Tight piston to cylinder clearance

Now you can install forged pistons with tight skirt clearances down to .0025 or .003" with the line2line piston coating. Customers have been using this coating and its been working out fine. The pistons will be tight on break in but will not scuff. After a hundred miles or so the coating burnishes down to the ideal clearance and stays there. You end up with tighter clearances than you could have with a bare alum piston and the life of the piston is doubled. For those who like it tight - see used piston skirt coating below.

http://www.line2linecoatings.com/slickCC.html

I had this done to Ms Peel in 2003 and Mz Peel 2010 by Swain so glad ya finally catching up and suspect next 'new' revelation will be cyro tempering and dry friction coating. Glad it seem to benefit tight pistons but await to see pictures of how much worn off after some racing and then reflect on the piston skirt texture patterns to put in areas the coating don't last long. We are talking lasting max performance not politeness.
http://swaintech.com/

I've used a baked on coating since the late 70s called Kal-Gard Piston Coat. I've even used it on Amal slides with good luck. You aluminum oxide blasted your pistons, wiped them down with MEK, then applied the coating. It was then baked in the oven on high for an hour or so. Kal-Gard recommended a couple of coats. It worked very well. Unfortunately I've miss placed my supply and don't see it in Kal-Gards web site. Maybe the Swain tech is the same. If so, I'd sure as heck recommend it. Don't bake it in your home oven if your wife will be anywhere near the house as it has a nice manly chemical smell

Interesting stuff, Jim. I've read up on it a bit after your other post discussing it. I'm assuming that the .0025" - .003" clearance is for the bare piston before coating, not after the coating is applied. Is that correct?

Ken

lcrken said:

Interesting stuff, Jim. I've read up on it a bit after your other post discussing it. I'm assuming that the .0025" - .003" clearance is for the bare piston before coating, not after the coating is applied. Is that correct?

Ken

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.0025 to .003" clearance is after the coating is applied. That way a little coating can wear away at any high spots and give you a perfect fit. If the piston only had .0025" clearance when it was bare aluminum then the added coating would wear down to bare metal again and you would lose the low friction benefit of the coating - and a bare alum piston would scuff/seize at .0025" clearance.

I've quizzed a few coating shops about clearance issues to be told these coatings are not meant to add filler clearances as both too thin and too fragile to retain initial clearnaces so tends to rub to base metal pretty quickly which defeats that use of coatings. I'd suggest knurling pistons for pretty close fit then the knurls get mashed/abraided to settle in with better clearance than if not kurled. If Jimmy says extends his pistons life then add this to Commando optimializing list. Personally I would spend more on cyro tempering pistons and rings and cylinder sleeves before other coatings and install. Might also look into 'dry friction' coatings, crank journals, bearings, tranny shafts and cogs etc.

What's wrong with 128,000 mile piston and ring life from a dead stock setup?
And now there is supposedly better stuff available.
Do we really need coatings?
Just seems to be another cost/complication that can go wrong and wreck the motor.
I'm speaking of bikes intended primarily for road use, which the vast majority here are.

Glen

Even "road use" pistons benefit from such coatings because the shape of our inexpensive lowest common denominator high silicon castings is less than perfect. This technology offers near perfect fit that will keep the rings square to the bore, enhancing seal, which is the whole point of a piston.

Admittedly my experience with internal engine coatings is limited to Nigel's report of that particular coating coming off and doing significant engine damage in just a short mileage( 2000?)
Im figuring why risk it when properly fitted standard pistons and rings seem to be almost impossible to wear out in the standard aged Norton owners lifetime?.

Has anyone here used a coating to get further down the road than 128,000 miles on one set of pistons and rings?

Glen

Do we need tight pistons to get higher compression or are we worried that piston slap might crack a piston ? What is the function of the piston rings and at what piston speed does ring flutter usually occur ? In a Commando long stroke motor the piston speed is very high at 7,000 RPM. I have always been under the impression that a loose motor is usually faster than a tight one.

My failed coating was ceramic thermal barrier coating, quite a different kettle of fish to this stuff. Ceramic is hard and brittle and sharp and nasty, hence it caused damage when it decided to flake off.

It didn’t come off the piston crown though, it came off of the head. It had been badly applied and was very thick around the valve seat area, which became brittle and flaked off.

‘Once bitten, twice shy’ though, the engine has no ceramic coating in it now!

The pistons are DiamonDyze hard anodised though. And personally, I would definitely try this coating Jim is offering if I were buying new pistons from him.

This coating is designed to rub off at high points where the clearances are too tight - its a lubricant so there is no damage to the motor. The coating also holds oil and provides extra lubrication.

Below is what I got from Bill at Bore tech. He's the guy who came up with carbide impregnation to double or triple the life of a cylinder.

"What I have found on race motors is that the coating helps maintain the minimal piston clearance that piston growth dictates. Tighter clearances will keep the skirts from distorting for longer miles. It also minimizes the chance for piston skirt scuffing with reduced friction at the skirt. Over time the coating will start wearing down in the areas of highest loads. By that time you have increased your piston life substantially. The only other processes that would be more durable is hard anodizing or nickel plating of the pistons.

