Water drips between head and Block...
 

I've got twin 420's, just went thru them last year, I noticed they have a small amount of rusty water marks that seem to start at the Heads and drip down the block, I made sure at rebuild that marine head gaskets were used. Can't figure out whats up, I do wash down alot to keep them looking good, also note I had ton's of surface rust on the block under the heads before rebuild when I bought the boat. Any thought's???

This has been posted before about 6 months ago and I don't rember if they ever got to the bottom of it.I to have the same thing going on and I had the same problem on my last motor.Both motors had the heads off.The new motor has GM gaskets and the last had Felpro.Hope this thread has a good answer to it and it's not any big thing :D James

Thanks,good or possably bad to here some other folks have seen this, I am thinking/hopeing it's coming from condensation or wash down water getting between the open gap between the head and Block where the engine paint didn't get too, Then sits there and rust's, then finaly drips down the side of the block.

What kind of exhaust do you have? Stock Merc. manifolds have plastic plugs tapped into the back side of them ( the side facing the head). I have seen them leak from there.

Mine Stainless Marine.

On BBC depending on the year you have to seal the threads on the head bolts because most go through the water jackets.

My Gen V 454, yes had sealer. The Gen VI 502 does not need it.

I have 454 as well with CMI headers, and sealer was used on the head bolts, wouldn't the head gasket keep the head bolts from leaking?

Heads/block resurfaced?
 

Were the heads and block resurfaced as part of your rebuild? If not, this could be the problem, especially if there was evidence of a prior leak.

My advice would be to run the engine for a while and visually inspect for leaks. Try it while the engine is cold, as well as after it warms up. I went through the same thing after I rebuilt my 454 - water was "weeping" from the interface between the head/block. Builder said that some of the silicon-faced gaskets rely on engine heat to establish a seal. I went as far as installing a 180* T-stat to try to get my temps up, with no success. I finally started seeing water in the oil, at which point I took it back to him and had him replace the head gaskets. Turns out that his flunkee that he had install the heads neglected to use thread sealant! :eek: He replaced the Ferea gaskets with FelPro's, and used thread sealant, and the problem was solved.

Thanks Budmad, yes the head's were surfaced and the Block was decked, the guy that built them is a very reliable builder and said he used sealant , I do remember asking him if Brass valve guides would be a good idea during the rebuild, and he said he dosn't like to put them in just because the valve guide cast is thin and he dosn't like to take the chance of water getting / eating the cast between the Cast and Brass guides, with this said I figuerd he did all possable to keep the bolts sealed. I guess I'll go have another talk with him..Thanks.

Sometimes the sealer dosent get down in the threads very well and have had to reseal some of them

Thanks turbo2256, here's the million doller question, I know I would never want to do this but since the motors only have 50 hours on the rebuild, is it a horrible idea to pull the short head bolts out 1 at a time and reseal???

another thought,alot of the head gaskets used need retorqed after the first couple of hours,theres only a few gaskets to accually be considerd as permatorqe.you might want to put a torque wrench on one or two bolts and see if they need to be gone over again....

Had to do it to mine they were studs too real pain but it worked used locktite 252 the second time. It was thin enough to get inbetween the threads. I think part of the problem is if the threads havent had a thread cutting tap run down them which thins the thread out and changes the class of fit (I have thread cleaning taps) there just isnt room for thicker sealants to run into the threads.

Oh yea you better check all of them some of the ones under the valve covers could be leaking to. Crack your drain plug if you can and check for water in the oil.

That weeping is pretty common. For whatever reason the gasket does not seal around that lower water passage. It should, but it doesn't.

We put a thin coat of Mercury Perfect Seal on the gasket around the passage, solves the problem.

Thanks, I guess that makes the decision for me I'll pull the heads this winter and ensure the head gaskets and bolts get some sealent, thanks for all the input....

Thats probably the best thing to do. Currently I am rebuilding an older 454 jet boat engine and have noticed the area around the large coolant transfer holes in the cylinder heads along the exhaust edge are rather pitted and sealing land area around them looks a bit shady. Some extra sealant in those ares might be needed.