454 Medium Duty V-8

[Bob B.]

I don't think the L21's were tall deck, though all the 8.1's were. Of course, the '79-'80 would have been a Mark IV, the '99 a Mark VI.

Never sure why the 454 was released as a medium duty engine for '79-'80. H.P./torque was only slightly better than the 427, fuel economy was about the same. I am thinking it was either because of emissions or GM was moving to eliminate the 427. The 427 was not available in California certain years in the early 80's.

[DirtyLarry]

Originally Posted by Bob B.

I don't think the L21's were tall deck, though all the 8.1's were. Of course, the '79-'80 would have been a Mark IV, the '99 a Mark VI. .

I’m privy to a lot of things 8.1L related and never known it to be a tall deck. I’m going to have to disagree on that one.

[Bob B.]

Originally Posted by DirtyLarry

I’m privy to a lot of things 8.1L related and never known it to be a tall deck. I’m going to have to disagree on that one.

That's what I was told some years ago, but I never measured one. The story was GM went with a tall block casting to be able to increase the stroke over a 7.4L and not have rod angularity problems. The 8.1L does not have a 4 ring piston like a tall deck Mark IV but does have a .25" longer rod.

Now I am confused!