Join Date: Aug 2003
Location: Tejas del norte
Thomas: "OK, I went & measured my '89 SC heads & my '93 NA heads, & they both came out the same ... 11/32. So I was wrong. I don't, however, have any '96+ heads to measure ..."
I just (finally) got around to measuring my '98 V6 valves, & they are 7mm. The question now seems to be: When did the 11/32 stop & 7mm begin? I would guess '94, tho it could be '96. Anybody?
Also, it appears that a cheap valve upgrade for the 7mm folks would be to get some '99+ intake (1.86" vs. 1.75") & exhaust (1.46" vs. 1.34") valves. This would increase the intake area by about 13% & the exhaust area by about 19% (assuming my math skills haven't gone the way of my memory).
And, if there is no difference in the OA valve length, the 11/32 guys might also be able to take advantage of the '99+ valve upgrade. However, they would also have to install 7mm valve guides. The narrower valve stems (11/32=0.344 & 7mm=0.276) will provide for slightly increased flow thru the ports. The more mods done to the engine, the more significant the hp gain.
Thomas: "As for swapping the two, I don't think so. The positions of the valves are different."
I would think that if the OA valve length, keeper location & valve stem diameter are the same (or correct valve guides installed, if not), the valve location w/in a given cyl head should not matter. It would merely involve opening up the existing valve seats to accommodate the larger '99+ valves.
'98 GT equipped w/Koni, Eibach, Cobra R rims w/Yokohama tires, Cobra brakes all around & 3.73 gears. Also a Boss330 4.6 Cobra block w/PI heads & stuff from Accufab, ARP, Centerforce, Comp Cams, Fidanza, K&N, Mahle, Manley & Borla exhaust w/Mac Pro Chamber thrown in for grins & giggles.
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