Hi all. I’m new to the board, but not so new to my '72 GS 350 (bought it in '94). It’s basically stock except for a 2-1/2 manifold-back exhaust and Flowmasters. I’ve been getting the itch to do a mild top end rebuild project and gain some much needed HP. Nothing crazy since it sees light street use only. One area for improvement I’m considering is targeted porting/polishing of the cast heads. I recently picked up a spare set (casting no. 1243452) which I understand spanned several years. Since they came cheap I’m not afraid to try porting these on my own, once I learn more about how to (and how not to) for the performance improvements I’m looking for. Before I disassemble and have these cleaned/magged, I’d like to know more about these heads: 1. Their production spanned '72 - '80 from what I’ve read. Are any years of this particular casting code more desirable? 2. How do I know what year these particular ones were produced? Each has “A•5” marked on the top left side as well. 3. How do I know if they are smog-equipped, and if they are, how do I “un-equip” them? ;-) 4. In general, is it worth me working on this particular set, or are there other more desirable (so harder to find) SBB heads that I should be searching for? I’m not much interested in modifying the heads on my car because a) it’s together/drivable now, b) if I sell the car I’d like to give the next guy the opportunity to restore it, and c) in case I mess up the heads I won’t spoil b) by doing so. Thanks for your help!
I would say 72-75 would be better then later. As per Michael Phillips from am&p , from a porting aspect. 72 has 8.2 compression. So shaving the heads some for a bump in compression would not be bad, although a piston change for compression increase would be better. But if your bottom end is good, and you have extra heads, why not. Matt had great luck with big valves ,porting and the crower level 3 cam advanced 4 degrees in a low compression 68 350. Quadrajet Power Performance built carb, and a trishield performance torque converter. With distributer recurve. He ran 14.00 on street tires with 3.42 gears. Lots of tire spin . Might as well go with what works. He did the oil modifications and TA front cam bearing. Stock rockers, new valve springs. Should not have to unequip emissions as early is just egr. Make sure your block does accept late heads or plug ports in Center of heads
Got it, and thanks for the advice. Still unsure of how to identify the casting date on these buggers. Motor has just 35k on it and I have no reason to suspect the bottom needs attention (yet).
