dreaux

iTrader: (5)

I had a worn out sleeve on a motor i was fixing for a friend. Well i had a old piston sleeve set that were completely worn out. Well so was his. Yet, i took his worn out piston and put it in my worn out sleeve and BINGO! I mean it runs great.

So??????


I know some will say "it's a better match and fit it they are new". Bologna. I have no doubt in my mind that if i got a new piston and put it in a old sleeve it would have great pinch.

I understand that buying a sleeve separate would not have the same effect. But if you had a big scratch in one it could probably work.

I just think it's a way for these little engine making companies to get more money out of us in a already way to expensive hobby.

I would love to see a engine company offer that. Does one?

what about a replaceable crank pin??? Alot of my klein electrical tools are hot riveted. they basically get it hot and put a cold pin in and let it cool to get a tight fit. Why cant they have a removable steel bushing that is "hot riveted" onto the crank, when i wears out you just cut it out and install a new one?

That is the only part of the crank that really matters or wears. Can't someone put a ceramic coating on it?

I see so many possibilities.

looper

iTrader: (19)

Pistons and sleeves are matched to each other, that is why they are sold together.

any more questions?

dreaux

iTrader: (5)

nope. No more questions. It was more of a statement really. Fact is, i can take a seperate piston from another sleeve and it can work as good or better then the original.

if i only need a piston i should not have to buy a P/S. The piston wears much more then the sleeve.

mcion

iTrader: (32)

If you look inside a new sleeve, you will notice that there is a silver lining inside the gold. That lining helps keep the pinch.

off road god

iTrader: (13)

Dreaux, sometimes you can find just a piston....not too many times but,sometimes. But you're exactly right...I've done this with a P5...twice. does mcion believe that the cylinder/sleeve wears out faster than the piston? In a ABC built motor (Aluminum,Brass,Chrome) the chrome sleeve (you know, the silver inside the gold) is the hardest surface. About the only way to ruin it is to suck some dirt in the engine.
A new piston will go in and be tight...like it was when you bought the motor...what do we do with a new motor? We break it in! What happens when we break it in? The piston wears into the chrome lined sleeve(you know,the silver part). I too wonder why every manufacturer doesn't offer a piston only option.

SteveP

Negative. You got lucky that it worked, but I've seen mismatched pistons and sleeves where the piston completely falls through the sleeve, and others that have so much interference the rod would snap the moment you try to start it. So, count yourself as fortunate that it worked this time. Next time around you probably won't be so lucky.

Shuming

Its the sleeve the expands under heat and the reason why it lose compression.

Davidka

iTrader: (86)

Not true, the oposite actually. The aluminum piston wears down in diameter. If the sleeve were wearing then the chrome plating on it would be wearing off (actually used to happen to old OS'). "Pinching" is the practice of squeezing down the sleeve to make a tight fit with the piston again because one can't add diameter to the piston.

I don't buy the piston/sleeve matching thing. They can certainly be made to close enough tolerances to not need matching, especially for the crazy prices they sell them for.

Shuming

Only going by actual measurements of a used piston and new piston.

improvement54

iTrader: (1)

That's where I think you might be wrong. I'm willing to bet that it's cheaper for the manufacturers to match them at the factory than it is to produce every piston and every sleeve to the exact same dimension. The relationship between high precision machining and cost is not linear.

You see this effect on 1:1 engines all the time. For example, the reason you can just buy a piston for your 1:1 engine and stick it in is because the compression and oil control rings take up the slack between the cylinder (sleeve in r/c) and the piston. Sometimes there is not enough extra room between the cylinder walls and the piston. That's where filing the ends of the compression rings comes into play.

You see the same thing with 1:1 engine crankshaft bearings. Even on a new crankshaft with new bearings and new rods, you need to use plastigauge to check the clearances between the bearing surfaces and the crank to make sure there is enough room for an oil film. I've seen what happens when this is not done and your clearances are too small.

There is a way around it though. It's called engine blueprinting and it is expensive. That's how you make a $1,000 V8 motor worth $20,000.

Roelof

Different productions can have different materials what will result in different expansion rates. Mixing pistons and sleeves from different productions can cause a short lifetime or even a bad tuning.

To be sure the piston fits the sleeve they sell it as a set.

A worn out P/S set can be fixed with a pinchtool oor by adding a coating.

dreaux

iTrader: (5)

wrong again. I did not get lucky. I have about 8 p/s sets (they are all o.s.) and i can just about mix and match all of them. I have done it several times. Never had a problem. I mean a new piston is a new piston. Production techniques with the cnc process are down to a science. They are so close now, you can forget thousands of an inch. THey can get them closer then that. a couple thousands of an inch is nothing. They can get it the same all the time, every time. but i do understand it would not be excact every single time due to whatever. But the ones that measure out to specs could be sold. Or maybe they could keep your sleeve specs on record? Just rambling. And i understand that no engine company could ever guarantee anything with this kind of product. People would blow engines left and right lol! But i would love to buy seperate pistons and rematch them with all my sleeves.


also. I have been researching ceramic coatings. they coat the pistons in real race cars to help with temperature etc. You can run them really hot and a little leaner.

Has anyone tried to coat a piston? Why not a tri nitride or dlc coating?

one8updragracer

iTrader: (5)

Don't let the word "blueprinting" fool you. All that really means is assembleing the engine like it should be. Checking clearances..yada yada. Shops started using that word to charge people more because it sounded fancy and most people didn't know that the so called "blueprinting" should have been done with every rebuild.

one8updragracer

iTrader: (5)

You may actually be onto something there. Your right that is used in many hi-po apps. I'm sure that our little engines would benifit also. I may look into this also. The size of our pistons compared to the 5" bore of 1:1 BB's the price should be pretty cheap.

22Racer

iTrader: (67)

I have mixed pistons and sleeves with good luck. You have to be pretty lucky to have one just fit right. I pinch sleeves and also can expand a sleeve to get it to the proper fit.

Rex