I like to learn some specifics about the crate LS-6's that were offered over Chevrolet parts counters in the mid 70's. What blocks and heads did they use (casting numbers)? Were they equipped with an intake manifold or were they shipped without? Specificly which solid cam did they come with? I remember that later on (maybe in the 80's?), these crate motors were changed. It seems to me the compression ratio was lowered. But I'm specifly interested in the way they were set up in 1975/76.

Set up was comparable to the 454HO of today, but with solid flat tappet cam and adjustable valve train.

Rick,the LS6 crate motors use the LS6 solid cam (242 @ .050,.520 lift,114 LSA)
I believe the head castings where 990's too
They where shipped with the high rise square port aluminum intake

In the late 70's I saw more then a few LS-6 motors that were offered by GM as crate motors. I believe that the selling price at the time was $4300. The machine shop I worked for had three that were to be used for its track car. I think the class was F/A. The first motor was installed straight from the box and lasted halfway throught the first day. The other two were torn down and the main and rod clearances were not as close as you would want. After align boring and hand fitting new bearings the motors were good. Other new from GM LS-6's came through the shop with the same problems. The owner of the shop said that he thought that the motors were pulled from the assembly line due to weak lower ends. GM might have realized the warranty problem and removed them from the line before they were put in cars. When they were sold (1979-1981) rumor had it that they were a rare find someone had stockpiled in a parts storage. I do remember that they had the solid cam and intakes and were sold in the New York/ new Jersey area.

Tom S

My dad bought a brand new crate LS-6 when they came out, the motor burned up due to an oil leak, but I still have the manifold and carb, the manifold is an aluminum high rise, the carb is a Holley 780 double pumper.

Does anyone know what part number the engine was sold under in 75/76 or perhaps have some literature concerning this? I recall seeing magazine advertising from some dealers offering them. One I remember was an ad from Berger Chevrolet listing the crate motors they offered. I believe quite a bit of info was in the ad (which cam, which heads, which pistons and so on). That was a formative time for me (just turning 16) so I'm trying not to trust my memory too much here. I concurrrrrrrrrrrr with Mr. 4 Speed on the cam and heads though.

My best friend at the time had gorgeous stock 70' Nova SS350 with a new out of the crate LS-6 in it. This relatively tame engine vaulted the car to "Fastest Car In Town" status for at least 2 summers. The subject/legend of this car still comes up when I get together with the "old gang" and I would very much like to aquire the car and restore it to exactly the way it was for those 2 summers. I've even begun rat-holing some period correct parts that are now somewhat difficult to find in nice condition (shifter, gauges, etc.).

This is why I would like to research the engine specifics. I realize that assembling an exact duplicate of a 1975 LS-6 will call for better fuel than we have available locally. That's fine, as the car will be a "Saturday Night" driver only.

Was this car as fast as we remember? Probably not. Anyone else out there have any thoughts/facts/memories on this?

Rick,

I have a second edition Chevrolet Power Catalog that was published about that time and might have the part number information. I'll check it out tonight unless someone beats me to it.

I'm looking at a 6th edition 1988 book right now with the following listed:

366250 Engine Asm, 454 CID (Typical of 1970 Corvette) Less Exh manifolds, distr & clutch. Open chamber CI heads with Closed chamber design piston. 10.2:1 CR, LS-6

3965774 Engine Asm, 454 CID HD, Less intake manifold, distr & clutch. Open chamber CI heads, 12:1 CR, LS-7

Bruce

The "crate engines" LS6 platform came with #291 Closed Chamber Square ports. G.M.(TRW) forged pistons 11:1, pressed pins, and 7/16 rod bolts The cam listed is the right one. I still have 2 pair of the "over-the-counter" replacement brand new castings in inventory. Can't be used for "resto" due to build date of 1975. These 2 pair were strictly a dealer item. I also have access to the original cams. I just sold them a couple of days ago, to one of my customers. Thanks, Gary in N.Y.

Bruce, your post proves my memory about the 80's version having lower compression. I think the fact that the LS-7 did not come with an intake manifold was what made me think the LS-6 didn't either. I believe I "transposed" those two engines. Now I remember seeing a still in the crate 1978 LS-6 on Ebay a few years back and it did have an intake on it. So, anyone know a part number for the intake?

I see we have some different opinions on which cylinder heads would be correct, hhhmmm. I know the 291 was used in the 1970 LS-6 Chevelle, according to my "Chevrolet By The Numbers" book. I find no listing for the 990 though, and I had it in my head that this was the primary rectangular port head for the old crate motors.

Gary, what number do your over the counter replacement heads have on them and would they have been the same number that came on the crate engine assy?

LS6 heads are #291's, the 990's were never an option on the vehicle. G.M. did put the 990's, however, on a "pump-gas-special" crate motor, which happened to use the LS6 short blocks which Chev had laying around. They sold these in the 1980's somewhere. They were sold as 10.25:1 C.R. and at that time were compatible with the fuel during the period. The 2 pair I have are 291's and made (cast-up) in the middle 70's. Thanks, Gary in N.Y.

366250 454, 1970 LS6 ( Less manifolds exh., Distr, & Clutch) 450 HP., 11:1 CR

This was a new part added to the 3rd edition Chevrolet Power Book.

John

My 2nd edition Power book is dated 1976. Here are the listings.

3965774 Engine Asm. 454 HD, Partial (less manifolds, Distr. & Clutch)

3981820 Engine Asm., Partial 454 11:1 CR (1970 LS-6)

3970699 Engine Asm., Partial 427, L-88, Open Chamber Design

Bruce

Ah Yes, the 3981820. Wonder where I could find out for sure what the casting numbers are for cylinder heads and intake manifold on that engine assy. I wonder if it used the 3933163 intake manifold.

OK, now we're getting somewhere. A few of us have different memories about the specific pieces used on/in a mid-seventies era crate LS-6. I pose this question to you, my fellow Cheveller's:

How do I find out for sure specificly what big parts (block,heads,intake) this 3981820 used?

Any literature?

Perhaps one of you still has one still in it's crate so you could look at the casting numbers. SCHWING!

If I can get a hold of him, there's a guy local here Ron B., bet he has old info like that.