aluminum corrosion
 

I am experiencing rapid corrosion of my aluminum Edelbrock heads on my 509. In less than 100hrs i'm getting water in #8 cylinder again. this happened the first time after about 4yrs with Felpro gaskets. this time I was using Cometics & the problem seems to be considerably worse. I also added an anode to the thermostat housing after the last repair. I had the heads welded & machined before going back with the cometics. I'm flushing the engine after every use & the boat runs in brackish water only except for a trip to Destin once a year. the Mercathode system is hooked up but i'm not sure if it's working. any idea whats making this happen so rapidly? many people in the area run aluminum heads for many years without a problem. most of my boating is in lake Pontchartrain so it's not very salty.

Sounds like you got electrical issue.

you NEED to have any aluminum part that sees salt water hard anodized to help it last longer. Do you have the marine edelbrocks or the std aluminum? How fast are you using your zinc's? Have you looked at your grounding?

If the aluminum heads have not been hard anodized and your running open cooling system in saltwater; then 1-3 years will be the life expectancy of those heads. I've had the same exact thing happen to me. Bought my boat from a guy. Motor rebuilt, had pro comp aluminum heads, 40 hours of use over 3 years. Previous owner bought it like that from a guy in Ohio (freshwater) who had one season on it, then he ran it on the Chesapeake Bay (brackish water) for 1-2 seasons and the heads were completely toast. On the 4th season (my first season with the boat) I experience water getting into the motor. Milky oil. I mistakenly listened to my mechanic who said the milky oil was a result of engine not getting hot enough so run it at WOT for a bit and it will clear up. I ended up droping a valve and tearing up an engine. Pulled the heads and this is what they looked like. I ended up repowering with stock 502's ...cast iron heads. I'd venture to say that yours look exactly the same. Don't run it anymore. Tear it down and replace the heads with hard anodized aluminum or cast iron. Sorry, but atleast you still have time to catch the summer.

Look closely at the water passages and you can see the corrosion.

standard aluminum I will be tearing it down tomorrow & I will inspect the zinc I installed in the thermostat housing.

If I'm reading this right, you had a problem with corrosion and had the head repaired? now your having the same problem, same head in a much shorter time span? After the repair they should have been sent out to be anodized. The repair material and repaired area are dissimilar metals and will corrode faster if not coated.

Pro Comps are junk
 

All aluminum is not the same. I had a set of Pro Comp aluminum heads. After 9 months of use in brackish water (always flushed thoroughly), the PC's were junk!!!

Switched to Patriots and the problem is not completely gone but much better.

Just my 2 cents.

do you leave boat at marina, might be shoretie problem aggrevating you problem. i would relocate the anode to supply hose going to engine, manifold is later part of flowpath. i would look for black hard anodize(military grade) will hold up best. run ground wire from block ground to heads and intake, use antiseize to help desipate electrolysis.

I pulled the heads today & they are corroded very badly. what I can't figure out is why the intake is in good shape but the heads are destroyed. I'm starting to suspect the quality of aluminum edelbrock uses as being part of the problem.

Depending on the generation block you run the head gasket can hold water against the head where the gasket adapts for Gen IV heads or Gen VI heads around the water passages. thats why the heads get torn up so quick.

Closed loop cooling was my solution. Never had another problems.