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What are "J" heads

71newp

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Sorry if this is too basic, but what are J heads? The ad I saw said "high performance". Thanks
 
Use on 71-2 340 with 2.02 valves and 71-2 360 with 1.88 valves. Casting number 3418915. They have a big J between two of the spark plugs.

Actually I have an early built 73 W200 truck 360 that came with them.
 
Yes but wasn't the 70 915 casting a U or O head? Same casting but just a different letter?
 
Here is a picture of where to look for the letter. Sometimes "U" heads can be mistaken for "J" heads.

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340 oil pump priming 006.jpg

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Look close at the first and last spark plug hole. This is a set of "U" heads. As the spark plug hole was machined from the blank casting, it removed a portion of the letter.

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And yes Mark, this is a set of 1970 915 heads.

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But they are not the "special" T/A heads that use the offset rockers.
 
Thanks for the feedback...These are 915 heads that have been cleaned, magged and a valve job with new valves (according to the seller.) Next question, I want to put together a 360 for "well behaved" street use. That is an engine that will run on mid-grade pump gas, mild (not lopey or choppy) cam, stock exhaust, etc. Are these heads too much for that? Would I be better off just leaving the stock heads (1976 360)? I looked again at your pictures, would a stock exhaust from a 1976 360 work with these?
 
Well to answer your last ? These can go one and the car can still run pump gas. They will make it a bit more misbehaved but not by much,by them selves . What kind of h.p. are you wanting and how responsive are you wanting it to be ? If your just wanting a car with looks then run your stock stuff and enjoy better gas mpg ,it's not always about go I've had a few cars the fast ones were ugle the slow to moderate were nice looking , I enjoyed the slower cars more they still had enough go to have fun here and there ,and I could drive my car everyday and not cry at the pump so give us a little more of witch way you want to go with it
 
Which valves do they have, 2.02 or 1.88?
My 73 360 came with 1.88 J heads. Don't see why a 76 360 wouldn't be fine with them.
Yes your E/manifolds will work fine. Same port size.
 
The 76 360 likely had a 587 casting head on it no real difference between it and a J head. I have run both and ported both extensively. ... fwiw the 587's would flow just a tad bit better than the 915 J head max ported... but for a street motor leaving them basically stock... no difference but the casting #.
 
Thanks for all the feedback! Basically the motor is going into a 1976 Cordoba that I plan to use as a summertime daily driver. I was hoping for about 300hp to make a bit more fun to drive and better freeway on-ramp performance. I still want to keep it well behaved (smooth idle and power band. Not choppy or peakish.)
I have never undertaken an engine build, just done normal things like tune-ups and brakes. With that in mind I was thinking about getting a re-manufactured block assembly because that would have a lot of the more demanding work done, yet I could still "expand my knowledge/experience base" finishing it off. When these (unassembled) heads became available I thought about getting a longblock and doing even more work/learning.
I think that with all the info I have gathered here I will stick with my original plan, and leave these heads for someone else.
 
Thanks for all the feedback! Basically the motor is going into a 1976 Cordoba that I plan to use as a summertime daily driver. I was hoping for about 300hp to make a bit more fun to drive and better freeway on-ramp performance. I still want to keep it well behaved (smooth idle and power band. Not choppy or peakish.)
I have never undertaken an engine build, just done normal things like tune-ups and brakes. With that in mind I was thinking about getting a re-manufactured block assembly because that would have a lot of the more demanding work done, yet I could still "expand my knowledge/experience base" finishing it off. When these (unassembled) heads became available I thought about getting a longblock and doing even more work/learning.
I think that with all the info I have gathered here I will stick with my original plan, and leave these heads for someone else.

Here is a 300hp 360 dyno test.

http://www.forabodiesonly.com/mopar/showthread.php?t=307012

Note that stock 360 heads flows will give you about the same flows as the ported 318 heads we used, so the results would be somewhat similar using a stock 360 head.
 
Also on AAR'S in 1970
OMG! Totally innnnnn-correct.

To the OP, the letter head series of heads are basically the same head with minor differences except the "T/A" head which has off set pushrod holes that open up the ports for a clear and unrestricted path in the port. The head uses off set rockers.

The other letter heads "O", "U" , & "J" are standard pushrod holes heads .

These heads are NOt high performance heads but just sime dead stock heads. They have a flow rate of approx 200/210 cfm. Flow bench results will vary!

The "J" heads as far as I have personally seen come with 1.88 / 1.60 valves. 2.02's can be installed easy.

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Thanks for all the feedback! Basically the motor is going into a 1976 Cordoba that I plan to use as a summertime daily driver. I was hoping for about 300hp to make a bit more fun to drive and better freeway on-ramp performance. I still want to keep it well behaved (smooth idle and power band. Not choppy or peakish.)
I have never undertaken an engine build, just done normal things like tune-ups and brakes. With that in mind I was thinking about getting a re-manufactured block assembly because that would have a lot of the more demanding work done, yet I could still "expand my knowledge/experience base" finishing it off. When these (unassembled) heads became available I thought about getting a longblock and doing even more work/learning.
I think that with all the info I have gathered here I will stick with my original plan, and leave these heads for someone else.

If the rebuilt heads are a good price it will at least save you the headache of rebuffing the smog heads.
A smooth idle cam should be listed at a 112 or larger. Crane cams often do there cams on a 112. Also use a split duration cam to help rid the engine of the exhaust gas for a cleaner and more powerful charge. Look at a cam with a intake duration of approx. 214 (or slightly greater) @ .050.
 
Thank you for the link. Great read. I will have to do some more reading on that site. Your posting there both reaffirmed and changed my thinking. I was thinking of going with a cam that is equivalent to the 340 cam, so I now know that thinking was/is correct. I thought I would need a higher CR, so there I was wrong. I'll probably look for an intake and carb (Edelbrock Performer & 600-650 cfm) this summer while driving and working on the rust. The engine build is a year away.
 
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