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Discussion Starter · #1 · (Edited)
I have a set of standarad pm7 pistons the shop doing the work said that I will need to go .030 or .040 over. I am going to get the .040 they said it was the max I could do before resleaving. The car is na running delta 272 cam and full valvetrain. It is convereted to obd1 using hondata s300. Just wanted to check into this further the shop said it would be fine
 

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91 CRX Si
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For NA purposes, i'd say you'll be ok going .040"...But your std pistons will not fit a .040" overbore.
 

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91 CRX Si
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Oh, ok. Your good to go then!
 

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'06 GMC Sierra Crew
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Who makes PM7s in 0.040 overbore? We're talking inches right? Cuz 040" ~ 1mm oversize, ie 76mm...
 

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Who makes PM7s in 0.040 overbore? We're talking inches right? Cuz 040" ~ 1mm oversize, ie 76mm...

ure right on the money a .040 over bore is 76mm. with a vtec single cam the .040 over will help with the motor breather ALOT BETTER!!! lets more air go inbetween the valvue angle and the cylinder wall compared to a std bore motor.
 

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Discussion Starter · #7 ·
Any other Opinions on this. Yes it is 1mm overbore. How strong are these walls on this motor?
 

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Im going 76mm on my new motor, also running a KMS block gaurd for a some added strength. I dont know if it is needed but I am going to run one for peace of mind.
 

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Block posting a better option ?

I'm considering a 150 shot and .040 over is tempting as I will be using Hi-Comp forged pistons anyway.
 

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Discussion Starter · #11 ·
With a 50 shot the max I would do is 20 over. I think if you stay with NA that 40 over will not be an issue. But with a shot you may run into problems. King motorsports said that 40 over should be fine and they have many cars with that bore on stock sleaves running NA in SCCA events.
 
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