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Old 02-20-2011, 08:36 AM
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Piston skirt coatings, who has the toughest?

Its been a bit since I posted. I will be starting a build thread here soon. LOL.

I am building a 1995 Mustang GT and am using a Gen II Viper v10 stroker motor. Building the engine With the guidance of Greg Good..

OK,I have a set of pistons that were in an engine built too tight, so the skirts are a little scratched up but otherwise they still look new. I just dont have $1200 for new pistons.

We had the block honed and its standard bore. The block was .003 under 4" and the pistons were for a 4" bore. Needless to say it was built way too tight from the beginning. After honing I have just under .005 clearance. I am looking into Swain techs PC-9 or PolyDyn coating. I will only be coating the piston skirts.

The only time I have ever used any coatings was for the inside of the block to help with oil flow.

So how tough is this stuff? I have heard Polydyn piston coating wears off rather quick or chips. When people rebuild there engines they can hardly tell it was ever coated. I was told by some folks that when they rebuild their engines, Swain tech coating is still on there pretty thick after many hard miles.

I wanted to see some pics of the coatings after hard use. To prove these claims.

I have asked this on a local board and since PolyDyn is local, alot of people recommend them. yet no one has any comparison pics for the wear of the coatings.

Many people have said the Pc-9 coating is the hardest stuff available.

So anyone have any experience with coatings?

Thanks,TC

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Old 02-20-2011, 09:00 PM
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no one?
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Old 02-20-2011, 10:08 PM
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That is because coating parts has zero benefit in certain situations. Some companies say it`s to reduce friction, okay it does that on what application? Street? highly doubtful. Race? Sure, you`ll have to replace it after every other run.
In the end what good did it do? The difference between showing proof of what a company claims and showing what is real is worlds apart. Especially when it comes down to what is everybody else using.
What I`m trying to figure up in your post is, if the bores were undersized how did you get the pistons in there to start with? Very very few forged or hyper pistons use the old clearance of .005 or more. Most of them now tell you .003 is too much. However in the end, if the piston company recommends a certain clearance go with it. What are the odds they are wrong?
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Old 02-21-2011, 10:35 AM
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I went back and checked what my original measurements were. the pistons were extremely tight.. I didnt buy the motor until after it had been built, ran a few hundred miles and then pulled from the viper when it was wrecked.

Block bore was 3.998 before hone and is 4.003 after hone. pistons measure 3.999. Its barely under .005 clearance now, which we were going for .003 to .006 max. Its a N/A motor.

I was told to coat the skirts to take up some clearance but the reason I was goin to coat them was to fill in the small scratches on the skirts. So the way its looking is that the coating is going to come off and actually not help with the clearance any. Its only benefit will be filling in the scratches?

So why coat them if it comes right off? Seems a waste of money

Thanks,TC
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Old 11-19-2011, 06:32 PM
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Quote:
Originally Posted by dually502
I went back and checked what my original measurements were. the pistons were extremely tight.. I didnt buy the motor until after it had been built, ran a few hundred miles and then pulled from the viper when it was wrecked.

Block bore was 3.998 before hone and is 4.003 after hone. pistons measure 3.999. Its barely under .005 clearance now, which we were going for .003 to .006 max. Its a N/A motor.

I was told to coat the skirts to take up some clearance but the reason I was goin to coat them was to fill in the small scratches on the skirts. So the way its looking is that the coating is going to come off and actually not help with the clearance any. Its only benefit will be filling in the scratches?

So why coat them if it comes right off? Seems a waste of money

Thanks,TC
Just saw this.

Most piston skirt coatings are designed to reduce friction and wear. Only one company I am aware of actually offers coatings to build up skirts and then top coat with a dry film lubricant. Tech Line Coatings, Inc.
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Old 11-19-2011, 07:08 PM
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Quote:
Originally Posted by dually502
... Block bore was 3.998 before hone ... pistons measure 3.999. ...
You either have that backwards, or your measurements are wrong.
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Old 11-19-2011, 08:58 PM
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Yes I had the measurements backwards, all the tolerances on this motor were too tight. Thats how the skirt got scratched so bad.

On the coatings: After having 2 sets of pistons coated by two different companies, the pistons skirt coating and all bearing coating was gone after just a few runs on the dyno.. The only thing that stayed on was the ceramic top coating on the 2nd set of pistons. So far it looks to me like they only sereve well for break in. Not worth the few hundred dollars in my opinion.
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Old 11-20-2011, 02:28 PM
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Quote:
Originally Posted by dually502
Yes I had the measurements backwards, all the tolerances on this motor were too tight. Thats how the skirt got scratched so bad.

