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Healey 100-4 Piston Crown Clearance needed to Cylinder Head

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M

mwagon

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Healey 100-4 short block is assemblyed using flat top pistons. The Piston Crowns protrude .007" above the block surface @ TDC. I'm concerned if will cause interference with the cylinder head. The block surface was faced to ensure a flat surface, but maybe too much removed. My plan was to use a nos Mowag laminated Copper Head gasket. The Head Gasket measures .079" th. uncompressed. I'm using a Elgin fast street cam with .43" lift. The distance bwteen the Head surface & closed valve is .457". I don't plan on driving car hard & won't see redline very often.
I would assume I need to also account for piston growth from expansion @ operating temp. & maybe some connecting rod growth too.Taking these factors into account + .007" piston above surface - compressed Head Gasket thickness (amount ?), does the piston still have a safe amount of clearance to the cylinder head?
Does anyone have experience with this?
 
mwagon said:
Healey 100-4 short block is assemblyed using flat top pistons. The Piston Crowns protrude .007" above the block surface @ TDC. I'm concerned if will cause interference with the cylinder head. The block surface was faced to ensure a flat surface, but maybe too much removed. My plan was to use a nos Mowag laminated Copper Head gasket. The Head Gasket measures .079" th. uncompressed. I'm using a Elgin fast street cam with .43" lift. The distance bwteen the Head surface & closed valve is .457". I don't plan on driving car hard & won't see redline very often.
I would assume I need to also account for piston growth from expansion @ operating temp. & maybe some connecting rod growth too.Taking these factors into account + .007" piston above surface - compressed Head Gasket thickness (amount ?), does the piston still have a safe amount of clearance to the cylinder head?
Does anyone have experience with this?
Click to expand...
I'm left with the underlying question of why are you building a "fast street" spec engine, if you're not planning to take advantage of it.?

There's an age-old practice of using a little layer of modeling clay on top of the pistons, bolting the head on (preferably with a used__compressed__gasket, torqued to spec, and slowly rotating the engine to allow the valves of each cylinder to fully open and close. A little oil on the valves will help them from sticking to the clay.

Remove the head and carefully measure and record the depressions in the clay. Your cam manufacturer should be able to provide you with allowable clearances.
 
Actually with the original clearance info I posted & the fact that the valves aren't open near TDC, there isn't a clearance problem for my setup. Cam is a mild 268 deg. duration. Intake opens @ 27 deg passes TDC, exhaust closes @ -27 deg from TDC
 
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