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I recently acquired a 73 Grand Am with a non-matching 455 of unknown origin. The block appears to be a '70, the heads are marked "X", which comes up as 73-74 455 SD, although everywhere else the SD heads should be code "16" I believe?
Anyhow, they appear to be round port heads (connected to 478141 header style iron exhaust manifold), screw in studs and pushrod guide plates.

Any help identifying these would be appreciated...Mr. Google is not much help here!

Thanks,
Tom
 

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Several things come to mind,
-Need to look at the casting of the cylinder head above the #1 exhaust port. Any evidence of grinding? Or a small stamped 722 or 614? If so, you have a pair of Service Replacement RA IV heads. The heads could also be pair of 197 '71 HO heads, will have a small raised 197 above the large 1 cast into the #1 exhaust port. Will also have an X cast to rh of the bolt hole in the center exhaust port.

-SR 614 RAIV heads were first Pontiac castings ive ever noted cast right after the Fall of 70 UAW strike (near 60 day strike from Sept 15- mid Nov of '70). Had a pair many years ago cast by Pontiac central foundery in late Nov of '70, they were also the first externally dated round port heads. SR 614's should have the X on the center exhaust port to the rh of the bolt, will also have the large C on the rear exhaust port, same as '71 197's.

-above the center exhaust port area, to the left hand side in the recessed area, is there an alphanumeric date code? Example L020, L080, A080? Those 3 dates are the most common dates on late style '71 455 HO heads, 197's. Early style '71 197's had no casting date. Have original sets of both styles on my '71 cars.

-Original '69 & 70 RAIV heads as well as early 197's did not have a cast date on them externally. Originals had a date cast, but it was under the valve cover where the head was machined for the exact center head bolt. When the machining took place, the majority of the date casting disappeared.

-All late roundport heads ('72 7F6 heads & '73-74 SD heads) have a fitting or temperature sending unit screwed into the side of the head.

By examining the heads carefully with above info should be able to narrow down what you have.

The exhaust manifold casting # is '70-72 driver side roundport Am struggling with noting exact date code, am on an old IPad.

Would be interested in the casting date of the block if you don't mind sharing. Thanks!
 

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Wow Pinion, that's some really helpful info. There are numbers over the #1 exhaust port but I did not jot them down...I'll try to take a look tomorrow. I'll bet it's the '71 HO you mentioned, because that exhaust manifold comes up '71-72 455 HO.
The block number is 9799140, which comes up as '70 455, didn't make out any letters, and I'd be interested to know if it's a high compression engine or not?

Thx, Tom
 

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Found a pic...197 over #1 e port.
Question: for this combination of parts (no idea what cam), this 455 doesn't make the power I would expect it to, and favoring originality, I was planning on dropping a nice running low mileage 400-4bbl I have from a donor '73 Grand Am into this car. Would there be any benefit using these heads on the 400? Maybe they would be a better item to sell?

Thanks,
 

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Tom on the 197's they work best on a 455-469. On a flattop piston, zero decked, .030 400 ones looking at low 7-1 static CR. Some guys have milled .060 -.080 off these heads, but that limits surfacing again & kills the value. On the block, the very earliest '71 HO blocks used late '70 production 9799140 casting blocks. Pm sent.
 
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