The rotor is pointing to the number one cylinder at TDC. And i didn't think the truck would run at all if it was 180 degrees out. And it has run for over a year just fine and then i checked the timing and it was way off. So i ifixed it and now it has started acting up. Thanks for the ideas though.

John

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Have you tried putting it back to where it was before you timed it?

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Could it be that it jumped time? Several things can cause it to backfire, one of them being a lifter not oiling and flattening a lobe on the cam. Backfiring means just what it says it's it's firing and the exhaust is coming back through the intake valve into the carb. Tww things are not clear. Does it actually run while it's backfiring? Did you pull the distributor?

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A stuck valve will do that, so will one that's adjusted too tight. In order to set up the timing mark on the little metal timing adjustment that bolts to the block, you have to do that when you know the number one piston is exactly at the top of the deck. Those things bend, and the best time to do that is when the engine is being assembled, before the heads go on . That way you can look at to see that is tdc top dead center. Then you buy yourself some degree tape and stick it on the harmonic balancer, putting the zero directly in the middle of the mark up above. Sometimes the harmonic balancer rubber inside will slip, I've been told. If that's the case the timing mark could be anywhere. Have you tried lining it up by bringing number one to tdc taking out the plug and put something in the spark plug hole to see if the piston will push out whatever you put in there. Be careful with that part of it. A 1/4 inch wooden dowel works well. Don't put something in there that's going to get caught or bend or score something really bad. Turn the engine over by hand if possible. You can also crawl underneath and put a screwdriver in the teeth of the flywheel, and turn the engine that way. Remember the piston goes to tdc twice during the four cycle revolution. One will be 180 degrees off. I'm writing this like you don't know anything, obviously you do, the probelm is I don't know how much so I've tried to cover everything. Hang in there.

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