Head refacing

[tightgroup]

Given I have a 7:1 compression head, how much refacing is needed to bring this to an 8;1 ratio.

Now the real question is , how can yoy tell if its 7:1 , I have no real visable markings except for a 5 digit code..

TG

 

[Yorker]

7:1 heads have no square boss on top of the head on the inlet/exhaust side midway down on the top. Actually that isn't entirely true apparently there were a few with that casting but they were stamped with a 7 there and the *:!'s were stamped with an 8. If you have a head without the boss all together then it was made as a 7:1.

3. Cylinder Head: If you have the earlier 7:1 cylinder head, you can have .0100 milled off and increase the compression to 8:1. It is possible with later heads of the 8:1 variety to mill further and try to get towards the 9:1 compression ratio. Reliability should not be affected.

http://www.lrfaq.org/Series/Engine.Uprating.html

I think the above is a typo, I believe the difference is .1" see:

Series Land Rovers

Cylinder Heads

By Hank Rutherford, Steve Denis, Peter Ogilvie
7:1 head is 3.700 in thick, chamber volume is 91 cc.​

8:1 head is 3.600 in. thick, chamber volume is 75.2 cc.

http://www.lrfaq.org/Series/Engine.CylinderHead.html

If I recall correctly I took .050" off of my new 8:1 head becase it was damaged in shipping- I had no ill effects from the change.
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