273 Cyl Head Differences

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waddney

waddney

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I've been chasing a set of heads for my build with the casting number 2658920, I have found a set casting number 2465315, are there
any differences between the two, I was told that the earlier style uses different intake bolts (smaller diameter) and at a different angle,
the heads are a distance away so I don't physically have them to compare
 
waddney said:
I've been chasing a set of heads for my build with the casting number 2658920, I have found a set casting number 2465315, are there
any differences between the two, I was told that the earlier style uses different intake bolts (smaller diameter) and at a different angle,
the heads are a distance away so I don't physically have them to compare
Click to expand...

920 heads are 67 heads that use the standard 3/8 intake bolts that have a 9/16" hex head. 315 heads are typically 64-65 heads that use 5/16 intake bolts on a different angle that have a 1/2" hex head. However I have a set of 315 castings that use the standard 3/8 intake bolts that have a 9/16 hex head. Not sure what was going on but appear to be virgin OEM heads. They even have the steel shim head gasket witness lines from the original .020 thick 273 head gaskets. Best advice I can give is to ask what size bolts those heads are tapped for. There are 66 heads that will interchange with the 920s and you can also use any 318 heads with a slight loss of compression.
 
Do not try to use the 64-65 heads with a 66-up intake. They will not seal the valley and it will foul the valves with oil instantly. BTDT. Hold out for 920s.
 
Look for 920s. 68-69 heads (675) will work too with a touch less compression but potentially higher flow.
 
waddney said:
I've been chasing a set of heads for my build with the casting number 2658920, I have found a set casting number 2465315, are there
any differences between the two, I was told that the earlier style uses different intake bolts (smaller diameter) and at a different angle,
the heads are a distance away so I don't physically have them to compare
Click to expand...
If you have the '66 and later intake, for sure use the 920's unless you want a bit lower compression with the 675's that came on the '68-71 318's. The 315's also were a bit more prone to cracks too.
 

66fs said:
920 heads are 67 heads that use the standard 3/8 intake bolts that have a 9/16" hex head. 315 heads are typically 64-65 heads that use 5/16 intake bolts on a different angle that have a 1/2" hex head. However I have a set of 315 castings that use the standard 3/8 intake bolts that have a 9/16 hex head. Not sure what was going on but appear to be virgin OEM heads. They even have the steel shim head gasket witness lines from the original .020 thick 273 head gaskets. Best advice I can give is to ask what size bolts those heads are tapped for. There are 66 heads that will interchange with the 920s and you can also use any 318 heads with a slight loss of compression.
Click to expand...
Interesting that you mentioned those 315's with the 5/16 intake bolts. I thought I was the only one who ran across those and had many arguments about them until I physically showed them to a few people. Not only that, but, I also had a pair of 920's with the 1/4 intake bolts! There must have been both rough castings produced, or, at least both co-existed on the shelf at a certain time before the final machine work was done.
 
really appreciate the info, I'll see if I can get old mate to measure the bolt diameter before I take the trip, I have two sets of 675 heads I was under the impression they were the same casting as 920 heads, why are they potentially better with porting?
 
I had someone offering me some truck heads with the centre water port, how do these compare ?
 
Unless you're racing, or have a high lift cam, the rotators won't hurt anything. They actually help valve life. The valves are sodium filled also.
 
toolmanmike said:
They require the truck intake I believe which you don't want. They will have valve rotators which you don't want. Let's see, what else?
Click to expand...
Sodium filled exhaust valves with much larger stems and bastard size guides.
 
The heads ended up being the earlier style, which were no good to me, but he had a set of J heads that I picked up off him
 
waddney said:
The heads ended up being the earlier style, which were no good to me, but he had a set of J heads that I picked up off him
Click to expand...

Make sure you check valve clearance to the block if they have 1.88 intake valves and if they are 2.02 you will probably need to notch the block. Also use a 340 or 360 intake to take advantage of the bigger ports. You should also mill the heads, block and intake side, to keep your compression up.
 
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