I'm willing to risk putting in stock bore pistons to raise the compression on my itr powered autox car.

Has anyone done an 81mm ctr piston in their c5?

I know most go 25 over, but I'm willing to risk it.

I could swap the pistons out with the motor in the car and be done in a day.

Thoughts?

 

Ken, LMK when your doing this. I'm in Greenville now.

As for the OS vs. STD pistons, what's the mileage on your motor now? My biggest concern would be out of round vs. scratches needing a bore. Any oil consumption issues right now? Healthy leakdown and compression test?

I put STD sized P30's in my old build without issues, so it can def. be done.

<---- Dave who recently say pictures of the FL meet and now feels old.

 

I made 260+whp all motor on stock honed B20 sleeves

Same block got honed again and just made over 450whp turbocharged...

However, I was able to measure my piston-to-wall while doing this with the forged pistons.

I also did the same thing on a B18C with cast P30 pistons and produced well over 220whp all motor with supporting mods of course.

It's all about the honing tool you use. Also pay special attention when prepping the block for honing.
Most cast pistons will require very little piston to wall clearance, so I think a 30 second hone with "dingleberries" per cylinder will be just fine.

Above all else, wouldn't this put you in an undesirable compression ratio if you're running pump gas?

And yes, the piston swap can be done in one day if you have all the necessary components ready to go in.

 

I know there's been a lot of discussions about this before but what does this bring the C/R to and what layer H/G to use? on stock C5?

 

If I recall correctly, 81x87's with PCT's and PR3 heads will give you around 12.5-12.8:1 with an oem 3 layer head gasket.

 

Thanks for the clarification. Be nice to use OEM parts but don't think it would be wise to run that even on 93 for just a street motor..

 

been there.. done that..
prob won't do it again
the ctr pistons are heavy.. and i think its little too much of c.r

 

What does this have to do with ctr pistons? They don't fit B20 sleeves.

 

Also, Ken... if it were me doing this I'd go with P30's again. Had great results on stock bore putting down 218 WHP.

 

Tonio, I've done this before but with stock cr pistons and a quick dingleberry hone (which it didn't need IMO) on the old gf's itr.

Everybody else: I'm running Toda spec C cams + itb's + hytech header, and could really benefit from the additional compression.

I'm not burning much oil, and that which is disappearing is mostly due to the valve seals.

I don't mind running e85 (there's a station really close to my house).

So that being said, I would pull the head and pull the oil pan, then unbolt the rods and pull the rod + piston out from the top. Then I would inspect the bore.

I would have the oem pistons pressed off, the new ones on, the rods fitted with arp hardware, and then reinstall in reverse order.


Dave, I'll look for p30's if you think they're good, but I kinda want max compression if I'm going in there, so I'm not ruling out pct just yet.

 

Has nothing to do with PCT's, but everything to do with honing stock sleeves and making power.

If you don't mind running E85 then go for it man!
You will make more HP with the PCT's than the P30's. Just make sure you check your clearances.
Usually, whenever you use new rings you must hone the cylinders. I'm sure there are some that have gotten away without doing it, but for the time it takes to hone them, I don't see why you wouldn't do it.
Make sure you get the big ends checked on the connecting rods after the arp hardware installation.

 

Ken, I'm thinking about doing the same thing (stock bore). I really don't think it's that bad of an idea as long as the motor isn't too beat to ****. Let me know what you end up doing.

Craig - Who loves 12:1+ compression

 

Ken, the P30's were awesome for my build. S2 Pro 2's, SMSP header and "race exhaust" Edlebrock IM and TB, Mugen intake, Mugen HG...

Not saying you couldn't use PCT's, but the P30's are easier to find, and weight significantly less. Also, because of dome height on the PCT's, you can run into issues. I'd personally look more into zero deck pistons with a lower dome to achieve the same CR your after.

 

x2

ctr pistons are heavy and are probably the easiest oe piston to detonate

 

I LIKE CTR'S PISTONS WORKS FOR ME

 

Any Dyno #'s?