2015 rules published and Director's cut

Questions and answers about CMC and NASA rules

Moderator: Al Fernandez

Supercharged111
Posts: 373
Joined: Sun Jul 28, 2013 9:18 am
Location: Colorado Springs, CO

Postby Supercharged111 » Mon Feb 09, 2015 6:51 pm

Now that they're signed, I think I found a flaw. GM's L31 heads came both as 062 and 906. The 062 was used in the light duty engines, and the 906 generally came in the 4 bolt main engines found in 8 lug trucks. Some claim the 906 doesn't flow as well as the 062, but that notion has since been widely discarded and both are considered equivalent. As far as I know, there is no such thing as an 060 L31 head.

7.13 GM Spec Carbureted Engine Option
Any of the following unmodified aftermarket components (and only these components) may be substituted
on a CMC legal GM V8 long block to create a carbed, spec engine:
5.0 liter (305ci)
1. Holley carburetor 600cfm-4bbl #4776
2. Edelbrock Performer intake manifold #2101, #2104, #2116, #7116, #7516
3. Edelbrock Performer Cam kit #2102 or Comp Cams #12-238-2
4. GM L31 #12558060 or L30 #12552520/12558059 heads
5. GM OEM H.E.I. distributor (non-computer controlled)
5.7 liter (350ci)
1. Holley carburetor 600cfm-4bbl #4776
2. Edelbrock Performer intake manifold #2101, #2104, #2116, #7116, #7516
3. GM Camshaft #24502476
4. GM L31 #12558060 or L30 #12552520/12558059 heads
5. GM OEM H.E.I. distributor (non-computer controlled)
Rocky Mountain CMC Director
#45 Camaro Challenge Race Car

Glenn
Posts: 2672
Joined: Tue Jun 01, 2004 3:53 pm
Location: Ft. Worth

Postby Glenn » Mon Feb 09, 2015 7:59 pm

Texas Region AI/CMC Series Director
Inferior Driver, Superior Platform…. since 2005.

Supercharged111
Posts: 373
Joined: Sun Jul 28, 2013 9:18 am
Location: Colorado Springs, CO

Postby Supercharged111 » Tue Feb 10, 2015 2:14 pm

Well I'll be damned. Kinda rules out junkyard heads though, doesn't it? That must be the latest, greatest casting because it looks like it comes on the crates now too.
Rocky Mountain CMC Director
#45 Camaro Challenge Race Car

Den34
Posts: 167
Joined: Wed May 02, 2007 6:54 pm
Location: Eureka IL

Postby Den34 » Wed Feb 11, 2015 8:13 am

Are we getting confused over part numbers and casting numbers?
The 12558060 is a part number for the Head assembly. Studs valves springs etc. The casting numbers 906 and 062 you refer to are the last three digits of the casting part numbers and is just a raw casting number. A 906 casting number may be part of the 12558060 head asssembly. Same for the 062.
Bob Denton
CMC #67
2000 Pontiac Firebird
Midwest Region Series Director

Supercharged111
Posts: 373
Joined: Sun Jul 28, 2013 9:18 am
Location: Colorado Springs, CO

Postby Supercharged111 » Wed Feb 11, 2015 6:05 pm

Yes I was. Seems it'd be better though to include casting numbers, or mention what they came from for the uninitiated because that part number is nowhere to be found on an otherwise not cracked legal junkyard head.
Rocky Mountain CMC Director
#45 Camaro Challenge Race Car

Supercharged111
Posts: 373
Joined: Sun Jul 28, 2013 9:18 am
Location: Colorado Springs, CO

Postby Supercharged111 » Thu Feb 12, 2015 3:52 pm

Yes I was. Seems it'd be better though to include casting numbers, or mention what they came from for the uninitiated because that part number is nowhere to be found on an otherwise not cracked legal junkyard head.
Rocky Mountain CMC Director
#45 Camaro Challenge Race Car


Return to “Rules Questions/Answers”

Who is online

Users browsing this forum: No registered users and 1 guest