Super Jet 701 Squish Test Video

[NVJAY775]

I've seen this topic come up a few times and just wanted to post up a vid showing how simple the squish test is. Hope it helps out!

Special note from egbrig, who's an awesome engine builder. "YOU MUST have a piece of solder on both sides of the piston pin to prevent the piston from rocking to get a correct reading. I put to two pieces of solder in the spark plug hole, each parallel to the pin, I also put a second 90* bend in the solder so I know where the solder is in relation to the pin. If you don't know where the solder is on the piston top then you could get much more piston rock and get a very far off reading. When I assemble an engine I use a slightly different system that takes longer to do but it gives a much more accurate reading of squish all around the piston."

Anybody noticing something I should add to this post, please post up and I'll add it to the OP here.

https://vimeo.com/62227100

 

[subhard]

Very nice. Thanks dude

 

[Little Trumps Super Jet]

Thanks jay!!!!! Really appreciate you taking your time to do that for me so my engine doesnt blow up

 

[burton148]

Thanks man. Appreciate it

 

[Kohldanielzimmer]

Thanks for the video

 

[ThatGuy]

Thanks. This is why I joined the X not for the winter drama.

 

[egbrig]

Not to be a "know it all" but there is some technique missing but I like the idea of an instructional video and this video is a good start. YOU MUST have a piece of solder on both sides of the piston pin to prevent the piston from rocking to get a correct reading. I put to two pieces of solder in the spark plug hole, each parallel to the pin, I also put a second 90* bend in the solder so I know where the solder is in relation to the pin. If you don't know where the solder is on the piston top then you could get much more piston rock and get a very far off reading. When I assemble an engine I use a slightly different system that takes longer to do but it gives a much more accurate reading of squish all around the piston.

 

[senor]

You said Parallel to the pin. Did you mean that? Shouldn't it be measured from the exhaust to the intake side to correct for the piston rock? I've seen some really different numbers on some loose pistons.

 

[NVJAY775]

I'm not sure. I'm kinda new to it actually. When I was trying to get my compression right for my pfp, PF told me to check my squish the way I video'd it. I'm guessing it's a descent way for an average joe like myself to get a close measurement. But it seems there's other ways to get a much more exact measurement.

 

[egbrig]

I want to say to JAY, thank you for not being offended. I did not in any way mean any condescension or attitude in any way and I'm glad to see that you took my suggestion as such, I wish more would respond like you have. BTW, I got an email and a suggestion on how to measuer squish after my post and both suggestions related to the more time consuming way of doing so. JAY you are right, when your squish gets to that fine line, then its more important on procedure.

 

[NVJAY775]

Maybe I'm just suckin up, cuz I am interested in one of your new top ends!

I am glad you posted up on this though. I got bored and tried using your method and then tried again with 4 pieces, so I could get both sides in line with the wrist pin and also ex and intake sides. That was good fun!

I came up with .040 on both sides of the wrist pin, .043 on intake side and .047 on ex side.

 

[egbrig]

I know its a pain in the azz, but now you have a much better indication of where your squisth is at and how your cylinder/head are machined.

 

[ThatGuy]

So what do you do with the 4 measurements? Average them together? Use the smallest? What if some are over spec and some are within?

 

[egbrig]

It's knowing where the clearance is at for best and worst case.