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what thickness head gasket
- Thread starter bajadave
- Start date
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alfred e numan
Senior Member
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your new top end
you need to make shure that your top end is made to fit the long rod crankshaft. your crankshaft is not a stroker crank. it is a standard crank with a connecting rod that is 30mm long- +2 mm. There are 2 ways to measure piston to head clearance. Most folks use electronic solder- with an assembled engine, remove the sparkplug. bend a piece of solder to this shape-- L -- roll the engine close to top dead center. insert the short end of the L into the plug hole. turn the solder in line with the ends of the crankshaft. move the short end of the solder sideways until it contacts the side of the inner cyclnder wall. roll the motor over by useing the flywheel with your hand. squish the solder 1 time. remove the solder and measure it at the thinnest point squished- The smallest point of your measurement is the engines squish. Most builders prefer .020" to .025" inches squish. Yea, i know this does not answer your question - If you tell me the precice top end you have, make shure it is intended to be used with a +2mm crank, I can get you real close to knowing how thick a copper gasket you will need to acheve the "proper" squish clearence. Its better to have quite a bit of squish clearance on a 2 bolt engine- a long rod engine makes extreme pressures on the little engines most times- its better to err on the side of caution-
you need to make shure that your top end is made to fit the long rod crankshaft. your crankshaft is not a stroker crank. it is a standard crank with a connecting rod that is 30mm long- +2 mm. There are 2 ways to measure piston to head clearance. Most folks use electronic solder- with an assembled engine, remove the sparkplug. bend a piece of solder to this shape-- L -- roll the engine close to top dead center. insert the short end of the L into the plug hole. turn the solder in line with the ends of the crankshaft. move the short end of the solder sideways until it contacts the side of the inner cyclnder wall. roll the motor over by useing the flywheel with your hand. squish the solder 1 time. remove the solder and measure it at the thinnest point squished- The smallest point of your measurement is the engines squish. Most builders prefer .020" to .025" inches squish. Yea, i know this does not answer your question - If you tell me the precice top end you have, make shure it is intended to be used with a +2mm crank, I can get you real close to knowing how thick a copper gasket you will need to acheve the "proper" squish clearence. Its better to have quite a bit of squish clearance on a 2 bolt engine- a long rod engine makes extreme pressures on the little engines most times- its better to err on the side of caution-
Deluge1
Senior Member
If the head has been modified to accept a +2mm crank, then go with a .020" gasket. Do a test fit so you can confirm that the squish is within spec. You can get a more accurate measurement by taping the solder across the top of the piston, parallel to the wrist pin. Then squish it, measure the thinnest point on both ends and average it.
KrashKrieg
Well-Known Member
Just for an FYIbajadave said:The head I bought was a kit Wich included a 2mm crank it was a big bore kit. The head was meant to have a longer rod.
2mm is achieved by that much offset where the rod attaches to the crank part...the rod itself is not longer just throws up farther...