J-Heads

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Xtreamist

Xtreamist

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I have a 340 in my 67 Barracuda that came out of a Duster (not sure exactly what year, I've been told 72 but maybe a 73) but that irrelevant because the heads on the motor are not the originals, the car came with an extra set. The heads bolted to the motor are both (360) J Heads, casting number 3418915, AAWJ. The date codes are what's throwing me from identifying what they are and I'm trying to determine what valves were originally in them. Yea they could have been machined but they are on the car and will not be removed anytime soon.

Both are date marked 0967, this would be Sept. 1967 right? From everything I've been reading on other posts here is that the "915" J Head wasn't molded until a few years after the, 70-71?
 
Maybe its the 67 day of 73, so February 7?

Jake
 
Xtreamist said:
I have a 340 in my 67 Barracuda that came out of a Duster (not sure exactly what year, I've been told 72 but maybe a 73) but that irrelevant because the heads on the motor are not the originals, the car came with an extra set. The heads bolted to the motor are both (360) J Heads, casting number 3418915, AAWJ. The date codes are what's throwing me from identifying what they are and I'm trying to determine what valves were originally in them. Yea they could have been machined but they are on the car and will not be removed anytime soon.

Both are date marked 0967, this would be Sept. 1967 right? From everything I've been reading on other posts here is that the "915" J Head wasn't molded until a few years after the, 70-71?
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There were no heads with the 360 cast into them until 1971 at the earliest.

In truth, there isn't a penny's worth of difference in any of the Pcar heads. The heads with the extended exhaust pad with no air injection holes are the best castings to start with because they are generally bigger as cast.

Other than that, it's valve size and the difference in power between the 1.88 and 2.02 valves is about nothing.
 
YR is right. Any passenger car head is a good stock replacement or mild bracket head. You can get going pretty good with them but there All generally equal to each other. The X head with 2.02’a are the best as cast stock issued head. The smaller valve heads can come close and/or equal the X when you install 2.02’s in a rebuilt set.

They can still make for excellent street performers.
 
What is the date code used for then?

Unfortunately I have no idea what valves are in the heads. Guess I'll find out when the day comes to rebuild. Is there any way to tell without taking them off?
 
I bet that 7 is actually a 2, so 96th day of 72, or 4/5/72. Do you have a picture ??
 
brian6pac said:
I bet that 7 is actually a 2, so 96th day of 72, or 4/5/72. Do you have a picture ??
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I'll post a better one up close when I get home. I thought date codes read the month and year. Does anyone recognize the rocker arms?

0629180951.jpg
 
It was a 5 digit then in 72 they changed to a 4 digit and the first 3 are day of year and the last is the year
 
brian6pac said:
It was a 5 digit then in 72 they changed to a 4 digit and the first 3 are day of year and the last is the year
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Well then...that explains everything! Only if the 7 is really a two of the 0967 date code.
 
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915 heads can have 1.88 valves OEM in a 360 or 2.02 valves OEM in a 340 from the factory. '72 were all 1.88. They were next in line after they quit using the 894 heads. They can have a 1970 casting date because they were used for the 340-6 pack engines in 1970, just had the intake pushrod hole machined in a different location to accommodate the offset intake rockers. Castings also needed to start in '70 for '71 model year 360s.
 
Xtreamist said:
I have a 340 in my 67 Barracuda that came out of a Duster (not sure exactly what year, I've been told 72 but maybe a 73) but that irrelevant because the heads on the motor are not the originals, the car came with an extra set. The heads bolted to the motor are both (360) J Heads, casting number 3418915, AAWJ. The date codes are what's throwing me from identifying what they are and I'm trying to determine what valves were originally in them. Yea they could have been machined but they are on the car and will not be removed anytime soon.

