Measuring Squish Test Results?

[CASPX]

I'm ready to mount the cylinders on the cases on my 787 rebuild and ran a dry test to get baseline squish and need some clarification on reading the results.

When reading the solder do I use the very thinnest part of the calipers (the very end) and measure the thinnest part of the squished solder? So it's the smallest measurement I can get on it.
Or
Do I use the thicker part of the calipers and get the thinnest part of the solder?


The difference in measuring styles comes out to a 0.004" - 0.005" difference which changes my required gasket from a .3 to a .4, this is why I'm asking before I buy another gasket.



Also my 6 Hole WSM comes out be .022" when it should be a .024", My original OEM 4 hole comes out right at .016" like it should be so does WSM gaskets have some tolerance issues VS OEM?

Are OEM base gaskets better/worse/same as stock since I need to get a correct base gasket?



Thanks

 

[Mekanix]

I think wsm only give you one option don't they ? It seems like the thickest gasket would be the safest and last the longest no mater what.

I did the same as you but I used an OEM gasket with the right thickness.

Are you measuring correctly ?

I ask that because with mine it was very different when I first bolted the cylinders down to when I got them properly aligned with the head.

What I did was build the cyinders up before installing them on the block.

So install the head on the cylinders and then look down the center to make sure the bores are centered with the head. Make some marks on the cylinder head and cylinders so that you can align them later.
Then bolt on the exhaust manifold to hold it together without the gaskets and remove the head.

With the head off try to install the double jugs on to the base.

Then reinstall the head and check squish. IT should be equal on both sides of the piston if you get it right and the other cylinder should show the same results as in both being equial.

Mine were off quite a bit which is why I had a need to align the cylinders to the head to get a good reading.

After that I did the same as you. Calculated what no gasket + gasket = proper squish.
I ended up with a 3 hole OEM gasket on mine.

Before all of this I was running the 6 hole wsm gasket and it was ok but it made a big difference when the squish was set right.


Much more snap on low end when the gasket was right. The engine seemed meaner and wanted to get up and go more vs smoothly reving up.

Surprising what that little difference makes.

 

[CASPX]

On RacerXXX's recommendation I used Harry Klemm's notes on how to precision set up the cylinders:
http://www.groupk.com/sd785updt.htm

I ended up with an OEM 0.4mm (4 hole) gasket (which is 0.015" not the 0.016" listed) with a skim coat of 1211 on both sides and my squish when all finished ended up Mag to PTO: 0.048"/0.049" | 0.0465"/0.0525" All acceptable clearances but a bit on the tight side and the last one threw me a bit but I measured it 4 times and got similar results each time.

On the measurements I used the smallest measurement point I could find across the squish tested piece of solder with the very thinnest end of the calipers. I'm 99.5% sure everything is good to go at this point and glad I did not go with a 3 hole as it would have came out even less and I would have been too tight once the cylinders where under proper torque.

Thanks for the help