Thread: cylinder heads

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How can I tell the difference between standard 390 heads and 390GT heads without reading the castings? Is it true that GT heads and 428CJ heads are the same or are the ports different?

The port size is the same at 2.34 x 1.34 intake and 1.84 x 1.34 exaust. It's the chamber size that differs. The 390GT at aprox 67-70 cc's and the CJ at 73-76 cc's. G.

Actually, the 390GT is a bit different from the C8OE-N head. The 390GT valve sizes are 2.02 intake (I) and 1.55 exhaust (E). The CJ head is 2.08 I and 1.66 E. The ports are the same on the exhaust side (1.28 x 1.84), but the intake is tifferent. The CJ head is 1.34 x 2.34, and the 390GT is 1.34 x 1.93.

The C8AE-N 427 Low Riser head is closest to the CobraJet (same for C8WE-A and C8AE-J).

The GT heads have 12-bolt exhaust flanges, to fit the Mustangs, Cougars, etc. Needed to have options on exhaust bolt placement, as the shock towers would get in the way of the center bolts with the vertically aligned 8-bolt flanges.

I've got a set of C8AE-H heads, which are also GT390 format. These have been hogged out to match the CJ port and valve sizes, but are still the 390GT castings.

Best I've been able to tell, the C8AE-H casting is to cylinder heads as GBGB is to navy vessel designations (Great Big Gray Boat) - it doesn't convey much information. There were 8- 12- and 16-bolt flanges on these things from what I've read. I had to measure and research a long time to satisfy myself that they were what they appeared to be.

Denny there are master catalog CD's available with the casting numbers. There is a 60-64 and 65-75 and something like $103 each plus shipping. Download onto the puter to keep handy. www.fomoco.com shows the 65-75 but email for availability of the 60-64 CD. G.