headwork and compression
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Joined: Nov 2014
Posts: 64
Likes: 5
From: Michigan
Listen to Scott and Kirby; they have only been doing this for a gazillion years.
Never hurts to measure deck height as suggested by Anthony Paul but 88" cylinders are typically, in my limited experience, down in the hole .003"-.005"; not enough to justify trimming cylinders to achieve 0.00" deck height for a "street" build. While it is said that .030" is "ideal" squish, nothing wrong with .040" either. Cometic also offers a .027" MLS head gasket that might come in handy in your endeavor.
Never hurts to measure deck height as suggested by Anthony Paul but 88" cylinders are typically, in my limited experience, down in the hole .003"-.005"; not enough to justify trimming cylinders to achieve 0.00" deck height for a "street" build. While it is said that .030" is "ideal" squish, nothing wrong with .040" either. Cometic also offers a .027" MLS head gasket that might come in handy in your endeavor.
Last edited by Anthony Paul; Nov 20, 2014 at 08:02 AM. Reason: spell check
HDF Community Team
Joined: Jun 2006
Posts: 12,763
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From: san antonio
Yep, but what I accidentally left out was that I never measure the squish with my .020 base gaskets in place because of the mathematical variation and design of the gasket. So in other words if you measure .003 in the hole without the base gasket, then after the gasket is added your now at .023 in the hole, then add your head gasket, say .030 and now your computed squish is .053. So to stay in the range of "GOOD SQUISH" you need to take around .018 of the the base of your cylinders. This is all for better performance all around. Hope I didn't confuse anyone.
In the situation you just posted, why use a .020" base gasket and then trim .018" off the base of the cylinder? In the OPs case, no case boring is required to the groove for the base o-ring is still intact so all that is required is to replace the o-ring. If cases have been bored and the o-ring groove has been removed, I have used Three Bond to seal the joint between the cylinder and the cases; no base gasket and the cost of cylinder trimming avoided. Of course, if base gaskets are used, one would proceed precisely as you describe with one exception. The cylinder should be torqued down with the base gasket in place to accurately measure deck height.
I know nothing about aircraft radial engines but have put a few Harley motors together.
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