X Heads or J Heads???

[agarcia5]

What would be better for a 340 street use?

J heads or X heads??

Regular pump fuel and street use

Thanks

 

[1970Duster]

X head =2.02/1.60 (in/ex)
J Head (early)=2.02/1.60
J Head (late)= 1.88/1.60 (Not 100% on exhaust pretty sure it is 1.60 though)
Both X and (early) J will work just fine and the (late) Js did come stock on 72 and 73 model 340s

 

[fishy68]

Their nearly identical heads except the newer J's have smaller intake valves. I don't think you'd see a hill of beans difference in either if their set up alike.

 

[moper]

Yup. Same same.

 

[agarcia5]

alright thanks guys

 

[EL5DEMON340]

if the j is a 1.88 it can be enlarged to 2.02 plus the valve will sit up higher say then an x that has had a couple V/J's already, just be sure if you put a 2.02 in the head to have a plunge cut to open the bowl.

 

[1wild&crazyguy]

if the j is a 1.88 it can be enlarged to 2.02 plus the valve will sit up higher say then an x that has had a couple V/J's already, just be sure if you put a 2.02 in the head to have a plunge cut to open the bowl.

There small differences, I like the early heads.

I dont see any later heads in ported form going much over 250cfm, meanwhile the older stuff nets 270's/280's.

I think if you know what you are doing 'porting wise' then to an extent/cfm level...you'll be fine with any of them.


Does anybody have any 587 heads ported flowing over 250-260's?

I'd like to see the flow sheet..