Tell me about these heads - 2658920 66-67 273-318ci

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KnuckleDuster

KnuckleDuster

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Any info or good sources for info?
Are these originally closed chamber?
Can anyone tell by the pics if someone added hardened seats?
Thinking about using these on a 318 I would put in a 85 truck.
Thanks!
 
These are closed chamber heads which is a good way to raise the compression ratio on a 273-318. They were only used on early 273's.
 
Those are 67 heads.

66 was 2536178...


But they are the smallest combustion chamber heads that will fit the small block and still have the later intake bolt pattern. Book spec is 57 cc's, mine measured at 63 cc...
 
If you put these heads on an engine whose pistons are .30" down in the hole @TDC you'll have around 9.1:1 CR and maybe a little more!!.

Treblig
 
They were used on late 66 273's but I haven't heard the transition date. If anyone has specific information on this, inquiring minds want to know.
 
Thanks so far. These came off a 67 Belvedere 2dr with a 318 I have the whole engine but no longer have the car handy, it's in GA on family property, from the history I know of the car, I'm pretty sure they came on it.
I was surprised to see the closed chambers, but wanted confirmation.
 
toolmanmike said:
They were used on late 66 273's but I haven't heard the transition date. If anyone has specific information on this, inquiring minds want to know.
Click to expand...

My book shows that the 64-65 273 head (Casting Number 2465315, 57-64.5 CC) was the first 273 production head. In '66 the 273 came with the 2536178 casting same CCs. Then in '67 Mopar changed the casting number to 2658920 but still had the same CCs. My book doesn't specify "transition dates", only years in which each casting was produced for that particular year's production.

treblig
 
66-67 273 or 318 heads. Closed chamber. No hardened exhaust seats that I can see from the picture. NHRA minimum legal cc is 57.3 In my experience it takes .040 cut to get the largest chamber to that cc. Therefore unmilled chambers should be about 65 to 63 cc. Very nice small port heads. 66 up heads used the standard Mopar small block intake bolts and angle.
 
Cool!
I've had this engine for probably 20 years, didn't realize there even was a closed chamber head used on 318's until I pulled the heads off. I thought maybe the had been milled. I got the whole engine for $50 from my Uncle.
Here's a pic next to some 80's 163's I also have for comparison. I was told the 163's have hardened seats? How can you tell by looking?

 
KnuckleDuster said:
Cool!
I've had this engine for probably 20 years, didn't realize there even was a closed chamber head used on 318's until I pulled the heads off. I thought maybe the had been milled. I got the whole engine for $50 from my Uncle.
Here's a pic next to some 80's 163's I also have for comparison. I was told the 163's have hardened seats? How can you tell by looking?
Click to expand...


I had my head guy put the hardened seats in when he did my heads.... They were definitely not in there from the factory... I had him port them and put 360 valves in them, and we always install hardened seats on the exhaust valves.

To see if it had hardened seats installed, you have to zoom in close on the exhaust valve and look for an insert pressed in for the seat, then they machine it for the valve after pressing in the seat. It may be hard to see sometimes if done as they are interference fit in the head.
 
KnuckleDuster said:
Cool!
I've had this engine for probably 20 years, didn't realize there even was a closed chamber head used on 318's until I pulled the heads off. I thought maybe the had been milled. I got the whole engine for $50 from my Uncle.
Here's a pic next to some 80's 163's I also have for comparison. I was told the 163's have hardened seats? How can you tell by looking?
Click to expand...

All 75 up heads had hardened seats. Your 80's heads would be induction hardened, not hard seats pressed in.
 
Funny that someone reacted to this old post today, I just started cleaning these heads up to get them ready for when I port them this past weekend.

20240515_172920.jpg
 
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