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Oil pan removal: What else to do while I'm in there?u

 
Old 05-15-2019, 04:37 PM
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mardyn
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Default Oil pan removal: What else to do while I'm in there?u

So my '73/L48 is about to go on the lift for an oil change, I figured I'll pull the pan off to flatten out the dented sump,
also to see if there's any identifialble reason for the marginal oil pressure that I seem to have.

My guess is nothing will be obvious, maybe the pickup tube is loose in the pump, but unlikely. Thinking about maybe
pulling the main caps and a few rods caps to inspect bearings for wear.

Any opinions on what else to look for while I'm in there?

Any comments or ideas are welcome and appreciated.

Thx
mardyn
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Old 05-15-2019, 05:02 PM
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Now is a good time to put in a new rear main seal.
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Old 05-15-2019, 05:06 PM
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use the one piece pan gasket and depending on how the bearings look replace the oil pump
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Old 05-15-2019, 05:34 PM
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Pull all bearing caps. Check the mains and replace the rod bearings. Read the bearing shells for size. .010, .020, std, etc. Also see if orig GM or aftermarket. Oil pump. Standard volume and pressure. Rear seal and front seal. Post pics of bearings.
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Old 05-15-2019, 05:57 PM
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I wonder if there could be a malfunction in the oil pressure relief valve causing my issues... I've never really hear of one failing before.

Either way, I''ll keep y'all posted on what I find once I get it opened up.

mardyn
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Old 05-15-2019, 07:27 PM
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OP mardyn

Your 73 original OE gage is a mechanical gage.

You should verify your true oil pressure with a known-good remote gage.

The original OE Cam gear/sprocket is aluminum jacketed in Plastic.

That Plastic jacket ages out, becomes brittle, and the Plastic breaks off into small pieces which drop right into oil pan.

The oil pump can (and some do) pick up those bits and then they get into the pump's pressure relief valve.

Sometimes jamming valve open (low pressure).

Not uncommon. Before dropping pan, Verify OP/gage first.
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Old 05-15-2019, 07:41 PM
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Lets not grab the engine hoist just yet posters.

What do you mean by "marginal" oil pressure? You only need 10 lbs per 1,000 RPMs.

Last edited by HeadsU.P.; 05-15-2019 at 08:04 PM.
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Old 05-15-2019, 08:04 PM
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Yes, the OEM mechanical gauge is in place and works but is inaccurate.

I have an aux mech gauge under the hood that verifies my low pressure situation at 40 psi cold and 30ish when
at operating temp.

I think the engine has been rebuilt somewhere along the way, it runs good, doesn't use oil other than a confounding leak around the fuel pump
area that might drip a few drops (on my clean concrete) if it sets for several days.

I'll be interested to see what's in the pan (if anything) and what the bearings look like once I get into it.

mardyn
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Old 05-15-2019, 08:13 PM
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carriljc
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Well, if it was mine I'd just fix the leak around the fuel pump. Oil pressure doesn't sound bad enough to tear it apart. If I was even a bit concerned I'd try heavier weight oil to see how it does... before tearing it apart.

That being said, if I was going, then I'd replace that plastic driveshaft that is used to drive the oil pump in stock engines with an aftermarket steel unit, the one piece oil gasket, the leak near the fuel pump, and the rear main seal.
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Old 05-15-2019, 08:15 PM
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Originally Posted by mardyn View Post
Yes, the OEM mechanical gauge is in place and works but is inaccurate.

I have an aux mech gauge under the hood that verifies my low pressure situation at 40 psi cold and 30ish when
at operating temp.

I think the engine has been rebuilt somewhere along the way, it runs good, doesn't use oil other than a confounding leak around the fuel pump
area that might drip a few drops (on my clean concrete) if it sets for several days.

I'll be interested to see what's in the pan (if anything) and what the bearings look like once I get into it.

mardyn
H-m-m-m-m-. The 40 is not bad. Not great, but not horrible

At what RPM is the 30?
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Old 05-15-2019, 08:19 PM
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Originally Posted by carriljc View Post
Well, if it was mine I'd just fix the leak around the fuel pump. Oil pressure doesn't sound bad enough to tear it apart. If I was even a bit concerned I'd try heavier weight oil to see how it does... before tearing it apart.

