Slight knock?

[Danimal08]

There was also a TSB I think I remember reading a long time ago that also when I was concerned about this very noise that discussed having to measure and replace main bearings in .001 sizes to correct a bottom end knock (I'm 90% was warranty complaint related)...dont recall the details exactly, but GM may have had some tolerance stack issues in the cranks/blocks that had some excessive clearance on some of the journals. As a guy who spent large amounts of time scouring warranty data for an OEM, I interpreted it as "this'll probably get it out of warranty"

 

[Orpedcrow]

Aren’t the anti-drain back valves only necessary on the horizontally mounted filters?

 

[Schurkey]

There was also a TSB I think I remember reading a long time ago that also when I was concerned about this very noise that discussed having to measure and replace main bearings in .001 sizes to correct a bottom end knock (I'm 90% was warranty complaint related)...dont recall the details exactly, but GM may have had some tolerance stack issues in the cranks/blocks that had some excessive clearance on some of the journals. As a guy who spent large amounts of time scouring warranty data for an OEM, I interpreted it as "this'll probably get it out of warranty"

GM assembles the engines with the option of using bearing shells in half-a-thou increments. For example, you might get a standard bearing shell on the cap, and a half-a-thou undersize bearing on the saddle. This gives GM the ability to keep oil clearance accurate to within a quarter-thou of "perfect". I don't know of any way to get those in-between bearing sizes in the aftermarket.

That's how GM produces "Rolls-Royce" quality with production-line parts. Super-accurate measuring of the finished journals, or finished bore sizes, and select-fitting bearing or piston size to suit.

Aren’t the anti-drain back valves only necessary on the horizontally mounted filters?

Define "necessary".

They're most-useful if the filter is mounted at an angle. Otherwise the oil in the filter itself would tend to siphon back to the pan.

They're still useful on engines where the filters are vertical, because it keeps the oil gallery above the filter filled to the level of the first leak-point, not just keeping the filter itself filled.

 

[Danimal08]

GM assembles the engines with the option of using bearing shells in half-a-thou increments. For example, you might get a standard bearing shell on the cap, and a half-a-thou undersize bearing on the saddle. This gives GM the ability to keep oil clearance accurate to within a quarter-thou of "perfect". I don't know of any way to get those in-between bearing sizes in the aftermarket.

That's how GM produces "Rolls-Royce" quality with production-line parts. Super-accurate measuring of the finished journals, or finished bore sizes, and select-fitting bearing or piston size to suit.


Define "necessary".

They're most-useful if the filter is mounted at an angle. Otherwise the oil in the filter itself would tend to siphon back to the pan.

They're still useful on engines where the filters are vertical, because it keeps the oil gallery above the filter filled to the level of the first leak-point, not just keeping the filter itself filled.

Rolls-Royce quality

 

[Hipster]

#1 main is the last to get oil pressure at startup and where I've seen the most wear on high mileage teardowns. They will run a good long while if you don't beat it. but still better to dig in an address before it wipes out a main cap/journal. Noise seemed loud , low, towards the front, at crank speed. Finding a shop that can grind a crank without giving you back race clearanced is a crap shoot.

 

[Hipster]

Rolls-Royce quality

Lol, kind of a stretch, but he's not wrong in saying a select fit build process was used, not uncommon to open one up and find .0006 bearings in it.

 

[thinger2]

Everything Shurkey said plus
A bad exhaust gasket or a cracked exhaust manifold can sound like a rod knock and then get less noticeable when the cast iron expands.
That is pretty common.
A stuck or hanging or burnt intake valve can sound just like a rod knock.
That is an open intake valve with a fuel charge that ignites on the exhaust stroke because the valve isnt seated.
20 psi at hot idle.
If that is verified by an actual mechanical gauge and not the factory dash friggen cup of tea leafs and chicken bones it is awesome.
20 psi hot idle on a small block chevy means that you have ten years to save up some money.
Open a new savings account and put 50 bucks into it every month.
Every ******* time no matter how hard things get and no matter how many friggen ramen noodles you have to eat you put that ******* 50 bucks in every damn time and you dont even ******* think about using that for anything else.
That isnt your money in the way you think it would be.
That is your older more experianced middle age telling to freak out about money.
And older you needs the ******* money.
Its a **** load easier if you have some.
The world is a courtyard in the kings castle where we decide if we are going to play the clown in hope of his mercy or if we have the balls to tell the king to **** off .

 

[Schurkey]

Rolls-Royce quality

You notice that in my previous post, "Rolls-Royce" was in quotation marks.

a select fit build process was used, not uncommon to open one up and find .0006 bearings in it.

Yes, the Vortec 5.7L core short-block I rebuilt for my '88 K1500 had upper main bearing shells marked .0006. It's been years, but I don't remember the lower shells being undersize...just the uppers. If that's correct, GM tightened-up the clearance by .0003 on that engine.

They looked beautiful, so I re-used 'em. Cam bearings looked terrible, and rod bearings had some wear, but the mains were great.

 

[Schurkey]

If that is verified by an actual mechanical gauge and not the factory dash friggen cup of tea leafs and chicken bones

Thanks for that. An excellent mental picture.

The voltmeter on my truck is an example of that. Lately the needle has been randomly going from 10 to 14 volts, even though the voltage at the alternator is a nice, solid 14+.



Thousands of years ago, I was early in my career. Sent lots of parts to a certain local machine shop, run by a Machinist/Philosopher named Dinkel. Great guy. Had an opinion on every subject, and generally well-thought-out.

Since that time, I've considered a _________/Philosopher to be a high complement. Mechanic/Philosopher, Consultant/Philosopher, etc. I suppose "Forum Poster/Philosopher" applies to you, unless you'd prefer a different description.

 

[Hipster]

You notice that in my previous post, "Rolls-Royce" was in quotation marks.



Yes, the Vortec 5.7L core short-block I rebuilt for my '88 K1500 had upper main bearing shells marked .0006. It's been years, but I don't remember the lower shells being undersize...just the uppers. If that's correct, GM tightened-up the clearance by .0003 on that engine.

They looked beautiful, so I re-used 'em. Cam bearings looked terrible, and rod bearings had some wear, but the mains were great.

I never paid much more attention, almost all I pulled apart had some issues on #1 main so 10/10 crank kit was the way I went.