1972 LT1 intake manifold torque

[Jerome P.]

Is the torque for the LT1 aluminum intake manifold the same as the base 350 intake manifold? That is 30 ft-lbs.

[Alan S.]

Re: 1972 LT1 intake manifold torque

Hi Jerry,
I looked in the 71 Chassis Service Manual and it too indicates 30 ft/lbs. It doesn't differentiate for aluminum manifolds.
Regards,
Alan

[Jerome P.]

Re: 1972 LT1 intake manifold torque

That is what I also found. Thanks for looking and your time. I just wanted a confirmation that I was not overlooking something.

Thanks Again.

[Joe L.]

Re: 1972 LT1 intake manifold torque

That is what I also found. Thanks for looking and your time. I just wanted a confirmation that I was not overlooking something.

Thanks Again.

Jerome------


Your application did not originally use flanged head bolts but they should have!

[Jerome P.]

Re: 1972 LT1 intake manifold torque

Thanks for the comment, Joe.

Curious, you comment because the LT1 has an aluminum intake and a flanged head bolt will distribute the pressure more evenly. Correct?

[Joe L.]

Re: 1972 LT1 intake manifold torque

Thanks for the comment, Joe.

Curious, you comment because the LT1 has an aluminum intake and a flanged head bolt will distribute the pressure more evenly. Correct?

Jerry------

Yes, that's part of it. In addition, standard hex head bolts will often "gouge" the area surrounding the bolt holes. There are also some smaller OD washers that can be used with conventional hex head bolts to achieve the same effect as flanged head bolts.

[Jerome P.]

Re: 1972 LT1 intake manifold torque

The original application, I think, had a flat washer. Am I correct?

[Joe L.]

Re: 1972 LT1 intake manifold torque

The original application, I think, had a flat washer. Am I correct?

Jerome------


Not that I know of. As far as I know, the standard hex head bolt seated directly on the manifold.

[Patrick H.]

Re: 1972 LT1 intake manifold torque

From the upcoming 70-72 JG, with photo references removed:

"350 aluminum intake manifolds have no washers under the black-plated hex-head bolts in 1970 and 1971; however, most 1972s have thick flat washers under the bolts that did not have a bracket under them. A few very early 1972s manifolds have been seen without washers. No split-ring locking washers are used in any year. Common headmarkings are C and AL. Often different headmarks appear on the same car."

[Jerome P.]

Re: 1972 LT1 intake manifold torque

From the upcoming 70-72 JG, with photo references removed:

".... Common headmarkings are C and AL. Often different headmarks appear on the same car."

Pat,

You mention common head markings. Are there other head markings beside the the "C" and "AL" markings that are not as common to the '72? Or are the head markings strictly limited to "C" and "AL"?

[Joe L.]

Re: 1972 LT1 intake manifold torque

From the upcoming 70-72 JG, with photo references removed:

"350 aluminum intake manifolds have no washers under the black-plated hex-head bolts in 1970 and 1971; however, most 1972s have thick flat washers under the bolts that did not have a bracket under them. A few very early 1972s manifolds have been seen without washers. No split-ring locking washers are used in any year. Common headmarkings are C and AL. Often different headmarks appear on the same car."

Patrick------


That's interesting; I was unaware of that. I guess GM finally got it figured out by 1972 (just before they stopped using aluminum manifolds for several years). They should have asked me. I wonder if 1978-82 Corvettes with aluminum manifolds used the washers? I've never looked.

By the way, this was no problem for big blocks. Big blocks always used flanged head bolts for the intake manifold. Small blocks, both cast iron and aluminum manifolds, should have, too.

[Patrick H.]

Re: 1972 LT1 intake manifold torque

Pat,

You mention common head markings. Are there other head markings beside the the "C" and "AL" markings that are not as common to the '72? Or are the head markings strictly limited to "C" and "AL"?

It was a production environment - you can never say never, and other headmarks are expected to occur.
This is especially true under the engine lift tab or other locations where bolts had more than one purpose.

[Joe L.]

Re: 1972 LT1 intake manifold torque

This is especially true under the engine lift tab or other locations where bolts had more than one purpose.

Patrick------


Yes, bolts that were identical with the exception of a difference in length, even a slight difference, often had different manufacturers (and, thus, headmarks).