340 J heads fs/ft 2.02 valve

[packers6947]

they are in great shape. they have been magnafluxed no cracks!!! i have origanal valves and springs if you want to them i recomend they be replaced looking to get 350.00 + shipping obo pick up welcome.
or trade
looking for 8 3/4 housing for a-body
steering column 4 speed 67-69
trunk lid 68
doors 68
finders 68
340 intake and carb holly 670
dart gts hood
and what ever else catches my eye let me know what you got
they are located in killeen tx 76549

 

[DionR]

Somethings wrong. Those numbers aren't for J heads (the last three numbers on a J head is 915), and there should be a J next to the spark plug holes, which there isn't. Those are late model smog heads (587). Stock they would have had 1.88 valves, did you have them cut for 2.02s?

Post a picture of the combustion chamber side of the head, of the full head, not just one chamber. Maybe I'm wrong.

 

[1wild&crazyguy]

J heads are mostley known for the 1st run [915] but actually were cast under diff #'s though out the 70's, and had a few minor differences.

this set '2nd generation' has the smog bosses but aren't drilled which could be a plus since these things can leak right below the header after a gasket match, typically there is not much flange width left there.

there are some 974 cast j's too.

sometimes when I look at the later 70's j heads they look different in the short turn, 'shorter'.

only cutting them in half and comparring, or talking to the engineer who designed them would say for sure.
but it's the early ones that people want, so...

 

[packers6947]

Somethings wrong. Those numbers aren't for J heads (the last three numbers on a J head is 915), and there should be a J next to the spark plug holes, which there isn't. Those are late model smog heads (587). Stock they would have had 1.88 valves, did you have them cut for 2.02s?

Post a picture of the combustion chamber side of the head, of the full head, not just one chamber. Maybe I'm wrong.

if they were cut for 2.02 it was before i got them? i will get more pictures when i get home? thanks for the info

 

[DionR]

J heads are mostley known for the 1st run [915] but actually were cast under diff #'s though out the 70's, and had a few minor differences.

this set '2nd generation' has the smog bosses but aren't drilled which could be a plus since these things can leak right below the header after a gasket match, typically there is not much flange width left there.

there are some 974 cast j's too.

sometimes when I look at the later 70's j heads they look different in the short turn, 'shorter'.

only cutting them in half and comparring, or talking to the engineer who designed them would say for sure.
but it's the early ones that people want, so...

Really? Never heard of that, learn something every day.

if they were cut for 2.02 it was before i got them? i will get more pictures when i get home? thanks for the info

Most J heads were 1.88's (as far as I know), but it's not uncommon for them to be cut for 2.02s. I have a set of U heads with 2.02s, but I am pretty sure the none six pack U heads were cut for standard 1.88 valves when they were run on standard 360's, just like they weren't machined for the offset rockers. So, I figure mine were cut at some later time, too.

 

[1wild&crazyguy]

J,U,O are all just J heads that didn't have the cast letter done right...

I have a set of 70-71 heads with a U on 1 and a J on the other, no big

915 'J,U,O ...was also used for the 6 pac, but it was not the same as the 915 most of us have.

 

[1wild&crazyguy]

look....

 

[DionR]

J,U,O are all just J heads that didn't have the cast letter done right...

I don't know about the letter not being cast right, there is definitely a difference between a letter O versus a U or a J, but I don't argue that there is little difference between them other than the letter. I think the casting number is more indicative of the design than the letter, but that's just my feel.

915 'J,U,O ...was also used for the 6 pac, but it was not the same as the 915 most of us have.

The 6 pack head wasn't cast any different than any of the other 915 heads, it was all in the machining. They had a different pushrod hole for the intakes so you could open up the width of the port was all.

 

[pishta]

Yup, I have seen J and U heads that look like a J on the spark plug hole but that was because the U was cut to look like a J when they drilled out the spark plug hole. Smogger heads are supposed to flow better than early heads (with the same porting) as they have a raised floor, and as noted, a better short turn radius. a sharp short turn causes a dead spot that hinders flow. And smogger heads all have hardened exhaust seats as a bonus.

 

[340wedge1971]

yeah,i have 587 heads that are stamped (587)