From top to bottom...What parts make up a true LS6 engine?

 

Might have forgotten something but basically,

Open air cleaner
Holley 800 cfm
Transistor ignition system
Deep grooved forged alternator pulley
Aluminum intake 3967474 or 3963569
Aluminum heads 3946074
Solid lifter cam 3863143, .520 lift/242 duration
9:1 forged pistons
Forged rods
Forged crank
Block 3963512 drilled for 4-bolt mains
Higher pressure oil pump

 

sly vette,

Interesting question, since there are two different engines using the RPO code LS-6 or LS6.

The LS-6 as engineered for the 1970 model, in which the Chevelle became the recepient was a closed chambered iron headed, 4 bolt main configured block with aluminum intake and 780 cfm Holley carbureted, with conventional points ignition system and log style exhaust manifolding, using 3 different air cleaner assemblies.

The LS6 as engineered for the 1971 model, was a direct derivative of the LS-7 engine slated for the 1970 model year and the recepient was the Corvette model. This LS6 version incorporated several components from the LS-7 engine, to include an open chambered aluminum head with recontoured intake port floor and re-shaped exhaust ports to better adapt for header match up. An aluminum dual plenum intake manifold flanged for a Holley 800 cfm 4bbl carburetor with the intake runners lowered to achieve adequate clearance for the stock configured big block hood, since GM stylists and marketing did not like the ZL2 ducted hood with the new lines of the '70 body. A magnetic pulse transistorized ignition was used, along with the heavy duty dual plate clutch assembly.

 

No aluminum heads on either a LS6 or a LS7. No LS6`s or LS7`s for Vettes. LS7`s had 12.25 compresion ratio pistons with iron heads an the 580/620 camshaft and also was strictly a over the counter service package engine with no intake, clutch, bellhousing, distributor, carb, waterpump, starter, nor exhaust manifolds. ...Not to be confused with the new aluminum engines with the same letters....

 

And the LS5???
Or better yet,What was the designation of the '74 454 MARK IV with open chamber oval port iron heads...118cc I think. The eng I have came out of a Camaro. 4.25 bore and a 4.00 stroke. Also appeares to have flat top dual relief pistons and 2 bolt mains. Don't know the specs on the cam,nor can I measure it due to the fact that it was wiped out when I got it. The pistons appear to be stock and the rods are forged.
Mark

 

There was a LS6 for the 71 Vette. You could get it by itself or the very rare ZR2 option. According to my books it used aluminum heads also.

 

mark....the LS5 was 70,71,72,and 73.I have a 72 BB coupe out back here.The LS4 was for 74,and the last year for the BB to be in a vette.The horse power came waaaaay down for the vette,and everything else for that fact.
You would have to look at the front pad to see what the engine came out of that you have.You are going thru it all anyways,so it doesn't really matter,and it won't be stock.You don't have to go crazy on a build to have a respectable fun street car,bud.
I took the 69 BB 390 horse out in the neighborhood yesterday afternoon,and w/stock exhaust,and needing a tune up....it will grab 3 gears w/out a blink.That's respectable for a toy.
Off to work I go on your ride.........

 

70-72 LS5
Open air cleaner (70E)
Dual snorkle air cleaner (70L-72)
Q-Jet
Iron intake
Iron heads
Hydraulic cam .461/.480 lift, 214/218 dur
10.25 cast pistons (70)
8.5 cast pistons (71-72)
Cast rods
Forged crank
2 or 4-bolt block



73-74 LS4
Dual snorkle air cleaner with cowl induction
Q-Jet
Iron intake
Iron heads
Hydraulic camshaft .440/.440 lift, 210/210 dur
8.25 cast pistons
Cast rods
Cast crank
2-bolt block





We are talking Corvettes here, you are talking Chevelle. True, the Chevelle LS6 and the over-the-counter LS7 crate engine had iron heads, but the 1971 CORVETTE offered it's own version of the 70 Chevelle LS6 and this engine had ALUMINUM HEADS and this is FACT. The planned 1970 production LS7 Corvette was to also use ALUMINUM HEADS unlike the Chevelle LS6. One LS7 Corvette was built and shown to the press and pictures in the magazine article clearly show the aluminum heads. Again, the engine in this car was NOT the over-the-counter LS7, but was a Corvette-only version that had 11.25 compression, ALUMINUM HEADS, and a unique solid lifter camshaft of around .520/.550 lift but Chevy killed it before it could go into production. Zora wanted to get some version of this engine released for 71 and that is where the Corvette-only 1971 LS6 came from (no other car used the LS6 in 71). The compression got dropped to 9:1 to comply with GM's mandatory 91 octane policy and the camshaft was swapped back to the old L72 (same as the 1970 Chevelle LS6) and it was released.

 

Can you answer me this...What eng came with the 781 heads? That is what I have.
Mark

 

Used on the 74 Corvette and Mortec says

336781.....73-85...oval port...OPEN Chamber...454, 118cc chamber, 256/114cc ports

So must have been also used on other passenger cars 73-75 and then trucks from 76-85.
Google "336781 heads", lots of info about them.

 

188 ls6 cars were made in 71, 12 zr2 cars. Carburator was a holley 3310-1 style 4150 with dual metering blocks, downleg boosters, vacumm secondary's with 72/76 jetting and a 6.5 power valve. heads were 074 and the intake was a 569. The 569 is the only GM rectangle port intake that will fit under the c3 big block hood, unless you have an L88 hood

 

I had a red 70 coupe that had the CRR (70 450 hp TH400) Chevelle motor. The steering was worn, and I couldn't get the brakes bled properly. It had Hedmans and turbos. It ran crappy until my mechanic brother replaced the throttle cable, I replaced the droopy timing set, and rebuilt the TH400. Then, this car was faaaaasst... I did not know that the motor was worth more than the car. I was looking for Vippers. 6 mpg or there abouts... I sold it for about 8 grand and bought my 68 427 Roadster. I never understood why that car was so fast.

 

The 70 chevelle LS6 was 11.25 to 1 compression with iron heads. Needs 100 plus octane fuel. The 450 HP rating was very conservative. Chevy rated these @ 450 HP @ 5600 RPM and they were detuned and ran iron manifolds and full exhaust. The HP rating was for insurance purposes. These pulled well past 6500. Close to 600 HP with headers. Built one 3 years ago.

 

did you build it at that high compression?

 

Yes. Built to factory specs. Except a .030 overbore and block align bored. Dimple rods, 6226 crank, 11.25 to 1 TRW pistons. 291 rectangular port heads, Crane factory blueprint cam, NOS carb, 569 intake. Engine block, heads were all three dated E-5-70. All other date codes within 5 weeks. Block pad was blank with original broach marks. I Sold it. It is going in a 1970 LS-6 Vert in Missouri.