73/74 intake differences?

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Jul 19, 2010 | 04:02 PM

C2C6Z06

Thread Starter

Burning Brakes

Joined: Jan 2008

Posts: 1,021

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From: Lake Havasu City, AZ

St. Jude Donor '08-'09-'11-'12

73/74 intake differences?

I have a July 73 built L82 motor with a 74 intake on it (340261 casting). Due to the late build, it seems reasonable to have the 74 casting on it rather than the 3997770 casting.

My Q is: are the performance specs on these two castings different? If so, in what way?

Thanks.

Jul 19, 2010 | 04:55 PM

Mike Ward

Race Director

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Can't comment on the performance differences if any, but most of the current books are wrong when stating that the 340261 casting is '74 only. It's common to see it on very late '73 cars, like yours (and mine). I've asked for a revision to be made to the NCRS tech manuals.

Jul 19, 2010 | 05:34 PM

Paul L

Team Owner

Joined: Aug 1999

Posts: 30,995

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From: Ontario

Quote:

Originally Posted by Mike Ward

And the #340261 does not continue into 1975 and 1976 as many sites state. Try to get the triangular EGR on it.

The 1973 and 1974 EGR is held on with a clamp. The post-1974 EGR is held on the intake with three bolts.

Last edited by Paul L; Jul 19, 2010 at 05:40 PM.

Jul 19, 2010 | 07:33 PM

cardo0

Le Mans Master

Joined: Oct 2002

Posts: 7,098

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From: Las Vegas - Just stop perpetuating myths please.

No one dyno tests each manfold made.

Quote:

Originally Posted by C2C6Z06

Are u going to change to a '74 intake for performance? The only performance improvement for a "stock" chevy intake manifold i know of is the LT1 intake 'bout 1970. If u want to improve your "stock" intake performance try Brzezinski racing at:http://www.castheads.com/. They have been porting stock chevy heads and manifolds for decades.

Good luck,
cardo0

Jul 20, 2010 | 09:46 AM

C2C6Z06

Thread Starter

Burning Brakes

Joined: Jan 2008

Posts: 1,021

Likes: 2

From: Lake Havasu City, AZ

St. Jude Donor '08-'09-'11-'12

I have the 34021 intake on the OEM motor already. Since I just found this car, I was checking numbers and saw the #'s were different than what I expected (the 3997770). No need to change on a matching motor.....

Jul 20, 2010 | 10:17 AM

Mike Ward

Race Director

Joined: Jul 2001

Posts: 15,892

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Quote:

Originally Posted by paul 74

And the #340261 does not continue into 1975 and 1976 as many sites state. Try to get the triangular EGR on it.

The 1973 and 1974 EGR is held on with a clamp. The post-1974 EGR is held on the intake with three bolts.

You're right. The NCRS book is correct though.