X or j heads

Gator

Gator

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What is the difference between x and j heads don't they both have the same size valves.
 
x heads have bigger valves 2.02/1.60. castings are almost identical. if you put 2.02/1.60 valves in the j head, they will flow the same.
 
It is possible to find J heads that were factory 2.02 valved. Calling them X or J head is kinda silly since they can have the same casting numbers
 
I bought a set of j heads with the bigger valves.I was just wondering why people want more money for the x heads.Thanks for the info.I'm in the process of building a 340
 
I also just pulled a set of swirl port heads off a car my buddy was selling.he says you can build more compression with those heads is it true.Thanks for the info
 
I have asked myself why people want x heads for years. I just don't get it. they do not make any more power.

as for compression, mill (shave) the j heads. I milled my j heads .060 to gain more compression.
 
I thought the X heads not only had bigger intake valves but they flowed better than the J heads. Not sure how they could have the same casting number as the J head. I currently have X heads on my 68 340 Barracuda.
 
You can buy stainless steel swirl polished nail head valves that bump compression up. I've actually have a 360 that I'm building for my 79 Aspen RT. J heads, 2.02.

image_1444186400379.jpg
 
x heads sound better than j heads when a car guy asks ya how ya built your motor ,,lmoa
 
They could have a variety of letters. I know of X, J, L, H,Y and W heads. The X disappears after they stopped producing 915 castings even though X heads came with other casting numbers.
 
i had 360 j heads on my 318 but when i did the motor work i put on 360 x heads 2.02 ,,anyone local want a free pair of 360 j heads ? needs new valves imo.i wont ship way to heavy can also have the oem rockers if ya want
 
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