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Posted: Fri Oct 04, 2013 9:54 am
by DaveEFI
Yes - if you use the later heads already reduced in thickness for composite gaskets, the CR should be the same. Skim them, and the compression ratio goes up.
Remember to omit the outer row of head bolts - or simply nip them up if you feel that would look strange.
Posted: Fri Oct 04, 2013 8:32 pm
by ThatV8sound
Dave,
is there a rule of thumb for what skim depth relates to a corresponding rise in CR?
Posted: Fri Oct 04, 2013 10:36 pm
by DaveEFI
ThatV8sound wrote:Dave,
is there a rule of thumb for what skim depth relates to a corresponding rise in CR?
Beyond me, I'm afraid. An expert should be along shortly.
Posted: Wed Oct 09, 2013 3:06 pm
by badger
Hotwire fuel rail fits if you crop one of the rear brackets where the coil pack would mount. Single-pipe fuel system is ecu-controlled, pressure regulated by pump. Vacuum servo offtakes is on the front "cross-plenum", opposite end to throttle body. Front of manifold can be machined out, drilled and tapped to take a standard thermostat and housing, allowing clearance for a distributor ( or a less-complex cooling system!).
Did this years back, ran a top-hat linered 4.6 in a 110 with a torquey cam on a Mark Adams re-chipped ECU. Pulled like a train to 4500rpm then fell on its face, but that was probably more to do with the cam than anything else...
Posted: Mon Oct 14, 2013 10:18 pm
by ThatV8sound
Badger,The mod to the inlet manifold sounds interesting, and would save some effort at the front end. Also the GEMS fuel rail has been mentioned earlier so its definitely worth a look and trial fit. I think in the absence of any recommendations to the contrary, I'll stick with the 3.9 EFI cam as a replacement for the stock P6 one, that way it should all play along together. I'm not looking to do anything except make it easier to use and more reliable.
Thanks for adding to the thread.