I'm currently in the middle of rebuilding the 4A-GZE in my 88 MR2, and I've been doing some basic research into the 8.9:1 GZE pistons, which can get pretty cheap through work. My question would be if running that much higher compression and boost (TRD head gasket + 8.9 pistons + 10psi from the HKS pulley) on my stock ECU+Gruntbox would be ok?
Looks like the rings are not the same, and pistons come with pins. Here's what I've found:
USA spec 8.0:1 GZE
Rings (standard):13011-16090
Rings (oversize 0.5mm): 13013-16090
Pistons
Standard:13101-16100
Mark "1": 13101-16100-01
Mark "2": 13101-16100-02
Mark "3": 13101-16100-03
Oversize 0.5mm: 13103-16100
JDM small port 8.9:1 GZE
Rings (standard): 13011-16210
Rings (oversize 0.5mm): 13013-16210
Pistons
Mark "1": 13101-16131-01
Mark "2": 13101-16131-02
Mark "3": 13101-16131-03
Oversize 0.5mm: 13103-16131
So basically I just need to wait to see what all needs to be done with the block as far as machining goes, then choose if I need oversize pistons or not. All 4 pistons in there now are mark "2". Also, I need to figure out if it is safe to run close to 9.3:1 compression on this motor. I always run 93 octane from Top Tier fuel suppliers, I just hope that 9.3:1 would be safe and not ping. Anybody have any ideas?