Decking the Block, Compression Ratio & Timing

[mack124]

Hi Guy,
Thanks for the info on my last post. It's all been very helpful but it leads me to a quandry. I had forgotton about skimming the head and block and as I don't want to tell you about my blown head gasket, I shall of course do it. If I take around 10 thou' of the the head and block that'll raise CR a bit to high.

for example the standard CR for the engine is 9:1. If I use my 124 CC pistons it will actually rasie it to 10.4:1 not the 9.8:1 as I'd thought (the 1756 Combution camber is a tad larger) then decking the block and head will take it up to 10.9:1. That's a bit high for me so I'll stick to the standard pistons, deck the block and head and end up with about 9.38:1.

The question is. How much will this alter my cam timing and is that going to be an issue? When you have had blocks and heads skimmed, how much typically needs to come off... roughly?

Thanks in advance
Regards
Gill

[Guy Croft]

3-7 thou" is typical on overhaul, that much is not going to have much effect at all on CR; as for cam timing use adjustable pulleys if you cannot time up cams properly, OK?

GC

[sumplug]

Also Gill, if you are worried, use a slightly thicker head gasket [measured compressed]. This will restore your CR.

Andy.

[Guy Croft]

Sure, I have a CR calculator if you email me.

GC