Piston/Sleeve Question

[mattyk6]

How far should the piston slide into a sleeve?

I purchased two used 21 motors that came with 3 p/s combinations. I have one piston that is almost flush with the top of the sleeve and I have two other pistons that come to about 1/4" to the top of the sleeve.

I'm about to send these off to OSRocket to have his magic touch done to the p/s combos.

What do you guys think?

 

[Clintd]

From what I understand, if you can push the piston through the sleeve, it's wasted. I am by no means a nitro pro, so I'm pretty sure someone will verify or correct my response. Just my

 

[mattyk6]

How far does the piston slide into a sleeve when they are brand new or with a fresh squeeze/pinch? The guy I bought the motors from said that one had a fresh pinch, by who I don't know.

 

[Clintd]

The last new sleeve and piston I bought you could push the piston a little less then half way in with little effort. To push further would require a lot of effort. As for a pinched sleeve, I have no idea.

 

[CorradoPsi]

all 3 need a squeeze.

 

[mattyk6]

That's what I was thinking, but I wanted someone else's thought on it.

Thanks,
Matt

 

[Tarant]

you guys are oiling then right, it is not a good idea to put a dry piston in to a dry sleeve,
I can put my piston so far it that their is only 1/8 of an inch of sleeve left at the top, but my engine is also wore out and I sent it away to be resized,
can you put the sleeve and piston in to a engine and turn the flywheel to feel if it is worn

 

[rocknbil]

For a big-block 1/4 to 1/8" is still serviceable, a .12 1/8", is almost too far, send both of 'em off to OS rocket.

 

[low10s]

i have to disagree on this. i have an RB x12, that runs too good. i took it apart to check the rod and p/s and found i could push the piston flush with the top of the sleeve and just a bit further, thought it was worn. put the head back on and it has good compression. talked to Rody at Rb about this, he said alot of people think the same thing, it is the Fit of the p/s that matters most. if the engine runs well and holds a tune and idles, it is still good. this was 2 weeks ago on mine and it still runs like new with good compression. do what you want but if they both still do the above things leave it be and run them.

 

[vbgagnon]

Low10s, a general rule of thumb is if the p/s can be pushed to the top or through the top then there is no more compression.

mattyk6 you could prob get away with running 2 of them, but the one you can push to the top is in definate need of a pinch. I would have all 3 pinched if your going to send to osrocket. I'll vouch for his work too, I had my 24.7 and hyper 8 ports done by him, and they are unreal. I didn't get a chance to run the 8 port because of a trade, but the 24.7 isawsome, runs better then when it was new!

 

[low10s]

i understand that part, but if you can push it through and it still has compression and runs well, why pinch it. i started to throw mine away or have it pinched after i thought mine was finished. instead i put it back together following Rody's advice and it is still running stronger than ever. it is the tighter tolerances of better engines that seal and give good compression. but to each his own. the kind of engine makes a difference also, a more sport oriented engine just may not seal as good. good luck