1970 Chevrolet Chevelle SS LS6 454 ? The Apex
By Pete Dunton
http://www.ericpetersautos.com/home/...3&Itemid=10684
Back in 1970 things looked great. The muscle car craze, which the 1964 GTO started, was in full swing. For 1970 horsepower and displacement were up, and there was a muscle car to fit everyone?s taste from all the different auto manufacturers. Unfortunately high insurance costs and legislative action were catching up with the muscle car. The low-performance era was right around the corner, and by 1975 performance in most cars would die.
Since its first model year -1965, the Chevelle SS had grown in popularity. By the late 1960s, the Chevelle SS with its strong faithful following was one of the more popular muscle cars. For 1970 even better things were in store for the Chevelle SS.
Due to an internal edict at GM, only full-size cars and the Corvette could have engines with displacements larger than 400 cubic inches. Because of the edict the 1965 to 1969 Chevelle SS only came equipped with a 396 CID big block V8. However by the late 1960s Chevrolet did get around this edict by allowing its Central Office Production Order (COPO) program to offer its full range of 427 CID V8s (including the L88) to customers who special ordered COPO Chevelles and Camaros. Though COPO allowed the production of some legendary 427 powered Chevrolet muscle cars, total production was very low. Only a few in-the-know racers and performance dealers like Yenko had used this program to get around the GM edict.
GM decided to lift the edict for the 1970 model year, and Chevrolet?s response was the introduction of the 454 CID V8 as a 1970 Chevelle SS option. The 454 V8 is a member of the Chevrolet Mark IV big block V8 engine family. The first Mark IV engine was the 396 V8, which first saw duty during the 1965 model year. In 1966 the Mark IV 427 V8 joined Chevrolet?s engine lineup alongside the 396.
For 1970, the 454 was not only new to the Chevelle SS but also to Chevrolet. The legendary 427 big block V8 was the largest displacement Chevy V8 in 1969. For 1970, Chevrolet decided to increase the 427?s stroke, which increased the displacement to 454 cubic inches. The 4.25 in. bore and 4.0 in. stroke of the 454 are numbers that bring a smile to any muscle car fan?s face. Chevy fans cheered the increase in displacement since larger displacement meant more horsepower and especially more torque.
Chevy provided two separate SS options for the 1970 Chevelle, the SS 396 (Z25) option and the SS 454 (Z15) option. With the SS 396 option one could chose from two Mark IV 396 CID V8s - the L34 (350 horsepower) and the L78 (375 horsepower). Chevy?s little secret concerning the 396 for 1970 was that it no longer displaced 396 cubic inches but rather 402. Chevy added a .030 in. overbore on the 396 block pushing its displacement up to 402 cubic inches. For some unknown reason Chevy decided it was best to call the 1970 402, a 396.
The SS 454 or Z15, a mid year option, gave the 1970 Chevelle SS buyer two powerhouse 454 V8s to choose from - the LS5 and LS6. The LS5 454 was rated at 360 horsepower in the 1970 Chevelle SS, but 390 horsepower in the 1970 Corvette. The reality is that the LS5 in the ?70 Chevelle SS is identical to the ?70 Corvette?s LS5. What we have here is a classic case of Chevrolet fudging horsepower figures.
The 1970 Corvette was slated to have a 465 horsepower LS7 454 as its top engine option, however Chevy changed its mind and cancelled the LS7 before it was produced. The 1970 Corvette was then stuck with the LS5 as its top engine option. The LS6 with its 11.25:1 compression ratio was factory rated by Chevy at 450 horsepower and a whopping 500 lbs/ft of torque. Helping to make this impressive power were solid valve lifters, a forged steel crank, TRW forged aluminum pistons, forged connecting rods, an aluminum intake manifold, and an 800 cfm Holley 4bbl carburetor. Getting the power to the wheels was the job of two available transmissions, a Muncie M22 ?rock-crusher? 4-speed manual and a 3-speed TH400 automatic transmission. A few different performance rear axle options were available for the 1970 Chevelle SS LS6, the most performance oriented being a posi-traction 4.10 geared rear axle.
