[95wagon]

Think the larger spec clearance on 5 is more to do with the width of the bearing ; rather than the thrust.

Thrust issue.
Not saying this is your issue but I have seen the following.
During the cap cut in preparation for align bore-hone they get the cut infinitesimaly off true.
This shows up the machined surface on the cap where the bearing flange is leans.
The tip edge of the thrust flange hits the crank before the rest of it.
You can check this with a little bluing or even a felt pen.
It will show up as a shiny spot .
If this is what it is the edge can be dressed on a surface plate with some 400-600 paper.

Picture later

 

[95wagon]

They cut more here

Or here

this or the other side leans

bluing or felt pen

mark on edge , front or rear depending on which why cap leans .

 

[sherlock9c1]

Hmm. I'll give that a try. I'm also wondering if the ARP studs are just too tight in the bolt holes, and so they don't allow the cap to move enough to line up. One was consistently rubbing the cap as I tightened it. Could I drill those holes out a tad for some clearance? I stopped at a local engine shop and looked at a stock SBC rear cap and bolts and there was plenty of clearance.

 

[95wagon]

If cap crank to flange clearance , or lack of is the same all the way around the half then yes it could be offset due to lack of clearance at the hardware.
If that were the issue I would be more inclined to run a 7/16 end mill down the hole offset a couple thou.

Further checks.
The clearance with the cap removed should be able to be duplicated cap on , no less .
Example even if in spec , if you cant get the same number the cap is ether leaning or hardward is holding it offset.

Try pulling the studs and putting bolts in.
If you can now get the same number as without cap on then you are likely correct, stud shank is likely holding it .

If the cap on number is still less even the tinyest bit that suggests the cap is leaning.

If crank was out you could check cap to block parting line. Undoweled caps should be able to go a little wrong in either direction.
Hardware should not , as you know, be pushing on the side of the hole.

 

[sherlock9c1]

I think I'll open up the bolt holes a tad. I don't have spare stock bolts laying around to try with.

 

[95wagon]

Just make sure that's what it wants first .
Any old bolt the right length would do for a test .

Maybe an old head bolt with washers , crap grade 5 from the store torqued to 35-40 , anything.

The med length end head bolts , my info shows them as .275 shorter than the rear cap bolts

 

[sherlock9c1]

Some updates. Does anyone else get a burst of creative energy right at bedtime and then you're up until 1am chasing a problem, only then to suddenly run out of steam and have to go to bed?

Here are overhead pictures of the rear cap studs. The oil filter side has always been the tight one. Non-filter side has plenty of uniform clearance.

Filter side is tight against the outside of the bore.

See the big gap on the inside? I swapped studs side to side without moving the cap and the same side was still tight, so it's not the studs.

I took the lower bearing shell out and tested it with a feeler gauge. I can get .005 in there easily and can barely force .006 so the upper and lower bearings have the same clearance. It's not the bearing.

 

[sherlock9c1]

Both studs are identical thickness.

So I drilled out the oil filter side with a 31/64" drill bit. Cast iron doesn't mess around. Very slow going and lots of cutting fluid.

I went very slowly to avoid breaking the drill bit.

I now have more stud clearance on this side.

 

[sherlock9c1]

Here is the rear thrust face prior to sharpie application.

I coated the thrust faces with a black sharpie (next time I'm using blue, just for the record. Don't use black.)

I made a specific effort to coat all the other edges of the bearings.

In rechecking the register prior to installation, my pick caught on a burr. You can't even hardly see it, but the pick kept getting stopped here.

So I got a small file and took the burr off, and dressed the other edges as well.

 

[sherlock9c1]

I had placed the dial indicator on the front of the crankshaft but discovered you can flex the middle portions of the crankshaft enough with a screwdriver to give you a false (positive) reading. So I tried this method. DON'T do this. Any force on the crankshaft will flex the engine stand mounting arms and give you a wildly positive reading. You need to reference it to the block itself.

