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Old 06-15-2010, 12:27 PM
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Spittin carb & restriction ????????

I've got a 1978 chevy 355 small block that isn't working right. when it's running and I give it gas, it'll pop/spit-back/backfire (whatever you want to call it) through the carburetor AND I can't get any rpms hardly. A good example is when it last ran, spat back, and cut off. I was backing up a hill with a very shallow slope, like 15-25 degrees, and it would only go to about 1200-1400 rpm (don't remember what, but it was in that range) and I just sat there. So I tried to give it more gas and noting happened, couldn't get anymore rpms out of it. I mean I Floored the thing and there was no rpm change, no movement, and the it spat back/ backfired through the carburetor.All cylinders are firing good, I fixed a cracked rocker, I've gotten the engine to stop smoking, I don't know what else to do Anyone have an Idea of what's happening?

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Old 06-15-2010, 01:05 PM
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Has the engine been rebuilt?? SBC's from this time period(mid-late 70's} are known for suffereing from flattened cam lobes, gives the symtoms you describe.

Could also be low fuel level due to needle and seat problems, float problems, or problems with the fuel pump and lines and filter. If you are sure the engine internals are fine i would look at these things.

What carb are you using??
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Old 06-15-2010, 04:10 PM
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Quote:
Originally Posted by ericnova72
Has the engine been rebuilt?? SBC's from this time period(mid-late 70's} are known for suffereing from flattened cam lobes, gives the symtoms you describe.

Could also be low fuel level due to needle and seat problems, float problems, or problems with the fuel pump and lines and filter. If you are sure the engine internals are fine i would look at these things.

What carb are you using??
It's a Rochester Q-Jet. The cams fine, It's a brand new CompCams XE-268/280 camshaft and the lifters for it. It had a fresh rebuild about a year and a half ago. New aluminum intake manifold w/a 2" spacer and an adapter for the carb to the intake. New high rise valve spring & retainer kit, and the engine was bored out thirty over to clear the flooding damage when we first got it. It's got a stock HEI delco distributor too. I "think" that that's just about it. If I've forgotten something I'll add that too.
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Old 06-15-2010, 05:01 PM
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Still sounds like a fuel delivery problem, either in the carb(float, needle and seat, dirt??) or before the carb(pump, lines, filter, tank).
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Old 06-15-2010, 06:59 PM
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Quote:
Originally Posted by ericnova72
Still sounds like a fuel delivery problem, either in the carb(float, needle and seat, dirt??) or before the carb(pump, lines, filter, tank).
Is that for the backfiring through the carb too?
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Old 06-16-2010, 12:59 AM
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Quote:
Originally Posted by durand322
Is that for the backfiring through the carb too?
Yes, a lean backfire is what spits back through the carb.

Check your ignition timing, too low timing can mimic the same thing somewhat.
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