CP piston Ring Gap
 

Sorry for this question, with a search I've found lot of answers but don't know which gap to put with my setup.
DRAG Setup around 650HP with a T6766.

Please help me because I don't get the CP Piston Spec sheet in the box.
- Top Ring
- Second Ring
- Oil-Ring

Thank you

Re: CP piston Ring Gap
 

CP and Wiseco use the same formulas:
http://www.aa1car.com/library/ringendgap_wiseco.pdf

For 650HP Id recommend bore x .007 top and .0075+ middle ring.

Re: CP piston Ring Gap
 

very nice! thank you.
My bore is 84mm (3.307''), in the table application it is written:
Top ring: 3.307''x 0.0055 = 0.0181 or 0.459mm?

Correct?

Re: CP piston Ring Gap
 

Why does GAPs are larger with DRAG and Nitrous applications?

Re: CP piston Ring Gap
 

Gaps are larger to allow blow by so cylinder pressures stay under control and everything stays free moving. Too tight of clearances and you crack rings/pistons.

You should think about ptw clearance as well with that much power.

Ptw of .040 to .050

Top ring .020 to .022

Middle ring .024 to .026

Re: CP piston Ring Gap
 

i have a stock sleeve b16 pushing 22psi with supertech pistons and i gapped my top ring at .020 and my second ring at .025 (oil ring was at supertech spec of .015) and i have massive blow by issues and am about to rip back in to my block and replace my ring with a smaller gap so i would recommend calling and engine builder of the piston manufacturer and asking them

Re: CP piston Ring Gap
 

you do not want smaller ring gaps, if the ring gaps are to tight with the extreme heat they can and most likely will gall the cylinder walls up. im running .022 top ring and .024 second ring on my stock sleeve setup and its just fine, you might not have the rings in correct place? or upside down or bad rings?

Re: CP piston Ring Gap
 

I feel you and I hate blow by. I like to have my second ring gap smaller. I usually do around low .020 top, .018-20 second and .015 for oil . I like this better cause of no blow by. I have boost up to 30lbs and average around 550hp with no problem.

Re: CP piston Ring Gap
 

I think I'm going to put these specs:
- Top ring .020
- Middle ring .024

For the PTW you say .040 but some guys tell .015 there are a lot of difference, I don't want to massive Blow by issues, what is the correct one?

Re: CP piston Ring Gap
 

If broken in properly, you would be suprised how big you can make your tolerances/gaps with no blow by issues. .0015 piston to wall is the stock honda spec, please don't use it. You want close to. 001 ptw for about every 100hp at least up to. 0040 to. 0050, though it does vary due to things like piston silicon content.

I like muckman's suggestions. I follow relatively similar numbers myself and do not have issues with blow by. Don't foget to have the rings clocked properly. I follow the helms suggestions, with the top ring gap by the left exhaust valve, the second ring gap 90 degrees away by the left intake valve and the oil ring gaps 180 degrees from that by the other exhaust valve

Re: CP piston Ring Gap
 

Cause of heat generated by these applications. AS the rings heat up the gaps close from expansion. If youre gap is not big enough when high heat is generated the rings expand and the gaps will close to a point where they will touch, then expand galling cylinder walls Creating a big mess. Its always better to be safe then sorry. i would agree .020-.022 and around .025 second should be fine. Like Black EG stated make sure the rings are positioned correctly. they have a diagram floating around from a helms manual

Re: CP piston Ring Gap
 

Id say PTW anywhere from .004 to .006" not .04....0015" is stovk specs and youll definitely will have problems with that

Re: CP piston Ring Gap
 

The new accepted practice is to gap the second ring larger than the top ring. Pressure that makes it past the top ring is then trapped by a smaller gap of the second causing the top ring to float leading to loss of ring seal. Preventing ring flutter is why manufacturers are shipping the second rings gapped large out of the box.

Re: CP piston Ring Gap
 

i like youre logic here muckman. i have always used the second gap larger. Never heard of people doing opposite. This makes complete sense tho, never really thought into why it was this way but that pretty much explains it.

Re: CP piston Ring Gap
 

I know that different piston and piston ring companies have different specs to gap the rings. I spoke to Elmer Cerritos from Arias Piston tech support and he told me to gap my top rings at 0.022 and my second rings at 0.017 for my 81.5mm bore B18C1.

Re: CP piston Ring Gap
 

I cant take credit for regurgitating someone else's research.

From John Levis @ Wiseco:
All of the ring manufacturers have gone to the larger end gaps on performance ring sets. The theory is that the larger end gaps stop leaking pressure from the top ring from building up between the rings. When the pressure gets too high it will lift the top ring off the wall hurting seal/performance. We have backed this up with our own test on in-house dyno.

Re: CP piston Ring Gap
 

In no way am I saying that you are wrong Muckman. What I am trying to say is different companies have different specs.

Re: CP piston Ring Gap
 

This is a good debate. I believe the 2nd ring gap theory is universal however it’s interesting to see what other companies recommend. Ask them why though. The old theory of 2nd ring gaps being smaller came from the belief that the 2nd ring was exposed to less heat therefore expanded less than the top ring.

Re: CP piston Ring Gap
 

Yes sorry .004 for the PTW, than you

I will put
.020 Top
.024 Middle
.004 PTW

I've never gap larger the second ring.

Re: CP piston Ring Gap
 

James@IPG gave me this link from CP Pistons that confirm the Second ring larger than the top.

But don't understand .015 for the OIL Ring?

http://cppistons.com/LinkClick.aspx?...D0%3d&tabid=74

Re: CP piston Ring Gap
 

Muckman's recommendation is what i would follow if i was in your shoes..

I use this method also on motors I've built and also my personal motor.

Re: CP piston Ring Gap
 

X2 the specs you just posted are pretty much my specs for an 81.5mm bore on an engine making less power

Re: CP piston Ring Gap
 

Same here

Re: CP piston Ring Gap
 

The oil ring gap just has to be a minimum of .015". Dont file unless the gaps are less than .015".

Re: CP piston Ring Gap
 

For me .015'' was very large, we speak about .004 to .008 above