That's not a happy piston. I wonder about the top ring gap on that engine.

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Joshua

doc what about a custom forged piston with .150 of clearance to top land, and tight separations between them comp rings, and then a wide oil scraper? I was thinking .750 of clearance between top of the pin and crown. Oh and either reversed dome or flat top. Create quench in the piston head instead of going wild on the cyl head.

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

Custom made forged pistons are great... as long as they fit your budget.
DD

Lot's of "kitchen table" work balancing pistons and con rods.

I have to love ebay for a wide selection of digital scales, I scored this little "pocket scale" for under $20.00 to my door... I have used the crap out of it ever since.
Be sure to get a scale that weighes to at least 600 grams because a stock SL6 piston is about 475 grams with-out the pin, 585 with the pin.
Many of the less expensive scales have a 500 gram limit.

Once you have a scale, the piston balancing process is pretty easy.
Weigh all the pistons without the pins and find the lightest one.
Drill / grind material off the heaver pistons so the weight matches the lightest piston. Do the same with the piston pins and con rods.


When I have the pistons, piston pins and cons rods "weight matched", I go back and stick the pin with the pistons and weigh the combination again. You can switch the pins around to help "fine tune" the weights.
DD

Buying KB's over there or having my own design custom made down here is the same amount of money. That's the reason why I asked the question, which is: do you think that .150 is streetable? (.150 from the crown to top land)

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

The KB version of the 2.2 piston has a ring land that is .22 down from the crown. That does not leave much ring land support or material cross-section when there is a big .180 deep dish.

The risk of breaking a piston ring land and destroying the top end of the engine is not worth the small benefit of the higher ring land.
DD

A friend gave me some special anti-friction and thermal barrier coatings so I figured I would use-up the stuff.
The maker is Techline Coatings and they have all these great claims about their stuff.
http://www.techlinecoatings.com

I had to buy a small air brush to apply the coatings. (thanks again ebag)
You have to mask-off the ring grooves, sand blast the surfaces, sprayon the stuff and then bake it on.



Overall, seems like way to much work to correctly apply the coatings and I get the feeling that the engine will simply wear or burn the stuff off the piston surfaces... time will tell.
Has anyone else out there ever use this coating?
DD

Had a friend that used to ceramic coat his piston in his quad race bike. He could set the tolerances tighter and it wouldn't cold seize on startup.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

thanks.

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Juan Ignacio Caino

Please use e-mail button istead of PM'ing. I do log in sometimes but I'll be answering quicker thru e-mail.

That'd certainly be close enough to make me shut up about moving it any higher!

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I have no experience at all with coatings, but I've talked to a few engine builders, a few of whom swear by them and some who will never use them.

It seems to depend on application- the guys that swear by them are actually COUNTING on the coating working, because they're building and tuning racing engines (often aircraft engines with LOTS of boost and alcohol/water injection at race power settings) for absolute maximum performance and detonation resistance, and without the coating their building/tuning would necessarily be less aggressive. Guys that want the engines to last significantly longer and don't tear down/inspect after very few hours of use are concerned about exactly what you are- burning away the coating in spots that then become the focus of all the destructive energy of the combustion chamber. A lot of these engines don't give much (or any) sign that detonation is going on until a piston burns, the crankcase pressurizes and all the oil blows out every orifice, so its not a situation where you can hear it and back off.

I have to say that my gut would trust a coating that is applied by the piston manufacturer AT the time of manufacture a lot more than an aftermarket coating, whether done by a company that sells you the whole process, or a DIY kit. Frankly, as long as your tuning and compressioin choice doesn't make the engine dependent on the coating, it can't really hurt much and might help a good bit.

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Thanks for the input... more is welcome.
This coating stuff is new for me so I have been asking everyone I know for input. As already noted, the opinions seem to be all over the map.

Well, you guys know me... when in doubt, give it a try and see what happens! Nothing ventured, nothing gained.

The good news is that I do not have a big investment in the materials and application tools. The big question is if this "secret sauce" will do more harm then good.
DD

Doug, unless you're going to be dumping the sauce down the carb, I can't see your experimental coating hurting anything.

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Official Cookie and Mater Tormentor.

My biggest concern would be experimenting on an engine with some rather rare and probably pricy parts. I would be inclined to prove the concept on something I could replace if it decided to self destruct. That scenario is probably a remote possibility but still real.

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David Kight
'62 Valiant Signet, White
'98 Dodge Dakota
'06 Jeep Liberty

Growing older is unavoidable but growing up is strictly optional.

I was kinda worrying along the same lines given that the coating means there'll be more heat trapped in the very scarce aluminum combustion chambers...

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一期一会
Too many people who were born on third base actually believe they've hit a triple.