Thread: Head gasket limits coolant flow? Check out the pictures

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The head gasket has a much smaller hole than the passageway in the block and the head. Is this right? Should I enlarge the hole?

On a side note, I was having cooling problems (not cooling enough) with no determined root cause (yes I know there are many reasons why this could happen). Could this small hole be limiting my coolant flow for no good reason? Why is the hole in the Fel-pro gasket so small?

Thanks in advance.

Those big holes in the block are that big to get the casting sand out after the casting process. Those small holes in the gasket are all you need. It slows the water down so that it actually has time to pick up the heat from the cast iron surfaces of the block and heads and evenly distribute water flow. What is sometimes done on race blocks is that 3/4 inch threaded pipe plugs are added to the 3 big water passages that go down the side of each bank then they are decked flat with the head surface and then drilled out front 3/16" middle 1/4" rear 5/16". As you notice the holes get larger as they go to the rear of the block and get furthur away from the water pump. This helps even out the flow and prevents local hot spots in the block and heads. Say if you opened up the gaskets to the size of the block holes 3/4" the water flow will take the path of least resistance so the front of the block and heads will be cooler but the rear of the engine will boil.

I would check for other reasons thermostat, air flow, fan speed, type of fan.
What type of vehicle is it in ?

Like the man says, those holes are sized like that for a reason. Some older engines that don't cool right, those gaskets have eroded over the years and are allowing too much flow where it shouldn't be going.

Originally Posted by southerner

I would check for other reasons thermostat, air flow, fan speed, type of fan.
What type of vehicle is it in ?

Thanks for the good info. It's a 1982 Jeep CJ7 with this V8 swapped in. I think the problem was due to combination of timingadvance, .030 over, and unreasonably crazy cam.

I run a full aluminum radiator, and dual electric fans.

After I re-do the engine this winter (new cam, etc), I hopefully will have eliminated the cause. There is (after this swap) no good reason why it should still run hot at all. Putting in a Edelbrock higher flow good quality water pump, higher flow tstat, and should have everything in good tune after this.

Thanks again.

I would look at putting in or trying to put in a good water pump driven fan and fan shroud. This really pulls the air through at slow vehicle speeds. Do an experimentplonk the bonnet up on your jeep feel the air displaced by the electric fans. Then go over to a friends car that has a big belt waterpump driven fan, you should detect quite a difference in airflow. The more air you can pull through a radiator the better job the radiator does of cooling the coolant.

I agree that mechanical fan will beat the electric hands down. What I'll do is when the cam swap and carb swap are done and I have it all dialed in, if I still have a problem, then I may swap to a mechanical.

Thanks for the advice.

Originally Posted by pnut

I agree that mechanical fan will beat the electric hands down. What I'll do is when the cam swap and carb swap are done and I have it all dialed in, if I still have a problem, then I may swap to a mechanical.

Thanks for the advice.

Glad to help, let us know how you get on