That being said, if I was going, then I'd replace that plastic driveshaft that is used to drive the oil pump in stock engines with an aftermarket steel unit, the one piece oil gasket, the leak near the fuel pump, and the rear main seal.
Finally. A decent, logical response without panic and over reacting.
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Old 05-15-2019, 09:20 PM
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The oil pressure situation is really not that bad and I’ve lived with it since purchasing the car 5 years ago.
It builds about 30 psi at 1500 rpm when warm and maybe a little more with additional rpm. Idle psi is
around 25ish when warm at 700 rpm.

My reasoning for looking into it now are several.
It’s finally a quart low on oil on the dipstick, it’s time for an oil change,
i need to take pan off to repair the dent in the sump, it’s gonna be on the lift anyway....

I’ve completed several other projects and this one is next in the rotation.

Im not really excited about the prospect of pulling the pan as it’ll certainly be an oily mess.

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Old 05-16-2019, 12:23 AM
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If you are set on removing the oil pan, fix pan dents and flatten the pan rail surface (especially the dimpled areas around the bolt holes); replace plastic tube at the oil pump [but pump pressures are fine for a standard GM oil pump]; remove bearing caps and check bearing condition ONE AT A TIME. Keep cap orientation the same so it can be put back exactly as it was; torque to GM specs. Check to see if the rear seal has been changed. If not, install a new Viton 2-piece seal on the pan per instructions and per advice on this Forum. Install one-piece Fel-Pro synthetic gasket, which can be reused after several removals (if not damaged). DO NOT USE SEALANT ON IT.

There's not much else you can do with only pan being removed.

Last edited by 7T1vette; 05-16-2019 at 12:24 AM.
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Old 05-16-2019, 02:01 PM
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Ok... for you guys following along with the thread.
Update#1:

A few surprises...

Engine has definatley been rebuilt before.

Rods are stamped, crank is marked Chev 350-442(?) in handwriting with a paint pen on the front counter weight.
Generally in clean condition and looks decent. Also already has steel oil pump driveshaft.

Surprise #1: Block is has 4 bolt main caps.... cool
Surprise #2: Oil Pump has the front two bolts that hold the cover over the gear/rotors are both loose and the threads
are stripped in the upper pump body/housing. Rear two bolts seem to be OK, but get this: they are all 10MM
bolts rather than SAE... WTF?
Surpirse #3: Pan is relatively clean, no sign of foreign debris or metal... dent appears to be about 3/4" deep but did not
contact the oil pick up.

More to follow after lunch....

Thanks for all the help so far.
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Old 05-16-2019, 04:27 PM
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show us some pics if you can....
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Old 05-16-2019, 04:51 PM
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At a stopping point for today....

Cleaned up the pan , ordered a new pump and gasket from Summit. Trying to decide if there is a need
to go further as Iím guessing (hoping) the stripped threads on the pump cover plate was allowing the pump to by pass big time.

sorry for the big pics... Iím still learning about this picture posting thing...

mardyn
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Old 05-16-2019, 05:16 PM
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While you have the pan off and if you feel inclined, get some Plastigage and check the clearance on some (or all) of the main and rod bearings.
https://shop.advanceautoparts.com/p/...E&gclsrc=aw.ds

It's not terribly involved and shouldn't take long to give you a good idea of the current wear on your engine.


Good luck... GUSTO

Last edited by GUSTO14; 05-16-2019 at 05:16 PM.
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Old 05-16-2019, 05:39 PM
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Your next important task is to go to Walmart in the toy section. Buy some Silly Putty. Apply a gob of it to the installed oil pump screen. Place the oil pan into position w/o gasket. Press up and firmly, then lower pan. The putty will show your pickup to pan clearance, minus gasket thickness. Should be 1/4" - 3/8".

Last edited by HeadsU.P.; 05-16-2019 at 05:40 PM.
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Old 05-16-2019, 06:35 PM
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mardyn
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I'm going to inspect a few of the bearings next... so far, they all pass the Hammer/Tap-Tap test - but I'll be
looking at #1 main bearing and one or two of the rod bearings as well.

I'd like to pick up some plasti-gauge if they've got it at the local auto supply... I'll stop by there in the morning.

More to come later...

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Old 05-16-2019, 06:54 PM
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I used Play-Doh to check clearance from the pickup to the pan. Not as sticky as silly putty. I covered the screen with speed tape so the playdoh wouldn't get mashed into the screen.
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