Ok the vc that's dirty underneath I'd the side that has 2 cyl with lower compression than the rest. Any guess as to why it's dirty underneath?

Blow by would have to travel down the cylinder, up through the cam tunnel, into the lifter valley, and finely into the heads.  How do the valve stem seals look on that side?  What about the valve guides, are they loose?  My guess is that you have some combustion residuals getting past the guides and seals into the valve cover.  Mmmmmmm...  o-ringed valve covers :-P~

Do you have a leak down tester?  If not, can you rig up something to blow air into the cylinders while each is at TDC on the compression stroke?

Listen for the leaking air; if you hear it coming from the exhaust, it is bad exhaust valve seat sealing.  If you hear it coming from the induction (carb, intake, etc.), it is bad intake valve seat sealing.

You will always hear some air coming from the oil pan, valve covers, dip stick, or anything else connected to the crank case but if the two known bad cylinders hiss louder, it is from bad ring seal.  You will always have a little blow by and it is bad if you don't have any, but > 20% leakage indicates that the rings (and probably cylinder bores) lifespan has ended.

Good luck,

Joe

Take the head from the dirty side and poor some type solvent or even water into the combustion chambers.  Fill the chamber higher than the valves and see if the liquid runs out the spring side of the valves.  Could be valves not sealing allowing the combustion gasses up past valve seals like Flusher's saying.  That would also explain your low compression.

These heads haven't ever been off before. Just got back from the machine shop, they showed me where the HG was blown between cylinders. Said my valves are probably fine, but since they're off the guys are doing a valve job and surfacing.

He also told me that the reason the gasket looks off kilter between all the cylinders is so the valves clear the gasket.

Machine chop surfaced the heads and says valves are fine, run it.

What head gasket will you run?

Still researching. I don't know the compressed thickness of the gaskets that are still on the block. plus 10 thousandths that was taken off the heads.

I'll ask the machine shop if they have any recommendations and likely give fel-pro a call and be that guy and pick someone's brain.

How deep in the hole are your pistons at TDC?  Try to keep your quench clearance < or = .055

I'll have to check when the weather dries out this weekend. He says my steel shim gasket was likely .038" and I'd be ok using that thickness.

They needed to take .02" off to make them flat..  I think I'd need a thicker gasket than what I had.

I don't own a micrometer yet but I will this weekend.

I believe what is in your pics is a composition gasket.  Below is a pic of a steel shim gasket that I pulled out of an '88 3500 454 core.  This steel shim gasket measures about .026".

http://m.harborfreight.com/6-inch-dial-caliper-66541.html is well worth the $20 for quick measurements.

It seems excessive to have .020 cut off your heads, just for a cleanup.  I was just curious what you were doing and not trying to get all up in your mix, but...  I have exhausted all of my resources trying to come up with an idea as to how much volume .020" removed from your combustion chamber.  Without knowing specifics, I think you will be just under a half-point gain if you use the same gasket.  Though the same gasket won't change your quench distance (piston top to head surface), it will tighten up your piston dome to chamber and piston to valve clearances a bit.  You might also have some issues with intake manifold alignment.  The thing that really concerns me is that it could through off your rocker geometry.

It looks like you have some healthy compression judging by your piston domes.  Opening up the quench distance could cause your engine to be more prone to detonation.  In researching the change in chamber volume per amount cut from deck surface, I found that Chevrolet recommends .035" clearance to be the minimum for steel connecting rods.

If your quench distance doesn't become an issue, I might lean more towards restoring the height so that it doesn't throw off your rocker geometry.  If you don't mind me asking, what type/size cam and style rockers are you running?  What RPM are you turning?  You might need to change push rod length.

Again, I didn't mean to overly complicate things.

Happy holidays,

Joe

I believe what is in your pics is a composition gasket.  Below is a pic of a steel shim gasket that I pulled out of an '88 3500 454 core.  This steel shim gasket measures about .026".

http://m.harborfreight.com/6-inch-dial-caliper-66541.html is well worth the $20 for quick measurements.

It seems excessive to have .020 cut off your heads, just for a cleanup.  I was just curious what you were doing and not trying to get all up in your mix, but...  I have exhausted all of my resources trying to come up with an idea as to how much volume .020" removed from your combustion chamber.  Without knowing specifics, I think you will be just under a half-point gain if you use the same gasket.  Though the same gasket won't change your quench distance (piston top to head surface), it will tighten up your piston dome to chamber and piston to valve clearances a bit.  You might also have some issues with intake manifold alignment.  The thing that really concerns me is that it could through off your rocker geometry.

It looks like you have some healthy compression judging by your piston domes.  Opening up the quench distance could cause your engine to be more prone to detonation.  In researching the change in chamber volume per amount cut from deck surface, I found that Chevrolet recommends .035" clearance to be the minimum for steel connecting rods.

If your quench distance doesn't become an issue, I might lean more towards restoring the height so that it doesn't throw off your rocker geometry.  If you don't mind me asking, what type/size cam and style rockers are you running?  What RPM are you turning?  You might need to change push rod length.

Again, I didn't mean to overly complicate things.

Happy holidays,

Joe

Joe, I have no clue as to what my cam specifics are. It's a boner stock marine power straight out of 1993. Turns 5100..

I could really use more information from the machine shop. He's well known and highly recommended, just maybe he thinks I know what I'm doing. Him saying valves are fine it was a head gasket problem doesn't provide an answer for the exhaust that's been flowing through my one valve cover.

Is replacing the valve seals at home a doable task?

Thanks

If it is the stock cam with stock stamped rockers, I'd be real tempted to put it together as is.  I've run stock stuff way harder with way worse geometry.  I think this is just me unnecessarily overcomplicating your head gasket job, but then again, with domes, I would like to check everything.

As far as can you change valve seals at home, it depends if you have the necessary tools.  Minimum, you will need a valve spring compressor and every valve needs to come apart.  Then, it depends on the type of seals.  If they are umbrella seals, they just snap into a groove in the valve stem just under the retainer.  If it is they are stem seals, you might need a tool to drive them on.  CompCams and others offer a tool to remove stem seals, but I have never used it.

I am going to say at this point, the valve seals had to be inspected when the machinist reassembled the heads.  If he is comfortable with them, I think I would do as he says and run them.

I'm going to talk to the machinist once more before I waste $100 on gaskets.

But yes this motor has never been taken apart before, stock cam. I don't believe the valve covers have been removed before.