Thanks, Cudamax!
Mine is a 1990.
Since I'm planning on doing a rebuild once I get it smogged, I'll just wait until then to fix that leak. I just wanted to make sure it wasn't a sign of something more serious.

WVZR-1,
Thanks, I'll keep that in mind. I plan to just take off one cap at a time so I don't mix anything up.


When I pulled out the rear main bearing cap bolts, they were SUPER sludgy. I'm talking chunky. The oil that dripped out of the bolt holes was black, like molasses. And I just changed the oil (haven't even driven it since, just ran it a bit for diagnosis).

EDIT: As I'm taking parts out, they're very dirty and oily. What should I use to clean them off?
Also, I got the cap off and both the bearing and the crank are somewhat grooved.

 

Hmm, diesel. Never would have thought of that, but now that you mention it it makes sense.

On my preliminary (and admittedly imprecise) plastigage measurement, I got about .0015 on the outside and .002 in the middle. When I plastigage the next bearing, I'll do a few things differently to hopefully get a more accurate reading.
That being said, the numbers are all Greek to me. What is a normal reading? What is the acceptable range? Does my measurement mean it's time to replace the bearings?

 

That's with the old ones. I wiped off the oil ahead of time, but it still felt a little greasy. I'm guessing I need to wipe it down with a solvent so it's totally dry?
I don't have it in front of me, but I recall seeing the bearings looking pretty tightly attached to the cap. Is there a trick to get them out?
I'll take some pictures tomorrow morning and post them.

Okay, I'll be careful about that. Thanks for the advice.
By "watch out for stuff like this", I assume you mean the different bearing sizes in the link?

 

I like the idea of using diesel fuel to clean things up cheaply... I'd spray some brake cleaner on the bearings before using the plastigage.

 

zip-lock bags......

You actually clean up parts PRIOR to disassembly by running the ATF thru the engine to dissolve the gunk BEFORE you tear it apart....

guess you missed that one with all the other post being thrown at ya

Yes, use your zip lock bags to ID parts and keep 'em separate. Sharpie on the bag and slide-seal it shut.

Bucket of diesel is the best/cheapest parts washer out there. There are gallon pales of carb cleaner/wash with a dip basket but those get pricey...$5 a gallon vs $25 a gal.

Brake parts cleaner....
USE CAUTION ! that stuff works great to dissolve oil film and grease BUT, it will also destroy ANY rubber/plastics the same way. It chemically pulls out any oils or polymers and leaves you with plastic minus the pliable nature. ( a cracker more or less)

DO NOT GET ANY CLEANERS OR DEGREASERS ON THE FRONT SUSPENSION COMPOSITE SPRING ! ! ! ! ! ! ! ! ! ! ! ! !

There are many degreasers and cleaners that will cause that epoxy/composite spring to delaminate instantly and break the first time it flexes...or tries. Do not allow anything to drip on it or even get fumes around the spring !

have fun

 

Hmm, I do seem to have missed that part. I was thinking you meant run ATF through it and drain the oil AFTER I got it put back together. I guess it doesn't really matter though, because I think I had already drained the oil and almost finished dropping the pan at the time you said that. Will it still work if I run it through after I'm done? Or do I have to drop the pan to get all the stuff out?
Using Ziploc bags is a great idea. I'll do that.
With the brake cleaner, would it be best to spray it on a rag and then wipe off the parts with the rag to avoid overspray?
Thanks again for the advice.

 

Hmm. I missed the part about supporting the crank. Guess I'll remeasure.

 

Here is a picture of the crank:




and here is one of the lower main bearing.



This is for the rear main bearing.

I'm still trying to figure out how to get the bearing out of the cap to check for numbers on the back. Any tips?
Also, I'm not quite sure how I should support the crank. I'm afraid if I use a jack I will put too much upward force on it. Thoughts?

 

Ahh, got it. Any tricks to remove the bearing from the cap?

 

Set the cap on a wood bench/table edges on a wood block, then with about a 12oz ball-peen gently pop it a time or two...that minor shock often will dislodge the insert.

Something worth mentioning here....looking at the wear, and knowing there was oil in there that had 40,000 miles between changes (looks like) some education in fluid dynamics is helpful...

if you think about the oil system, and knowing there are reliefs between the pump and the gauge port, showing real LOW pressure only means there is little pressure at THAT point...where its measured. That can also mean that in this case, that the pressure has been absorbed or lost not only due to worn bearings, but to being dumped off to the reliefs. If the oil is TOO HARD to push, it gets dumped off. The remainder is what makes it to the upper end where the gauge port is located....much less than what started the trip thru the system. That follows the earlier discussion regarding oil too heavy for the needs...same principles at work,.

