MLS or Composite Head Gaskets?

[Guanfy]

Through a series of unfortunate cooling events I blew the head gaskets on my newly repaired B3000... sigh. In any event which would be a more forgiving gasket for a 25 year old block? The composite gasket offered by Mahle or the MLS gasket offered by felpro? I've cleaned and checked the flatness of the block and its good within .002 in, but every little bit helps. I'm also planning to do an engine flush using evaporust to fully ensure that I get all the rust out of the block. Any thoughts on that? I'm pretty sure that what caused my overheat condition was clogged coolant channels to the head due to rust.

 

[Guanfy]

Well, ultimately went with the Mahle gaskets. The composites should offer better sealing than the MLS.

 

[RonD]

Yes, composite, if block and head(s) are both cast iron

MLS was developed for aluminum heads
Aluminum expands 5 or 6 times more than cast iron when heated
When aluminum heads were first used in daily operation the composite head gaskets would fail as early as 30k miles but most by 60k
They were being "rubbed" into failure, by daily heat up cool down cycles
The aluminum head would expand and contract when heated and cooled more than the block, so rub-a-dub

MLS(multi-layer steel) allows the head to "slide" instead of "rub"
But in the early days of MLS in daily use, they would leak coolant on very cold days, aluminum shrunk too much, lol.

But they got most of the bugs worked out for daily drivers

MLS in racing engines was never an issue, they never used them long enough to find out these issues

 

[Guanfy]

Informative post as usual Ron. Thank you!