Big block
Tech Contributor
Joined: Aug 1999
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From: At my Bar drinking and wrenching in Lafayette Colorado
The most powerful C3 was the '69 L88 427. The most powerful 454 C3 was the 1970 LS7 at 465hp. In 1971 the high-horse LS6 454 was rated at 425 hp gross (LS5 was 365 gross). In 1972, power ratings were changed to net ratings, and the LS5 454 was rated at 270 hp. Since both the '71 and '72 engines were low-compression engines designed for low-lead or no-lead fuel, the actual power of the '71 and '72 LS5 engines was very close to the same.
Last edited by lars; May 8, 2021 at 12:50 PM.
Tech Contributor
Joined: Aug 1999
Posts: 14,370
Likes: 6,364
From: At my Bar drinking and wrenching in Lafayette Colorado
Why don't you just install a big block in your '76? It's no more work to convert a '76 to a big block than converting a '70. Finding an LS7 is not very probable: although the option sheet in 1970 showed the LS7 high perfromance option, and Chevy did develop the engine, there weren't any Corvettes actually built with the engine. The best you could actually buy was the LS5 at 390 horsepower. So any engine you're installing will be a custom built engine anyway, so it makes no difference what year chassis you start with nor what the horspepower rating was for any given year. You can build the engine with whatever power level you want - since you're going to "install a big block" in a '70, you're obviously not trying to find an original or correct car.
In 1971, only 188 of the LS6 cars were built, so you're not going to find one of those, either, making the highest power 1971 454 you're realistically going to be able to find an LS5 at 365 hp. You'd be better off finding a 1970 LT1 350 at 370 horse, or convert an existing base 1970 ZQ3 to the LT1 specs. It will run better than a stock '71 454.
In 1971, only 188 of the LS6 cars were built, so you're not going to find one of those, either, making the highest power 1971 454 you're realistically going to be able to find an LS5 at 365 hp. You'd be better off finding a 1970 LT1 350 at 370 horse, or convert an existing base 1970 ZQ3 to the LT1 specs. It will run better than a stock '71 454.
Last edited by lars; May 8, 2021 at 02:11 PM.
Tech Contributor
Joined: Aug 1999
Posts: 14,370
Likes: 6,364
From: At my Bar drinking and wrenching in Lafayette Colorado
No, but if you're converting a car to big block, as you stated you're doing, then it is no more work to convert a '76 than it is to convert a '70, '71, or '72.
I can't imagine what that conversion will cost you in France, and the level of difficulty in finding all the accessory parts for the conversion... I'd build a kick-*** LT-1 look-alike before trying to clone a big block car...
I can't imagine what that conversion will cost you in France, and the level of difficulty in finding all the accessory parts for the conversion... I'd build a kick-*** LT-1 look-alike before trying to clone a big block car...
Last edited by lars; May 8, 2021 at 02:18 PM.
Race Director
Joined: Jul 2015
Posts: 13,082
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From: SW Florida.
take your time. you may be better off finding one here in the states and shipping it. these cars are rare and pricey in europe. and restoring is even more pricey. even here where parts are easier to find. and time consuming. from 1 to 15 years is common. 1 year being the least common.
Last edited by derekderek; May 9, 2021 at 10:54 AM.
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Tech Contributor
Joined: Aug 1999
Posts: 14,370
Likes: 6,364
From: At my Bar drinking and wrenching in Lafayette Colorado
Some good info about the high-horsepower 454 engines can be found in this article:
https://www.spokesman.com/blogs/autos/2015/jul/31/collector-car-corner-solving-chevy-ls7-454-engine-mystery/
https://itstillruns.com/gm-1970-ls7-454-specs-7617778.html
Lars
https://www.spokesman.com/blogs/autos/2015/jul/31/collector-car-corner-solving-chevy-ls7-454-engine-mystery/
https://itstillruns.com/gm-1970-ls7-454-specs-7617778.html
Lars
Last edited by lars; May 9, 2021 at 10:59 AM.
