Question About J Heads

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SassyGrassScamp

SassyGrassScamp

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I just picked up a bare set of J heads with casting numbers of 3671587.

I've de-coded them and found that these heads could be from the following:

1973, 340
1973-74, 360
1976, 360

My questions are, how can I tell which ones I have, and does it make a difference?

All 3 show 1.88-1.60 valves, but I'm not sure if the chambers or ports are different.

Any help would be appreciated.

Thanks,
SGS
 
They're all the same. The early 915s are the "J" heads the are different because of the larger 2.02" valves.
 
They are all the same castings. Ports and chambers are the same. Differences from 340 or 360 HP would be premium valves and valve springs. They also have Induction hardened exhaust seats. By the way , they are not "J" heads. "J" heads ran from about 71 to 72 on 340's and 360's. They still flow well and have the good ports.
 
AdamR said:
They're all the same. The early 915s are the "J" heads the are different because of the larger 2.02" valves.
Click to expand...

Thanks Adam....Assuming they are stock, do you know if I can I machine larger valves into these heads?....Looking at the valve seats, I don't see how....They look like they're almost touching as they are....Who knows, maybe they're not stock....I won't know with out measuring them.
 
their all the same, 340/360, you should have a 4 digit # cast in them that is the date code like (3002) three hundreth day of 1972 so it would have been on a 73 car since the factory change over to new models started first week in August.
 
SassyGrassScamp said:
Thanks Adam....Assuming they are stock, do you know if I can I maching larger valves into these heads?....Looking at the valve seats, I don't see how....They look like they're almost touching as they are....Who knows, maybe they're not stock....I won't know with out measuring them.
Click to expand...



yes 2.02 valves can be put into the small valve heads.
 
Biggest I've done was 2/05/1.65. But with those heads you could go 2.08/1.60 if this was a race(max) effort. If it's a street car, 2.02/1.65s are fine.
 
EL5DEMON340 said:
their all the same, 340/360, you should have a 4 digit # cast in them that is the date code like (3002) three hundreth day of 1972 so it would have been on a 73 car since the factory change over to new models started first week in August.
Click to expand...

The casting number is 2872, which I guess means the 287th day of '72....What does the little pointer tell me?....There are the numbers 1-2-3 with the little pointer pointing to the "2".....There are also the letters "AAWJ".
 
1973 heads, pointer is second shift, aawj is just a foundry code or the like that same aawj is on a lot of the blocks also. good head and with it being a 1.88 when you put a 2.02 in it the valve will sit nice and high in the head unlike a original 2.02 thats had a few v/j's
 
Yes ,...2.080 in mine..many years all good never a problem.
And has been stated above..they are the same castings just smaller 1.880 valves. Have your guys put in 2.020 and you are good to go.

Terry
 
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