effect of crank endplay on pistons/rods?

auditude at cox.net auditude at cox.net
Mon Jan 13 14:46:04 EST 2003


I might be getting some used 20vt pistons and rods, with about 75k on them.  However, the engine they came out of had a thrust bearing problem, and the crank apparently walked enough to cause some damage to it and the block.

I'm wondering if the crank walked that much, if these pistons and rods aren't also somehow damaged.  Since the pistons are not going to move longtitudinally in the engine to allow the whole reciprocating assembly to move, and there is probably not enough room on the rod "pins" of the crank to let the rods sit still as the crank takes a walk, should I assume that something bad happened to these parts?

Is there some sort of check that can/should be done to these parts to ensure servicibility, or should I just run away?

The idea would be to use these parts to bolt up a 7A head to an MC-1 to get a better-for-turbo-streetcar compression ratio than the resulting 6.something:1 that I would get if I used the MC-1 parts.  This would be an interim stage towards further mods, and I would want to get about 300hp or so using these and other used parts.

This combination would reported get me the AAN-ish c/r of like 9.35:1 or so, which I would try to be running with the motley crew of a MAC11B ignition, Megasquirt EFI, and Saab APC boost control.

Does that high of a compression ratio on a turbo motor "require" the sophistication of the native 20vt Motronic engine management?  I've been targeting a c/r of around 8.5:1 for the final configuration, hopefully able to reach 400hp still using the above wierd stuff.



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