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Discussion Starter · #1 ·
Did a squish check (rosin solder) on my late season rebuild.

.059" on PTO and .064" on MAG. Is any squish difference allowable or am I going to run into problems? Do they need to be exact same squish?

Weird thing is the tighter squish has 5psi less compression. 153/158

500SS motor with rktek head.

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Not an amateur question at all. Good on you for measuring squish. The difference could be just the inaccuracy of using solder, it could be a difference in cylinder height because of a matching operation on a rebuilt cylinder, it could be someone only replaced one piston and cut a base gasket in half that didn’t match the one on it. This is all if it’s a series 3 engine. I suspect it’s a discrepancy in reading. I use an accurate depth gauge to measure and haven’t seen that big a difference. If there is that much difference in height, either matching or using half a base gasket to match them would work. When blueprinting, matching squish,volume, crank phase and port timing exactly per cylinder is everything for maximum power,but what your doing is just good practice for any trail engine.
 

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Discussion Starter · #3 ·
9 hole base gasket. I'll pull the head in a few weekends and measure with a good depth mic. If there is a difference, can one simply cut a base gasket in half?

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Piston projection is easier and more accurate to compare both sides, but you'll need the cup from BRP and the appropriate fitting that comes with a 2S dial indicator kit.

I use projection and solder, but I did put the time and effort to find a method with solder that works and coroborates with deck height. Imo this is worth doing as it removes the opinion factor out of the equation. Best of luck.
 
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