Does anyone check the squish when building an engine

[bobhatton]

One think I have never seen on any of the MR2 sites when talking about building engines is checking and adjusting the squish. This is a very important part of putting and engine together and goes with head gasket thickness and desk height.
If anyone has done the work what clearance has been used?

Bob

[ali86]

i do at work (jag), i will when i come to rebuilding my 3s.

[GTS GAV]

can you exspaned a bit more bob so i can get a better understanding of what you mean

[3sgte]

can you exspaned a bit more bob so i can get a better understanding of what you mean

the squish zone is where the profile of the top of the pistons is close to the cylinder head this is what forces all the fuel and air mix into the middle of the combustion chamber and into the firing line of the spark plug . if you skim the head too much and dont compensate with the proper size headgasket the you either end up with too large or too small squish zone ,this alters the way the fuel/air mix swirls into the combustion chamber in turn altering the efficiency of the burn

the angle of squish can also be altered with different profile pistons also affecting the way the fuel/air mix flows

hope that makes sense

[blogsy]

How do you measure it and would you need to have a gasket made in order to make such fine adjustments. It sounds worth doing.

http://hammerperf.com/ttcheckingsquish.shtml

[Donato]

would you need to have a gasket made in order to make such fine adjustments.

Once you calculate the amount that has been skimmed off the head, you can buy different thickness head gaskets to compensate. Toyota sell different thickness head gaskets for their engines.

[bobhatton]

How do you measure it and would you need to have a gasket made in order to make such fine adjustments. It sounds worth doing.

http://hammerperf.com/ttcheckingsquish.shtml

You keep whatever size gasket you have designed the engine to use and skim the block to get the piston to head clearance correct.

[bobhatton]

would you need to have a gasket made in order to make such fine adjustments.

Once you calculate the amount that has been skimmed off the head, you can buy different thickness head gaskets to compensate. Toyota sell different thickness head gaskets for their engines.

Sorry but you are incorrect.
Doing that will make the clearance wrong.

[blogsy]

Any suggestions on the clearance.

[Bern]

would you need to have a gasket made in order to make such fine adjustments.

Once you calculate the amount that has been skimmed off the head, you can buy different thickness head gaskets to compensate. Toyota sell different thickness head gaskets for their engines.

Sorry but you are incorrect.
Doing that will make the clearance wrong.

Bob, you just said that you can deck the head to fit the size of gasket that you've selected for the engine...then in the very next post you say don't get a gasket that compensates/matches how much decking is done. Very confusing, please explain yourself.

Cometic also sells various thickness hg's, you should definitely adjust/buy the appropriate size gasket depending on how much decking is being done, and also considering if its ever been done before on that block previously.

The hg thickness also affects compression ratio so take that into consideration, along with your pistons. Stock hg is 1.3-1.4mm so if u deck and go 1mm, your comp ratio will increase.

[glen n]

Bob said skim the block,thus altering the clearance to the head. Skimming the head will keep the clearances the same,I think that's why he said its incorrect.

[bobhatton]

Any suggestions on the clearance.

Top of piston to head for high revs and or large bearing clearances 1mm, for lower revs and stock bearing clearance 0.8mm

So you can use a 1mm gasket if you want to have a clearance of 0.8mm the pistons need to stick out the top of the block by.02mm