Dear Guys, something I've always wondered about...the horsepower rating for a 1970 Chevelle LS 6 car I believe is 450. The top of the heap Corvette in 1970 I think was 460. I'm just going by my long and poor memory here. I have also seen 465 in print. Were these the same LS 6 engine, or did the Corvette come with an LS 7? Thanks R. B.

The LS7 was never installed in a production vehicle.It was only available as a replacement eng.Their have been many different ratings on the LS6. I've heard and have read many times that the LS6 was under rated for insurance reasons and also heard of actual dyno tests showing closer to 500hp.

The difference between an LS6 and LS7 were the LS7 had 12.5:1 compression, full floating piston pins, boron steel rod bolts and top of the line rods.and used open chamber heads.
The LS6 had 11.0:1 compression, presed pins, knurled shank rod bolts and the same rod as the LS7 also both engines used the same mechanical cam used in the L78 high performance engines. .500in lift and 306 degrees duration.The LS6 used closed chamber large port heads.In 71 it got the open chamber aluminum heads.
In 1970 the LS6 was rated at 450/460hp and the LS7 was rated at 460/465hp

This may be more info than you were looking for but I hope it helps.

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71 Chevelle 454 best 11.92 @ 110mph 1.66 60ft
65 Elco 4x4
68 Firebird 400 4spd. Conv.

From everything that I've read, the highest hp rating for a factory installed engine belongs to the 1970 LS6 which was exclusive to Chevelles. It's compression ratio is 11.25:1. Crate motors are a different ball game.

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Mark
1970 SS454 LS6 (nom)
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"Those who would sacrifice their freedom to achieve a measure of 'safety' deserve neither freedom nor safety."

I'm pretty sure the LS6 was installed in both the Chevelle SS and the Corvette in 1970. I've read in more than one place that the 'vette had the lower horsepower numbers on paper. The reasoning was that the 'vette was a sports car, which already put it in a very high risk insurance category. Cheating the horsepower down a notch on paper was the General's way of getting around this.

The engine was the same in both vehicles, it was only different on paper.

BTW, Mark, I really like your sig. Wasn't that Franklin?

I thought the LS7 was the lower powered engine that came out later,

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My Elky Page (http://www.geocities.com/chadjlandry/index.html) Updated 7-21-00
"Think for yourself. Don't let popular opinion make your decisions for you."
Chad Landry
TC Member #643
'68 El Camino

The HP ratings bounced around for different reasons. The 1970 LS6 454 Chevelle is 450 Hp. The early 1966 L72 427 Corvette was rated at 450 Hp and some left the factory with the 450hp decal but then Chevy lowered it to 425hp with no modifications to the engine. The 70 454 Corvette was not released with the LS6 or the LS7. In 1971 the 454 Corvette was available with an Alu. head LS6 rated at 425HP. No cars left the factory with the LS7 according to what I have read.

Just think if we all were old enough to buy one of these cars in 1970 and knew what we know now. I would have gone to the bank, borrowed about 50K and bought a couple, amoungst others.

The LS-6 was rated 450HP which was a little conservative. But in my opinion the most conservatively rated engine was the L-88. Although it was probably a little harder to get and not many made, the original ones I've seen had a 430HP decal on them. One car magazine in 1970 was supposed to have dynoed an L-88 at 550-560HP. Of course the dyno was using headers instead of stock exhaust manifolds. FWIW http://www.chevelles.com/forum/smile.gif

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-Mark TC# 717
ACES #1641
1967 Chevelle SS396/375 (http://www.chevelles.com/showroom/1BadRat2)
1964 Chevelle 283/195
1975 Corvette 396/375 (http://www.chevelles.com/showroom/1BadRat1.jpg) Looks are very deceiving!