On paper the LS6 was the most powerful production engine during the muscle car golden era. The Chevelle SS LS6 consistently obtained 13 second range ¼ mile times in magazine tests back in the day, which is extremely impressive when you consider a LS6 Chevelle SS has a weight of around 4,000 lbs with driver and fuel. The fastest LS6 ¼ mile time recorded by an auto magazine (back in the day) was in the November 1969 issue of Car Craft. Car Craft rocketed their stock ?70 Chevelle SS LS6 through the ¼ mile in 13.12 seconds at 107.01 mph. The 1970 Chevelle SS LS6 was also no slouch around the turns with its heavy duty F41 suspension which not only included heavy duty suspension components but also 14x7? wheels and F70x14 tires.
Even though it was a mid year option, the pricey 1970 Chevelle SS LS6 454 sold pretty well for a low production car, with 4,475 units sold (total ?70 Chevelle SS production was 62,372 units). Helping sales was the stylish new look of the Chevelle SS for 1970. The 1970 Chevelle SS was essentially a carryover Chevelle bodystyle that was first released in 1968, but did have a new front and rear end design. The new front-end styling provided a very muscular look that matched the performance under the hood. Even the chrome tipped dual exhaust added to the style of the ?70 Chevelle SS. The 1970 Chevelle SS 454 could be ordered in two body styles ? the 2-door coupe and convertible. The real news for the 1970 Chevelle SS, was the new optional ?cowl induction? hood (ZL2), which had a solenoid-operated flap that opened to provide cool air for the carburetor via the air cleaner assembly.
By 1970 most muscle cars were leaving the dealer lots loaded with many factory options, a far cry from the stripper muscle cars of a few years prior. The Chevelle SS LS6 with its many available options was no different. It was not cheap, it started at around $4,500 and the price increased as more options were added. Back in 1970 the average family income was around $10,000, making a Chevelle SS LS6 454 an expensive purchase for the average buyer however it was worth every penny.
The LS6 454 returned again in 1971 but it was only available on the Corvette, producing 425 horsepower. The horsepower loss was due to a loss in compression. All GM engines in 1971 suffered a substantial compression ratio drop in order to meet new federally mandated unleaded fuel standards. The party was now over, and the new race for auto manufacturers was to see how fast high performance engines could be detuned or eliminated. After 1971, the LS6 454 left and never returned. And soon after, the 1973 Chevelle SS became the last Chevelle to wear the SS emblems.
Every once in a great while a freak of nature occurs, something so different from the average or norm that it blatantly stands out. In 1970 the Chevelle SS LS6 was just that - a freak of nature. It was the complete apex of an era of skyrocketing horsepower ratings when it seemed like the sky was the limit. Looking back now, it?s quite clear the 1970 Chevelle SS LS6 was the Mount Everest of the muscle car golden era.
Nicely done, Pete - thanks!
I have never been lucky enough (so far) to drive a 454 Chevelle, but back in the mid-1990s, up at Hemmings Motor News' old car museum, I and a few others were permitted to take test drives of some neat old rides, one of which was a '69 SS 396 convertible. It wasn't as quick as I had expected it would be, but it pulled strongly and had a great sound. This car was an automatic - and did "chirp" the tires on the -12 upshift under WOT!
Eric,
I also never drove a LS6. But back before I bought my W72 TATA, I ran into a nice Chevelle SS LS5 454 Convertible for sale ($20K) at a used car lot. It was in excellent condition, and it performed very well. I would say in gross horsepower it made at least 390 horsepower maybe a little more. And the torque (500 lbs/ft) was phenomenal, it probably had the best low-end torque of any muscle car I have driven. With that said, the LS6 being even better in horsepower and having the same torque rating, I can only imagine how much better the LS6 performs.
Very nice commentary Pete. I am fortunate enough to own a 1970 Cranberry Red fully documented LS6. It has 4.10 gears and TH400 automatic. It has ALL its original sheet metal and drivetrain with 56000 miles. The car is awesome and quite frankly with the correct f70-14 wide ovals it really uncontrollable. Those tires just won't hook up and even if I roll out at 30-40-mph and then get on it, the tires and back end break loose and you can find yourself going sideways very quickly! I really only take it out 5-6 times a year to a local cruise night that is only 5 miles away. For my driver, I am lucky enough to have a 1967 Corvette, 427/390 convertible. It came with PS,PB, M20 wide ratio 4 spd and a 3.08 rear. It also has original side exhaust from the factory all backed up with the Tank Sticker and POP. The car is a pleasure to drive and will run 70mph all day long at 2650rpms on correct size radials. It is strange that no one ever questions the authenticity of the Corvette,but I get questions all the time on the Chevelle and that is why I had a show board made up with color copies of all the original GM docs including the original sales agreement and title.
