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tips, technology, tools and techniques related to vehicle driveline components

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dartonit
Tamás Háfra

(9 posts)

Registered:
06/06/2008 05:35AM

Main British Car:
Sd1 head skim
Posted by: dartonit
Date: April 15, 2010 06:53AM

Hi guys!

I have a 3.5 SD1 engine (home ported heads, edelbrock carb and inlet, 3.9 efi cam, lightened flywheel). I use composite gasket (not the tin ones, because the oil leaks), but it reduce the compression.
I want a bit higher compression, because i would like to use E85.
It's really cheap in my country (and have 105 RON!)
95:1,13 GBP/l
E85: 0,76 GBP/l
Please help, how many mm(or thou) can i skim off the heads?
A guy said he had 27 thou skimmed off the heads. Ok, that's the difference of the tin and composite gaskets. But 8 thou is worth 1cc out of the combustion chamber, so his chambers will now be around 33cc in size, or not?
Can i have a problem, with the valve lifting? I don't know the distance between the valves, and the pistons, when it's fully open.

Thanx for help

Thomas from Hungary


castlesid
Kevin Jackson
Sidcup UK
(361 posts)

Registered:
11/18/2007 10:38AM

Main British Car:
1975 MGB GT Rover V8 4.35L

Re: Sd1 head skim
Posted by: castlesid
Date: April 20, 2010 09:06PM

Tamas,

If you have 30thou of the heads the compression ratio will be marginally more than with the standard heads with tin gaskets and your lifter preload will be virtualy unchanged.

To clarify, you are just replacing the metal milled from the heads with the extra thickness of the gasket.

Kevin.


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