Falcon67 wrote:
We've hashed this out over the last 20 years - feel free to study the list
http://www.351c.net/archive/parts/cleve ... ate-codes/Sample - CC = "closed chamber":
D1AE GA 0F17 17-Jun-70 no Dot CC Bill Gallagher
D1AE GA 0F17 17-Jun-70 no Dot CC Carl
D1AE GA 0G13 13-Jul-70 Dot CC Lowell
D1AE GA 0G13 13-Jul-70 Dot CC Lowell
D1ZE CA 0G22 22-Jul-70 Dot CC Kieth
Yes, all US 2V heads are OC. Some numbered, some not. After 1975 the exhaust ports on the 2Vs got modified and are virtually unusable. They -all years - are way prone to cracking around the exhaust valve seat.
At some point they started casting the 2v heads with the letter M cast in them instead of the 2. I have a set from '75, but I ground the M off. They have the shitty exhaust port with the extra material around the guide for the smog crap, but surprisingly after porting they actually flowed a little better than a similarly ported early 2v head.
I am pretty sure all the 4v heads I have gone thru were all matched as far as dot or no dot.