Yeah, there IS wear there, but you have to wonder how much true pressure was lost or misdirected that WAS available, and just didn't make it that far? I'd bet a good 10-15 psi just because the pump was pushing mud thru clogged passages !

another thing.....

see those tiny "pits" or holes in the bearing surface? that's from oxidation. Oxidation in motor oil that is acidic enough to cause pitting is from moisture being present and never being burned out or changed. That's the Number-1 reason why we WANT our nice expensive EFI engines to run HOT....to burn off the naturally occurring moisture from condensation thus keeping the oil cleaner, longer and less toxic to the soft metals inside the engine wear parts.

Your crank is not that ugly....not at all. The bearing is shot, but the crank ain't scary.
You'll get more than 1000miles out of this "job" if its done well...

 

Thanks guys. I set the edges of the cap on something and lightly tapped a wide punch through the hole in it to dislodge the bearing.

The back of the bearing says:
GM
Al-6
10 89
C 23

And I'm trying to do this as quickly as I am able to. I just don't want to screw something up by going faster than I should.

Leesvet,
I think this is what you're saying, but I'm not positive. Given scoring on a bearing, does the clearance even have any bearing (no pun intended) on whether or not new bearings are needed?
What you say about pressure in the oil system makes perfect sense. Thanks for the lesson.
I didn't know about moisture in the oil being a reason why hotter is better. That is also good to know.

 

Hmmmmm...


The goal is to melt away and dissolve the CRUD that's glued itself to every corner and every flat surface inside that engine where oil can pool...and that in turn traps and holds all sorts of metal shavings and wear particles. You want to dissolve that "stuff" so it can drain out and exit the crankcase/pan.

here's the deal....
by flushing with ATF or other flush agents, you loosen all that goop and the metal contaminates that it contains and its now circulating in the system all thru the engine again....
BEFORE doing some work, heck yeah,. you got everything to gain by getting all that crap OUT and if the pan is coming off anyway, that's a bonus 'cause you can sterilize it and get 99% of the nasty out.

BUT

with brand new bearings....under normal circumstances, I WOULD NOT do a flush because it WILL free the dirt and metal bits to circulate thru your nice new bearings....

BUT then AGAIN,

This "job" is only supposed to be a temp fix and a weekend crash course in engine building, so for THIS SITUATION, knowing that you WILL be tearing it apart again soon, YES! GO FOR IT.

Leaving all that crud in there allows it to do other damage to other things. IMO you are NOT EVEN close to having a serious engine problem. Your wear is not horrible, the bearings took most of it, as designed, and the crank LOOKS good for another 50,000 if it had to do it.

IF you're still going to rebuild in the next few weeks/months, yeah, add a qt or 2 of ATF, let it run for a while, even a few days and drain it while hot. You will see some nasty black sludge and slime crawl out of the drain hole and you will see the rest of your old bearings drip out too !

I do this "trick every couple years to combat sludge in the case. Of course I do not go more than 4000 miles between oil changes and I use synthetics, BUT the heat cycles still cause at least some sludge to form, somewhere. The ATF is still lubrication but ATF is FULL of detergents and solvents to operate hydraulics and keep very tight tolerances clean and free of sludge and gum, so its very helpful in dissolving old stuff. The Marvel Mystery Oil is good as well. Both are still OIL, but its not designed to do any hard duty work as engine oil....it will be ok under normal situations for a few days. The ATF also seems to help clean piston rings and get them free and loose again and its great for valve guides and especially HYD LIFTERS !
I notice a slight "pep" return to the engine during and after these "treatments".

Gum/mud and old oil will flat out FU hydraulic lifters...they're little hydraulic cylinders with tiny ports and the plunger inside can get sticky and never transmit the full stroke thus giving you valves that are slow to respond and possibly never fully open or seated.

Get that engine clean inside and I assure you that you WILL feel a difference !
>=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=<
Brake parts cleaner.....yeah, you want the hard spray to help "blow" crud off but sometimes where there is some sensitive stuff nearby you are right in thinking rag and over-spray. That stuff is hard on painted things too.
Just be careful around your spring. Can't say that enough.
That's such an issue that GM sent out a service bulletin regarding solvents and cleaners causing front or rear spring failure. I've personally broken or cracked at least 3 rear springs from allowing chemicals to contact the spring surface. All it takes is once. My current spring is rubber coated to help protect it...

You're thinking right. because you're never done it before, there are questions.
The single biggest secret is CLEANLINESS. Next would be proper process, like knowing toque values, having the proper tools, like torque wrenches and after that its a matter of desire. How bad do you want it and are you willing to put in the time AND effort?

