Just looking for a ballpark number. I would have thought that if it was listed as 10.75:1 on the 400, it would have been less with the larger bore of the 455. I didn't think about compressed volumne tho. Still, 11:1?
96 cc is typically the best starting point for a street 455. 1971 #96 and 1972 #7K3 are the two out-of-the-box big valve heads with that size chamber. Then you can look at 4X and 6X variants which will need valve and some minor milling work to get there.
The #7K3 heads are reasonably inexpensive, but lack the outer two exhaust bolt bosses which lead to sealing problems with headers. You can use brackets made by Spott's, or you can have a competent shop weld up some bosses and have them drilled and tapped. I chose the second route on the #7K3 heads for my 455.
Well, if I'm not mistaken I have a set of 7k3s in the garage. I'll have to check it again. Do they normally have hardened seats already? How about the castings, do they lend themselves well to porting?
Mine ported just fine and they supposedly already have hard seats since they were designed from the onset to run unleaded fuels. I added new seats anyway. Just a habit, I guess.
7K3's don't have the end boltholes for the exhaust manifolds, though. Makes them difficult to use, if you plan on using headers. Floyd & Jim Hand concocted a method to make them work, though.
'67 Coupe, 455, pump gas, 11.46 @ 115.4, in Feb '05 HPP Shootout article
