EA 81 pistons in an EA 71 - lower compression ?

[howpow]

Hi fellow enthusiasts. I have a 1976 GF 1600 with Twin Port 1350 GSR Heads. The heads have been opened up a bit but the compression is still too high. After reading some threads here am I right in thinking that changing to EA81 pistons would help. My pistons are flat, are the EA81s dished or shorter. any thoughts would be appreciated.

[Crazyeights]

Both EA71 and EA81 pistons are flat top. The EA71 pistons are about .020" taller from the pin to the top. So yes, the EA81 pistons should slightly reduce the compression ratio in your application.

[howpow]

Hi Crazyeights. Thanks for the info. That being the case do you know if they are different castings or is the EA81 piston simply a shaved EA71 piston?

[subiemech85]

you may want ea82T pistons

[howpow]

Thanks subiemech85, I hadn't thought of that, the penny hadn't dropped that the bore in these two engines is the same, could be the way to go.

You don't happen to know the cc capacity of the recess in the turbo piston do you?

[subiemech85]

it appears to be fairly big!

 

from http://www.ultimatesubaru.org/forum/showthread.php?t=95356&highlight=ea82t+piston

 

can look at more this weekend

[howpow]

Thanks subiemech85. Yes it is quite large, would probably do the job nicely. I'm wondering if an EA71 piston could be safely machined to this depth. I looked on Ebay but no EA82T Pistons at the moment. Being in Australia make freight an issue as well. I'll have to check out a few wreckers.