Head modification

[Stuart Giles]

I have machined many heads by wedging them. The stud holes do not need easing and the head will drop straight on. For me it is far easier to turn them in the lathe. 
  It is certainly less expensive to wedge a head than buying a new one.

Never occurred to me to use my 'big' lathe for cylinder heads; the larger of its two faceplates is about 26" diameter so it would be OK from the capacity perspective. I have power feed to the table on my Bridgeport so just set it up and have a cuppa while it gets to work. 



I think I've done 6 or so 'wedge' A7 heads now, the ones I've done have .060" of wedging and .125 off after doing some work in the combustion chambers.







060" of 'wedging' is about 1/2 a degree if you do the SIN calculation with the head width as the hypotenuse. All of these have just dropped onto the couple of spare blocks I have here without any trace of binding.

Neither has any binding of the studs/bolts been a problem even with much deeper cylinder heads I've machined than the A7 ones. Wedging is a common tuning modification on OHV motors that have angled valves (AKA wedge)  combustion chambers, simply because the edge of the big inlet valve seats these heads have (typically 2"+ diameter inlets on all the motors below)  would be compromised by 'parallel' skimming of anything more than a few thou'. This issue is probably most visible in the second photo below.

1967 Ford "Small Block" Ford Mustang:



1972 Truck Chevrolet Small Block:



TVR Tuscan: apologies for the poor quality photo..