Heads Mark V or VI fit IV block?
11-10-2002, 08:21 AM
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Heads Mark V or VI fit IV block?
Can I use Mark V or VI heads on a mark IV block? I was considering getting some HP 500 or 502efi heads used to use on a Mark 4 454 shortblock that I am building now. Thanks
11-10-2002, 12:33 PM
#3
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Yup.....like these Merc. Rect. heads. More grunt. You have to use the Mark IV head gaskets and add a small water passage hole in them. Use the old gasket as a template if you still have it. If you don't, just line it up on the block or the head and mark the center. Use a punch to put the hole in the gasket.
Check into manifolds too.....I was running a single plane and liked the upper range....but recently switched to the Merc. dual plane magnum manifold. Lost nothing on top, gained some low end torque for better planing, and it seems to have more midrange throttle response.
Check into manifolds too.....I was running a single plane and liked the upper range....but recently switched to the Merc. dual plane magnum manifold. Lost nothing on top, gained some low end torque for better planing, and it seems to have more midrange throttle response.
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11-10-2002, 03:27 PM
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Ironman
It will work sometimes but not every time. The water passages at the top of the head and the block are really different. The intake and exhaust ports are identical between all of the rectangle port heads (there is no advantage to using Gen V or VI heads on a Mark IV) so you would be much better off installing Mark IV rectangle port heads on your Mark IV block. Be patient, a set of Mark IV heads will show up sooner or later (they are not hard to find)!
Sincerely
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE
It will work sometimes but not every time. The water passages at the top of the head and the block are really different. The intake and exhaust ports are identical between all of the rectangle port heads (there is no advantage to using Gen V or VI heads on a Mark IV) so you would be much better off installing Mark IV rectangle port heads on your Mark IV block. Be patient, a set of Mark IV heads will show up sooner or later (they are not hard to find)!
Sincerely
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE
11-10-2002, 04:48 PM
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And of course, Dennis is right. I just happened to get a REALLY good deal on my V heads (and I mean REALLY good). So I couldn't NOT buy them.
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[b]M Go Blue.......Gator boots, gator luggage, gator purses... all at cut rate deals!!!!
[b]M Go Blue.......Gator boots, gator luggage, gator purses... all at cut rate deals!!!!
11-10-2002, 07:22 PM
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Changed manifolds?
We at FAMILY AND PERFORMANCE BOATING have a Baja with a carbed 500 HP and are going to do an intake manifold test. We are going to test the Dart single plane against the Chevrolet dual plane for performance increases or decreases. We are trying to get a Merlin Marine single plane for the test also but for some reason Mitchell Sr. of World Products doesn't want to work with us and loan us a manifold for the test. If you want to see this manifold compete against the other two give Mitchell Sr. a call and tell them to loan us a manifold!
Sincerely
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE
Sincerely
Dennis Moore
FAMILY AND PERFORMANCE BOATING MAGAZINE
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