DCR
New Member
I have a 1972 340 motor with 360 j heads on it and I brought a set of 340 x heads can I use the same rocks arms and push rods on the x heads
X heads vs j heads
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PRH
Well-Known Member
Yup.
middleagecrisis
Well-Known Member
Your engine and you will never notice the difference.
do the J heads have 2.02 or 1.88 intakes - I believe they came both ways...
harrisonm
Well-Known Member
I was always told that J and X heads are the same except for the intake valves. If the J head has 1.88 intakes and you have 2.02s put in, you essentially have X heads. That is the way I understand it.
ALL X heads have 2.02 valves.
DCR
New Member
Thanks everyone for your help
MMissile
Well-Known Member
This.
Read this. Like 100 times. ^^^^^
Correct. They did. Most had 1.88s but some got the 2.02s.
4spdragtop
Well-Known Member
I believe the runner floors were different between the X and J.
340sFastback
Well-Known Member
They are but the two different castings don't have any significant differences. The X heads have the legendary magical 340 vibe to them though.
Probably about like their big block counterparts the 906s and "everything else". I remember Jim Laroy saying they are a tic different, but it doesn't amount to much. But you know Chrysler. They did it for a reason.
340sFastback
Well-Known Member
Some people think X heads have some type of magic in them. The 340 legends. But thats a good thing for people selling X heads. The X casted in and visible between spark plugs that them special heads and what not.
Well.....they kinda do. I mean, if you're going for a restoration and don't have heads, or yours are cracked.....then I could see them being "special". But they ain't as "special" as some of the prices I've seen asked for them. lol
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They weigh about the same.
I would check the needed length of the pushrods regardless of the seemingly direct interchangeability.
Great point! I I would add along WITH rocker shaft location, because that varies head by head.
There's a six-page discussion of the difference between X and J heads on this forum, started back in 2014. I posted a link above (#11). Has anyone even looked at it?
Sorry, I'm kinda grumpy because I've been trying to figure out how to use my new A/C service equipment to recharge the A/C in my truck. Not making much progress. Would have been much easier and quicker just to pay someone to do the job.
Sorry, I'm kinda grumpy because I've been trying to figure out how to use my new A/C service equipment to recharge the A/C in my truck. Not making much progress. Would have been much easier and quicker just to pay someone to do the job.
furrystump
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In FULL tilt effort ported conditions 10-12 cfm difference is what I have heard from very smart guy. However, I know of J’s that out flow my X’s.
Dartswinger70
Well-Known Member
The x heads have 2.02s the Js some say they do but it was an easy machine shop thing to install 2.02s back in the day. X heads have smaller combustion chamber cc size than the J heads and, as I understand it typical intake runner cfm for x heads is 195cfm, J heads is 185 cfm just what I've read I didn't flow test them I have a set of 1.88s and 2.02 j heads I've always suspected someone had 2.02s installed in the Js.
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