Water leaking from exhaust valve HELP!!!

[cableguy1979]

1996 454 magnum mpi engine. I have water leaking from a exhaust valve into the cylinder and exhaust manifold. Looking under the valve cover I of course see mixed water and oil but no fresh water like what is leaking into the cylinder. How can fresh water get into the top of the exhaust valve but not be under the valve cover. Is there a water jacket and maybe there is a crack internal? Picture added.

 

[Maclin]

Mostly likely sources are a cracked exhaust manifold internal cooling passage or manifold to riser gasket leaking.

 

[tpenfield]

Could be a valve guide rusting through. Been there done that.

 

[cableguy1979]

That's the bottom of the valve spring where water is leaking so I know it isn't coming from the exhaust manifold its coming from above the valve but below the spring. The isn't anything above the valve cover with water in it so I don't think it's a valve guide.

 

[Rick Stephens]

There's water jacket all through the heads. You have a crack.

 

[cableguy1979]

Any other possible cause?

 

[Bt Doctur]

nope, a crack under the port or the seat or a rot hole

 

[cableguy1979]

Ok I'll take it off and maybe it can be repaired by a machine shop?

 

[TurtleTamer]

Ok I'll take it off and maybe it can be repaired by a machine shop?

Not very likely, but maybe they can source you a bare head for cheap that you can swap your valves and springs over to.

 

[cableguy1979]

Is it that easy? The 454 magnum need special heads?

 

[Rick Stephens]

Regular ol' GM heads.

 

[tpenfield]

The 454 Magnum uses the rectangular port heads, the standard 7.4/454 uses the oval port heads. You can match up your heads with replacements via the casing number on the head.

 

[cableguy1979]

OK so I just need to find the same casting number and move all my valves and springs and put in new guides.

Is there any chance that a bad valve guide could let water in from a water jacket? I know its not coming from under the valve cover but i dont know if there are water jackets in the valve seat hole.

 

[TurtleTamer]

A bare casting *should already have guides in it. To put this in perspective, I took an LT1 head to my machine shop to have a horribly repaired and then rebroken exhaust bolt removed, when my guy said "hang on," walked in the back and came out with a brand new bare casting and said "$75."

​​​​​​Bottom line is the repair would have been upwards of $200 just in labor and I'd still have a repaired head vice new. You may find this issue to be cheaper to fix than you think.

 

[cableguy1979]

Man I hope so. I will look around for the right casting. It might be best to let the machine shop determine the cause of my leak. I am just curious if there is water hole in the seat area that can go over to the water jacket. I dont think so but hoping someone else would know.

Thinking now since the engine has had so much water in it and there is some rust internally maybe I should just re ring it and put new bearing in it. I found a kit to purchase for it but I dont know if its the same quality as the original marine one install new, Can someone verify this will in fact work ok for my situation? Anybody know if the gen v is a one piece rear main?

https://www.ebay.com/itm/Mercruiser...0:g:sioAAOSw3mpXINeM:sc:UPSGround!37336!US!-1

https://www.ebay.com/itm/Mercruiser...b:g:ndEAAOSwubRXIKzo:sc:UPSGround!37336!US!-1

 

[cableguy1979]

Doing some research it looks like all 454 heads up to 98 had water cooled valve guides? Does that mean this could just be a simple valve guide replacement?

 

[cableguy1979]

Man that would be awesome if that was a possibility.

 

[Rick Stephens]

The 454 Magnum uses the rectangular port heads, the standard 7.4/454 uses the oval port heads. You can match up your heads with replacements via the casing number on the head.

Learn something new every day. Thanks tpenfield.

 

[cableguy1979]

Took the head's off tonight and no sign of bad head gaskets. Will take the heads to the shop tomorrow.

 

[Bt Doctur]

Research suggests the exaust guides are wet, meaning they pass thru the water jackets