I picked up some good used heads from a Mark IV engine. I know that there are differences in the cooling passages between the Mark IV heads and the Mark V and VI blocks. I am looking for head gaskets to use and/or I read somewhere about a modification kit to the Mark V block which allows you to use Mark IV heads. Can you guys whom have accomplish this indicate what has been sucessfully used. Thanks

Dean,
There is no way to make this work unless you want to modify the block. Somebody makes a cast iron piece that you can bolt to the block after drilling and tapping some holes, but I always thought it was a shaky deal. I have heard of guys that swear they bolted the heads on and the water passages just barely sealed up, but I have not seen one yet that would work. I think you will be way ahead of the game just selling the heads and finding a set that is correct for you block.

Dean,
The only way I know of to make the Mark IV heads work on the later block is to weld material to the critical sealing areas of the heads. This is not too much of a problem with aluminum heads, but welding cast iron is pretty tricky. Of course the heads will need to be surfaced after the welding is completed. Might be cost-effective to locate the correct heads for your block.

Dean, I run this combination that you are trying to use. I run a '95 mark V 454 block and '70 alminum gm heads mark IV. I did some research and found that a company in Lubbock, Tx, Scoggin-Dickey Parts Center, sells what you need. There tech line is 1-806-798-4108 or there order line is 1-800-456-0211. There web address is web page (http://www.SDPC2000.com) . It's an adaptor kit that consist of some pieces that go between the block and head gasket. It blocks one water port off and reroutes another water port. I believe the part cost $50, can't remember the part number. You have to run a special head gasket from Fel-pro, part number FEL-1017-1. They cost about $40 each. My local Autozone had to order them in. I just recently got my motor fired up and I have no water leaks. I have yet to drive the car to be able to see how hot its going to run. I did get the motor up to 200 degrees when I was breaking in the cam. Let me know if you have any other questions on running this set up. I ran across a few other things in my case that I had to address and fix. graemlins/beers.gif

Chris

Chris,
It will be interesting to see how your setup works long term. I have seen the blocks you are talking about and was not real confident that they would maintain sealing pressure on the head gasket in a long term street use engine. I would certainly be keeping a real good eye on the oil for any signs of coolant.

ok, what's the rule here?? what gen heads fit which blocks???? i assumed i could use my gen iV heads on my Gen VI 502... can't i :confused:

Bill, I was very skeptical about doing this, but the tech man at Scoggin-Dickey was very adimate about how much sucess they have had using there kit. All it looks like is a stamped piece of special metal thats real thin and sets down in the cooling passage holes in the block, one of them has what I would call a steam port to direct the flow of water.I went ahead and studed the heads to get better sealing pressure on my gaskets, as per recomendation of Scoggin-Dickey. I am definetly going to keep a close eye on my oil for any signs of coolant. I have about $5500 invested in my motor, so I want to prolong its life as much as possible. I would have probably bought new heads, but I already had the heads that I am using and I didn't want to spend another $1800 on another set.
graemlins/waving.gif

Chris