I tapped down the cap, torqued the stud nuts, released, then smacked the crankshaft rearward and then forward, but I was only able to see maybe 0.003" total movement on the dial indicator with a lot of shoving between the #4 and #5 crank journals using a careflly placed screwdriver. I rotated the crankshaft about 20x and still have a tight spot. Here's what the thrust bearings then looked like.

 

[sherlock9c1]

So I think what I'm seeing is where on the outer edges of the thrust bearing?

 

[sherlock9c1]

In a small block chevy one piece rear main cap, you can see the front thrust surface while assembled, but not the rear. So I did some eyeballing. Here is the passenger side. I can get an 0.003" feeler gauge in that gap at the parting line no problem.

Same on the driver's side.

But the top of the bearing seems not to have any clearance. I tried rotating the crankshaft again and although visually the clearance did not change, I could feel a tight spot as I rotated it. Perhaps the thrust surface is off by half a thousandth?

So I rotated the crankshaft about 20x to get some more wear pattern on the thrust surface and got this.

 

[sherlock9c1]

So I decided to polish .003" off the front surface of the rear bearing. I measured 1.716", the same as I've measured with every single one of the new and old Clevite H series thrust bearings I have on hand.

It did not take much polishing on 400 grit sandpaper to get 0.003" off.

I also noticed a couple of tiny burrs on the inner radius that I filed off.

I was able to get 0.003" endplay via the polishing on the front face. I polished a little more to see if I could get closer to .0055" which is what I'm reading with rear cap off.

Alas, multiple cap tightening attempts yielded actually less clearance. It is possible to shift the rear cap forwards and backwards on each side. I got tired of messing with it and set it aside.

 

[sherlock9c1]

Sometimes it's good to just walk away for a bit. So I radiused the edges of the pistons for more hot spot (detonation/preignition) resistance.

Before:

Sharp-eyed observers will note that the intake valve pocket actually has some factory porting at the center of the relief cut. This allows for intake flow to not be blocked by the piston when the piston is near TDC. Nice work by Diamond Pistons.

After (a Dremel with a metal bit, a round stone bit, and then some 320 grit sandpaper):

It doesn't look like much, but that's the point. Just enough to round any sharp edges or points off.

 

[sherlock9c1]

Well, the Impala's fuel pump is dying, so as I pumped the tank out, I figured it was time to pump the wagon's tank out as well, since it had been sitting since 2016. The wagon has a Racetronix fuel pump harness which runs a power wire from the alternator directly to the fuel sending unit plug, and has a relay that the factory fuel pump harness controls. Since the engine bay harness is out, I just directly wired a battery to the fuel sending unit harness. It's definitely got an aftermarket pump in it; it sounded very different from the Impala's pump. Maybe a Walbro 255? We shall see once we drop the tank.

What to do with 6-year-old gas? It smells old but not terrible. Can I burn it off in my minivan in small quantities?

 

[95wagon]

Oh , I would

 

[shakenfake]

Put it in your lawn mower is another option

 

[Caddylack]

You should use it to burn down a GM plant.

 

[sherlock9c1]

I'm leery of using it in older lawn mowers that were already calibrated to run on straight gas, then along comes ethanol and stoichiometric isn't what it used to be. At least with a fuel injected car with oxygen sensors, it can adjust.

I poured it out through a strainer into my minivan after adding a similar amount of fresh gas. Looking into the gas cans, I saw a dark blob slinking around the bottom. So as I got to the bottom, I poured it into a clear cup so I could inspect. It looked like red blobs of water that quickly settled to the bottom.

After I let it settle a bit more, I slowly poured off the top and this was what I was left with:

Another pour out of the other gas can yielded similar results.

I dumped this blob material out on some concrete that didn't care.

 

[95wagon]

Besides, a lawn mower is more valuable than a mini van!!!
I might retract my first statement after your photos.