340 mismatched heads?

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HotRod20

HotRod20

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Picked up a set of 1970 340 engine heads from the cars original owner who decided to go with
a 392 Hemi conversion. He still has the block and crank. So while looking at the heads, I noticed one was a O head and the other was a Z head. I measured the intake valves on both heads and both measured with a digital caliper @ 2.02. Looks like the heads were cast a month apart,10069 and 11129. Part numbers were both 915's
Kind of odd dont you think??.. I guess anything goes at the factory back in the day...Lol..

O head.jpg


Z head.jpg


O Head date.jpg


Z Head date.jpg
 
HotRod20 said:
Picked up a set of 1970 340 engine heads from the cars original owner who decided to go with
a 392 Hemi conversion. He still has the block and crank. So while looking at the heads, I noticed one was a O head and the other was a Z head. I measured the intake valves on both heads and both measured with a digital caliper @ 2.02. Looks like the heads were cast a month apart,10069 and 11129. Part numbers were both 915's
Kind of odd dont you think??.. I guess anything goes at the factory back in the day...Lol..

View attachment 1715677339

View attachment 1715677340

View attachment 1715677341

View attachment 1715677342
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Could have been what it left the factory with but who knows for sure. Or sometime along the history of the engine, somebody changed a head. I had 2 different heads on my 66 273 but the odd head matched up with the oddball rod bearing with a later date. Something happened along the lone.
 
Normal.

Side note is i found a set of 318/273 heads that had an x where it would be shown on 340 heads. Can't remember the casting, been 20 yrs now..
 
I had a pair of TA heads J/O.
The Z is rather uncommon. I have heard of them but never actually seen one before.
 
I have a pair of Z heads I picked up years ago. I've heard all kinds of stories about them being prototypes, engineering mules, and how they're made of unobtanium. They're both stock, in great shape, with 2.02/1.6 valves. I can post some pictures if anyone is interested, like maybe Alaskan T/A? Paul.
 
70 Dart340,..Yes please post your Z heads, everyone would like to see I'm sure..:) Oh, and AlaskanTA, thanks for the reference post. Thats cool. I printed it and stuck into my "go to" binder.
Thanks
HR20
 
Sorry it took awhile PT after my knee surgery has slowed me down. I dug out my "Z" heads, and took a few pics on my phone. I bought them about 12 years ago at a swap meet in Spokane for $200. They pressure checked good, and I slipped a set of 2.02/1.6 stainless valves I've had laying around. I'll take more detailed photos if anybody's interested. I'll have my son help me upload the pictures I took, I'm old and suffering from CRS. I'm not really attached to them, so if a member here has to have them, I'll sell or trade them for any reasonably offer.
 
I'll try this. These are the real deal, nothing hokey. I'd like to know the history between the different castings. If someone here has a "museum" of the different 915 castings, I'll help them out. I know they're not gold, but a matched pair seems to be unusual. I'm open to all trades.

Resized_20210216_174810.jpeg


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Nothing spectacular about any of the letter heads, big or small valve. The differences are so minute, you'd likely not even see it on the dyno. I always chuckle when guys have an X or Z and think they have something rare and experimental. I think the Chevy boys started it with the X casting Chevy stuff. Also, almost every single Ford Cleveland, 351M and 400 have a series of X's cast in the lifter valley. You should hear those Ford guys talk. lol It's just another letter. That's all.
 
Back in the day I remember Hot Rod magazine getting a 273 power pak engine for a build up. Chrysler provided the motor. When they took the heads off the pistons on one side were the high compression version, and the one on the other side were lower compression flat tops. How embarrassing !!!
 
RustyRatRod said:
Nothing spectacular about any of the letter heads, big or small valve. The differences are so minute, you'd likely not even see it on the dyno. I always chuckle when guys have an X or Z and think they have something rare and experimental. I think the Chevy boys started it with the X casting Chevy stuff. Also, almost every single Ford Cleveland, 351M and 400 have a series of X's cast in the lifter valley. You should hear those Ford guys talk. lol It's just another letter. That's all.
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Apparently they're rare enough for you to not have a set! LOL, Paul.
 
70dart340 said:
Apparently they're rare enough for you to not have a set! LOL, Paul.
Click to expand...

Only because I don't have any small block stuff. Had some of all of them in the past. There's nothing rare about them at all.
 
No insult meant, just a small 3 Stooges eye poke. I know they're not worth any more than any other 915 head. They fell in my lap for cheap, and I bought them because I could afford them and they were different. I'm hoping some fanatic must have them and offers me a bucket full of cash, otherwise they'll keep their job as doorstops. Paul.
 
ECCB1CAC-7766-4BFE-84C7-9A460D45BE57.jpeg
2A447B86-EEB9-4130-90FE-6B8A5FD4F1F5.jpeg
6F306BB0-94B9-43AA-B0EB-EFEF9224AD0E.jpeg
Alaskan_TA said:
I'll post this again......

View attachment 1715677417
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Thanks @Alaskan_TA .

I have a 73 340 with a Z and O head. I was trying to find out how to decode the date on them. What this attachment you posted is telling us is that there are Z and O heads that are 1.88's and only the 1970 Z and O heads are 2.02"?
Did they make Z and O in 1973 or are these not original to the engine? The engine and trans are original to the car.

My heads have 3418915. Both the Z and O. The Z has a casting date of 10099 and the O is 10249. How is this transferred into a day, month, and year? Just trying to determine if they are 2.02" or 1.88".

Thanks.
 
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