1980 L48 70K+ miles

Replaced the lifters and valve guides but noticed some small chunks of black "coal" like crud spread around. When I took the intake off to clean and paint, noticed some small residue in the valley under the intake as well. I removed most of it, but am a little worried some may have fallen into the heads or other places spreading through the motor.

Since I have a leak around the oil pan, am planning to remove and install new gasket.

Before the work, oil pressure was 23 at warm idle and go up to 45-50. Now oil pressure at warm idle is 30 and only goes to 40-42. It primarily stays around 38-41 most of the time. Pretty consistant.

I am wondering if any of this "coal" oil residue made its way into the pan and clogging the screen on the oil pump pick up?

The main question is should I just drop the pan and clean the screen if in fact there is any residue on it? Should I drop the pan and as preventative maintenance replace the original oil pump with an new OEM unit since it is 31 years old? Should I replace oil pump with a high volume unit?

One other question, should I use a can of engine flush to remove whatever residue may be in other parts of the motor and then change oil or is that just asking for problems? One buddy tells me to pour a quart of transmission fluid in it, let it idle "for awhile" and then change the oil. The trans fluid acts as a cleaning agent.

Thoughts?
Thanks

 

DO NOT install a hi-volume oil pump unless you are prepared to remove the crank and install an oil restrictor kit (without it the hi-volume pump will flood the heads with oil giving you a whole new set of problems). Clean as much of the 'charcoal' as you can; and yes you should drop the pan and clean it and the pump pickup as well. As for the oil pressure numbers there is no cause for concern as long as you don't get abusive with it. Obviously it's an old tired motor so if you're not gonna commit to rebuilding it the best thing to do at this point is clean it up and run it.

 

Not planning on rodding or increasing power in the future. No plans to race.

Could new residue partially clogging the oil pick up screen have dropped the oil pressure while driving? From a stop, the oil pressure did increase after the work was completed.

What about using engine flush or a quart of transmission fluid to additionally clean the engine and then changing the oil. The engine flush I read said use, let idle for 5-10 minutes, then drain, and add new oil.

Am wondering if I am creating problems by trying to flush/clean the engine, loosening any more crud that may be hiding, possibly plugging oil holes?

The previous owner drove the car very little over a 12 year period based upon inspection receipts. He put maybe 750 miles on it for the last 3-4 years he owned it, it mostly sat. My guess is he changed the oil based upon mileage, not age of oil.

 

Without using any flush I would recommend two-three oil changes maybe a couple of weeks apart depending on how much you drive. Get coupons from the paper or someplace else for Jiffy Lube, Sears and these sort of quickie oil change places.
Don't make the mistake of letting them put in synthetic, just plain Jane dynosaur oil.
Add a bottle of break in additive to keep the zinc levels up.
Should maybe cost $50 all together.

 

did you use the same weight oil as before?

 

I bet those chunks of "charcoal" are your old valve seals. I replaced mine last year and the ones that were still on there shattered into little chunks. New the seals are rubber but over time they harden up and become very brittle. I know that some chunks made it through the engine down into the oil pan. I have changed the oil twice and still find little pieces. I thought I got them all. No damage and I have put about 2000 miles on the car since I changed the seals.

 

I use to use a about a half a quart of kerosene.let it idle for about 5 minutes and drain and change the oil.I put another 60,000 miles on car that already had 100,000 on it when I bought it.that's all the motor flush in a can is.at least that's what it smells like.

 

i vote for valve seals too. i think engine flush is for heavy sludge deposits for badly neglected engines.I'd use a good synthetic with the proper zinc levels.synthetic oils have a better detergent package and clean a motor very well.

 

That old 390 I had wasn't too bad but had about 1/4 of crud in the heads around the valve springs.the darn thing still ran like a sewing machine.they must have done something right back then.

 

Your motor will be fine. Do a couple extra oil changes. The oil pressure is fine you only need 10 lbs per 1000 RPM to properly oil a motor.

 

As easy as it is to do, I would still pull the pan to clean it. Oil pump is up to you, for 30 bucks I always do it. Screens can get caked up a bit depending on history of engine.
Oil will cool a bit better with a clean pan.
I wouldn't use any kind of flush other than more oil changes or even just more filter changes.

 

I'd drop the pan, as others have said. Clean, replace the pump since you're there anyway. If it were mine, I'd mic check the bearings for wear. You may detect an issue that may be in your future. I'd check the mains and the rods. A tool or two extra, no big deal.
If you know someone with a bearing mic or a variner mic and compare to a fresh bearing size, or at least the parting line of your bearing to determine the wear or lack of wear.
How many miles on your engine?

 

Yes, same oil...Valvoline 20W50 with the higher ZDDP rating.

 

Miles on engine is approximately 70K. Looking at the crank and mic checking is beyond my abilities.

 

It would smoke at start up and slight lifter noise which is why the lifters were replaced with new valve guide seals/umbrella's. No smoke at start up now.

Will replace oil pump when I drop the pan.

Thanks

 

Forgot to follow up from my post. When I dropped my pan, there was some of the black crud in my oil pick up screen area. Installed new oil pump with pan off and cleaned screen completely. New oil/filter. Buttoned back up. Also installed new sending unit as it was leaking.

My dash oil guage reads low from actual engine oil pressure. About 5-10 lbs low depending whether idle or steady 2000 rpm.

New oil pressures from sending unit: cold idle 50psi at start up (850 rpm), warm idle (750 rpm) 35psi, cold 2000 rpm 62psi, warm 2000 rpm 54 psi. For example my interior guage at warm idle reads 25psi when it is actually 35psi. The pressures from the the guage attached to sending unit read steady.

I think my oil pressures are good.

What I have found is the the interior oil guage is not always accurate, so put a guage on the sending unit to be sure of the accurate readings.