[gloryrestoparts]

could the cc difference be original dated heads vs later dated service replacement heads?

[Rocky Rotella]

I measured the #48's from Jon's 350 H.O. before any machining was performed. The engine hadn't ever been apart. They measured exactly 66cc.

I searched every square inch of them (and took countless pictures) for any sign of an application stamp or 350 H.O.-specific identifier and there wasn't anything to be found.

[U47]

Originally Posted by Jim Robertson

I have played with a few #48s over the years and yes we have found two different combustion chamber volumes. 66ccs and 72ccs. No question about the originality of the heads. The difference is in the depth of the chamber and the scallop on the spark plug side of the chamber. In all my searching and buying I have only found one set of #48s that measured 72 ccs all others measured 66cc. Definitely a difference in the machining operation when produced. If you place one of each side by side you can see the difference. The 48s pictured on my website have the 66cc chamber - about 5ccs due to milling.
Jim
www.racev8s.com

Jim, here is a twist for you. The NHRA Min. cc for a # 48 head is 65cc

D.

[Ron Landis]

Originally Posted by U47

All 69 350" 2bbl heads are cast #47. The valve sizes are 1.96 and 1.66 ( the intakes are larger than 60-61SD's (389's) and 63-66 H-O's (389 @ 421's) at 1.92.
The # 48 head for the 400" are 2.11-1.77 and the chamber volume is 72cc. with a compression of 10.75 to 1. The 350 # 48 has a compression of 10.5 to one. To me that means the 350 # 48 head has a different chamber volume than the 48 400" head, just look at the bore size difference 4.12 vs 3.88 ! That dosen't equate .5 in compression.

Don

The 350 HO #48s are purported to be shaved @ .020 for @ 68 cc chamber as opposed to the typical 72cc 400 head. Stands to reason, as well. This I learned form a GM worker.