Grey head thumbprint ........

[fingers]

Does anyone know what the standard depth of the thumbprint on a grey motor head is from the factory .......the grey motor I,m building for my FJ ute is bored to 3 and 3/16 ...the block height decked to zero ....probably 20 thou of thumbprint remaining ...after checking the cc of the chambers the comp ratio comes up to 8 to 1 ...... the problem is that when fitting large valves the combustion chamber needs to be machined out to fit and allow for some flow around the valve and can take the chamber capacity out reducing the compression ratio......I need to machine the surface more ..how much below the thumbprint has any members gone .....Fingers

[Trev]

Mine were gone after decking the head .

[fingers]

Mine were gone after decking the head .

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Do you know how far past the prints they decked it ............thanks mate .........Fingers

[Trev]

Sorry no I don't, I think it would have gone just past level.

[choppedfan]

Sorry no I don't, I think it would have gone just past level.

You really know the head's been shaved when you have to get a file to elongate the sparkplug holes in the sideplate so you can get the plugs in

Mick

[fingers]

Sorry no I don't, I think it would have gone just past level.

You really know the head's been shaved when you have to get a file to elongate the sparkplug holes in the sideplate so you can get the plugs in

Mick

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From memory we used to take off around 100 to 124 thou from standard and needed to elongate the holes around the side plate to get them to line up ....... ..........Fingers

[fingers]

after some investigation and some talk with holden gurus Roger Hancock from Holdenman ,Ross from South Gippsland Engine Reco,ers and Bluey from Blueys Engines in Bunyip the following info was obtained .............the standard holden grey head is measured for total thickness from the surface on top of the head where the rocker cover gasket sits and the bottom surface that bolts to the block the standard measurement is 3.250 inches .. Repco recommend the a minimum thickness to be 3.190 inches so 60thou is the maximum that should be shaved from the head surface according to them ...it seems that from what I have been told the thumb print is approx 60 thou deep but this varies on different castings ...so the important measurement is the 3.250 inches total thickness ...I have heard of heads being shaved up to 125 thou ....but this seems a little dodgey by todays quality of heads with them being 50 years old the inner water jackets are getting thinner with rust and scale build up so 100 thou would be suspicious at the best ...also the surface deck gets thin at this amount of machining and sealing between the head and block can be compromised and fail as a result ............Maximum compression ratio of around 8.5 to 1 will be acheived machining 60.to 80 thou off ..this can vary with any work on the combustion chambers ..this figure will still allow the motor to run on 91 unleaded fuel and have good performance figures... well as good as can be expected from Grey...I guess if it were about performance then you wouldnt be messing around with a grey motors .....For me its about a lumpy idle , carbys hanging off it everywhere and that distinctive grey motor note ... ....oooooohhhhh yeah .............Fingers