On the coatings: After having 2 sets of pistons coated by two different companies, the pistons skirt coating and all bearing coating was gone after just a few runs on the dyno.. The only thing that stayed on was the ceramic top coating on the 2nd set of pistons. So far it looks to me like they only sereve well for break in. Not worth the few hundred dollars in my opinion.
There are two basic types of skirt coatings. One is "hard" but does burnish off, the other is "soft" and is designed to run with what is in effect a "0" build up and while it burnishes to the eye it is still there and functional. If I knew who did the work I could probably tell what you had/have.
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Old 11-21-2011, 09:00 AM
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Most 2004+ V8Chev engines use coatings on the piston skirts and on the piston tops.
Food for thought.

peace
Hog
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Old 07-10-2012, 12:42 PM
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How did your build go?

What coating did you end up using on your pistons? ******************

Last edited by 68NovaSS; 07-11-2012 at 11:32 AM. Reason: Commercial advertising plug, here and other sites
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Old 07-11-2012, 07:10 AM
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I can't post a pic, but I have a set of Ross pistons here that were used in Dirty Bird. 475 CID Pontiac making about 2K HP. The skirts were coated at Thermal Tech in Hopewell, VA. Their products are very similar to Swain, who is also a first-class operation.

Anyway, after 40 passes (including the first 6.50s and 6.40s passes of a Pontiac-powered car ever), the pistons are now "collapsed", where they measure a full .010" smaller at the skirt than when "new". The coating is still at least 90% intact on ALL of them.

They were also coated on the head with a thermal barrier. I attribute the fact that all 8 pistons that were in it on the first pass, were still in it on the "last" (with that combo) pass to the effectiveness of these coatings. A third coating, Teflon inside the piston can also be used to keep oil from "clinging".

Jim
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Old 07-11-2012, 09:41 AM
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Quote:
Originally Posted by JamesDean70mc View Post
*** is the best skirt coating in my opinion.
And you wouldn't have any bias in that regard, now would you??

A quick search shows you *********** yesterday over at Yellow Bullet (also your first/only post there, just like here). And at ************. Also yesterday, also first/only post. I'm sure there are others, but suffice to say that it seems you suddenly have some sort of agenda, JD.

BTW, the thread you responded to had been dead for 7 months.

Last edited by 68NovaSS; 07-11-2012 at 02:31 PM.
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Old 07-11-2012, 09:44 AM
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Piston skirt collapse

Quote:
Originally Posted by Mr. P-Body View Post
I can't post a pic, but I have a set of Ross pistons here that were used in Dirty Bird. 475 CID Pontiac making about 2K HP. The skirts were coated at Thermal Tech in Hopewell, VA. Their products are very similar to Swain, who is also a first-class operation.

Anyway, after 40 passes (including the first 6.50s and 6.40s passes of a Pontiac-powered car ever), the pistons are now "collapsed", where they measure a full .010" smaller at the skirt than when "new". The coating is still at least 90% intact on ALL of them.

They were also coated on the head with a thermal barrier. I attribute the fact that all 8 pistons that were in it on the first pass, were still in it on the "last" (with that combo) pass to the effectiveness of these coatings. A third coating, Teflon inside the piston can also be used to keep oil from "clinging".

Jim
***************************

Last edited by 68NovaSS; 07-11-2012 at 11:34 AM. Reason: Commercial advertising plug, here and other sites
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Old 07-11-2012, 10:02 AM
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Quote:
Originally Posted by cobalt327 View Post
And you wouldn't have any bias in that regard, now would you??

A quick search shows you ************yesterday over at **********(also your first/only post there, just like here). And at **************. Also yesterday, also first/only post. I'm sure there are others, but suffice to say that it seems you suddenly have some sort of agenda, JD.

BTW, the thread you responded to had been dead for 7 months.
Hi JD thanks for replying! You are right. We just jumped in. Our parent company is a *** auto supplier. We have spent 9 years perfecting this technology for pistons. Everything we say has hard, credible data behind it, some of which we can share. We recently launched a forum campaign to improve engines and awareness.

BTW, engines still operate the way they did 7 months ago.

Last edited by 68NovaSS; 07-11-2012 at 02:36 PM. Reason: Commercial advertising plug
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Old 07-11-2012, 11:39 AM
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Quote:
Originally Posted by JamesDean70mc View Post
Hi JD thanks for replying! You are right. We just jumped in. Our parent company is a *** auto supplier. We have spent 9 years perfecting this technology for pistons. Everything we say has hard, credible data behind it, some of which we can share. We recently launched a forum campaign to improve engines and awareness.
You'll have to do your "forum campaigning" elsewhere, read the board guidelines. Commercial advertising is not allowed on this board, even less so when you're tied to the product/company.
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