Mine is 10.5 CR with a solid roller as close to the original spec LS6 cam as I could find.
So it is like a 70 LS6 Chevelle motor but with AL heads.
Or like a 71 Vette LS6 but with 1.0 - 1.5 pt more CR.
I have found 2 or 3 dyno runs and 480 HP is about dead one for an 11:1 LS6, and 455 HP for the 71 9.5:1 CR version

Mine might even be exactly like the 465 HP LS7 mentioned in the 70 C3 AIM. From what I can tell that one had the AL heads, 11:1CR and possibly the LS6 cam. That cam is hard to figure out from the AIM with the way GM spec'd cams. (I know the "commonly" available LS7 as an over the counter crate engine was a completely different beast. 12:1 CR, Iron heads and the L88/ZL1 cam or similar).

I have searched but found conflicting info on proposed the 70 Vette LS7.
If you have any good info please share!
Flat BB hood or L88 hood?
780 or 850 DP?
Flat intake or high-rise?
LS6 cam or L88 cam?
Anyone know?

There were several other BBs scheduled for that year as well, a 454 with Tri-power, and a 454 L88 version with 12:1 CR
One of them was coded an LT2 IIRC.
They all died a shortened model year death or due to the "engine" option deploliferation program. Too bad!

 

Where there two different LS7 BBCs? Corvette LS7 differs from the crate LS7?
Thats would be news to me! Do you mind to elaborte on that? Is it just head material? Or specs in cam etc.?

 

AFAIK, crate LS7's came with iron heads.
I also think that LS7's had their own specific camshaft, different than L88, different than ZL1. AFAIK.

I would also guess that the 1 or 2 cars that were tested, probably did have alum heads, and high-rise L88 intake manifold. I doubt it had a 750, probably the 850, one of those with the air flow diverters built into the carb for flow, mixture equalization. but just my guess.

 

Yes there were two LS-7s.

The planned / stillborn production line version, and the over the counter CE version. I have some specs on the widely sold CE version below. 3965775 part number. 12:1 CR & ZL-1 Cam. Long block no intake.


I have dug thru the 1970 GMHeritage site archives and the 1970 model year information has a lot of detail on the 1970 LS-7. It must have been "killed" very close to production, It is in the color brochures etc. with a flat hood too. It is VERY close to a Chevelle LS-6 with a couple of notable exceptions. They rated it at 10 more HP and 10 less TQ at the same rpms as a Chevelle LS6.460/490 at 5600/3600. Flat BB hood, pancake 569 manifold. L88 Aluminum cylinder heads, 780 CFM Holley, Vette exh manifolds, H.D. rods (big bolts), looser clearances, etc. The cam is the most interesting item. The L-72/LS6 cam was a single pattern cam. This one was a dual pattern cam. Very similar to the LT-1 Dual pattern cam which also came out that year, but possibly a few degrees more duration for the bigger motor. As far as I know I have never seen info on this cam anywhere else. Even the radiator is spec'd as being deeper than a LS-5 one. Chrome open element air cleaner, and an AIR pump. Only other 1970 engine to get an air pump was the LT-1. Car weight is listed as only 62 lbs heavier than an LT-1. That includes the larger rad, 11" flywheel, and rear swaybar.

The LS-7 cam Lift works out to a lobe profile exactly the same as the LT-1, Just higher ratio rockers 1.7 (BB) vs 1.5 (SB)
This cam is no where as near as radical as an L88 or ZL1 cam. Their lift alone is in the 560 to 620 range. Just like the over the counter LS7.

But it is not a L71 cam either. Below is the curious part about the cam. They list 347/359 dur LS-7 vs the 69 L-72/LS-6 at 316/302 (excluding ramps) The LT-1 is listed at 317/346. The LT-1 has been tested at .050" as 242/254 dur and the L-71 at 242/242 dur. So very similar at .050", except for the exh. The LT-1 254 exhaust is the same as the old 1963 single pattern 30-30 cam, or LT-1 exh. So I am inferring that this one has an intake in the 254s like the 30-30? That seems to jive. But then the exhaust is even bigger and matches no known Chevy cam except perhaps the 302 DZ off-road 140 cam. That exhaust has 346 & 264 dur and the .512 lift on a SB would be .580 lift on a BB, so that seems close but not exact. So I am going to "guesstimate" 254/264 dur @ .050" for an almost-Production LS7 cam. And .520/.550 lift. More than the L-71 / LS-6 cam, but certainly less than the 264/272 in the L88/ZL1/CE LS7 cams with .560/.620 lift..

