LS7 Head Info Needed

[mockingbird812]

Looking for info on LS7 heads. Heading to a friends house to look at a pair of supposedly LS7 heads mounted on an LS6 motor. I looked thru my Colvins but couldn't find info on these heads. My understanding was that, although there is folklore saying that LS7 motors made it into production cars, these were only available OTC.

Questions:

1. Cylinder Head Casting #?
2. Correct date range for heads (how long were they available)?
3. What are the external identifying features/marks i.e. casting flash line feature
4. Composition: Iron or Aluminum?

Any other pertinent info to ID these heads.

Thanks,
Sam

[Pantera]

Most people would not know a LS-7 if it bit them.
There is not one factory installed and delivered LS-7 motor documented. When some people see these they mistakenly think they have something special. Unfortunately, that is usually not what they have.

A correct head would be made of alum. If you go over there you want to look for a alum head ending in # 074 inside the valve cover. You will have to decide if you want that date head on your car. These heads are date coded on the inside so the date is not that important unless you are going to use them on a car that is correct for them which is quite rare.

These are the same head as used on the open chamber 427 ci. L-88, motor.

Pantera

[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

[John]

...are the "aluminium "074" LS7 heads ..the same heads they used on the ZL1..? http://www.yenko.net/ubbthreads/images/graemlins/confused.gif

[Pantera]

They show to use a 3946071 head on the ZL-1 motor. I think they have a couple of extra head bolts. I don't have much experience with the ZL-1. My car had a LS-7 and now has a LS-6 which is quite a motor.

[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. http://www.yenko.net/ubbthreads/images/graemlins/scholar.gif

[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

[Pantera]

This is what Mor-tec says about the usage of these heads

3946074 69&71 rect OPEN 'Aluminum, ''69 427 L88, ZL1, 118cc chamber & '71 454 LS6, "round exhaust port"

3994026 71 rect OPEN '454 LS6, 118cc chamber

6272990 70-up rect OPEN 454 service replacement, used on some MKIV crate engines, 118cc chamber

I just went out and looked at some heads that I have and after quite a while looking I think I see what you are refering to on the hump. I only have HP heads # 840 # 990 #208 here at the house and they all have the hump. It is about the size of the end of your finger?

I learn something everyday on here. I never noticed these before. I have no oval port heads to compare to.

If someone has a low HP motor check and see if this is different on your heads to see if this is correct?

[mockingbird812]

I guess I am a bit dense here. The application of these heads (3994026 '71 rect OPEN '454 LS6, 118cc chamber) are supposed to be for a '71 LS6 CHEVELLE, but there was no such animal. So what,if any, car were they used in?

Sam