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HP500 heads on a MarkIV?

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Old 09-05-2009, 11:19 PM
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Default HP500 heads on a MarkIV?

Do HP500 heads bolt on to a MarkIV block? I am pretty sure they do, but can someone verify?

Anyone have 2 sets of fresh head rebuilds with Inconel valves?
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Old 09-06-2009, 01:39 AM
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If the hp500 heads are Gen V/VI, then no, they will not bolt to a Mk IV block. You can put Mk IV style heads on a Gen V/VI block, but you can not put Gen V/VI heads on a Mk IV block.
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Old 09-07-2009, 10:25 AM
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I thought the Merc 400-420 heads were the same casting as the HP500 heads??? large rectangle port?
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Old 09-07-2009, 10:33 AM
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I have been told that you can put the GenVi heads on the Mark IV blocks with a special headgasket from FelPro. This is only what I have been told, I have not had time to verify it.

You may try calling FelPro and getting the info from the source.
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Old 09-07-2009, 12:00 PM
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Maybe one out of 15-20 will work.(Gen VI head on Mk IV block) The problem is that the head overlaps into the lifter valley. There is not enough material for the gasket to seal. The way to check it is to put the head on and scrib a line on the underside of the head where it meets the block, in the lifter valley. Then remove the head and see how close the line is to the water jacket in the head.
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Old 09-07-2009, 02:59 PM
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thanks for clarifying this Eddie. You the man!
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Old 09-07-2009, 03:01 PM
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I was under the impression is was a matter of one set of water jacket holes lining up......?
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Old 09-07-2009, 07:05 PM
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Hi Guys,

I just got onboard a few minutes ago. I have a 1982 Bertram 33 FBC cruiser and was hoping to learn about my engines (and other stuff). Could someone post a link and/or explain the Gen 4 Gen5 Mark 4 Mark5 designations for 454 engines I'm running the original 2 Crusader 454/350 inboard engines ???? They are still running ok but looking into replacing'rebuilding them. Thanks in advance
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Old 09-07-2009, 09:33 PM
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Skyking,
If the engines are the original 1982 engines they will be mark 4. The Gen V came along in 1990, and you can differentiate the two by the different timing cover and the one piece rear main seal on the gen 5/6 motors. The reason it went from mark 4 to gen 5/6 was Lincon having some trade mark on the mark 5 name. Poeple use gen and mark interchangeably, but is technically Mark IV, or Gen V/VI. You can post casting numbers, found on rear flange of block where the bellhousing mounts, and see what engines you have for sure.
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Old 09-08-2009, 08:25 AM
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Most aftermarket BBC heads are designed to be used on all BBC blocks. I never understood why Chevy didn't make them that way.
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