So what do y'all use for forged piston to wall clearances?

[BuickMike]

When I had my motor built I did a lot of homework and had my machinist set all the bearing clearances to my specifications the best he could. Everything came out .0018 to .0020 ish. It's a good thing because I think he wanted me to go .0025. The motor is good, been running solid for years, great oil pressure, runs strong as hell....but I do have one beef now that I have experienced a friend's stock 10k mile GN. It has some piston slap when cold and a little high on the blow by. I file fitted the rings to .015 -.018 if memory serves me right. That should all be good, however my Wiseco pistons said to set piston to wall clearance at .0050 and that is exactly what my builder did. I did the assembly and I double checked. I'm thinking now that this is awfully loose and wanted to know what you guys shoot for? What to TRW, JE, etc recommend for their clearances and do you follow them?

Not like I'm gonna pull my motor apart because it runs great. I can live with it like it is but just wonder if I could have gone a little tighter. Just for fun I'll also get myself a leakdown tester in the next few weeks and make sure that my rings seated alright. Thanks!

 

[fastblackracing]

I have used the wiseco pistons in most of my builds with good results. I shoot for 4 1/4 to 4 1/2 thou on the initial build and its tough when your trying to spec out quarter and half thousandths on the specs. Sometimes it ends up at closer to 5 thou. You should be fine with your build, the noise is kinda part of the deal when you go with a forged piston compared to the stock pistons which where awesome in my opinion. Now there are some things you can do on future builds that would help with the noise , I usually spec the skirts to be a little longer, quarter inch than their standard issue pistons and you can have the wrist pin holes offset .050 or so also . wiseco is very good to deal with and you can custom order your stuff if you know how to spec it out with a little effort. Most just use standard issue stuff with out knowing you can have it made how you want it. Same goes with the ring groove specs you can get it how you want if you ask. HTH

When I had my motor built I did a lot of homework and had my machinist set all the bearing clearances to my specifications the best he could. Everything came out .0018 to .0020 ish. It's a good thing because I think he wanted me to go .0025. The motor is good, been running solid for years, great oil pressure, runs strong as hell....but I do have one beef now that I have experienced a friend's stock 10k mile GN. It has some piston slap when cold and a little high on the blow by. I file fitted the rings to .015 -.018 if memory serves me right. That should all be good, however my Wiseco pistons said to set piston to wall clearance at .0050 and that is exactly what my builder did. I did the assembly and I double checked. I'm thinking now that this is awfully loose and wanted to know what you guys shoot for? What to TRW, JE, etc recommend for their clearances and do you follow them?

Not like I'm gonna pull my motor apart because it runs great. I can live with it like it is but just wonder if I could have gone a little tighter. Just for fun I'll also get myself a leakdown tester in the next few weeks and make sure that my rings seated alright. Thanks!

 

[BuickMike]

Good to know. The car runs awesome but until recently I forgot how smooth a stock GN / TR is.

 

[750H.P.V6]

Mike,

Don't sweat it it's all good, .005" is about where you want to be. Forged pistons need more clearance and some piston noise at startup is a byproduct of that. If you want to hear a motor that sounds really horrible on start you can put an ear to mine. Needless to say the 6.500" rods and short skirted pistons make quite a racket.

Neal

 

[turbodave231]

I built a Stage engine for a friend with Ross pistons. His piston specs called for .010 clearance. That really made me nervous, but it turned out great.....a bit noisey cold, but that was expected.

I wouldn't worry about .005 with forged slugs.......I'd never run a cast piston that loose.

 

[earlbrown]

Just saying ''forged'' is a little overly simplistic when talking about cyl-to-wall clearances.

Wisecos use 2618 aluminum forgings and they expand more than 4032 forgings. That's why you have to put them in so loose.

The goal is to have them ''right'' when warm. With the greater thermal expansion, the noise is just a necessary evil.

 

[dr_frankenstein]

I typically go .007 in my motors for a typical forged slug... but i use alot of spray too. Block heater goes along way to keep the noise down.

A.j.

 

[BuickMike]

Thanks for the responses guys. I am constantly paranoid with this car about something. Part of it is because my HR mounts, plus u joint steering shaft and poly body mounts transmit more noise / vibration into the car and every little thing is amplified. I put softer bushings on my drivers HR mount and replaced the pass side with a stock mount. That helped quite a bit. Then I got into a stock, low mile GN. It is a thing of beauty to see one of these things unmolested. So quiet and smooth. No funky smell or any sign of blowby.