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What would cause this to happen on the underside of my intake? The oil pan underneath was rotted out in the center...so something to do with that? Do I have an issue here?
coolant leak on the manifold? How did the oil look?
oil was fine. Under the valley pan I did find some grey sludge, which was weird, and some milky oil. But otherwise, and other places, the oil looked fine. However the gaskets all around appear to be toast, so maybe a small leak? I just want to make sure it isnt indicative of something major.
also, what’s purpose of the large recessed square plug on the bottom?
I think the plug there was part of the casting process. Did this motor sit for some time, or has been running and driving?
It was my daily driver until I found a rocker arm slapping around, so it sat until the weather turned warmer...maybe 2-3mo, in my driveway...and now I’ve been tearing it down to see what all needs rebuilt. But before I bought it a year ago, it sat for quite a while. I did find rust on the push rods, and evidence of moisture in the block. When I bought it, the valve gaskets were shot, so I’m thinking it was taking on moisture while the last guy had it sitting.
edit: not moisture IN the block, as this is the first time I’ve torn it down to the block, but rather carb, cylinder heads, springs, etc...as well as several rotted hoses.
351 doesn't have a wet intake, just air injection. Could be exhaust back feed from bad gasket at injection port between head and intake or from exhaust crossover port.
Last edited by 5851a; Jun 4, 2021 at 04:21 PM.
Reason: spelling
Its just corrosion best to give the bottom of the intake a sandblast. That is unless you are running a valley pan then just give it a brush-off and reinstall.
I recently had a similar experience,
I have a 351 Cleveland that was sitting in a vehicle with air intakes in the hood of the vehicle, I had left the hood slightly open and as the car had been sitting a while heavy rain appeared to get onto the top of the manifold.
When I pulled the manifold recently, I noticed rust and white-water oil on top of the alloy plate that sits under the manifold, and rust under the manifold.
As the Cleveland is also a non-water passage manifold also and the radiator was still full, I surmised that the water had entered via air intakes onto the centre sides of the manifold (where there is an opening) and dripped through on the metal plate, no moisture was found underneath the manifold heat plate so it can only entered from the manifold sides.
So if water could have entered the engine bay somehow that would possibly explain the corrosion.
I have started and driven the vehicle recently and have not had any oil or water contamination.
I used a wire wheel on an angle grinder to clean up the bottom of the manifold then a tannic acid rust converter before repainting.
