72 350 heads question
Thread Starter
Heel & Toe
Joined: Jul 2023
Posts: 19
Likes: 1
72 350 heads question
On 72 350s they have heads with same casting number but options for different size intake valves 2.02 and 1.94…I’m not sure how that works, are the bare heads the same for both options? Do they mill out at factory for the larger valves?
Please advise and thank you in advance for the knowledge.
Please advise and thank you in advance for the knowledge.
Team Owner
Joined: Sep 2006
Posts: 31,273
Likes: 4,366
From: Westminster Maryland
Hello,
Interesting.....
All the small block engines that were destined for Corvettes were machined and built at the Flint engine plant.
They were shipping about 5000 engines each day and were building them in as many as 100 configurations.
The Corvette engines were just a smallish drop in the bucket.
There were 2 engine lines, one producing an engine every 21 seconds and the other producing an engine every 31 seconds.
John Hinkley (rest his soul) has written some very interesting articles about Corvette and Camaro production from his first hand experiences.
Regards....
Interesting.....
All the small block engines that were destined for Corvettes were machined and built at the Flint engine plant.
They were shipping about 5000 engines each day and were building them in as many as 100 configurations.
The Corvette engines were just a smallish drop in the bucket.
There were 2 engine lines, one producing an engine every 21 seconds and the other producing an engine every 31 seconds.
John Hinkley (rest his soul) has written some very interesting articles about Corvette and Camaro production from his first hand experiences.
Regards....
Last edited by Alan 71; Oct 29, 2025 at 05:17 PM.
Drifting
Joined: Jun 2025
Posts: 1,715
Likes: 597
Just one example; other head castings treated similarly:
Most '72 C3 350 heads have casting number 3973487. The very same casting can be machined for either 1.94" or 2.02" intake valve seats. Same for 1.5" or 1.6" exhaust valve seats.
Similarly, same 3973487 casting can be drilled for press-in rocker arm studs. OR stud towers can be milled flat and drilled-tapped for threaded rocker arm studs; to fit pushrod guideplates.
Non-Vette GM example:
Much later mid-Nineties - early 2000s iron Vortec 5.7L heads have a variation while using same 12558062 casting. Some exhaust valve seats are induction heat-treated while some heavier duty versions' combustion chambers are milled to accept a hardened steel exhaust valve seat insert.
Most '72 C3 350 heads have casting number 3973487. The very same casting can be machined for either 1.94" or 2.02" intake valve seats. Same for 1.5" or 1.6" exhaust valve seats.
Similarly, same 3973487 casting can be drilled for press-in rocker arm studs. OR stud towers can be milled flat and drilled-tapped for threaded rocker arm studs; to fit pushrod guideplates.
Non-Vette GM example:
Much later mid-Nineties - early 2000s iron Vortec 5.7L heads have a variation while using same 12558062 casting. Some exhaust valve seats are induction heat-treated while some heavier duty versions' combustion chambers are milled to accept a hardened steel exhaust valve seat insert.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Yep, some castings #'s had multiple variations....the weirdest one is the 1969 L-46 which uses the "186" casting like a 302DZ and has 2.02/1.60 valves but has press in studs....total oddball, GM saving that $5....
Kinda like "010" blocks can have 2 or 4 bolt mains....
Jebby
Kinda like "010" blocks can have 2 or 4 bolt mains....
Jebby
Le Mans Master
Joined: Mar 2004
Posts: 7,493
Likes: 1,502
From: Little Rock AR
For '72 LT-1 (and Z/28) heads, the factory would hog out the bowl area under the valve for more volume. The rocker arm bosses were cut down, drilled and tapped for screw in studs and guide plates. The obround pushrod holes were drilled out to a round hole.
Burning Brakes
Joined: Sep 2016
Posts: 956
Likes: 443
From: Dutchess county New York
Interesting thread.
Are you referring to 3927186 ?
I have a '69 L-46 with an Oct 14 68 build date. It has a CE block with an Oct 16 68 cast date.
Both heads are 3927186 and the driver side head dates to Sept 68 but the passenger side dates to Dec 71.
I think somebody blowed this thing up real good back when and got this CE block and a newer head as a result. I have to pull the pan and timing cover this winter to seal it up and will have good look at what it actually is.
Are you referring to 3927186 ?
I have a '69 L-46 with an Oct 14 68 build date. It has a CE block with an Oct 16 68 cast date.
Both heads are 3927186 and the driver side head dates to Sept 68 but the passenger side dates to Dec 71.
I think somebody blowed this thing up real good back when and got this CE block and a newer head as a result. I have to pull the pan and timing cover this winter to seal it up and will have good look at what it actually is.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Interesting thread.
Are you referring to 3927186 ?
I have a '69 L-46 with an Oct 14 68 build date. It has a CE block with an Oct 16 68 cast date.
Both heads are 3927186 and the driver side head dates to Sept 68 but the passenger side dates to Dec 71.
I think somebody blowed this thing up real good back when and got this CE block and a newer head as a result. I have to pull the pan and timing cover this winter to seal it up and will have good look at what it actually is.
Are you referring to 3927186 ?
I have a '69 L-46 with an Oct 14 68 build date. It has a CE block with an Oct 16 68 cast date.
Both heads are 3927186 and the driver side head dates to Sept 68 but the passenger side dates to Dec 71.
I think somebody blowed this thing up real good back when and got this CE block and a newer head as a result. I have to pull the pan and timing cover this winter to seal it up and will have good look at what it actually is.
Jebby
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Le Mans Master
Joined: Mar 2004
Posts: 7,493
Likes: 1,502
From: Little Rock AR
Interesting thread.
Are you referring to 3927186 ?
I have a '69 L-46 with an Oct 14 68 build date. It has a CE block with an Oct 16 68 cast date.
Both heads are 3927186 and the driver side head dates to Sept 68 but the passenger side dates to Dec 71.
I think somebody blowed this thing up real good back when and got this CE block and a newer head as a result. I have to pull the pan and timing cover this winter to seal it up and will have good look at what it actually is.
Are you referring to 3927186 ?
I have a '69 L-46 with an Oct 14 68 build date. It has a CE block with an Oct 16 68 cast date.
Both heads are 3927186 and the driver side head dates to Sept 68 but the passenger side dates to Dec 71.
I think somebody blowed this thing up real good back when and got this CE block and a newer head as a result. I have to pull the pan and timing cover this winter to seal it up and will have good look at what it actually is.
The "186" was an earlier head casting produced by Flint with smaller chambers and different machining operations. The "186" heads were used in '69-'70 available in large and small valve versions. The large valve versions had the bowls opened up and combustion chamber modifications to unshroud the intake valves for better flow. The "186" heads all have pressed in studs for '69 and no guide plates. Screw-in studs and guide plates came in 1970 with the LT-1's and Z/28. The '70 L-46 350-350HP would still have big valves, pressed-in studs and no guide plates same as '69. The "186" was not used in production after '70.
The "041" head casting is basically identical to the "186" head, but it was not used in big valve configuration from the factory. The "041" was only produced at the Tonawanda plant which did not produce any small block SHP engines They did not have the machining equipment stations to build them.