[Crazytrain]

Dude that is way over my head???

[74GTODude2]

Well which heads are better to build 4X or the 6X? I have heard from some of my back yard mechanics friends conflicting information. One is telling me the 6x is the head to build up and the other is telling me the 4x is the way to go. They have argued over that one for ten minutes. I have 4x and was looking to buy a set of 6x.

[BVR421]

Originally Posted by 74GTODude2

Well which heads are better to build 4X or the 6X? I have heard from some of my back yard mechanics friends conflicting information. One is telling me the 6x is the head to build up and the other is telling me the 4x is the way to go. They have argued over that one for ten minutes. I have 4x and was looking to buy a set of 6x.

Pretty much any 1967-1979 factory Dport is as good as another if you are going to spend good money to have them pro ported and rebuilt. Some folks have their favorites but they all have close to the same potential.

What is important is the combustion chamber size. It has to be appropriate to your application mostly what fuel you will run. regular pump gas? premium pump, race fuel? methanol? 400?, 455?, 535?

example: stock 4x on a 350 would have about 6-1 cr lucky to get it to start, 4x on a 455 about 7.5cr great if you want to burn 87 octane or throw a PDude supercharger on there. 6X-4s have a smaller chamber, great for 400s on pump gas, 6X-8s great for pump gas on a 455

Pick a compression ratio thats realistic for whatever fuel you will be using then choose a head based on that.

[Ben M.]

Originally Posted by 74GTODude2

Well which heads are better to build 4X or the 6X?

According to Rocky's in-depth testing, 4X heads flow no differently than 6X heads, either in stock form or when worked up effectively. So either head of the appropriate CC will get you where you want to go. Which works in your favor as most people consider 4X\4C heads to be doorstops and scrap and the 6Xs are worth their weight in gold - when they are pretty much the same head.