390 block differences?
Postmaster
Joined: Nov 2002
Posts: 3,447
Likes: 1
From: Littleton, CO
66 and 67 390's were offered in cars, not truck, so they have a higher compression ratio, same with all the car vs. truck compressions. Most of the post 72 motors, found in trucks, are lower compression than cars, as previously stated... And the motors from 71-72 on will have hardened valve seats in the heads for unleaded fuel.
--Mike
--Mike
Needsmorecoffee.
Joined: Oct 2004
Posts: 3,624
Likes: 2
From: CT
Yep some of the early to mid 66 engines still used the lowriser port heads. The later 66 heads were the new port velocity design we know as the medium riser style. Mike G nailed the other points. Foundrys changed from DIF to MCC in the early 70's. Some blocks had thicker cyl walls but it's a crap shoot unless you knock out a freeze plug and gap the cores. I've seen early castings were a little nicer and somewhat smoother than the later.
G.
G.