Just for information standpoint. My Buddy (passed away last Easter) bought an LS6 crate motor to put in his 68SS He had it dyno'd before he put it in. It came up at about 437 (saw the dyno sheet a while ago so I am going from memory but I remember it being in the upper 430's) He ran it like that for a while but wanted more so he pulled it, added a different cam, intake, and reworked the heads. (I think that was all but he may have changed the carburator too) After that was all done, he went back to the same dyno and it tested in the 530's or about 100HP gain. A freind of mine (also his freind) bought the car out of his estate so it is still around here and according to the new owner it is a screamer and he has 3 other SS's to compare it to.

So based on this experience, assuming the crate LS6 is the same as the production version, I would say the the 450 number is pretty accurate.

Just curious...has anybody ever dyno'd a bone stock LS6 and had similar experience???

Mytmouse


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67 SS 396 350HP 4 sp 3:55 Posi, Butternut Yellow w/Black Vinyl Top
70 SS 396 350HP 4 sp 3:55 Posi, Black on Black
68 RS Z/28 302 350+Hp? 4sp 4:10 Posi, Euro Red on Black
Mytmouse: A.K.A. Robert Stacho

Marc,
I WAS old enough in 1970 to have the chance to get an SS, but opted for the malibu 350 instead. Why? I drove my friend's '69 SS396 a few times and knew that bad things would happen if I bought one! http://www.chevelles.com/forum/biggrin.gif In fact, my friend kept his for about a year and traded it for a '70 Monte! At least I still have my Malibu. The SS was a nice car, but impractical for transportation. Most people back then had only one car, so it had to be a fairly practical vehicle. Oh, and 50K back then could buy you two nice houses PLUS a nice car! Ahhh, how times have changed! http://www.chevelles.com/forum/smile.gif

Mytmouse brings up a point that I've been wondering about. As far as crate LS6 engines go, did they come with the same heads (#3964291) or were they different. The reason I ask is that I've seen heads advertised as LS6 pieces that had casting number 3964290. I don't have my book in front of me but are those heads the ones used on the 71 425 hp versions? My other question is this: I have been told that all the LS6 crate engines were built for the 70 model year and most were manufactured in 69. I don't know how reliable that info is but assuming it is, why would an LS6 crate engine have lower hp open chamber heads that were used on the 71 LS6? Doesn't make sense.

BTW, thanks CJ. As a matter of fact it is Benjamin Franklin. Smoke any good fattys lately? I'm going on another cruise in March. Hopefully I can score some more Cubans to hold me over for a while.

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Mark
1970 SS454 LS6 (nom)
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"Those who would sacrifice their freedom to achieve a measure of 'safety' deserve neither freedom nor safety."

[This message has been edited by markcord (edited 12-07-2000).]

From the Sept. 2000 issue of Muscle Car Review:

A guy had found an original LS-6 Chevelle next to a gas station and snapped it up. It had 30,000 original miles and he had the motor freshened up, including a .030 overbore, everything balanced and blueprinted, with a new cam with slightly modified exhaust duration suitable for a closed exhaust system (no specs posted). Total timing advance 36 degrees, 110 octane racing gas, headers and flowmasters, no fan, stock distributer with MSD coil, Holley 750 vs. stock 780, two air filters stacked. Results were as follows (factory rating was 450HP at 5600RPM):

Run 1: 454.7HP at 6297RPM

Run 2: 465.7HP at 6300RPM

Run 3: 467.5HP at 6300RPM

Keep in mind that in 1970, HP ratings were net, comparable to dyno testing today.

Also, I read in another thread that Chevy typically tried to keep official HP ratings less than 1HP per cubic inch to keep from raising the ire of insurance companies. This would explain the Corvette change in rating for the L72 427 and the LS6 rating. I think the exception, the 427 L88 435HP rating was just to add 10HP to the L72 rating and differentiate it from the lower output motor. I agree the L88, ZL1, and LS7 would be the ultimate BB variation(I have driven a true L88 Vette with 4.56 gears and 4spd, WOW), but they really don't make the big HP unless they go OPEN exhaust. This is the only way to take advantage of the cams they ran. The one I drove had the headers gapped to help a little. When I hit the lotto, my next project will be a L88 car, not sure which yet, am considering a Vette, need to finish the 67 first!

