Correct Heads on '72 LT-1

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Jul 9, 2010 | 03:47 PM

CoolShark

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From: Gotham City CA

Correct Heads on '72 LT-1

I am getting my engine gone through and found two different head numbers. It is a matching number block and has the correct intake and card, but one head is a 3998993 and the other is a 3973487X. According to my books, they should both be 3973487. I get all kinds of info from different sites for '72 LT-1's. Any info from the experts here?

Jul 9, 2010 | 04:14 PM

garage-ghost

Melting Slicks

Joined: Aug 2004

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From: www.Z16.org North/West Pennsylvania

NCRS judging guide says “1972 Base engine & LT-1 3973487(X), 3998916 & 3998993”. Why the different numbers they don’t say.

I'll keep looking.

I'm back

OK now I’m confused… I think the 3998993 might be a replacement. If it were my car I would stick with the 3973487X heads.

Last edited by garage-ghost; Jul 9, 2010 at 04:43 PM.

Jul 9, 2010 | 05:00 PM

Alan 71

Team Owner

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From: Westminster Maryland

Hi cs,
The Vet Vue's 68-72 Fact Book by Dobbins lists 3973487 (x) as the Lt-1head for the 72 model year. It's the same as the base engine's head casting number.
Regards
Alan

Jul 9, 2010 | 05:26 PM

CoolShark

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From: Gotham City CA

Best I can tell, the cfm on the 993 is 150/91 and on the 487 is 161/65. However one site also said the intake is 10 cfm different on the 487X and another said not. I'm so confused

Jul 10, 2010 | 12:34 AM

Solid LT1

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Joined: Dec 2003

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From: Fremont CA

487X on my 72 LT-1, they are for sale

Jul 11, 2010 | 11:20 AM

CoolShark

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From: Gotham City CA

PM sent.

Jul 11, 2010 | 12:01 PM

ZBRA

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From: Lafayette LA

I have a base model '72, and both of my heads are 487X.

Jul 15, 2010 | 04:22 PM

markdtn

Le Mans Master

Joined: Aug 2003

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From: Chattanooga TN

I think I have a single 487x head that needs a new home, i'll look tonight.

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Jul 15, 2010 | 11:00 PM

7T1vette

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From: Crossville TN

The "993" head may be the correct service replacement part provided by Chevrolet. {That would make it "equivalent", as far as Chevy is concerned...but they aren't exactly the same.}

Jul 16, 2010 | 10:56 PM

#10

USALT1

Racer

Joined: Feb 2007

Posts: 262

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From: FREDERICKSBURG VA

I have owned both a '71 & a '72 LT1. The '71 had 487 heads & the '72 had 487x heads. The standard 350 in '71 had 487 & '72 had 487x, the difference is the LT1's have 2.02/1.60 valves & screw in studs with guide plates. You can take a standard head & the machine work done for the valves & screw in studs.

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