Head #'s Tim The L89 option used closed chamber heads,842's I think. The 074's are 118cc open chamber.I'll check on mortec.
aluminum heads actually for the date code on those heads, 4/6 and 4/7/70, according to the book I use, Chevrolet by the numbers they were only used on ZL1 camaros and corvettes, and L88 corvettes. im almost positive those heads were never used on L89 chevelles, camaros, etc. The heads used there were 842 heads and there was a difference in the cc's. The 074's had a 118.0 cc and the 842's had like 106.8 cc's. Besides, the 842 heads was no longer made in 70, they stopped making them in 69. The valves also had a difference too. so those heads were not used on L89 motors. Also the 074's were used on 71 corvette Ls6 engines. :Comp:
aluminum heads sorry forgot to list something, the 842's were colsed chamber heads, and the 074's were open chamber. :3gears:
