Squish

[slobanshee]

What is the preferred squish on a 10mil cub on alky. What would be ideal? Iv read and see answers all over so I'd like to know what you guys think. Also way that your measuring it. Thanks!

[lms1977]

It's probably gonna depend on the dome you used, meaning the angle and width of the squish band, also what cc your running (or overall cr)

[camatv]

dome shape, riding style. length of runs, how rich its ran, weight of bike/rider, all have factors in squish.

 

i have personally ran anywhere from 40 to 65 clerance on motors. most larger cc longer stroke engines i have done seem to like in the range for 50-55 ish on a drag bike... but thats me.

 

i check it all assembled witht he base gasket you plan to use everythign tq'd to where its going to be at, the actual pistons that are going to be used. 2 pieces of soder plaed across the pin and spin it around. remover measure it also can show the angle if there is one and what it is. also run across the other direction ( front to back) and you can kinda get an overall idear..

 

other thing you can do is clay it if you really want to. or make a mold..

[RadarRacing]

Im with Cam. You probably want .050 thous give or take a few thousandths up to even .055. Bolt the cyl down and put a couple dabs of grease on the crown of the piston on each transfer side of the piston and put about a 3/4" long piece of solder on the grease and install head, then turn over motor to mash the end of the solder and remove the head to get the pieces out. It should be the flattest or tightest squish out at the edge of the bore and probably be a couple thousandths thicker at the inner edge of the squish band. Maybe like .048 at the edge of the bore and .050 at the farthest from the cyl wall. You should have a piece of solder that is mashed for about 11-13mms. If its smaller than about .042 you may need a different dome or thicker base gasket. If its between .43 and .055 you are in the ballpark.

Edited August 8, 2012 by RadarRacing

[J-Madd]

Squish clearance is not to make sure the piston hits the head; it's to get the correct MSV (Maximum squish velocity). As mentioned, you need squish band, angle, piston angle, combustion chamber volume, etc, etc, to calculate MSV. That being said, I have never calculated MSV. It usually takes software to plug in all of the variables.

[BigRed350x]

Squish clearance is not to make sure the piston hits the head; it's to get the correct MSV (Maximum squish velocity). As mentioned, you need squish band, angle, piston angle, combustion chamber volume, etc, etc, to calculate MSV. That being said, I have never calculated MSV. It usually takes software to plug in all of the variables.

 

Software or a Nerd Status Rating of 7.5 or higher.

[J-Madd]

As long as you know all the formulas its not terribly difficult, but I've long since forgot calculus and physics. The squish ranges mentioned must be in the ballpark, because that's what a lotta folks run.