12 minutes ago, madkaw said:

the scoring behind the water pump is not part of the head . That’s the timing cover that will need to be replaced .

Well, of course you are correct.  I know that, but somehow my feeble mind typed it out anyway.  Yes, I'm a nimrod.

I haven't seen the crank and I too can't see how the scratches would clean up by polishing.  I got that info from the shop owner, not the guy who did it, so we'll see.  Cutting it again wouldn't be the end of the world.

Anyway, I plan to mic the head tomorrow or Thu.  More to tell then

@siteunseen
The exhaust seats show some good pitting (I'lltry to get some pics). 

These were cut clean with a 3-angle finish way back when.  They may clean up with a valve job.  I suspect the time on the engine stand had something to do with it but that's really just WAGuessing.  I have never seen pitting this bad before.

Anyone notice the debris at the water pump cavity in the TIMING COVER 😉?  Or at the exhaust ports?  How about these pics of what was a brand new oil pump...

Truly, now a wasted pump. Some serious debris has been through this motor.  Why did the oil filter not catch it?  Perhaps bc it went into bypass during winter starts and that 5hit went right on through to ruin the oil pump, timing cover, cam towers, and score the cam and crank journals.  Maybe more.

What I've not commented upon is the fine grit I found in the oil pan.  I've spent a lot of time reflecting on what was going on at that time in my life ('96 - '97) to try to understand what might have happened.  I've considered my negligence or oversight by allowing debris in the area while building this motor, machine shop debris left in passages (again, my oversight for not clearing it), sabotage by employees (I had received several serious threats), contaminated oil and antifreeze (IMPOSSIBLE), and so on. 

My principal concern is to avoid it happening again!  The cost to have the original machine work done was painful then, now it'll be much worse.

More later...

I have an aluminum pump on my 240 and Melling steel pump on my 280. I haven't had them apart since the rebuilds but it does look like you have some extra pitting. Could be coolant mixed in with the oil. Just a guess but that's what it does to the water pumps that I've seen with head gaskets gone bad.

If you have any oil pan debris left, put a magnet on it to see if it's ferrous or not.

I was thinking the pump was a hardened material?

If so it took something significant to damage it like that

I've seen oil pumps look like that.  If I see any denting, I pitch it and buy new.  Every dent will result in lost flow/pressure.  It should be pristine.  

There was zero leakage of oil or antifreeze.  I am certain the pitting and gouges are from debris.

The pump gears are hard, but not like tool steel.  A file scratches them.

So, I finally got to measure the head today.  Got in onto the bench and was rolling it into position and guess what I saw?  Metal filings and glass beads in a water passage.  Interestingly, the same machine shop did the work back in '96.  Maybe cleaning after milling ain't a happening thing.

I didn't find any metal in the oil pan, but definitely hard, rough, very small particles.  Also, when I built this motor I capped it off with a polished valve cover from MSA.  My search for the source of debris turned up a problem with that valve cover.  The vent baffle perimeter is sealed with a material that is extremely hard (probably started as firm and flexible).  I found several pieces of that sealant in the debris field.  The pieces are quite brittle.  If some of these made their way through the motor, I could easily see them causing this damage.

If that is true, then any valve cover is essentially a time bomb.  As if there aren't enough things to keep us awake at night. 🤯

Oh yeah, measured the head.  It's been cut a total of .106" with .007 off the top (machine shop just did it) and the balance off the bottom.  Combustion chamber now measures 43.5cc.

 

 

13 hours ago, ETI4K said:

The vent baffle perimeter is sealed with a material that is extremely hard (probably started as firm and flexible).  I found several pieces of that sealant in the debris field.  The pieces are quite brittle.  If some of these made their way through the motor, I could easily see them causing this damage.

I've polished a few valve covers now and it's always a good idea to chip off the rest of that original hard epoxy sealant and remove that vent baffle so you can clean the accumulated muck behind it, on a couple of them I found glass beads from a previous restoration.  I used a permanent flexible sealant like ThreeBond or Motoseal on the baffle after reinstalling.

Even when I get a head back from the machine shop and it has been been sealed up with cling wrap it still has to go through a complete cleaning process. 

On 4/29/2021 at 2:55 PM, ETI4K said:

Oh yeah, measured the head.  It's been cut a total of .106" with .007 off the top (machine shop just did it) and the balance off the bottom.  Combustion chamber now measures 43.5cc.

 

 

 

 

 

 

My P79 is right at .080 and with a standard Nissan head gasket is on the verge of ignition ping if I go anything past 12 degrees base timing(my vac advance is currently bypassed due to busted diaphragm).

Is that your combustion chamber volume?  If so, what do your compression numbers look like?

I think the reason the head didn't explode when I drove it is because they also cut the new pistons to have .000 protrusion from the deck surface, that's about 25 mils, so it kept the same compression ratio (close anyway).

This whole thing is beginning to look a lot like a CF.

It's right at 10:1,  I haven't checked compression yet.  I put about 150 miles on it since the build and started prepping the car for paint. 

That's good that your pistons are cut.  Hopefully you can salvage it.  Sounds it's got the bones for a pretty good build.

Edited May 1, 20213 yr by Reptoid Overlords