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Old 03-16-2002, 07:48 PM
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Question New engine puffing back through carb on startup only?

I have a new 350 chevy engine. It has only run about 150 miles+ plenty of break and warm up time. new HEI, plugs and wires with engine. has a new double roller timing chain. (long block crate engine)

I think I know what's wrong, but wanted to see what some of you more experenced guy's thought. I put a new HEI 48,000V distributor (replacing points type) and new wires, that have a little bit of extra length in them (had to make kind of a dip with the wires behind the engine) some of them are kind of close and I'm thinking it's Inducing a current in a wire next to it and causing another cylinder to fire out of sequice.
the thing that's weird is it only happens on a cold startup. the weather is cold out so I use a bit of the manual choke, plus a pump of the throttle to pump some extra fuel in it. some time's it starts right up, others it will puff back through the carb once(like it's one cylinder doing it) The engine Idle's great once warm, and just slightly rough before warm-up (it's still cold here and it has no stove pipe) (plus it has a bit hotter cam than stock)
I was thinking that it's not a flat cam lobe, because the engine seems to run flawlessly. once started. and I primed the pump, preoild the engine with a drill, and then turned the engine over a few time with the plugs out to make sure, and checked the rockers for oil, then had a proper break in.

I plan on using a vaccum gauge to check at idle and to look at plug wires, for cross firing.

Any ideas what else to check??? (timing's good up to 2000rpm- didn't check higher)

(they did say to check rocker arms for adjustment once it had run- posible problem I guess, if it's too tight) 1/4 turn down from slight resistance, RIGHT?\

any other ideas
suggestions on what to check?
thanks

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Old 03-17-2002, 05:58 PM
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I had this exact same problem with one of my cars and it was caused by a slack timing chain. It seams had to believe this would be the problem, with the engine you describe but it will cost you nothing to check it. Take the cap off your distributor, put a wrench on your crankshaft, turn one way then the other. If the shaft in the distributor turns each time you move the crank shaft your chain is OK.
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Old 03-26-2002, 04:54 PM
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Or the timing is retarded.
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Old 03-26-2002, 05:31 PM
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When you pulled the plugs, were they wet with fuel? I hope your not using platinum plugs, if so switch to R44's and if that doesn't prove to be hot enough move up to R45's. Gap em' at a loose .45. If the motor has been running too rich it could be fouling the plugs almost immediately. Fouled plugs will cause it to crank and run as you've described.
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Old 03-26-2002, 09:17 PM
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thanks for the ideas, but 1bad80 hit it right on. the timing was too retarded. Since I changed the timeing no more problems.
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