CP Piston Ring gap.. F'n Help me..

[HellonFire]

Ok.. I have my girlfriends block here, 86.5mm CP Pistons. Does anyone know the recommended ring gap?

She's planning on a GT28RS or bigger I think, so take that into consideration as well.

Because this makes no sense.

Originally Posted by CP Website

Determining Ring Gap
To determine the ring end gap look for your application in the proceeding
table. ALL BORES MUST BE CONVERTED TO INCHES.
Example: Bore size is 81mm – to find top ring end gap for a
street application:
.016” is the minimum allowable clearance.
CP Piston Ring Recommendations
Ring End Gap Chart
Ring Orientation Diagram
81mm/25.4= 3.189 inches
(3.189 x .005)= .016”

Application Top Ring Second Ring Oil Ring
Street/Hi Bore x .0045/.005” Bore x .005/.006” Min. .015”
Performance
Drag Racing Bore x .006” Bore x .0065/.007” Min .015”
Circle Track
Nitrous/Turbo Bore x .0065/.007” Bore x .007/.008” Min .015”
Supercharged
Motorcycle/ATV Bore x .005” Bore x .006” Min .015”

Should I do Street/High Bore or Turbo? I figure turbo.. So..

Top Ring should be.. .022-.023
The gap on the Ring that CAME with the pistons is .025

Second ring should be.. .023-.028
Ring CAME .017

Oil Rings.. They don't even fit in the damn block.

So am I doing this right? Or should I be using Factory recommendations which I think is like .015??

If so.. Anyone have a ring file?

Also, it also says this.

Originally Posted by CP Website

Important: Ring sets are manufactured to fit specific bores.
For every .001” over the intended bore size, ring gap will
increase by .00314”

Does that mean since I'm .5 over stock my gaps should be increased by .00314x5 or, if I was running 86.5mm pistons in a 87mm block that would be the case?

Thanks for any help..

Tyler

[TheWolf]

what is the bore of the block. If you plan on boosting over 15psi I would go with the "Turbo" setting.

[HellonFire]

Block is also 86.5..

And yes, over 15psi is what is going to happen.

Thats not really the question though.. This is.

1. The ring gap on ring one is larger then recommended.
2. On the second page, it says "Do not modify expander in any way"

My expander won't even fit in the cylinder without it overlapping..

Tyler

[steve shadows]

It should be expected to use the ring file to make the perfect fit with an application like your doing.

It could be possible they shipped you a set of rings assuming youd be using it for a particular setup ie, stock bore for street use.

I have never heard of them shipping out the wrong rings or pair of rings but there was one incident of a mix up I read about on Freshalloy.

your pistons are for stock bore I take it? Was your motor honed?

Why don't you give CP a call and talk to them in person maybe that would be more helpful that coming on here immediately.

[HellonFire]

I did call CP, but I was just wondering if anyone else had this problem before.

I know that I have to file the rings that are too small of a gap larger. But I cannot file to make the gap smaller! LoL..

How could my bore be stock? They are 86.5mm pistons, for an 86.5mm bore. Yes the block has been bored over, 30mm darton sleeves installed, and honed.

No, they didn't ship me the wrong size rings. When I talked to them, they gave me the correct part number for the ring package, and thats what I have.

The things that got me were what I said above.

Originally Posted by HellonFire

1. The ring gap on ring one is larger then recommended.
2. On the second page, it says "Do not modify expander in any way"

My expander won't even fit in the cylinder without it overlapping..

CP said..

1st ring.
Its fine they said. Couple thousands doesn't matter.

2nd ring.
Just file to .027-.028 and it will be ok.

Oil Rings and Expander
.015 on the rails, and the expander I can cut with wire cutters, and file smooth...

Kinda makes me nervous. LoL..

I wasn't coming on here to see if anyone knew the answers from CP, I was asking if anyone had this situation before. So I didn't come on here immediatly.

So do you have any experience with these problems? Or did you just post to put me down?

Tyler

[boostin13b]

I haven't had any issues with CP. All the sets I've installed have been pretty dead on. I've done all 86.5 builds as well. I haven't done any sleeving with CP's yet, but I've been impressed with their products.

[steve shadows]

dude im sorry for not being more helpful, it seems no one cares for your issue on this board. check out FA and search around, there was a thread related to this verything but Im too lazy to check right now and ive never personally had this issue because ive always used stock pistons even for 500hp levels.

[JJ240]

I ran 86.5mm CP pistons in my engine, and yes the oil rings were huge, and a major pain in the ass to get installed. They WILL fit just work with them (its supposed to be tight). Make sure the expander ring doesn't overlap as it goes it, you will get it eventually its just a battle. I did alot of swearing before I finished