[Pontiacman469]

Bottom line i have a chance to get a set of 4x heads for next to nothing.Would you?From what i understand all d-ports are equal in the 70s (Come from the same casting?)Question 1:How much difference is there between the 6x & 4x?2:How streetable is the 4x?(2.11-1.66?)3:How are the cc's on 4x's? Thanks -Andrew

[WDCreech]

Here's a list of heads with uses and chamber sizes:

http://www.wallaceracing.com/headsearch.htm

[screamingchief]

Depends on the specific engine these would be for,and the specific 4x heads in question,there are like a half dozen different variations of the 4x castings,each with it's own pluses and minuses.

Other than that,reports suggest the 4x castings are more prone to cracking than the later 5c and 6x castings,so magnafluxing any potential castings is mandatory.

But that should be the case with all castings regardless...

[Mr. P-Body]

To add to what SC says, if you're going to have them ported (or are going to port them yourself), the casting number is of little consequence. No advantage from one to another except chamber volume and stud type.

Jim

[fiedlerh]

Here is the list of 4X head variations. Some are more desirable than others. Try to get a version with screw-in studs and large intake valves.

http://fiedlerh.home.att.net/4xheads.htm

[Cliff R]

A few days ago I had a discussion with Dave at SD Performance, about 4X vs 6X heads. In stock form the 6X head has a few advantages, better exhaust port (double pass down both sides of the valve guide), and the intake port has some minor advantages as well, something about the floor and short turn, etc?

I do agree that any differences quickly disappear with correct porting, but as cast I'll take the 6X heads over the 4X every time.

The 6X-4 head also offers another advantage of having a smaller chamber. The vast majority of the castings I've prepared here have 91-92 cc chambers before milling. A few have been down around 89cc, and few up around 96cc. Most 4X heads are at least 98cc or larger.......Cliff