Both are date marked 0967, this would be Sept. 1967 right? From everything I've been reading on other posts here is that the "915" J Head wasn't molded until a few years after the, 70-71?
Click to expand...
That could mean September the 6th 1970. A friend has a 1970 360 block. The heads differ in port volumes and shape, slightly on the exhaust with 2 DIFFERENT versions of air injection bumps. The 974 casting has the better set, the others are further away from the seat. The intakes vary in volume and floor shape , X are different than J, J are different than 596 etc...most later years are the same. You basically have to have all the heads in front of you at once or a few pairs to see that there are differences in the castings. The early J head has more of a flat ramp transition as it approaches the short side peak . The 894 has a plain at the peak, about 1 1/2"or more just before it descends down the short side. The factory 2.02 J head ime peaks higher as cast than the x head. I'll post more or edit this in a min. Some of the later heads do worse due to the valve they use on the exh side. To say the later 74 and up heads all flow about the same is fairly accurate. I believe the j head has about 10 cfm over the x head. I tested 218 for the 894x head and 228cfm for the 2.02 915 J .
Another thing I've found is that the early castings have more meat, the exhaust port roof are thicker. Later heads are thin, pop an end plug out of a 596 smog head and you'll see the roof kink is only .085 Tops!
I'll think of the other things and edit
 
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@MOPAROFFICIAL

What can you pull out of a full ported stock head?
How do the years vary? (CFM spread)
Have you found a more favorable head to port over another?
 
rumblefish360 said:
@MOPAROFFICIAL

What can you pull out of a full ported stock head?
How do the years vary? (CFM spread)
Have you found a more favorable head to port over another?
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The later heads without the air holes usually start out the biggest. You can get 270ish depending on the bench but I'd give up 20 CFM to fix what is wrong with them when you get them that big.
 
I’ve heard guys getting that before. And before any mods, like moving the pushrod or welding on the head.
 
rumblefish360 said:
I’ve heard guys getting that before. And before any mods, like moving the pushrod or welding on the head.
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Yep, but it's a giant PITA, and you need to sonic test everything, or like me, you get down to the short strokes and blow through a thin spot.

Then, you make up new cuss words, throw some tools, beat the dogs and star over.

It sucks.
 
Locomotion said:
915 heads can have 1.88 valves OEM in a 360 or 2.02 valves OEM in a 340 from the factory. '72 were all 1.88. They were next in line after they quit using the 894 heads. They can have a 1970 casting date because they were used for the 340-6 pack engines in 1970, just had the intake pushrod hole machined in a different location to accommodate the offset intake rockers. Castings also needed to start in '70 for '71 model year 360s.
Click to expand...

I pulled the heads off a wrecked county police cruiser, 1971, the J heads had 2.02 valves in them, it was a 360, paid $20 for the heads, could have bought the whole engine for $50, but as a broke high school kid, the heads are all I could do at the time.
 
So I've got the valve covers off my J-heads for an intake install. It is a late 70 340 block. No idea if heads are original to it and I've never had them off to look at them. They have 360 on one end, the 3418915A part number and a five digit code of what looks like 05050 or it could be 05080. Would that make them May of 1970? That would seem odd with the 360 stamp. Any guess as to intake valve diameter?
 
gzig5 said:
So I've got the valve covers off my J-heads for an intake install. It is a late 70 340 block. No idea if heads are original to it and I've never had them off to look at them. They have 360 on one end, the 3418915A part number and a five digit code of what looks like 05050 or it could be 05080. Would that make them May of 1970? That would seem odd with the 360 stamp. Any guess as to intake valve diameter?
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It's not really that odd. The same casting number can be machined to many different specifications.

Locomotion or perfacar need to chime in here. The Stock eliminator guys have this stuff memorized.
 
The cast in “360” has nothing to do with engine displacement.
 
sireland67 said:
I pulled the heads off a wrecked county police cruiser, 1971, the J heads had 2.02 valves in them, it was a 360, paid $20 for the heads, could have bought the whole engine for $50, but as a broke high school kid, the heads are all I could do at the time.
Click to expand...
Interesting.......was the motor a 360 or were the heads 360?
 
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