High Comp build on B17 blk and head

Hi there, I am starting to buy my head and block parts and am looking at stage2/3 cams. Understandably I’ll need some high compression pistons. Any recommendations? CTR/ITR pistons from what I’ve read are where it’s at but will PR3/30 be fine too? So far I have supertec bronze valve guides, blk nitrate valves, and seals, a 3 layer cometic gasket, skunk2 adj cam gears and an ITR intake manifold (stock tb, injectors and fuel rail).

Any other suggestions or recommendations would be appreciated. Along with this build, there will be a port and polish as well as some block work and tuned using a Hondata S200.

  1. Decide the compression ratio you want
  2. Determine how much your compression ratio will be affected by any milling you may or may not be doing during the rebuild so you can factor that into the equation
  3. Determine which pistons will yield the compression ratio you’re looking for
  4. If pistons aren’t available that yield the exact CR, then you can fine tune by milling more/less or by changing head gasket thickness.

You’re putting the horse before the cart by thinking about step #3 before steps #1 & #2


My favorite simple CR calculator.

Yeah good idea. So maybe bore the block first and then decide on pistons and sizing or would I basically be able to throw in some ITR pistons and rods and call it a day?

This is STILL your first step. If you haven’t had the block at the machine shop yet, then your second step is actually to have them look at the block. Don’t order pistons until they look at it. If all you need is a hone, then you can use the stock bore pistons, if you need to overbore a little bit due to scarred cylinder walls then you’ll need to step up into oversized pistons (81.25mm or 81.5mm). If you bore over this will change your CR slightly, so take that into account when you’re calculating what pistons to use to get you to your desired compression.

Again, decide on the CR you want. Then find the pistons you need to achieve that CR. As for the rods, no you can’t use those, use your stock rods, or aftermarket rods made for a b17a. ITR rods will be a different length and this will change everything.

CR range varries. I’m not really anal about how much I want. 10-11? Won’t be upset if I got more out it. I’m not really sure what numbers I’d put out. I just want to build with the parts I have so far. What other machine work should I consider and what’s the difference from a 3 angle and 5 angle when doing a pnp?