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Boat Repair/454 Big Block 450HP

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Expert: Jeff Grigg - 2/22/2008


Question
Jeff,  I am having my 454 Mercruiser rebuilt. The block casting # is 1405445 and is a Mark IV block.  The old Mark IV heads, casting #6272990 are junk.  My engine builder told me that he can get new GM Performance Gen VI heads #12562920 and they will work.  My question is that I have heard that there could be a problem with water leaking into the valve valley because the cooling holes don't line up.  He said it was all about using the right head gasket, he would use a Fel-Pro #1037 head gasket.  Any insight would be appreciated

Answer
Bob, sorry but this is outside my area of expertise. Your mechanic should be able to see if the gasket, heads fit. You may want to contact Mercruiser and get their opinion. I would personally go back with what ever replacement heads Mercruiser recommends. Also make sure your mechanic will give you a warranty in writing.
Jeff

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Jeff Grigg

Expertise

Can help with most any question related to outboards, high performance, hull repair, rigging, if it floats and uses a motor. From a 9.9 on a aluminum boat to DFI two strokes. Outboard motors are my specialty. I can help with some I/O questions as well. Ratings are the only way we know if we are helping. If you are pleased with the help, please rate us. 20% don't bother reading my answers! If you are not going to read the follow up then why ask? Keep in mind we do this at no charge and are not paid. We do it to help you!

Experience

32 years in the marine business. Own a service facility, in coastal South Carolina certified Master Tech by Johnson/Evinrude, certified Mercury/Force, Tohatsu/Nissan. Former technical director for DMI Pistons. 30 year racing career including 3 APBA Formula V National Championships

Organizations
AMTECH, APBA

Publications Written For
Boat & Motor Dealer, Car Classics, Custom Vans (tech articles), Miami News, powerboat racing column

Awards and Honors
Certified Master Technician Johnson/Evinrude

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