You have a hondata tuned obd1 motor thats boosted then change the pistons. Let's say you keep everything the same on your motor but go from a 30 over bore to a 40 over bore. How off will your fuel curves and ignition tables be? Assume that your timing stays the same as it was when it was tuned (distributor is in same position). How long would you say a re-tune take?

 

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You are basically increasing displacement a little, so you might need just a hair more fuel. Unless the pistons are exactly the same but larger, I would think the detonation threshold for your motor will have changed a little. A stock cast piston is relatively weak, but there are no sharp edges that invite detonation.

All things being the same, if you went another .010" over vs where you were, you will have bumped your compression ratio up a little bit, too.

Sonny

 

The new pistons are actually custom 40 over's made for 9:1 compression... All specs were included in the design of the new pistons. Anyways, i just wanted to find out what kind of safe-range my motor was in with the old base map so i do not undergo any type of detonation issues.