effect of crank endplay on pistons/rods?

[Jim Green]

--- auditude at cox.net wrote:
> Hello,
>
> 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?

I'd just see if they came in contact with the crank,
if not, all you should need is new bearings.

> 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.


Man, that's pretty high, just the higher compression
of the MC2 makes it much more succeptable to knock
that my old MC.  I'd say that's just a little to high
for that ECU to control without some major
programming.  You could add some water injection with
the dual table code of the megasquirt and you may be
able to pull it off.  Also, from what I've heard,
you'll be pushung your luck, and maybe your car if you
run 400 hp with those rods.

Later,

=====
Jim Green
'89 90tq 034EFI, Haltech IG5
http://www.geocities.com/jeg1976/car_home.html

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