I read the following post a couple of days ago by 93LSivic:

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 93LSivic &raquo;</TD></TR><TR><TD CLASS="quote">
But I think most stock bore pistons will have the valve relief problem where its cut out to the side of the piston face.</TD></TR></TABLE>

What's the word on this? Anybody here know if this the same deal with CP pistons?

 

i saw that too. i am going to be uising JE 9:1 81mm pistons. why wold someone say that? is there any truth to that?

 

I was going to go that route same as you nextel, but decided with custom 9.5:1 84mm pistons, would be interesting to know what truth is with this also for future knowledge.

 

What valve relief problem?

I have both JE and CP pistons in 81mm bore. Nothing hits anywhere that I'm aware of.

 

bump

 

bump

 

 

the problem is that where the valve reliefs are,they have to cut through the side of the top edge of the piston.this makes that spot very week.i have two sets of 81mm je pistons that are melted right there.just about any brand will be this way,not just cp

 

About what size is this no longer a problem?

 

anything over 82or 83mm... This is not brand specific, it's just that at 81mm bore and the size of our valve reliefs, there's hardly enough meat in there...
You'll see a lot more area with a larger bore...

I used to run 81.5mm and never had any problem....

stan

 

but you know,thie sad thing is,if you look at a stock 81mm piston,it isn't cut out of the side like an aftermarket one.

 

I'm not even sure if CP is built like that, I was wondering if anyone might have known. Well, my 81mm CPs will be here in a day or so, I'll compare them to my stock pistons and post some pics.

 

My 81mm JE's were fairly rough on the edge near the valve relief also. That material in that area is very thin. I'm running 81.5mm this time around though.

 

^bump to be placed in my recent threads.

 

i can vouch for what 93lscivic is saying . i had 81mm JE pistons that melted in that same spot.they were very ruff when i got them and he did sand thme down nice and prep thme good, but i didnt trust them once i took them out of the box the 1st time.

 

People should be looking at their tune if they are melting pistons. Dont blame the piston company. I dont care if its made of gold and you have detonation it'll break it.

art

 

hell tony1 built my first drag motor with 81mm JE never had a problem ran the same motor all season. Art can vouch how it did in houston even with the nos on that one year it was tuned conservative as well

 

Because tony is the man. Dont tell him I said that because he think I am the man.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Arturbo &raquo;</TD></TR><TR><TD CLASS="quote">Because tony is the man. Dont tell him I said that because he think I am the man. </TD></TR></TABLE>

Don't make me link the picture.

 

i never said that causes the melting, i said they are ruff and need to be prepped and sloppy IMO and i too melted them at the same spot

 

I can tell you that the Endyn/Wiseco's are a lot beefier in this area over JE. JE is paper thin, crazy. Good tune or not they will melt in that area at higher HP levels.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by VaporTrail &raquo;</TD></TR><TR><TD CLASS="quote">I can tell you that the Endyn/Wiseco's are a lot beefier in this area over JE. JE is paper thin, crazy. Good tune or not they will melt in that area at higher HP levels.</TD></TR></TABLE>

John, is this for JE's only or is it for every aftermarket piston with a stock bore size?

 

I guess I should have commented in the post about the piston reliefs that tuning will have a detrimental affect on the potential hotspots (which will induce detonation) these pistons have.
Just to answer a couple questions on what brands have this.
I personally have 81mm JE 9.8:1's that I burnt. In front of me I have new in the box CP's for customers engines Im getting ready to build. One is stock bore 9:1 and they have the reliefs cut into the sides very slightly on the intake side. Much less than JE's and they actually look like they were touched up and deburred a bit from CP....where as with the numerous JE's Ive used I had to do this my self. So bad that if you were to run your finger across with enough pressure that it'll slice it wide open.
The other CP's I have here are +.020" D series in 9:1. These pistons reliefs are cut into the side on both intake and exhaust side. Again, touched up nicely from CP.
Hope this answers some questions for you guys. I would like to comment again that tuning is tuning. But IMO if a engine is slightly out of tune and cylinder temps are a little too high then this problem with the reliefs will cause detonation and if this problem was not there (ie, going with say an 83mm) than possibly the engine could have went through the same "bad or out of tune" condition and may have lasted through it because of no potential hot spot (again can cause detonation which will eventually turn into a melted piston) scenario.

 

Good info

 

good info Dan