Early LA motor compared to Later LA motor?

[Badart]

What are the main differences between a 318 made in 68-69 from one made in 74-75 other than pistons and compression ratio? Stronger block? Enlighten me.

 

[tyler_s18]

suscribe lol. i am curious as well. i think they had smaller valves lower compression and egr stuff on them. idk what else tho.

 

[fstfish66]

lower compression is correct after 1970 starting in 1971 same valves on a 2bbl 318 LA motor,,,but on a cop car 318 they used the 360 head,,which would make even less compression from every thing ive read,,,

find a chiltons or a motors manual,, and compare the years,,or go to

www.allpar.com search 318,,

 

[moper]

Thye are identical except for piston design, and some head changes depending on the model. 4bbls had 360 heads, some had better cams, and windage trays later in the 70s and 80s. The std 318 heads were always the same. Smaller chamber but still open design, I think it's in '72 they make the chamber a little larger, but no real changes at all from start to finish.

 

[RedFish]

Later engines built for unleaded fuel got hardened valve seats

 

[C130 Chief]

Water pump and timing covers changed in 70. Induction hardened valve seats in 72. Electronic ignition phased in 72-74. Steel cranks in 318-340 phased in after 71. Compression down on 340 in 72. 340 & 360 heads same in 72. 318 compression varied slightly but trended downward after 70 (nominally 8.5). Various emission control hardware added, especially from 72 on.

 

[Badart]

Thanks guys. I knew the the head designs have changed over the years, but I was just wondering about block design.

 

[1wild&crazyguy]

Like the 340 in 1970 the blocks were cast with extra ribbing around the center freeze plug to stiffen it up.

360's got a larger thrust bearing and lil thinner cylinder walls in 1974.

318's got 360 rods in 1973-74.