Head Gaskets with Slits not Holes

[Doorkicker]

I promise I searched for this answer before posting assuming this is a basic question, but I think it's too basic. So I'll be the first dummy.

I have a '77 440. The block has enlarged coolant ports (figure 8's.., see pic) and the TF 240 heads have offset large holes that line up with one side of the fig. 8 holes in the block.

With all that being said, why do the head gaskets have a small slit opening for coolant when the holes in the head and block are so large?

I searched for head gaskets for '75-'79 blocks, because that's the years I understand the 440's has this configuration, but the gaskets all seemed to have the same small slits as opposed to holes.

What am I missing?

Thank you in advance as always!

 

[khryslerkid]

The slots are to restrict coolant flow.

 

[Doorkicker]

The slots are to restrict coolant flow.

Interesting and I sorta figured that. But why would you want to restrict coolant flow?

It's worth adding that this engine originally ran hot. So, I'm inclined to ensure as much cooling as possible.

 

[khryslerkid]

Interesting and I sorta figured that. But why would you want to restrict coolant flow?

It's worth adding that this engine originally ran hot. So, I'm inclined to ensure as much cooling as possible.

It was a design change to help with cooling. If coolant going through the block and heads happens too fast it won't have the time to cool down in the radiator.

 

[RemCharger]

It's worth adding that this engine originally ran hot. So, I'm inclined to ensure as much cooling as popossible.

Pop out the rear frost plugs and see how much sh*t is packed in there.

 

[Doorkicker]

Pop out the rear frost plugs and see how much sh*t is packed in there.

LOL! There was a TON of cr@p in there. I hot tanked the block, replaced all the plugs. Still had to dig old stuff out. Nevertheless, now it's down to metal again, I'm going to triple check.

 

[Doorkicker]

It was a design change to help with cooling. If coolant going through the block and heads happens too fast it won't have the time to cool down in the radiator.

OK.. that makes sense from a physics perspective, but then why enlarge the holes in the first place? See my confusion? Go about 90% down this page and see the short description about these holes. I'm curious what you think.

440 Source.com Everything you've ever wanted to know about blocks and more....

 

[khryslerkid]

OK.. that makes sense from a physics perspective, but then why enlarge the holes in the first place? See my confusion? Go about 90% down this page and see the short description about these holes. I'm curious what you think.

http://[URL]http://www.440source.com/blockinfo.htm

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Maybe I should have used the term "heat transfer". More time in the passages means more time for heat transfer. Maybe it's why they wanted larger passages in the newer blocks and heads?

I'm using 452 heads on a '67 block. Using those same gaskets with no overheating problems at all.

 

[Geoff 2]

Post #4 is wrong, an old wives tale. You want the flow as fast as possible, not as slow as possible. It is a closed system. If the coolant stays in the engine longer, then it picks up more heat.....more heat for the rad to dissipate.
The large holes in the block [ or heads ] are coring holes, merely aids to manufacture. The holes that control flow rate are in the gaskets. The size of which arecCarefully designed & tested at the factory....

 

[1 Wild R/T]

And one more time.... The slits have always been slits dating back to the 50's... The reason is water is pumped into to lower passages of the water pump, through the block front to rear then up into the heads out to the thermostat & then the radiator...

If you open the slits coolant will take the short path from the front of the block up into the heads without ever travelling to the rear of the block or heads... The front cylinders will run nice & cool, the rear cylinders? Not so much...

The slits allow trapped air to escape from the block...

 

[Rick62]

Cylinder blocks are sand castings. The purpose of the holes is to remove the sand after casting. The purpose of the slits is to reduce the coolant flow to what it needs to be for proper cooling. This may be helpful: