Hello fellas

I typically post over in the idi section but I recently did some work on my Donzi boat powered by a ford 460 4bl (basically the same engine in your trucks) and had some questions.

I pulled the intake manifold off of my boat because it needed new gaskets. I had the intake media blasted and then I repainted it (ford blue, of course). I then went to get new gaskets for the intake. As I am sure all of you know the intake gaskets on these engines have water ports on either side of the gasket going from the intake into the heads, they look like this:

Fel-Pro Q1231 - Fel-Pro Performance Intake Manifold Gasket Sets - Overview - SummitRacing.com

On a marine 460 there is another water port in the middle of the cylinder heads and intake and the water port at the back of the engine is sealed off on both sides of the intake (only on the intake, there is still an open water jacket in the cylinder head). The marine intake manifold gaskets for the ford 460 look like this:

Fel-Pro Q17368 - Fel-Pro Performance Marine Intake Gaskets - Overview - SummitRacing.com

Notice the middle water port. Now the actual port itself on the intake and cylinder head is about 1" squared. If you look at the intake manifold gasket you will see that there is restriction on that port. The hole in the gasket is about big enough to put your pinky finger through (significantly smaller than the actual ports on the head and intake.

When I replaced my intake gaskets i just used the automotive intake gasket and then used a box cutter to cut out the middle port. I cut the entire port out mind you so there is no restriction now.

Well, now my engine is running hot when it never did so before. It will slowly creep up to 200 and then I shut it down. It used to go up to 155-160 and stay there whether I was idling or full throttle.

Is the lack of restriction on that middle port what is causing my overheat?

Why is that restriction there on the marine gasket?

Why are the back ports closed off on the marine intake manifold?

What would be the repercussions of using an edelbrock automotive intake with water ports on either end of the intake rather than the marine intake with one on one end and a restricted port in the middle??

Thanks for your help.

 

michbol,

I have absolutely no expertise [or experience!] with boats, but sometimes, restriction is a good thing. Years ago, stock car racers were removing the thermostat on their vehicles and found that the engines ran hotter. The water [coolant] was circulating so fast that it did not have time to absorb the heat from the block and heads and then transfer it to the radiator. Some high RPM applications actually benefitted by drilling holes in the water pump blades to decrease the water flow... something to think about!

 

I did several performance upgrades on the engine that all help it run much better (electronic ignition, new sparks and wires, New 750cfm carb with riser). The only difference to the engine before and after I did this work is that there is no restriction on that middle port and now I am overheating. I think may have just signed myself up for another 2 hours of work because I tried to save $20 on an intake gasket....