LS7 Head Info Needed

[rszmjt]

OTC Crate LS6 engine assemblys, got the cast iron OTC crate LS7 Open Chamber head installed i think mid to late 80,s . I heard that GM did this to lower the 11. to 1 Compression to around 9.6 to 1 because of piston damage because of diminishing poor fuel octane rating.
The casting number is 6272990 for the LS7 Cast Iron open chamber heads. I personaly have taken apart a few later model LS6 crate engine assemblys and they had the LS7 open chamber head.

Hope this Helps.

[mockingbird812]

Here is the info I gathered from the heads that I looked at last night:

* Casting # (both): 3994026
* Casting date (both): E 17 71
* "HI PERF" cast on both
* The Pass. side head had a hump cast in the casting flash line. The Drivers side head did not.

Colvin's Chev. by the Numbers reports that the application was for a 1971 Chevelle 454/425HP. Also there is not a note about a characteristic casting flash line feature (i found a hump on the drivers side head). I thot the only application for that cu.in. / HP combo was for the 1971 Corvette LS6?

Sam

[Pantera]

According to Mor-tec that head is not a LS-7

Here is what they show.

3994026 71 rect OPEN '454 LS6, 118cc chamber

Is that a alum or steel head. They don't say which one it is?


Pantera

[mockingbird812]

Yes, I realize now they are not LS7 heads. They are iron. Any comments on the hump on one of them or the applcation (by model) of these heads?

Sam

[Pantera]

Unlike a SB Chev, I know of no "hump" on the outside of a BB head, that will help id it as something special. I think you may be thinking of the way to ID a small block chev head by the different casting on the front of the heads.

It sounds like those are a desirable date coded Chevelle '71 LS-6 head. I bet someone would be interested in them, if you don't want them.


Pantera

[COPO_Anders]

The 1970 Chevelle LS-6 used iron heads. In 1971 the LS-6 was only available in the Corvette. It used aluminum heads.
I have learned that they took the ZL-1 open-chamber aluminum head and used it on the LS-6 short-block with close-chamber heads to lower compression. The very last Corvettes got the new iron open-chamber heads that were developed in 70-71.

Anders

[GTO_DON]

The square port heads have 1 small hump in the front identifying as the high horse head.

[mockingbird812]

Pantera,

I realize that the casting symbol is usually found on SBs, but LS6 heads (291's) from 1970 had characteristic single humps in the casting flash line. The hump I was referring to is at the front of the head (facing the fan). It is a quick (although not conclusive) ID w/o looking inside the valve covers. I found it odd that Colvins does not call out this hump in the description of this head. One had it the other didn't. I just can't figure out why it has it.

Sam

[mockingbird812]

I guess I am a bit confused. Colvin's calls the heads I looked at the other night (3994026) as being for a 1971 Chevelle LS6 454/425. But there never was such a beast (at least in production). So if what COPO Anders says "In 1971 the LS-6 was only available in the Corvette. It used aluminum heads." Then what application did the heads I looked at have?

Sam