[Mwieczorek]

Like the title says, I bought a 66 tripower setup. The tripower came with a 400.

I'm gonna post a million questions about the tripower in the tripower tech area... For now I have a question about the 400 that came with the tripower.

The block is a 9790071, it date codes to 1968 production, and is a YE code, so it was originally a 340 hp engine. According to Wallace Racing's site it should have 16 heads, but it has 15 heads which is kind of a bummer.

I got it home and of course got curious and started taking the 400 apart. It looks like it was barely broken in. It's 0.040" over, but there is no cylinder ridge, there is visible cross hatching, and a quick pass with my bore gauge shows no real taper.

It had a Crower M-280-H camshaft, with 3 broken lifters and a couple others that look suspicious. I'm wondering if the lift of the Crower cam was incompatible with the retainer to guide clearance in the heads? Either way the lifters and cam are going in the scrap pile.

The disappointing thing is that they used cheap 8 valve relief pistons.

I have a magnetic bridge coming so I can check how far down in the hole the cheapo pistons are. Once I do that I'll finish tearing it down and check the rod and main bearings.

So, dumb question... If all the bores look ok after teardown, can I install some decent pistons without boring it out to 0.060" over? I know the piston to cylinder wall clearance requirement is different for cast, hypereutectic, and forged pistons and also depends on what alloy was used to make them. Can I likely find a decent hypereutectic or forged piston, hang them on rods, hone the bores just enough to freshen up the cross hatching and run it, or am I asking for trouble? I wiped the bores with some carb cleaner and a rag. There is some discoloration at the top ridge area, but you can't feel it and certainly can't catch a fingernail on it. The bores are all measuring 4.1615 to 4.1652 on my bore gauge (that I set as best I could with a 4-5" micrometer, after checking it with a 4" standard pin). IIRC 0.060" is the last stop for a Pontiac 400 and that's with sonic testing recommended, so I hate to bore it if I don't absolutely have to...




Does anybody know what brand this piston is? It's marked as being 0.040" over, but does anyone recognize the other mark?