squish questions

ski4

gonzo
Location
cleveland
what happens when squish is more than .045? i keep reading it should not be less than .045.
how much higher can it be than that , and what happens if it gets to big?

the reason i ask is that i had to have paul machine some domes for my superjet. the cylinder was decked to much and the pistons were coming out over the deck. i measured last night and i am thinking i am running .065 clearance.
 
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Mark44

Katie's Boss
Location
100% one place
If your squish is .065 you need .020 off of your cylinder remember you are looking for .040 to .050 I run .050. If you machine the dome your measurement will increase and from what you said it is already to large. You may need to recheck the squish just to make sure what is up.

Mark44
 

ski4

gonzo
Location
cleveland
yeah i am gonna check it again but it's probably right that's is what i got in both cyliders.over the pin.

dont really want to maching the cyliders , the dome i could shave down some, not sure if that will work in a removable dome head though??????
what are the sx's of too mush squish clearance
 

Mark44

Katie's Boss
Location
100% one place
If you cut the head down and the domes down you would make that head special to that motor. You will also be reducing the o ring groove if you cut the head. The proper way to do this is to deck the cylinder. It’s only six bolts to pull and not even that depending on the girdle kit you have. Any machine shop can deck it for you and should only run about 50 bucks.

Brap!
Mark44
 

ski4

gonzo
Location
cleveland
yeah that makes sense, i hate to ruin this head since i have 1 manybe 2 overbores left on this top end, it's just been decked too much already will that cause any problems

will too much squish casue detonation?
 

Matt_E

steals hub caps from cars
Site Supporter
Location
at peace
Too large of squish? No detonation...just not optimal power, from what I understand.
 

ski4

gonzo
Location
cleveland
actually or i guess i can have paul machine another set of domes?? prolly more cost effective to just deck the cylinder though, but damn, that's a lot more work :banghead:
 

Mark44

Katie's Boss
Location
100% one place
f

actually or i guess i can have paul machine another set of domes?? prolly more cost effective to just deck the cylinder though, but damn, that's a lot more work :banghead:

You can wait till winter it won't hurt anything just a loss of power. You can leave the exhaust and intake manifolds on during the machine process. It takes about a half hour to machine. More time in set up.

Mark44
 

ski4

gonzo
Location
cleveland
cool thanks guys. just still not happy with my carb tuning so i was just making sure squish is not causing my sx's.
back to the carbs
 

Legdragger

Bringing it back
Location
New Hampshire
Squish should be .035 to .040 on a freestyle motor, not sure if it good in race application though. It can be measured with a piece of sodder bent 90 degrees then stuffed in the spark plug hole over the wrist pin and cranked over, but ideally it should be measured with 4 pieces of sodder in th front, back and both sides to get a really accurate measurement. You really need to place the sodder on the piston with the head off but it might be possible through the spark plug hole using the bent sodder method.

Too much squish is fine if you want the motor to last forever but not ideal for maximum effeciency. Too little squish clearance will cause detonation and eat pistons.
 

Quinc

Buy a Superjet
Location
California
Get a nice non acid core piece of solder



bend said piece of solder




put solder into cylinder




solder in place- make sure you have the end up against the cylinder wall- rotate engine over 1 revolution




measure the flattened piece of solder to get your squish #






This is just a pic of what the solders position is in relation to the head when being crushed



Hope this helps :)
Bri


Anyone happen to save these pictures?
 
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