NPC! Engine problem Options

[ripper911]

I am here to draw upon the wealth of mechanical knowledge on this forum to help diagnose my brothers chevelle. I don't know much about that type of engine.

I believe the engine is a 400ci that has been destroked to 377ci.
It recently started flattening the spark plug gaps. He doesn't think the rods have stretched because they are supposedly high quality. It doesn't sound like the crankshaft is moving around or anything.

He's a mechanic, neither he, his boss, nor anybody else he's asked has been able to figure it out.

[Tom_T]

I think the above are all good suggestions to look at, but it may be in the build itself where the TDC is higher than original spec & it's just taking some time banging away to flatten them - but it's actually happening from the start, & not all of a sudden now.

So he probably needs to check the deck height of those pistons at TDC, & if they're domed that could be a problem because IIRC the OEs were flat topped & wouldn't have a clearance problem either.

However, I had the Pontiac 400ci with 4 spd. AT in my old 69 Ventura & worked on it back in the day (my car #2 of 5 ... ever) - a great powertrain, but for the life of me I can't understand why anyone would want to destroke it down to 377!!?? (IMG:style_emoticons/default/confused24.gif) (IMG:style_emoticons/default/huh.gif)

Good Luck! (IMG:style_emoticons/default/beerchug.gif)
Tom
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