Hi Guys, looking to get a new cylinder head for my 1992 4wd Cossie. I guess I can use existing cams etc. Any help appreciated.

 

Hello,

I know at Burton Power is selling new heads (not COSCAST) in the UK.
See https://www.burtonpower.com/motorspo...b-sc1207a.html
I notice at this head is using 36.24mm inlet valves and 32mm exhaust valves, so you should find out can you use original valves in this head.

Original 4wd valves are IN 35mm and EX 31mm.

Nowadays it`s really difficult to find good used head. Usually used heads are skimmed already to minimum thickness. Going by the ford manual its 138.68mm. You can use heads after minimum thickness, but then you will need to use thicker head gaskets.

 

Thanks for your help on this. I cracked the head on mine when I screwed in the wrong oil union for the turbo feed. I got it fixed but there are excess amounts of alu weld around the hole..,.

 

the importance of the Ford specified limit on head thickness has been the subject of much discussion over the years. originally heads were 139.1mm (I think) and every skim will increase the compression ratio to a small extent but that aspect of it is largely irrelevant as most engines will have had different pistons / valve cut outs etc. and many folk run higher comp than 8;1 these days anyway. a thicker gasket is also another way to reclaim compression volume but second best to piston machining.

a more important consideration (so the arguments goes) is that each skim brings the inlet valve seat closer to the head face which could reduce the clamping force around it and result in the seat falling out. this may be even more of a concern if the head has been overheated at some point as the aluminum of the head may have softened.

I have 2 heads which are under 137.5mm thick which means that the edge of the inlet seats is actually on the face so the edges required a very slight grind so that when they head is skimmed the tool doesn't hit the seats. both of them have done 30+ K miles running 30+ psi without any problems.

so my experience of the 138.6mm is ignore it!

using larger (typo - edited to say smaller) diameter valves than the seats were ground for will result in the smaller valve being recessed into the seat which will likely be a similar effect to reducing the lift of the cam.