compression and wisco

compression and wisco

Postby RAYH2 » Sun Aug 28, 2016 10:14 pm

one of my H2s is reading around 170psi on all 3 cyls , fitted with wisco 72.5mm set. Is the compression too high? , I thought normal is 142 ish , the shop manual indicates to high a compression will cause pinking, it does it a bit when hot, just checked timing 2 and 3 were a couple of degrees out as well. I see the kit actually takes out the engine to 790cc, so with the same size cyl head profile I can see why compression may increase . My initial thought is a thicker copper gasket for the head
Thoughts appreciated ,
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Re: compression and wisco

Postby mr crankshaft » Mon Aug 29, 2016 6:03 am

you've answered it yourself
yes thicker head gaskets will resolve this problem , what happens is your increasing the swept volume in top of cylinder so basically what that means is when the piston covers the exhaust port as it closes the volume left in there gets compressed in the head , rebore means more volume
I can supply you with head gaskets , not sure if I have any in stock at moment but if you require them it takes about 3 weeks if not in stock regards Gary 07779094462 £30 a set
cheaper than a holed piston
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Re: compression and wisco

Postby Wolfie » Mon Aug 29, 2016 7:37 am

Yep, I had this problem after a rebore and Wossners, but only when hot... Mine was also around 175psi.

A set of Gary's thicker gaskets got me down to just below 160 and she was happy again..

I checked more recently and we are down to around 140 now we have a couple of thousand miles on them.
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Re: compression and wisco

Postby RAYH2 » Mon Sep 26, 2016 11:14 pm

Yip down to 150psi , running much sweeter
Thanks guys
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Re: compression and wisco

Postby mr crankshaft » Tue Sep 27, 2016 8:36 am

there you go
glad I could help :D
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