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MagicPowerboats 02-19-2025 01:30 PM


Originally Posted by 87MirageIntruder (Post 4920579)
I don't mean to insult anyone's ability, just making a suggestion because it has happened before. Are you sure the head gaskets are on in the correct orientation? The 496 is slightly different in cooling passages from the front to rear of the engine and the gaskets can be installed backwards, causing cooling issues.


Also, how old are the Raylar heads? Early versions did have some issues with cracking.

Would never insult me we have owned an auto repair shop for 40 years, we do build race motors for the off-road community as well. We are aware of the head gasket’s orientation but when someone ask is it done correctly I have to wonder if I did do the right way. I am not perfect but I do specifically remember checking and re checking. For me if I messed up that bad I will be laughing at myself along with the online community cause I will put myself on blast lol.

RAYLAR heads were completely reworked with no cracks. Per the machine shop. You would think they would inform me. They have been doing our machining for 30 years.

MagicPowerboats 02-19-2025 01:30 PM


Originally Posted by snapmorgan (Post 4920592)
One would think so. At cruise speed you may have 25-35psi seawater pressure inside of the heat exchanger. At what pressure did you test the cooling system?

cooling system can only test up to 15 PSI

MagicPowerboats 02-19-2025 01:32 PM


Originally Posted by snapmorgan (Post 4920592)
One would think so. At cruise speed you may have 25-35psi seawater pressure inside of the heat exchanger. At what pressure did you test the cooling system?

It would be nice if there was a way to see the water in the coolant lol

MagicPowerboats 02-19-2025 01:35 PM


Originally Posted by BillK (Post 4920561)
Do you know anyone at an automotive shop that might have a combustion gas tester ? If not they are not that expensive and it would be easy to see if it is a head gasket leaking combustion gas into the cooling system.

https://www.harborfreight.com/combus...tor-64814.html

Another alternative would be to use a radiator pressure tester but I dont know what your cap is like and if there would be an adapter available to fit.

From the symptoms you are describing it almost has to be a head gasket.

I would have to agree with you about it being a head gasket. But the tests are inconclusive thought about running a test with pressure gauge between tank and heat exchanger overflow hose to see if pressure increases quickly which it shouldn’t if head gaskets are good. Only raise pressure as heat climbs.

underpsi68 02-19-2025 04:27 PM


Originally Posted by MagicPowerboats (Post 4920595)
It would be nice if there was a way to see the water in the coolant lol

the coolant will be watered down/ lighter in color. You could always test the coolant with a tester to see the freeze/boil value.


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