The 70 Chevelle LS6 and the 71 Vette LS6 both ran the prior L-71 cam.




So now you have gotten me really curious about this LS7 option. Anyone know any more?

 

This is a 1973 cover sheet of the 3965774 crate engine

This is official GM Performance parts book dated 1993

And then there is the blueprint cam from crane, with a little different advertised duration:


ZL1/LS7 Reproduction cam from crane


As can be seen regarding lift: The 1973 sheet says 579/620 lift, the 1993 catalogue says 580/620, crane reproduces it with 575/615.

There are also small differences in advertised duration, but all share the ~580/620 lift split and ~262/272 duration split.

I got an isky cam in my Vortecpro 496 with adv. dur 284/294 and 238/248 @.050 duration and also a .578/.608 lift splilt.
Just now i realize that it resembles that ZL1/crate LS7 cam, just in a shorter duration version.
Better fitting to the lower rpm level of the 496 and also better in trapping the charge to not lose the already lower compressed charge (9.75 CR instead of 12.25 CR).
Its appears to basically be the "street version" of the LS7 crate engine: pump gas, good manners, high vacuum, low end torque, hydraulic roller
The rest is the same: forged rot. assembly, 4-Bolt mains, Iron heads, open chambers, 2.19/1.88 valves.
Differences being that its stroked, internally balanced and using ported Oval ports instead of stock rectangular ones..
Seems like Mr. Jones orientates himself in the very best engines (ZL1/LS7)... but somehow that doesnt surprise me ^^

 

Your 238/248 should be a great street cam. Or street/strip.
It's very similar in duration to a stock LS6 cam, But more lift.
It's no joke that Mr Jones knows what he is doing.
From what I have heard the oval ports seem to make more power on a street engine, they keep the airflow velocity up.
AJ Rothm has a 496 with very similar cam specs to yours, with heavily Jones ported ovals, and it makes 650HP and runs 10.50

 

You need to work on the heads some more.

 

I am glad you chimed in. As far as I know they are 100% stock and do not look to have been ported at all. They have a good multi-angle valve job is all.
I was however anticipating a little more out of this build.
Any recommendations on what is possible?

 

Think AJ went to a solid roller may have been last yr?
Thats a good combo he has, driveable too. Need to get a BB sometime...sure miss that torque

 

Here is our latest stock restoration type build if you’re interested...



This is a real deal numbers matching 427/435hp 67’ convertible. We just went through the motor, built exactly to stock specs besides the cam/lifters. Even used the original 11.0-1 dome pistons. The only thing we changed was to a hydraulic roller so I don’t have to keep up with valve train maintenance. This is a pretty rowdy hydraulic roller. Should mimic the 435hp cam pretty well I think....

 

Yeah we changed mine a bit when Mark refreshed it back in 18’. It’s now a 248/258* hydraulic roller, but we have solid roller lifters on it, a low lash solid roller type deal. I like it, it makes a little more power, especially in the upper range. It peaked 500 rpms higher and carries it out longer.

 

I picked up a reproduction LS6 intake and wondered if having the divider cut down was worth the cost and how far should I go? Thanks such a great thread!

 

I would just leave it. It will help the TQ to keep the two halves separate. I know they did that on the L88s but that was before the days of good single plane manifolds. If you really want more HP you can gain 20-25 or so by going to a 67 style R-Port high rise. But then you'll have to lose the stock BB dome hood and go to a L88 hood.

 

Hey Leigh, did you see this LS6 engine on BAT?
Hard to believe someone would remove it from a '71 running and driving Corvette.

https://bringatrailer.com/listing/19...olet-corvette/

 

There is so much wrong with this......starting with no build sheet. How do you even put an engine like this out for sale with all of the info? This is very common on BaT and I for one think it shouldn't be that way......if you do not know what is in it, then you are just an "enthusiaist" bidding on garage art. Sad.

Jebby

 

The sad thing is that someone will buy it and think they can drop it in and go.

 

And you might be able to.....$10,000 gamble....
Kinda dumb.

Jebby

 

Some people have the $10,000.00 to gamble, some of us don’t and are smart enough not to take that gamble.

 

Well what I see:

• Wrong heads. These are 842 closed chamber 68-69 heads. Not correct. Should be 074 open chambers. No "square plug"
• Block pad stamping looks incorrect. No broach marks, no partial vin, letters much too even, pad way too smooth.
• Valves covers could be correct versions but are on backwards. OTOH they might be 72 covers.

Run Forrest Run!

 

I do not like 842 heads at all, only used on a correct numbers type build. I have a 1969 L72 COPO Yenko 427 going on the dyno Friday.