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tahitijet
10-07-2001, 11:39 AM
I have been told i should instruct my machinist to allow for a little extra clearance for jet boat applications. What does everyone else think? is there a general rule of how much clearance above normal to use? We don't really have any good boat motor builders in the area so i will need to tell the auto machinist what the specs should be.. also do i need to allow more for hyperutectic then for forged?

HammerDown
10-07-2001, 01:38 PM
That's correct, the boat block due to running colder wont expand as much as a auto.As far as Hyper pistons,there suppose to hold there size better than a forged.I tried Hyper pistons in my Harley (air cooled)had a bad experience.Can't say for a boat app.

tahitijet
10-07-2001, 10:52 PM
any idea how much? My buddy says 9-10 thou. for hyper pistons but that sounds like a lot to me..
thanks

ponponracing
10-08-2001, 03:10 AM
Tahitijet, you have to determine what material your piston is made of and to set clearances accordingly. Call the pistons company and they will tell you what.

Clutch
11-03-2001, 07:28 PM
Tahiti,
Hi, I would run only forged pistions if you can afford them as far as cyl. wall clearance abouy .006 thou but ck w/ the piston manufacturer.FORGED because if you EVER plan on running NO2 you will need them.