I believe that there are about 100,000 miles on this motor.
I believe, because about 4.5 years and 20,000 miles ago I bought it sight unseen having been told it was an 80,000 mile motor.
I jumped to a number of wild, irrational conclusions when the oil pressure started triggering the check gages light more readily.
The original engine wore out (knocked, shook, overheated) at about 190,000.
I thought that the piston rings nearest the crankshaft were oil scrapers.
That’s what I was referring to.
George,
Good reply - I have a better grasp of what's going on in your engine bay.
And the good news is that the photo of the plugs you pulled would tend to support
the 80,000 (purchase)/100,000 current estimated mileage on the current engine.
As for why you have excessive clearances on your bearings, there are several
variables we would have to consider, including:
* Original build (or rebuild) quality?
* How often were the oil changes performed by the PO?
* What kind of driver(s) operated the engine before you purchased it? Elderly
couple who drove it gently to the church & the farmer's market? Or did Dad
drive it normally, but when borrowed by #1 son it was driven as hard as only
a motivated teenager can manage to do? Why was the engine available for sale?
Previously mentioned teenager pit-maneuvered by the Arkansas Highway Patrol
after an extended chase...leading to the insurance company totaling the vehicle?
The point I'm making is that depending upon exactly how the engine was treated
by the PO, we could wear out none, some, or all of the engine. For example, thanks
to a poor cooling system (yet at the same time high quality synthetic oil used) I've
seen cracked cylinder heads from overheating, yet the engine still shows very good
oil pressure.
****
Thanks for your clarification on the scrapers. Based on your spark plug photo, I
would concur that your oil rings are still working properly. And in order to
preserve
the status quo and not upsetting the delicate balance/interplay inside your engine, my
conservative recommendations are based upon a tried-and-true "Measured Response"
approach. So instead of me just saying a blanket 'no' to the high-volume oil pump,
let's try this no-cost mind experiment:
1) Instrument the engine with a mechanical oil pressure gauge. (
Done - good)
2) Mechanical oil pressure gauge agrees with dash gauge. (Meaning the
'Check Gauges' circuit isn't be lied to by the oil pressure sending unit. (
Done - good)
3) Compression check engine & verify overall health of the 8 combustion chambers. (Done - good)
4) Replace spark plugs & read old plugs for any signs of mechanical failure. ( Done - good)
5) Change oil to higher viscosity in accordance with/meeting Service Manual recommendations. (Done - good)
6) Verify hot oil pressure is good enough for quiet engine operation & 'Check Gauges' light remains out. (To be Accomplished)
7) IF Step #6 gives desired results, stop repair. Monitor for the next 1000 miles/12 months. Revisit Oct '24.
Cost: oil change. Risk: None mechanically. Will require good battery to ensure continued good starting in colder weather.
8) IF Step #6 fails to solve issue, then decision time. In order of preference, my recommendation would be:
8a) Retrofit factory engine oil cooler from the HD cooling version of your truck. (@L31MaxExpress 's recommendation)
Preferably sourced from the Treasure Yard. Pro: Cooler engine oil temp gives thicker oil during
a hot idle. Con: Time, Effort, & Expense could be considerable depending upon if you do this yourself,
or pay someone else to do it. Risk: Used engine oil cooler could have been contaminated by prior
engine failure & would spread this to your engine?
8b) Go for the high volume oil pump. Pro: Good chance this solves the hot idle oil problem.
Con: 100,000 mile rings may or may not be able to handle additional oil splash described in
in post #5...and we turn the engine into an oil burner. Q: How much oil is it currently using?
How much oil does an engine have to burn in order for it to exceed your threshold of pain?
Do you feel lucky?
8c) Decide to install rebuilt long block. Pro: No more worries? Con: $$$$. Can this be
justified given the 1000 miles per year that it is driven?
****
That's all I got. For what it's worth, in a previous life I would be identified as the guy who 'wouldn't sign
off a Code 3 write up' on the flight controls on a F-16, making me most unpopular with those who wanted
the tail in order to meet the mission requirements. I used to tell them *no*, figuring they wouldn't
understand the technical reasons behind my decision. Guess what? This invariably led to more heat than
light shed on the subject. ;-)
This is where I learned to instead give leadership ALL the scenarios, from what I recommended (downtime to
troubleshoot the wiring harness) to what was legally possible per the T.O. (quicker box swap & aircraft passes
follow-on ops checks on the ground.) I would explain my measured response, but then let THEM actually decide
what to do/own the problem.
And then cheerfully follow their orders. And after a few sorties of having the aircraft not get well despite
filling it with 'new/supposedly good' black boxes from other airbases, then they would let me have it back so that I could
troubleshoot the wiring harness like I originally wanted to do in the first place. :0)
Over time, my track record was such that they learned to trust my recommendations, and from that point
forward more light than heat was shed on any Code 3 jet I was involved with.
****
The moral of the story? I needed to be accurate and own my recommendations, and share them clearly with the 'owner'.
But at the same time, I had to learn to let the owner make/own the final decision.
One last thing. If you wanted to run all this by your mechanic who (correctly) asked about the compression test,
I would think that is a great idea.
Apologies for the length. That's all I got. Let us know what you uncover.
Cheers --