The end result is simply a reflection of the above listed items...

Have fun !

 

Absolutely. Thing is, the more the scoring the less useful the bearing as a reference point. Yes, it still matters because you need to know how much material WAS there. This tells you what has to go back in.

This is where they told you in math class that math would save your life someday.

In this case, from what I see, the bearing has done exactly what it should. The bearing being a softer mate than the hardened steel crank,. has absorbed the majority of the wear/damage. That's GOOD.

Now, discovering how much and whether it was bearing or crank will tell you what has to go back in. Between that and the plastigauge you can get it damn close and enjoy a 25-30 psi hot idle.

I take GOOD care of my engine and its got well over 200,000 on it, and a really hot day where its 110 outside and I'm stuck in traffic, the engine idles at 235-240 degrees with 15-20 psi. That ain;t bad...

I think you need to go buy lottery tickets tonite ! By the look of it, You got lucky once today, try again at 7pm !

you are tearing into this thing before its a total disaster and by doing so you WILL buy yourself more time to prepare for the full rebuild....

Regarding oils...
you want to TRY to let the engine oil heat up to operating temp and stay there for a few minutes every time you drive,. this allows the moisture to boil/burn off and clean the oil. This prevents sludge and slows the oxidation process. I've seen "milk-shakes" disappear after a days worth of driving at the 200* or higher temp range. No 2 ways about it, water boils and turns to vapor at 212 degrees. That's nothing to be afraid of !
Some guys worry that 212* is some horrible, scary number that their engine couldn't possibly survive! I think its because they don't know how LOW the boiling point of water really is...
212 is where your engine is healthy ! and the water that formed and collected inside the crank-case as it cooled down last night, is now turning into a vapor that can exit the oil that it WAS trapped in.
Short trips, and not letting it get hot enough are the things that kill engines early. AND, form sludge.

start it up, warm it up and drive it like you stole it !..................well, maybe in a few more years !

 

Thanks, Leesvet! I really appreciate your long, detailed responses!
Just a few more questions (for now ).
So I would do 3-4qt oil and 1-2qt ATF for a total of 5qt?
I need to order all my parts online by tomorrow, so I want to nail down what I need. Sounds like the following, but I just want to make sure:
Main and rod bearings (I listed the numbers on the back of the bearing - from what I can tell they're standard size?) http://www.ebay.com/itm/SBC-CHEVY-35...-/350596477232
High volume oil pump (I'd really like to get off without this one if I can - thoughts?) http://www.summitracing.com/parts/me...view/year/1990

Is it obvious if an oil pan gasket needs to be replaced?
Are there any parts (no matter how small) that I need to replace? I'm making a list of absolutely everything I need to get.

 

Hmm, didn't know that. I got this car to learn about engines and it seems to be working!

Sounds like a plan

 

And Please...take your time and do it right. Don't try to hurry and end up with problems. Better to do it correctly once than do it twice.

 

if you cant find the upper main bearing removal tool(copper or aluminum),you can make a set from large cotter keys--just put them in the oil hole and gently flatten the loop against the crank.then rotate the crank in the proper direction to roll the upper cap out. the same tool will push the new bearing in .

 

Thanks; that's what I'm aiming for.


Okay, thanks for the tip.


Can anyone help me with my "shopping list" of things to order? Like I said, I have to order it all by tomorrow (8/10) and I don't want to order it and then find I needed something else.

 

Looking at pics posted the crank and bearings are FINE. If you are getting .0015 to .002 clearance I would not waste my time replacing the bearings, as you will accomplish absolutely nothing replacing the bearings for low oil pressure. With new bearings, the clearance will be the same.
I would button it up with the stock bearings and replace the oil pump with a high volume pump and hope for the best.
The low oil pressure is caused by worn CAM bearings, not main or rod bearings!!!
On race engines I have ran .003 on the mains and .0025 on rods, with a stock oil pump. Way looser than your plastigauge specs are showing which are within factory specs. In fact, the clearance numbers you mentioned are dead on factory specs.
Put a new oil pump in it and some 20/50 oil. Thats all you can do until you rebuild the engine and replace the cam bearings.

I have been building and machining small blocks for over 30 years, drag, circle track and boats. Not my first rodeo. If you can get 10 lbs at idle and 40 running down the road you are fine.
There is nothing wrong with the crank or bearings in the engine you are working on.

And when checking bearings, pull the main closest to the front of the engine and check rods #1 or 2. They are the furthest away from the oil pump and will show the most wear if oil starvation is or was the problem.

 

There's very much good in "PcolaPaul's" response related to your situation but the reference to check the furthest from the pump may certainly help the next guy.

You're doing this all "LOCAL"? I certainly would.