Regards,
Bill Moeller"

It would seem like a good idea for engines that are not going to get a thorough warm up but effectively thrashed whilst still cold (ish) The piston will get to its working temp and expansion before the cylinders do. Or am I missing somthing?

oldmikew said:

It would seem like a good idea for engines that are not going to get a thorough warm up but effectively thrashed whilst still cold (ish) The piston will get to its working temp and expansion before the cylinders do. Or am I missing somthing?

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Yes it will help in that situation but its never good to thrash a cold engine no matter what. On the other extreme - the coating could save your pistons when the motor is overheated to the point of seizure or melt down.

But its really just about running tighter clearances for those who want tighter longer lasting motors.

What's wrong with 128,000 mile piston and ring life from a dead stock setup?
----------------------------------------------------------

You must have the only stock Commando in the world with 128,000 miles on the original bore, pistons and rings!
Congratulations!

If the128k mile wonder had the fancy coatings, might be working on 1/4 million miles by now, with no end in sight, duh.

My meager observations imply, if no scuffing seen or wear off of side wall coating then clearance and low friction was good to go w/o coating so nil benefit gained. Not bad to coat sides, just may be over rated on detectable benefits to expect.

Here's how Ms Peel 8000 mile pistons looked, similar to 10,000 m Corvette black coated side walls after loads of tire ruining fun. Scroll to see photo example and study closely.

https://www.corvetteforum.com/forum...d-pistons-how-long-does-the-coating-last.html

Its hard to find photo of used coated pistons as vendors sure don't. Again not saying a bad thing just pointing out facts of coat life to consider how to evaluate why JMS still have pristine coating. There are better proven oil holding textures than hard smooth coatings and friction coatings only function with contact, which leaves evidence. Mz Peel is coated in/out chambers out through exht ports, valve faces and backs, JMS pistons too, in case it helps get away with my engine murdering a bit longer. Bore endurance are the main benefit to have done by likes of Bore Tech.

Wiseco coating nicely worn.
https://p.vitalmx.com/photos/forums/2017/04/12/187515/s1200_IMG_0384.jpg

Normal expected coat wear
https://honda-tech.com/forums/all-motor-naturally-aspirated-44/normal-looking-wear-pistons-2634145/

JE Pistons thoughts on coatings for race applications

Quote:
The thermal coating will flake off during detonation. We would have to do a custom piston and can move the top ring down and increase thickness for strength. Having the piston anodized will increase strength but will not allow the piston to absorbed the heat and after a mile or two will detonate and actually make the part fail faster. The anodizing it only for nitro applications.

ALEX RUSSELL
JE PISTONS

Ancient warning that applied to over thick or wrong type coat on poor surface prep. Does not apply to what's available now by reputable vendors. Look up JE piston complaints failures for perspective of dramatic blame aiming.

Plain ole alu anodizing to sapphire/ruby surface may be risky on some piston uses, but just like anodizing allows impregnating pigments, newer anodizing with various metal elements does toughen for all piston uses.

JE Piston changed opinion couple years ago to jump on the bang wagon with their own coating also advertised to take up some clearance and purposely applied 'over thick' to rub off excess. *If not some obvious rubbing* coating ain't got nothing to do but keep looking pretty. JE boldly states - Beware all others not nearly as good. ; ) Race level use implies pistons are like tires and chains, can't expect to get much economic life, just incremental extensions, unless not committed to win. Note: Jimmy has shown prior raced pistons with crown edges suffering but not much on the skirts. No coatings I know of so far applied above top ring, so maybe a bit more let down of expectations on skirt coating in obsolete clunkers. Ceramic crowns are cat's meow!

http://blog.jepistons.com/jes-patented-perfect-skirt-coating-is-a-breakthrough-in-piston-technology

Personally I rate cyro temper 1st, tungsten dioxide burnished in dry friction coat 2nd, ceramic heat shield reflector 3rd, skirt oil texture pattern, 4th, skirt coating 5th and black body emissions coat polluting engine or even to flush down toilet. But hey whats an over blown hi CR big block 87 octane project know about any this stuff?

worntorn said:

JE Pistons thoughts on coatings for race applications

Quote:
The thermal coating will flake off during detonation. We would have to do a custom piston and can move the top ring down and increase thickness for strength. Having the piston anodized will increase strength but will not allow the piston to absorbed the heat and after a mile or two will detonate and actually make the part fail faster. The anodizing it only for nitro applications.

ALEX RUSSELL
JE PISTONS

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Hmmm, seems a tad negative. Possibly biased towards their own offerings?

I must have ceramic coated dozens of pistons. I used to do them myself with a simple DIY kit, after a few initial aborted attempts it was a very reliable process. Laterly I had them done professionally. I don’t think I’ve ever had ceramic coating flake off of a piston, in race or road use. My only flaking issue was with the Cdo head, and I am certain that that was 100% due to poor application.

Currently, in the Cdo, I have anodised pistons and a ‘bare’ head. Seems to run just fine. But then again (before you say it Glen) it would probably seem to run just as fine sans anodising !

FWIW, I do not pursue coatings to extend piston life. I will not do 128 thousand miles on my Cdo in my lifetime! My interest in coatings is to provide an extra element of protection to facilitate safer thrashing !

I do like a good thrashing you know.