In one of my older threads I mentioned picking up a set of AFR heads for the top-end redo of my 502 MPI engines. I’m slowly gathering parts, and though I had planned to start working on them during the current off-season, plans just didn’t work out that way so I’m gearing up for next fall/winter.

I’ve been doing a lot of reading about mating these MK-IV style heads to my Gen VI blocks and I have some pretty serious concerns with corrosion around the water passages between the heads and block.

I do not need rebuilds on the short blocks but I have some good hours on them in salt so converting to closed cooling may be a pretty big pain and ultimately lead to big problems.

My reading has led me to believe that salt can get trapped between the head sealing surface and the head gasket. The heads are a huge investment, and I don’t want destroy them.

Is there a head gasket out there that prevents this issue? Or can the heads be modified to alleviate the possibly of trapped salt? The heads appear to be anodized but this issue isn’t corrected by anodizing.

Any recommendations? Sealant/hylomar in these troubled areas maybe?

I would think you would want to use a stainless MLS gasket, not sure about the trapped salt.

Looking at older threads from back about ten years ago or so, there were concerns about corrosion on certain parts of the mating surface of the head where there was no support under the head gasket. Salt water could get trapped in these areas and lead to damage of the head even when the head has been anodized. That's my concern. Outside of closed cooling, what else can be done to protect these heads on a raw water cooled set up that will see brackish and saltwater exposure?

I'll probably just plan on closed cooling and clean out the heat exchangers as needed if a problem comes up, but I'm interested in ideas and individual experiences.

On a side note.... how much heat exchanger do I need to handle 600 HP?

Thanks!!

Tom, I am using a stock mercuiser heat exchanger from a 454 mag. It has no problem keeping my 625 hp at 150* even on long hard runs. You won’t regret running the closed system. I picked the heat exchanger up for $200 and the rest is plumbing.

I think my issue is plain over thinking!

Closed cooling it is! Considering all the room behind the engines, it shouldn’t be too hard to rig up.