Howdy,
That weekend I've realized I got scammed by the seller with my ride
In general, after LIM gaskets I've replaced the oil for synthetic 5W30. I took a blazer for a longer ride and after driving 2hrs on a highway - fuel trims were awesome - +-2%. My happiness last till the moment I've decided to stop for a while. Since the RPMs went idle, lubricating pressure dropped down to zero and I got a loud knocking sound.
Today I've disassembled the top if the engine and I've figured out that all the valve lifters are long time gone. Seller must have been aware of the engine condition, as the push rods have the marks of being held in tweezers, so filled into the engine the thickest oil ever and crossed fingers to sell it to the very first buyer (=me). Since I've replaced that for 5W30 all the worn off elements started rumbling. A plan for my summer vacation has just blown

Long story short - I've been checking the lubrication diagram for the engine - it only indicates the way oil goes down to the oil pan, but no info of a way the oil gets up to a valve lifters. Does anyone know the flow path there?

And yet another question - what are the chances that engine body (the valve lifters bore hole) survived? I will take the body for measuring, just wanted to know what are the perspectives.
For now the perspective is to replace a cam shaft, push rods, valve lifters, most probably a camshaft/crankshaft/connecting rods bearings only of the engine body is in a good condition.

Cheers, Mike

 

The lower part of the 95 should still be the same as the late 94's.

It features hydraulic roller lifters, fed by a separate gallery branching from the main gallery.
The hydraulic lifters need oil under pressure to take up the slack. Pressurized oil is then fed to the lifter rods through an orifice in the cup on the lifter to the rocker arms.

The lifter bores would have to be measured (dial gauge) to be cylindrical and of the proper diameter.
Some repair may be possible.

Oil pressure dropping to zero with an adequate oil may indicate some more problems which may have to be figured out.

As for the perspecives...

... IMHO. If you are into taking it apart and can afford it sitting for quite a while I would disassemble and check. Once determined what the causes are you should also have different options from where to go further.

Repair is possible, Rebuild is possible, Replace.

Before throwing a single $ at parts I would make sure the engine (whole) is within specs to be worth a new camshaft and repair parts.

 

Thanks
I haven't mentioned - my engine is from '00, with a plastic plenum on the air intake, not the aluminum as in '95.
To be more detailed, I bough a car with a fresh oil of unknown viscosity. Then I had an oil filter change, but not oil. Made approx. 1k miles with it w/o any significant problems. From time to time I had the feeling an engine is misfiring, and for now I could say it might be a valve lifter that did not expanded properly. Problems started on engine running 5W30. I found loud knocking valves at idle, unfortunately till that time I've been running a highway for about two hours. I made an instant look up into the service manual and found the oil pump above the lowest limit for 1k/2k/3k rpms.

As a side note, all my folks here are surprised that the Vortec engine should run with 5W30 or 10W30. They tend to say, that for a gas engines 10W40 should be used.

I would be grateful if someone could post a photo with the underscored part in Your quotation. I wonder if the problem I've encountered may be related to a clogged branch.

The problem source is still somewhat unclear to me. I had quite amount of oil right under the valve covers. That would mean I had a lub. oil passing through the lifters to the rocker arms. Maybe the pressure was too low, i.e. the relief valve in the oil pump got damaged?

In a some way I have to locate the source, don't want to kill a rebuild engine over again.

I am going to follow the routine You say - 1st I'll take out the engine and ask a workshop to measure the bores to see if the engine block may be rebuild.

 

It's just like a small block Chevy V8. There are three plugs in the front of the engine right above the camshaft. These are located at the front of three oil passages that run the length of the block. The two on the sides of the cam are for lifters/pushrods and these passages can actually be seen down the lifter bores with the lifters out. The one in the center is for oiling mains/rods/cam bearings. Oil is pumped from the pan through the oil filter into the rear of the block where it splits into the three passages.

I'm really sorry to hear someone have this problem with a newly purchased vehicle, same as me. Take a listen to the video at the beginning of my own original 2001 Blazer thread. You can hear a collapsed lifter after extended driving on highway and low oil pressure at idle. Problem was excessive clearance in engine bearings. Mine was a nightmare before I got it fixed. Yours could be something else, but also might be the same....

 

My 94 service and even the unit repair manual do not show better diagrams.

As your's is a 2000 I'm at loss for proper documentation.

I think that's a reasonable way to go. Unfortunately with engine knocks it normally ends up with disassembly to figure out the problem.

Good luck.

This may help a little for a 2000. It's not directly related but you may find it useful.

http://www.kohlerpower.com/onlinecatalog/pdf/tp6103.pdf

 

Just google "SBC Oiling System" and select "Images" and you can see the three passages.

10W40 is for engines with bearing clearances intentionally suitable for the viscosity such as engines from the 1960's. Bearing clearances were reduced in later engines so that less viscous oil would still be able to maintain pressure. Next was 10W30. Purpose was fuel mileage increase. 5W30 is correct for 4.3v6 and pretty much all GM engines of the 90's and early 2000's. My 2008 Ford Ranger which I recently sold took 5W20.

 

Please advise what was found to be wrong with the lifters.

 

I found it while I was looking for torques for doing LIM gaskets. Since that time I keep it on my cellphone. It has an oil flow diagram I was complaining about

 

Les I owe You
The photos taken of my camshaft:


and a valve lifter. They all look pretty much same:

It all makes sense to me. I had something thick in my oil pan and a worn off bearings with excessive clearance were compensated by a high viscosity. 5W30 was unable to compensate, so the lubrication pressure on idle was gone and it eventually killed valve lifters.

P.S. I got 115k mileage.

 

I only had 65K miles! Mine had the LIM gasket replaced, but apparently the damage to the engine bearings from coolant in the oil was already done. My camshaft and lifters were not so bad, but still one was collapsing from low oil pressure.

Time for engine to come out unless you're going to put 10w40 in it and try to sell. Pull #1 rod cap and main cap and check bearings - I bet these would be the worst as they are furthest from the oil pump and would starve for pressure if others are getting loose. You may want to evaluate scoring in lifter bores before spending any money on that block.

Unfortunately none of this is a good outcome for a new owner. Crank kit + camshaft and roller lifters are pretty big expense in an engine with old rings and valves. If you want to keep vehicle you might want to check into another engine or even a rebuilt. Not sure how much it takes to import but Jegs has complete GM Goodwrench engines for about $2000USD. I have no way of knowing what would be best for your situation, given your location.