72 LT1 head numbers help
Thread Starter
Racer
Joined: Sep 2007
Posts: 298
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From: DERRY NH
72 LT1 head numbers help
Calling all 72 LT1 owners and or Vette gurus. I have a 72 LT1 with 44k original miles. Every number on this car checks out with the possible exception of the heads. The car was built in July 72 (526171), block date is June 17 72, heads date June 9 72, so far so good. The heads however are 993 heads with screw in studs, push rod guide plates and LT1 spec valves. My question is, could these still be correct since this was the last month of the last year for the LT1 CORVETTE? Maybe they ran out of 916s and 487s and modified some 993s on the line? Any thoughts or experience with this situation would be appreciated.
Racer
Joined: Apr 2002
Posts: 345
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From: ny
How do you know what the heads date? I have a 71 non LT1 car that came to me with LT1 heads. Casting numbers on them is 3973487 . Research tells me thats the 75cc heads that came on 71-72 350sbc LT1 cars.. dont' know if this thread helps you or not http://www.hotrodders.com/forum/rook...ion-43799.html
Race Director
Joined: Jul 2001
Posts: 15,892
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It's not rare to see part number change overs that don't line up exactly with model year transition. Without being familiar with any physical differences between the two casting numbers that would prevent them form being interchangeable, I would say it's very possible that the 993s that were to be introduced for the '73 MY ended up on your car. 
Thread Starter
Racer
Joined: Sep 2007
Posts: 298
Likes: 0
From: DERRY NH
How do you know what the heads date? I have a 71 non LT1 car that came to me with LT1 heads. Casting numbers on them is 3973487 . Research tells me thats the 75cc heads that came on 71-72 350sbc LT1 cars.. dont' know if this thread helps you or not http://www.hotrodders.com/forum/rook...ion-43799.html
Thread Starter
Racer
Joined: Sep 2007
Posts: 298
Likes: 0
From: DERRY NH
It's not rare to see part number change overs that don't line up exactly with model year transition. Without being familiar with any physical differences between the two casting numbers that would prevent them form being interchangeable, I would say it's very possible that the 993s that were to be introduced for the '73 MY ended up on your car.
Race Director
Joined: Jul 2001
Posts: 15,892
Likes: 42
Team Owner
Joined: Jun 2000
Posts: 38,923
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From: Southbound
Cruise-In II Veteran
My NCRS Specifications Guide says the 993 heads may have been used on the 72 base engine cars and says usage is unverified.
Have you posted on the NCRS Forum?
See if you can find Rowdy Rat. He knows his way around LT-1s.
Articcatt: sent you a PM.
Have you posted on the NCRS Forum?
See if you can find Rowdy Rat. He knows his way around LT-1s.
Articcatt: sent you a PM.
Last edited by Easy Mike; Jul 28, 2011 at 12:50 PM.
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Thread Starter
Racer
Joined: Sep 2007
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From: DERRY NH
Thanks Mike, I'll keep an eye out.
Thread Starter
Racer
Joined: Sep 2007
Posts: 298
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From: DERRY NH
Racer
Joined: Jul 2007
Posts: 430
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From: Florida
John,
The data I see on the 993 head shows 1.94/1.50 valves, vs the normal Lt-1 head, 3973487x which has 2.02/1.60.
As a comparison I have a late June build Lt-1 also, with one 487x head, dated Mar 7, and a replacement head on the other side. The other head is a 333881, with 2.02/1.60 valves, screw in studs, and guide plates.
http://outintheshop.com/faq/casting/heads.html
Hope this helps,
Chris
The data I see on the 993 head shows 1.94/1.50 valves, vs the normal Lt-1 head, 3973487x which has 2.02/1.60.
As a comparison I have a late June build Lt-1 also, with one 487x head, dated Mar 7, and a replacement head on the other side. The other head is a 333881, with 2.02/1.60 valves, screw in studs, and guide plates.
http://outintheshop.com/faq/casting/heads.html
Hope this helps,
Chris
Burning Brakes
Joined: Aug 2007
Posts: 1,084
Likes: 8
From: Illinois
According to my NCRS 1970-72 tech info manual & judging guide.
Base engine & LT1
1971: 3973487
1972: 3973487 X
1972: 3998916
1972: 3998993
X indicates that an X-casting foundry proofmark appears after the seven digit casting number on later 1972 cylinder heads.
On 350 heads, the driver side head casting number can be seen if the oil fill cap is removed. On LT1's the push rod guide plates are also visible.
Hope this helps.
Base engine & LT1
1971: 3973487
1972: 3973487 X
1972: 3998916
1972: 3998993
X indicates that an X-casting foundry proofmark appears after the seven digit casting number on later 1972 cylinder heads.
On 350 heads, the driver side head casting number can be seen if the oil fill cap is removed. On LT1's the push rod guide plates are also visible.
Hope this helps.
Safety Car
Joined: Dec 1999
Posts: 3,587
Likes: 829
From: PA
The 993 heads are possible, but it is certainly not the norm.
Most of the heads on 1972 LT-1 Corvettes that I've seen over the years are either 487 or 487x (my own mid-June car has the 487X heads). Still, if the casting dates are in line with the rest of the engine, they most certainly could be the original heads.
What are the casting dates on these heads?
Regards,
Stan Falenski
Most of the heads on 1972 LT-1 Corvettes that I've seen over the years are either 487 or 487x (my own mid-June car has the 487X heads). Still, if the casting dates are in line with the rest of the engine, they most certainly could be the original heads.
What are the casting dates on these heads?
Regards,
Stan Falenski
Thread Starter
Racer
Joined: Sep 2007
Posts: 298
Likes: 0
From: DERRY NH
The 993 heads are possible, but it is certainly not the norm.
Most of the heads on 1972 LT-1 Corvettes that I've seen over the years are either 487 or 487x (my own mid-June car has the 487X heads). Still, if the casting dates are in line with the rest of the engine, they most certainly could be the original heads.
What are the casting dates on these heads?
Regards,
Stan Falenski
Most of the heads on 1972 LT-1 Corvettes that I've seen over the years are either 487 or 487x (my own mid-June car has the 487X heads). Still, if the casting dates are in line with the rest of the engine, they most certainly could be the original heads.
What are the casting dates on these heads?
Regards,
Stan Falenski
John
6th Gear
Joined: Feb 2012
Posts: 6
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