Red Label

The 70 LS-6's had closed chamber heads, in the mid to late 70's you could not buy a crate LS-6 with cylinder heads installed. Just an assembled short block, no heads. Eventually chevy supplied LS-6 crate engines with open chamber heads, the same as the LS-7's had. This dropped the compression and hp rating to 425. Don't forget the LS-6 was a baby, idled almost smooth at about 950 rpm but was a screemer at WOT, the LS-7 454 and L-88 427 were racing versions of the "tame" factory installed big blocks. Extremely rough idles and in need of some steep gearing to move the cars properly. I read in a recent magazine a guy dynoed his fresh rebuilt, stock LS-6 and cranked out just over 450 hp. That was with the restrictive low rise intake, 780 holley, dyno headers/mufflers.

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http://msnhomepages.talkcity.com/yosemitedr/quintillis/index.html

Interesting interesting. So the 437 number on the dyno sheet I saw for the complete crate motor was about right for what appears to be a 425HP rated motor. I have seen the dyno sheets after he did all the rework and the 530+ number is accurate. Unforunately I do not know what cam he put in off the top of my head, but I am pretty sure he had the documentation for that when my other friend bought it. As I recall it was a roller cam and when he had the heads redone (ported/polished for sure but I am not sure about anything else) I think he put in roller rockers also. I am pretty sure he is running an 780 or 850 Holley on top of an Edelbrock Performer RPM manifold. Wish I knew more and could be more specific so one could see what it took to get to the 530+ number. Unfortunately my freind travels alot for work and i just can't seem to be able to hook up with him on the weekends but when I do I will post (even if it is a new post) everthing that I can get my hands on even the HP@RPM right off the dyno sheets hopefully

Mytmouse



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67 SS 396 350HP 4 sp 3:55 Posi, Butternut Yellow w/Black Vinyl Top
70 SS 396 350HP 4 sp 3:55 Posi, Black on Black
68 RS Z/28 302 350+Hp? 4sp 4:10 Posi, Euro Red on Black
Mytmouse: A.K.A. Robert Stacho

Mytmouse, I would say those dyno sheets are pretty close. It didn't take much to add 100HP to the L-78's, LS-6's and LS-7's. Like jmw said, a good exhaust system or open exhaust really woke up those engines.

jmw, I too have driven an L-88. It was in a Camaro. Not the original engine for the car but it was an honest to goodness factory L-88. Have mercy! You should have had to file a flight plan to drive that thing. And remember, the L-88's had 12.5:1 compression instead of the 11:1 of the L-78 and LS-6. The L-78 and LS-6 had the same cam(approx .520 lift) but the L-88 had close to .600 lift. I think it might have been split at .560/.580 if my memory serves me right.

MalibuJerry, how times have changed. http://www.chevelles.com/forum/smile.gif



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-Mark TC# 717
ACES #1641
1967 Chevelle SS396/375 (http://www.chevelles.com/showroom/1BadRat2)
1964 Chevelle 283/195
1975 Corvette 396/375 (http://www.chevelles.com/showroom/1BadRat1.jpg) Looks are very deceiving!

The LS-6 and LS-7 DID NOT use the same cam. The LS-7 grind was far more radical, and barely streetable, if at all.

The numbers. LS-6 cam: advertised duration 307/298 242/242 @ 0.050, gross lift .520/.520, lobe centers 114.

The LS-7 cam; Advertised duration 327/333, 262/273 @ 0.50, lift .580/.620, lobe centerlines 110.

For the doubters out there, my numbers are quite legit. Both cams are still available from GM and are in the GM Performance Parts Catalog. Check it for yourselves. Also, they agree with a 1989 GM catalog that i've got, so these are not recent changes.

For comparison, the L-88 cam specs as follows: 264/270 @ 0.50, with 112 lobe centers. I can't recall the lift, but it was only slightly less than the LS-7 cam.



