Slant 6 Head Gasket Question

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Glue Man

Glue Man

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I had to have my slants head gone through recently. Once it was back together, it overheated rather quickly and I popped the head gasket. I have bought a new head gasket and had the head decked.

My question is, do you guys know if the coolant port on the forward side of the head is supposed to be blocked by the gasket? I dont have the original gasket to compare it from, but I do have the first one that I installed prior to over heating it. The gasket I installed prior to overheating has that port blocked. The newest gasket that I bought also has the forward coolant port blocked. It sure seems like that coolant port should not be blocked, and that's why the car over heated so quickly. The owner of the machine shop told me that sometimes, they are designed to be blocked. Nothing I can find on the internet is telling me one way or the other.

Anybody know for sure which is which? Im stumped.

First picture shows the back end of the head with the two coolant ports. The second picture shows the forward coolant port that my head gasket doesn't have a cut out for.

IMG_0223.JPG


IMG_0222.JPG
 
The front coolant ports should be blocked by the head gasket...this is for sure. This is designed so that it forces all the coolant flow to go from front to back in the block, and then up into the head in the rear, and back to front through the head. In this way, all parts of the head and block receive cooling flow.

It is common on the old steel shim gaskets for the gasket to rust through up front and allow the coolant to bypass part of the head and block, which is not good.

Once back together, then take it easy and see if it tends to overheat again. Then come back and work on the issue. BTW, did you pull the block drain plug and flush it all out real good? This would be a good time to pull off the water pump and look into the block to see if it is full of crud.
 
Last edited:
nm9stheham said:
The front coolant ports should be blocked by the head gasket...this is for sure. This is designed so that it forces all the coolant flow to go from front to back in the block, and then up into the head in the rear, and back to front through the head. In this way, all parts of the head and block receive cooling flow.

It is common on the old steel shim gaskets for the gasket to rust through up front and allow the coolant to bypass part of the head and block, which is not good.
Click to expand...

That's what I was afraid of. Thanks for confirming this. Now I need to find out why it over heated to begin with.
 
How's about personal experience? When younger and dumber, I compared the new gasket to my slant six head & block and decided one coolant passage should not be blocked by the gasket (probably the port you question). No internet then (we are so spoiled now), so ASSumed it needed a hole there and made one. Started the engine and after ~5 min idling it "seemed hot", checked the dash gage and it was pegged. Since everything was new, I was able to lift the head up 2" w/ the manifolds on and slide a new, unmolested gasket in and all was well. Best guess is that "port" is a "core hole" so the factory could shake the sand out, and was never intended to flow in any engine. Did I mention I had an M.S. in Mechanical Engineering at that time? Real-world experience is better.

Did you check the water pump? Mine has a sheet-metal blade that could corrode away. I verified mine using a $15 USB "endoscope" from ebay.
 
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