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Piston to head clearance
- mark1122
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- Keep twisting it
There seems to be different opinions on what this clearance should be.
My local builder says i can get away with .040" .
Paul Gast says i should go for .048" to .053".
What I'm getting out of this is i can get away with .040" but if i get pre ignition i may have to adjust cam timing .(= larger lobe centers= less torque.)
It seems to me that the tighter the squish, the more turbulence u have to get a better burn and prevent pre ignition. And at the same time it will raise cyl temp and promote pre ignition.
I ran about .050" successfully, on my last 1135cc build. That will be my target for my currant 1200cc build unless you wise men change my mind.
If i go with more clearance i will not have timing issues. Less clearance = less than 1 HP gain.
Does anyone have a Minimum number that they can back up with experience?
What is your opinion and why.
76 KZ, frame gusset work,1200CC.Ported by Larry Cavanaugh, 1.5mm.over intakes, Carron Pipe, ZRX12 rear end, and seat,96zx9 front end.
01 CBR600F4i Track bike.
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- BSKZ650
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- mark1122
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I will be sure to recheck all clearances when my new pistons and block arive. Thanks for the heads up though.
76 KZ, frame gusset work,1200CC.Ported by Larry Cavanaugh, 1.5mm.over intakes, Carron Pipe, ZRX12 rear end, and seat,96zx9 front end.
01 CBR600F4i Track bike.
Cobourg, Ont. Can.
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- steell
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www.speedomotive.com/t-showbymodel.aspx
KD9JUR
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- 77KZ650
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forged pistons run loose in the bore untill they are up to temp compared to cast pistons. so allow a complete warm up before thrashing on it or your pistons can tag the head if they rock in the bore if they are cold and you are running really tight clearance
make sure the rods are ok (good idea to have them resized if they are showing an egg shape in the big end) and make sure the rod bearings are correct. too loose and you may get pistons touching the head
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Speedomotive (long time hot rod motor builder) has a lot to say on the subject.
www.speedomotive.com/t-showbymodel.aspx
Excellent article! Thanks.
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- mark1122
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Speedomotive (long time hot rod motor builder) has a lot to say on the subject.
www.speedomotive.com/t-showbymodel.aspx
Thanks Steel. That was a good read.
Thanks for all the input guy's. It seems i can run .040" but i will likely go with .050".
My block and pistons should go in the mail to me, mon or tues from Fast BY Gast.
76 KZ, frame gusset work,1200CC.Ported by Larry Cavanaugh, 1.5mm.over intakes, Carron Pipe, ZRX12 rear end, and seat,96zx9 front end.
01 CBR600F4i Track bike.
Cobourg, Ont. Can.
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- mark1122
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76 KZ, frame gusset work,1200CC.Ported by Larry Cavanaugh, 1.5mm.over intakes, Carron Pipe, ZRX12 rear end, and seat,96zx9 front end.
01 CBR600F4i Track bike.
Cobourg, Ont. Can.
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- martijn
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Did I miss something??
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