[This message has been edited by Larry (edited 12-08-2000).]

There were different specs for the LS7 intended for production and the parts counter engine. Here is a part of an old post on the LS7 by Stan F. who has alot of Corvette info.

The LS-7, as many have mentioned, came the closest to actual production and was actually listed in most of the sales information for 1970. Changes and revisions to the LS-7 option were still being made as late as May 1970, so it is pretty obvious that Chevy was still trying to produce it this late in the model year. It was NOT a simply a 454 cid version of the L-88, in fact, it had much more in common with the 1970 LS-6 than the 1969 L-88. The production version of the LS-7 had an 11.25 to 1 compression ratio and would have used closed chamber aluminum heads. The camshaft was something of a hybrid between the solid lifter street cam and the first design L-88 cam with lift at .520/.550 and an advertised duration of 347/359. The LS-7 also used a distributor with provision for vacuum advance which is typical for a car intended for the street (L-88s and ZL-1s did not use a vacuum advance in Corvette applications). The LS-7 also configred to use a choke unlike the L-88/ZL-1. Finally, the LS-7 did not use a fresh air system that had been used on the L-88/ZL-1 previously. As far as horsepower rating, the sales and technical information that I have seen points to 460hp - the air cleaner label part number is 3969863 for those of you enterprising enough to track it down. As can be seen, the LS-7 intended for production was more a street engine than a race engine. As far as why it was dropped, the best explanation is a combination of cost and emissions. Chevy wasn't about to drop a lot of money into certifying a low volume engine that would not have a prayer of making it to production the following year.

As mentioned, the LS-7 available from the parts counter was an entirely different animal utilizing cast iron heads and was closer to the L-88 than the production LS-7 (which may be the cause of some of the confusion).

Hope this information helps.

Regards,

Stan Falenski

Thanks, Joe. I deliberatly stayed away from the LS-7 in my previous post because of the confusion. I remember several years ago(7-10?) the local Chevy dealer here had an LS-7 CRATE engine on their floor and it was basically an L-88 with iron heads, but with 454 CI. Seems like it had a 465HP rating from what I recall??

Wish I had bought a couple of those things. As I recall it had a $2899 price tag. Not too bad!



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-Mark TC# 717
ACES #1641
1967 Chevelle SS396/375 (http://www.chevelles.com/showroom/1BadRat2)
1964 Chevelle 283/195
1975 Corvette 396/375 (http://www.chevelles.com/showroom/1BadRat1.jpg) Looks are very deceiving!

1BadRat, my drive was in a 66 Vette. This guy was way into BBs, and this was 1979, 80. He had a garage full of blocks, heads, etc. All HiPo stuff. He talked me into buying a L-78 shortblock to hop up my 325HP Chevelle. He sold me a set of large port heads and the HiRise aluminum intake to complete it and man was I glad!! By the way, I think I remember getting the brand new from Chevy L-78 shortblock assembly for something around $850.00. Wish I'd bought 10 of them.

I rode in the Vette often and never even asked to drive it since I knew how much effort he had put into the car. He did hundreds of hours of body work and a friend did a great black paint job on it. He put a 67 Vette hood on it cause he liked the look better than a 66. It was a convertible and can you say Babe magnet??? Anyway one night he asked if I wanted to drive and of course I did. Banged gears into third then let off. The Vette tach needle must have been 6 inches long and I think was cable driven and that thing swept up to 7000 in the blink of an eye and bounced all around as I shifted.

I didn't know all the L88 specs then, but we both would ride out to the local airstrip together since he was running 12.5:1 and I was at 11:1. We'd put in 5-6 gallons of AVGAS, then mix it with premium, which we felt left us with about 100 octane. He was a stickler for detail and I remember him jumping for joy when he finally located an original correct GM Holley for the L88, so I am pretty sure it was true through and through.

If you're ever in LA (Lower Alabama) and see a black 66 Vette with Centerlines and a skinny blonde headed guy driving, watch out, he'll eat your lunch!!

Red Label