checking squish height

[Tom w]

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[Jerry Wyss]

That .003" play would mean .006" rod clearance wouldn'tit? why would you have that much?

JW

My bad on the .006", thats not right,, Bad Coffee, Bad Coffee!

Thats all the wrong thinkin' I'm admittin' to right now

 

[Jerry Wyss]

...will affect measurements. how much "fudge factor" is involved in the on the bench vs running parameters? static squish, compression and squish/quench velocity is all affected by these differences...

Not if you use the height gauge. The liner actually raises when the piston comes up toward the top and with the dial indicator, it will still measure the TDC super accurately. You then push the liner down with the piston anyplace except at the top and make that measurement to the top of the liner (pushed all the way down and seated on the case). The difference gives you the measurement from TOL to top of piston. Then just measure the head button projection and the difference is the head clearance down to .0005".

I guess that you can "build in" some amount of difference in measurement, but I personally like to know EXACTLY what the measurement is. It took a LONG time to be able to measure all of this accurately. I started with a degree wheel and light to try to estimate timings, etc. like most people have.

Marty Davis

Man, Thats gotta be one of the best methods I've read yet,, specially with the super tight P/S fits I've been heating up all this

time,,, and I have that exact height guage for doin'it that way. Thanks for this stuff Marty, it's all good.

"peanut gallery"

 

[jydracing]

Hi All this is what i do. If the engine is new or a new piston and sleeve has been installed i use a piece of solder and set the head clearance at about .020 and break in the engine. There are two reasons that i do this. The first one is that i set an engine up at the head clearance that i was going to run at and when it borke in the piston started hitting the head. the secand one is that by breaking in the engine first I can see where the flow staning on the boost and transfers are and that tells me if i need to do any port matching in the engine.

Then i break out the computer and marty's program and go to work. If you ever took a degree wheel and worked out the timming numbers and than figured the compression ratio it would take about a hour or more for me to do. With marty's program I have been using it for about 6 years now I can go through an engine in about 20 min. It is great when you put in the numbers and the computer figures the degrees of timming and compression ratios then you change the numbers that you put in to achieve the deg of timming that you want and cut the sleeve to that.

But you need to rember that any thing that you use it is only as accurate as what you are working with. hope this helps Jimmy

 

[Tom w]

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