71 Chevelle LS6

[Clem Z.]

the GM/NHRA specs for the 71 corvette 454

are 10.1:1 CR,103.1 CC aluminum head,.095 piston dome,13.10 CC dome volume

[Joe L.]

Re: the GM/NHRA specs for the 71 corvette 454

clem------

Now that makes me lose some faith in NHRA specs. The cylinder head used for the 1971 Corvette LS-6 was an open chamber design and of, nominally, 118 cc chamber size. GM never made an open chamber, big block head with a combustion chamber as small as 103 cc.

[Joe L.]

Re: the GM/NHRA specs for the 71 corvette 454

clem------

Now that makes me lose some faith in NHRA specs. The cylinder head used for the 1971 Corvette LS-6 was an open chamber design and of, nominally, 118 cc chamber size. GM never made an open chamber, big block head with a combustion chamber as small as 103 cc.

[Clem Z.]

Re: the GM/NHRA specs for the 71 corvette 454

they list the head # as 074,077 and 401 but they listed the CCs the same as the cast iron head. . must be a screwup,NHRA needs a proof reader. i never noticed it was wrong.

[Clem Z.]

Re: the GM/NHRA specs for the 71 corvette 454

they list the head # as 074,077 and 401 but they listed the CCs the same as the cast iron head. . must be a screwup,NHRA needs a proof reader. i never noticed it was wrong.

[Joe L.]

Re: the GM/NHRA specs for the 71 corvette 454

clem-----

The '074' was the original head used for 1971 Corvette with LS-6. The '077' and '401' are replacement heads that are NHRA legal for use on a 1971 Corvette LS-6, but they were never used on a PRODUCTION engine, LS-6 or otherwise. The '401' is, by far, the best of them and anyone using one of the others when they can get away with the '401' must be nuts. However, the '401' is only legal if it's GM PART #12363408. Other heads are made from the '401' casting, but none of them are NHRA-legal. All of these heads have, nominally, 118 cc chamber size.

In any event, in this case, they got both the combustion chamber size and CR wrong. However, perhaps that happened because they starterd out with the wrong combustion chamber size and computed the compression ratio themselves. That would result in their arrival at a CR number that's higher than actual and that's just what they've got.

GM advertised the compression ratio of the 1971 LS-6 as 9.0:1 and I believe that's about what it really is. It may even actually be slightly lower than this figure.

[Joe L.]

Re: the GM/NHRA specs for the 71 corvette 454

clem-----

The '074' was the original head used for 1971 Corvette with LS-6. The '077' and '401' are replacement heads that are NHRA legal for use on a 1971 Corvette LS-6, but they were never used on a PRODUCTION engine, LS-6 or otherwise. The '401' is, by far, the best of them and anyone using one of the others when they can get away with the '401' must be nuts. However, the '401' is only legal if it's GM PART #12363408. Other heads are made from the '401' casting, but none of them are NHRA-legal. All of these heads have, nominally, 118 cc chamber size.

In any event, in this case, they got both the combustion chamber size and CR wrong. However, perhaps that happened because they starterd out with the wrong combustion chamber size and computed the compression ratio themselves. That would result in their arrival at a CR number that's higher than actual and that's just what they've got.

GM advertised the compression ratio of the 1971 LS-6 as 9.0:1 and I believe that's about what it really is. It may even actually be slightly lower than this figure.

[Clem Z.]

Re: the GM/NHRA specs for the 71 corvette 454

i get the specs off of the NHRA website http://nhra.com/tech_specs/engine/index.html i remember back in the 60s when i did drag race tech inspections the car companies sent out the spec to the racing assocation and they were to be what the car companies listed with the AMA. i guess some mistakes have been made during the updates on the website

[Clem Z.]

Re: the GM/NHRA specs for the 71 corvette 454

i get the specs off of the NHRA website http://nhra.com/tech_specs/engine/index.html i remember back in the 60s when i did drag race tech inspections the car companies sent out the spec to the racing assocation and they were to be what the car companies listed with the AMA. i guess some mistakes have been made during the updates on the website

[Joe L.]

Re: the GM/NHRA specs for the 71 corvette 454

clem-----

I have found a lot of mistakes in the AMA specs. It's the last place you'd expect to find errors, but errors there are. In fact, I've found so many errors in these specs that I no longer have any real confidence in them, at all.

[Joe L.]

Re: the GM/NHRA specs for the 71 corvette 454

clem-----

I have found a lot of mistakes in the AMA specs. It's the last place you'd expect to find errors, but errors there are. In fact, I've found so many errors in these specs that I no longer have any real confidence in them, at all.

[Clem Z.]

Re: the GM/NHRA specs for the 71 corvette 454

i guess in the days before computers things were more accurate because i never had a problem on any teardown using the auto company supplied specs.

[Clem Z.]

Re: the GM/NHRA specs for the 71 corvette 454

i guess in the days before computers things were more accurate because i never had a problem on any teardown using the auto company supplied specs.

[Tom P.]

Re: the GM/NHRA specs for the 71 corvette 454

And I'm fully aware of the differences between the 70 Chevelle LS6 and the 71 Vette LS6 (heads, compression, etc). I was simply pointing out that the Chevelle folks say there was no LS6 available in 71, but there was an LS6 (many of them and well documented) in the 70 Chevelles. And that there was not an LS6 in the 70 Vette but yet there was an LS6 in 71 for the Vette. Too bad the LS7 never made it either. Actually, its too bad that a lot of things never made it to production.

[Tom P.]

Re: the GM/NHRA specs for the 71 corvette 454

And I'm fully aware of the differences between the 70 Chevelle LS6 and the 71 Vette LS6 (heads, compression, etc). I was simply pointing out that the Chevelle folks say there was no LS6 available in 71, but there was an LS6 (many of them and well documented) in the 70 Chevelles. And that there was not an LS6 in the 70 Vette but yet there was an LS6 in 71 for the Vette. Too bad the LS7 never made it either. Actually, its too bad that a lot of things never made it to production.