502 HEAD GASKET QUESTION

Anyone know if the Mark 4 head gasket is any different then a mark 5 or 6 head gasket? Take a look at the pics cyl. 4 piston melted. look at the gasket the engine builder used on it and how it is blocking half the water cooling hole and how the other pics show they are unblocked.

That is typical for that coolant hole to be partially covered. The piston melted because of cylinder temperature, not water temp.

That cylinder looks like possibly water getting in. The quench area at the top looks like it was steam cleaned. If that is the case, water increases the compression, takes the place of some of the air/fuel mixture, and causes high cylinder temps.

The whole compression gland area of the gasket is distorted..warped head?

Either way looks like BDMar said, internal coolant leak into the combustion chamber.

It was defenitly a detonation issue once we removed the piston you could see that the wrist pin was almost beat out of it.

SBMech said:

The whole compression gland area of the gasket is distorted..warped head?

Either way looks like BDMar said, internal coolant leak into the combustion chamber.

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Are you talking about the gasket at 2:30 and 7:30? If so, those are there for blocks that have a relief for the valves.

namba860 said:

Anyone know if the Mark 4 head gasket is any different then a mark 5 or 6 head gasket? Take a look at the pics cyl. 4 piston melted. look at the gasket the engine builder used on it and how it is blocking half the water cooling hole and how the other pics show they are unblocked.

Click to expand...

No Doubt the 3 gaskets are not the same. This is 2017. This was ironed out by 2001. What heads, blocks and gaskets etc. are compatible with a few variations being on the cusp due to casting tolerances is easy to find on the net and in Books for the BBC. Those are Marine gaskets with SS sealing rings. In the first pic I see rust in the cylinder and one rust droplet on the gasket where it should not be in notation "A". Second notation B shows signs of seepage of some sort. No pictures of the offending cylinder head so it is a guess. C and D are suspect areas that could be oil introduced through the head bolts, but I thought all 502 BBC were blind but I have never owned one. All this said, were the Head bolts ever re-torqued?
I find the Forensics of a failure very interesting and just throwing out what see. It is a science within itself. No stone should go unturned and all results should be posted.



My image is small so one might resort to the original post to make comparisons of the areas I noted.

BDMar said:

That is typical for that coolant hole to be partially covered. The piston melted because of cylinder temperature, not water temp.

That cylinder looks like possibly water getting in. The quench area at the top looks like it was steam cleaned. If that is the case, water increases the compression, takes the place of some of the air/fuel mixture, and causes high cylinder temps.

Click to expand...

i know this is an old thread but it created a question i hope you'd be able to answer for me. looking at the original post, second picture and center piston has a clean area above the valve relief. what causes this? the reason i ask is because my recently built 555CI BB has the exact same clean areas, just not as big on all eight pistons, my engine has less than 10 hours run time that is mostly low rpm time. is this normal? i am getting conflicting info from two different builders. thank you in advance.

Nates270 said:

i know this is an old thread but it created a question i hope you'd be able to answer for me. looking at the original post, second picture and center piston has a clean area above the valve relief. what causes this? the reason i ask is because my recently built 555CI BB has the exact same clean areas, just not as big on all eight pistons, my engine has less than 10 hours run time that is mostly low rpm time. is this normal? i am getting conflicting info from two different builders. thank you in advance.

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my question is: how do you know that? Did you have to remove the cylinder heads? If so why? What problem are you having?