Should these water holes be blocked?

[CamaroMan]

Hi - busy cleaning a head for the atomic 4.. Owner didnt know anything about flushing - either way been spending alot of time clearing the water passages. about 1/3rd of them were completely blocked requiring drilling out the muck.

I noticed these holes (line up with water holes in the block) but they seem blocked, is this correct?




Also curious if these are possibly the original asbestos gaskets ??

[CajunSpike]

You can compare against this pic of a new head.

https://moyermarine.com/product/cylinder-head-late-model-aftermarket-ovcm_01_193/

[Don Moyer]

Water passageways in heads

Universal changed the coolant flow pattern somewhat over the years between the block and the head. They did this by eliminating certain holes in the head. Hole patterns in MMI heads reflect the latest Universal configuration. Universal never changed the hole pattern in the head gaskets however, which is why you will see "witness marks" on heads where holes have been eliminated. Don

[CamaroMan]

Thanks! Good to know - i can proceed now safely. I found no stat when removing the housing but the bypass was not blocked, can I just pop a marble in?

[Don Moyer]

Marble

Not sure what you mean by "pop a marble in". Don

[Al Schober]

Original gasket would not leave fiber on the head or block. Original gaskets were asbestos fully encapsulated in copper. Compressed thickness of these original gaskets was about 1/16". New gaskets are 1/32", hence the need for two.
As for clogged coolant passages, make sure the ones in the block by the valves are clear.
My choice of cooling lineup is no thermostat, bypass blocked (or non-existant). I like to run the engine cool. This is for an engine with glycol/heat exchanger. Folks that are trying to make hot water for a shower will want to run the engine warmer.

[JOHN COOKSON]

found no stat when removing the housing but the bypass was not blocked, can I just pop a marble in?

I assume you are considering restricting the bypass with a marble?
It would be better to run the bypass water through a ball valve. The valve would allow you to meter the amount of water going through the bypass.

TRUE GRIT