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Discussion Starter · #1 ·
Briefly the setup...

Toyomoto s/c with a brand new replacement C30-94 blower running around 10 psi at 6500 rpm. The impeller speed is at its maximum...can't get any more boost out of this blower.

I'm running my original bottom end, and at 110k, my rings or ringlandings are going out. Occasionally getting blow-by.

Just to clarify for the 'just go turbo folks.' I do not ever intend on swapping to a turbo in this car...I've spent however much money on this setup, and it works. I like having no CELs with the EMU vs. a standalone, which i would go with in the case of swapping to turbo. I also plan on buying a supra shortly after I graduate, and I intend to make it my unreasonably fast car, and leave the IS as a daily.

So on to the question...

The bottom end needs to be replaced or rebuilt. I have a used GTE shortblock available to me for cheap-ish to get remachined .20 over and get custom compression pistons. I'm trying to decide what compression to go with. My options are...

1) Keep it high (stock) and just replace the rings, etc. for much cheaper. (assuming there aren't any major issues with the block I have)

Also...i know 10-10.5 psi is a lot to run stock compression, but too much?
Obviously, max boost is only at max rpm, so the 10 psi is very brief.

2) Custom compression -> what compression? ->
Since I'm staying with the same setup, what are the relative losses I'll see from lower compression (9:1)? Would something around 10:1 be worth having a 'lower' compression than stock at all?

3) Or do I want to buy a brand new shortblock and be done with it?

If the questions seem juvenile to some, I apologize, but any insight from experience or otherwise would be great. Thanks.
 
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