Correct Heads 1972 L65 [Archive] - Chevelle Tech

: Correct Heads 1972 L65

Jul 15th, 05, 10:00 PM
Hey guys, I just pulled the valve covers off of my 1972 El Camino. The engine is the stock numbers matching 350cu 165hp 2bbl (RPO L65). The head numbers are 3986339X. The casting dates are correct for my motor.

I'm the second owner of this car and bought it as a low milage (67,000 miler) in 1997.

I checked Colvin's book (Chevrolet by the Numbers) and he lists these heads as being 1971 used on 307cu engine installed in Novas, Chevelles, and Camaros as well as on 350cu 270hp (low compression) engine in full size cars. The book lists these heads as having 1.72/1.5" valves and 74.56cc chambers.

My question is there any other documented 1972 L65 engines found with these heads? What heads are usually found on L65 engines?


Jul 16th, 05, 12:35 AM
Had the same engine in my 72 Chevelle. All original. Head # 3998993 Mortec shows these as 3998993....72-73...307/350......75cc chambers

Jul 16th, 05, 7:57 AM
Sorry, these numbers are very hard to read, after looking again, I have determined that the number on the heads is actually 3988336X.

Okay, this number is not in Colvin's book, does anyone know the valve size of these heads?


Jul 17th, 05, 12:53 PM
I don't know the casting numbers so I can't help there, but all stock 307s used 1.72 / 1.50 valves while the L65 & L48 used 1.94 / 1.50 valves. 400s used 1.94 / 1.60 valves and the LT-1 uses 2.02 / 1.60s.