Can anyone tell me if todays Mark V big block will accept the old Mk IV flywheel?
Thanks, Frank.
Thanks, Frank.
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Re: Mk IV, Mk V
Frank-----
No, they will NOT interchange. The Mark IV engines use a 2 piece rear main seal. Gen V and Gen VI big blocks use a 1 piece seal. Consequently, the bolt pattern for the crankshaft flywheel flange is different, with the later engines having a smaller bolt pattern than the Mark IV. So, the flywheels and flexplates are unique and specific it each. There is absolutely no way that either type flywheel can be modified to adapt to the other application.In Appreciation of John Hinckley -
Re: Mk IV, Mk V
there could be a balance problem because the mark V uses 2 different flywheels depending on the crank material.Comment
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Re: Mk IV, Mk V
joe i thought that the BBC bolt circle was 3.580 with either 1 or 2 piece rear seal. i know the SBC has a different bolt circle,3.580 vs 3.000.Comment
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Re: Mk IV, Mk V
clem-----
Yes, I may have erred on that point. However, I'm certain that the Mark IV and Gen V/VI flywheels and flexplates are not interchangeable.In Appreciation of John HinckleyComment
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Re: Mk IV, Mk V
Thanks men, Thats what I figured. I know about the 1 piece 2 piece seal thing but in my memory banks I thought I had heard something about the flywheels not interchanging.
Now I'm want to know what you mean about the sb using 3.00 bolt circle and the bb using 3.580. Is that 1 piece seal talk?
I know that excluding balance considerations, the 2 piece seal flywheels interchanged.
Could you also explain the differences in the possible flywheels of the MkV due to crank material?Comment
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Re: Mk IV, Mk V
The two different 4" stroke Gen V cranks (nodular cast iron vs. forged steel) require different external balance-weighting, although they're dimensionally identical (14" flywheel, 168 teeth, 3.58" bolt pattern).Comment
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Re: Mk IV, Mk V
Thanks John, Good info.Comment
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Re: Mk IV, Mk V
Can anyone tell me how to I.D. the correct flywheel. Part #, distingushing characteristics etc.
Come to think of it, how do you tell what crank is in the engine? With the small flange I don't think a guy can see the parting line?
Frank.Comment
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Re: Mk IV, Mk V
Frank-----
The flywheels can be identified by casting number. For flex plates, I'm not sure. I don't know if a part number is stamped upon them, or not.
As far as what flywheel to use, they say to balance match the flywheel/flexplate that you take off to the one that you're installing. If you start from a "complete unknown" situation (i.e. an assembled engine with no flywheel/flexplate to match to), then I don't know what you do.In Appreciation of John HinckleyComment
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Re: Mk IV, Mk V
Joe;
That doesn't sound good. I'm looking at a '91 454 with "all the tbi stuff" but it does not come with the flywheel. The donor vehicle was a C20 with a manual shift. Maybe I should pass.....?Comment
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Re: Mk IV, Mk V
that would be a cast crank,only HO engines use forged crankshafts. i would think you need flywheel # 10101169 which is for all GEN V with CI crankComment
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Re: Mk IV, Mk V
Unless it is a great price and it is something you want for a project or a hauler, I'd pass if it is anything like the '89 454 TBI in my '89 GMC.
My 402 and my 427s would crack your head over backwards when you mashed the loud pedal but the 454 just seems to push you in the seat some. I think the heads must be junk as far as flow and HP. I think the only reason the 454 in the late 80s/early 90s made more HP than the 350s was sheer mass.
I'd rather build one with late '60s heads and cam to make it run.
Just my 2 cents.Comment
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