Squish

[willaduncan]

I have been doing a rebuild and sourcing all my information from here and the clymers.... everyone on here says the aim point for squish is between .030 and .045??? my squish was checked at .05 by myself and was told by a bhq member that was WAY TOO far off, so I called Kevin at HJR who did my motor work and he said thats dead on. Squish levels should be from .045 at lowest to .060 and some of his fastest motors were at .060. He also said the .030 - .045 is for the 4 stroke motors so why does everyone in their mother think thats the correct squish on here??? I guess I am just looking for more insight on the matter, Im running what kevin said .050 no matter the response Im just a little curious on why there is so many people saying different then the builders and also to help others with this part of their build.

[Redline Racing]

I have been doing a rebuild and sourcing all my information from here and the clymers.... everyone on here says the aim point for squish is between .030 and .045??? my squish was checked at .05 by myself and was told by a bhq member that was WAY TOO far off, so I called Kevin at HJR who did my motor work and he said thats dead on. Squish levels should be from .045 at lowest to .060 and some of his fastest motors were at .060. He also said the .030 - .045 is for the 4 stroke motors so why does everyone in their mother think thats the correct squish on here??? I guess I am just looking for more insight on the matter, Im running what kevin said .050 no matter the response Im just a little curious on why there is so many people saying different then the builders and also to help others with this part of their build.

 

 

If you choose Kevin to build your mtr than you must trust HIS squish desighn. There is more to squish than you can imagine, total dome profiel ,Exh shape and duration, PIPES, fuel.......

This is a FORD CHEVY debate. Everybody has a different target on there dome profile. I would agree with Kevin on his squish numbers, on a well set up motor. On a poorly setup mtr you will half to tighten squish and crank timing to make it work. Which is not user friendly due to detonation.

 

LISTEN TO YOUR BUILDERS PEOPLE!!!!! NOT THE SKEETERS AND N20's on here.

[RadarRacing]

Many good motors run in the .035 or even .060 range. 90% of builders want to be in the low 40s. With that being said there are many motors that have record passes with .050 or even .060 so listen and trust your builder and you will be fine. Theres a lot that goes into it but if the pipe works and traps well the motor will like looser squish. Timing, fuel , dome shape, squish band width , velocity, and many other things change the way a builder will want to set em up.

[RadarRacing]

Haha Resline, was typing at the same time.

[007banshee]

Sorry but im new to building. What is squish? How is it measured and how do you obtain the.correct clearance on say building a stock shee motor. Don't mean to hyjack.

Nick

[willaduncan]

Thanks for the replies ... Squish is the space in between the top of the piston and bottom of the dome at cylinders top dead center, it is measured by squishing a piece of solder by placing it through the spark plug hole and kicking the motor over and measuring the squished piece of solder with a vernier caliper

[007banshee]

Bend it at a 90* so it gets squished on the edge of the plug hole? What if your squish is out of spec?

[Jereme6655]

Bend it at a 90* so it gets squished on the edge of the plug hole? What if your squish is out of spec?

 

yes you want to bend the solder at 90* and then place it INLINE with your wrist pins.......so you want to put the solder in and to the SIDE of the bike.....and make sure it is up against the cylinder wall so that you get a clear reading....

[Redline Racing]

Do not do it by bending solder at 90*. You must take head off and put a piece of solder in line with wrist pin using a dan of grease to secure it. Reinstall head to proper TQ then rotate mtr over. By doing it thru spark plug hole you will get an innacurate reading on some motors die to piston rock.

[willaduncan]

As long as you are right over the wristpin you will have NO piston rock going through the sparkplug hole is perfectly fine as long as you put it where it needs to be

[willaduncan]

As long as you are right over the wristpin you will have NO piston rock going through the sparkplug hole is perfectly fine as long as you put it where it needs to be

[007banshee]

Then measure the thickness of the solder with a dial indicator? So after you do a top end(im doing a full rebuild and am going by the manual)you would check for squish? And im still not sure what exactly that's measuring, faulty rod bearings? Crank issues?

[BigRed350x]

As long as you are right over the wristpin you will have NO piston rock going through the sparkplug hole is perfectly fine as long as you put it where it needs to be

 

This is not true. The method outlined by redline racing is the correct way to do it. Your readings could be off by as much as .005" by doing it through the spark plug hole. Try it both ways and see for yourself. I used to think the spark plug hole trick was ok, until I was taught the correct way to do it. Then I compared my readings from the two methods and the spark plug hole reading is very inaccurate.

 

Tim @ Titan Racing will tell you to do it the same way. Remove the head, place solder across the top of the piston in the center of the bore, parallel to the wrist-pin. Install & torq head down and bump it back and forth at the top of the bore by hand, then remove the head and measure your solder.

 

- Jared

[willaduncan]

I'm not saying that is wrong I'm just saying plug hole is way easier and when a builder says it works ill do it but like I said both ways will work but both can be just as accurate

[armyvet]

spark plug method has been workin all these yrs.banshee motors arent exactly high tech.not building airplane engines.so what if its pl opr minus .000000000001.thats the equivalient of reading to different calipers.