Valve covers. (but you can reuse the intake and distributor as well)

The Mark IV was the same design that was introduced back in 1965. The Gen V was the next iteration of the big block, and though the head bolt pattern is the same, and the heads will bolt up; Chevy changed the cooling passages in the block of the Gen V that prohibit old Marl IV heads being used (they will cause a water leak). The Gen V block has a one piece rear main seal (so it uses a different crank but with the same stroke and journal size; and a one piece oil pan) that prevents a Mark VI crank from being used with out an adapter. The Gen V block uses a hydraulic roller cam with a different timing chain and timing chain cover (now made of plastic) than the old Mark IV block. Finally the Gen V block has no provision for a mechanical fuel pump (no boss, no cam eccentric to power it, no push rod in the block). The Gen V block also comes with "Peanut Port" heads that have intake runners that are 30 cc smaller than the old Mark IV round port intakes (but use the same size valves).

The Gen VI block fixed the problems customers had with the Gen V block (or a lot of them). It allows you to use a new "Peanut Port" head or the old style Mark IV head because the water jackets were modified. The biggest change with the new block was the option for Siamese bores that allow up to a 4.5 inch bore if you get the 502 block. All GMPP blocks are four bolt high nickel blocks and have the provision of using a roller cam. The stock production pick-up truck blocks are still two bolt engines but they do use roller cams.

The 454 uses the same rods and pistons for Mark IV, Gen V, and Gen VI. Same oil filter. The new heads use non-adjustable rockers, but you can use the old 7/16th studs off of the Mark IV to re-use the roller rockers and studs on the new heads. Basically the changes were to control oil leaks so most parts can be modified orreplaced with aftermarket parts regardless of generation.



Larger Dave

 

I believe the difference is the Mark V & Mark VI have a 1 piece rear main seal instead of a two piece which the Mark IV's have. From what I know about the Mark V & VI the oil passages are different along with the deck height.

The 454 had a bigger bore than a 427. That also means some internals like the pistons will not interchange.


Here is some great info on the Mark IV http://en.wikipedia.org/wiki/Chevrolet_Big-Block_engine
Here is another one http://www.superchevy.com/features/sucp_0607_mark_iv_big_block_chevy_engine/


There was a great article from either Chevrolet High performance or Super Chevy that I saw this past summer/early fall. I think I still have the magazine. I wil look for it...The magazine explains in details about the Mark V & Mark VI 454 used in trucks today vs the Mark IV from the muscle car hey day.

 

Sorry Dave,

I was typing out my post at work but got distracted for an hour. You mentioned everything I wanted to say.

Thanks!!

Greg

 

Mark IV is all the early stuff, 2-piece rear main seal.
Gen 5 uses a 1-piece rear main seal and has 12 timing cover bolts. It's a pain to get the correct gaskets, etc. for in order to use early heads.
Gen 6 uses a 1-piece rear main and is easy to recognize by it's 6 timing cover bolts. It can use all cylinder heads, is set up to use OEM hydraulic lifters and they've moved the main oil galley to run parallel to the cam. An adapter to allow use of 2-piece rear main cranks runs $50 - $100 and opens this block up to using even your older style crankshafts.

 

He, He!!

It's the 8100 Vortec BB engine that is different here!!

4.25" b x 4.37" s = 496"...

Tall decker to boot with cathedral intake ports in the heads like an LS- SB but BB exhaust ports..

pdq67