Hi Skyman,Originally Posted by skyman51
Welcome to the site, first of all!
I especially enjoyed your comment about your Chevelle being essentially uncontrollable with the stock wheels/tires... I can relate to that. I have a '76 Trans-Am with a fairly built 455 and 3.90 gears; like you, I have to "roll it out" before getting into the throttle - unless I want to get sideways... but that is part of the fun of these cars, isn't it?
Nice 'Vette, too, by the way!
skyman51,
Wow sounds like you have a real rarity there. Finding an '70 LS6 Chevelle SS is becoming a very hard task these days but to own an original one with such low mileage, that's a real find and that car is certainly a keeper. I always loved the '70 Chevelle SS, it's looks in my opinion make it the best looking Chevelle SS ever produced. I remember seeing from time to time '70 LS6 Chevelle SSs at car shows, unfortunately now when I do see them at a show it's such a rarity. It's not surprising that due to their rarity and with the increase in people making '70 Chevelle SS LS6 tribute cars, that the authenticity of your '70 Chevelle is always questioned. Unfortunately on very rare cars these days it par from the course. A friend of mine owns an original '65 Shelby 289 Cobra - he recently had it in a big local car show. Every question he got was - Is that a real Shelby Cobra?
I have also known a few guys over the years that owned them, unfortunately most had to sell them for one reason or another. The '70 LS6 Chevelle SS is truly king of the hill, it did not get any better.
I test drove a 390 horsepower 427 (convertible) Corvette with sidepipes several years ago. It was a blast to drive the sound of the 427 emanating from the side pipes with the top down was by far the best V8 resonance I have ever heard.
BTW - Welcome to the forum board.
Also sounds like the '67 Vette is another gem, wow with factory exhaust, 4-speed, and a 390 horsepower 427 - that's one heck of a nice daily driver. I drove several years ago the
Back in 1970, I used to be a draftsman for a landscaper. he bought an El camino SS454 for his business. He never let me drive it alone, but I did get to a few times with him in it. I remember having some difficulty keeping the tires planted. that El camino had lousy weight distribution, compounding the problem. I remember sensing all this tremendous power and not having the vehicle to properly apply it. Later, I discovered it was easier to take off in second gear and keep from spinning the skinny shoes in back. <G>
1970 Chevrolet Chevelle SS LS6 454 ? The Apex
By Pete Dunton
http://www.ericpetersautos.com/home/...3&Itemid=10684
Gareebee,
Thanks for sharing your experience with the '70 El Camino LS6. Those were even more rare than the 1970 Chevelle LS6. I would imagine with the light pickup truck type rear of the El Camino and the tons of low-end torque and horsepower that hooking up those rear wheels was a monumental task. In fact I am sure even in second gear those tires were still spinning like crazy.
I love it!Back in 1970, I used to be a draftsman for a landscaper. he bought an El camino SS454 for his business. He never let me drive it alone, but I did get to a few times with him in it. I remember having some difficulty keeping the tires planted. that El camino had lousy weight distribution, compounding the problem. I remember sensing all this tremendous power and not having the vehicle to properly apply it. Later, I discovered it was easier to take off in second gear and keep from spinning the skinny shoes in back. <G>
1970 Chevrolet Chevelle SS LS6 454 ? The Apex
By Pete Dunton
http://www.ericpetersautos.com/home/...3&Itemid=10684
What could be better for a "business car" than an SS 454 El Camino?
America used to be a great country....
Thanks to all you guys for the nice comments. You are right my 67 vette is great,but right now I am just overwhelmed by the 70 Red LS6. I look at the car and then the original docs and I know I have a real keeper. I am thinking of taking it to Vette Fest in April. This year they are having a tribute to the 70 LS6 and there many cars already registered.
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