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crankcase stuffing

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crankcase stuffing

Postby yamaha-sucks » January 7th, 2002, 12:48 am

has anyone ever stuffed a crankcase with epoxy so that there was less "dead air space"?
i need some information about it. it is supposed to make monster torque, but i wanted to know if anyone has done this?



*This Message was edited on 07-Jan-02 09:51 AM by yamaha-sucks*
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crankcase stuffing

Postby snodrifter » January 8th, 2002, 12:07 pm

Never heard of doing the epoxy thing. There used to be spacers available for some old ski doos that you could put in the case to fill it up. I haven't even heard of doing this on the new sleds. It did make a difference on those old ones.
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crankcase stuffing

Postby OldCatRacer » January 8th, 2002, 2:57 pm

I had an uncle try it on a '74 440 tiger back in 74 and it never helped it. I could still beat him with mine stock.
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crankcase stuffing

Postby yamaha-sucks » January 9th, 2002, 4:01 am

i found an old racer that used to use this trick on his drag sleds. one was a gpx 340 and the other was a 643. he said that it does not help larger diplacement engines. anything over a 340, and it won't work. he tried it on the 643 and nothing changed. it only works on a short stroke and high revving engines. he said that there was a noticable increase on the gpx.

you are supposed to build the case sides up, just so that the crank has enough room to turn.
screws should be added to help give the epoxy something to hold onto, if you have a large gap to fill.

this mod adds 1-3 ponies, on the smaller engine sleds. the higher they rev the more power it adds.

he said it was the perfect "cheat" to run in the stock classes because they never check the crankcase.
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crankcase stuffing

Postby gspaulding » January 9th, 2002, 11:51 pm

This was an old mod that worked sometimes prior to the development of efficient exhaust systems. It can help, in rare occasions on newer engines, but simply filling in crankcase volume will usually result in less power. Its not the "tight case" that makes one engine better than another, it's the correct primary (crankcase) compression ratio. A good rule of thumb is 1.45-1.0 regardless of engine size.
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crankcase stuffing

Postby yamaha-sucks » January 10th, 2002, 2:12 am

i was wondering if anyone has heard of "poor boy porting?" where you stick two base gaskets together and then make a .010" head gasket out of copper? i thought that you also had to do something with the exhaust pipes to make it work, but would you have to with an old arctic cat can muffler?

i have an old go karting book, that gives instructions on how to build a volume tuned pipe. all it is is a seventy degree diverging megaphone with the "can" chamber on it to silence it. the exhaust exits out a small stinger in the middle of the pipe. the book states that the volume of the pipe should be 10 times that of the cylinder. would this be a ballpark figure? would this type of pipe make my engine more powerful and "breathe" better than it does now?


thanks for all the info on the stuffing, i never knew that it could be so complicated! i am glad that i asked around before i tried it. how do you measure crankcase pressure? would you put a pressure gauge on the fuel pump impulse line?

THANKS!

*This Message was edited on 10-Jan-02 07:21 AM by yamaha-sucks*
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crankcase stuffing

Postby yamaha-sucks » January 10th, 2002, 2:19 am

i just remembered something else! the guy that told me about the poor boy porting also said to make the 0.010" copper head gasket big like an extra cooling fin. would this cool too much or work like he said?

THANKS!!!
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crankcase stuffing

Postby Riley » January 10th, 2002, 2:19 am

Yam Sucks Yes I have heard of it. It increases the crank case pressure which pushes the fuel and air through the transfer ports with more pressure. It is also hard on seals. The extra pressure will blow the seals out. Can't give you any more info on it but yes I have heard of it and it does work.
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crankcase stuffing

Postby yamaha-sucks » January 10th, 2002, 2:22 am

tell me everything that you know!

thanks!
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crankcase stuffing

Postby ZR800XC » January 14th, 2002, 12:08 pm

thicker base gaskets generally are used on case reed engines. If you do it on a piston port design engine, you raise up your intake port. Therefore, you have to cut the skirt off the piston to get close back to where you were before you started, but not all the way, or you're only raising the exhaust port, and increasing RPM, and decreasing torque...so then the heads gotta be cut. Then depending on compression and Peak RPM you have to time the engine to perform in it's powerband Yep, it all sounds simple....Right? And now that ya got all this newfound power, you have to jet and clutch for it, or you'll never see the new horsepower reach the track!!!!!!!!!


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