Possible Experiment - Replacing Connecting Rod Bearings Through oil pan

[Trent_McAllister]

1974 c-20 custom camper, rusted and bent every panel, blue ribbon ugliest truck winner but ran fine until last week when I drove through a large 8" deep puddle on driveway because of flooding.

I have a restored 1968 C20 and I would buy another beater farm truck before I would spend the time and money on a quality rebuild or crate, but I am willing to play around with.

Immediately developed what I considered a loud "ticking" coming from rear of engine. I assumed it was in the heads but a friend thought it was lower. I almost immediately shut off and sorry to say, I did not think to look at oil gauge and see if there was pressure but I believe there was. I started and parked it in a spot quickly and girlfriend made video of noise.


I've pulled valve covers and see nothing wrong.

I decided to pull oil pan. I found the 7 & 8 had some play (Made video), mostly side to side so I removed connecting rod bearings. the crank looked really good, I felt nothing with fingernail. Bearings did not look spun or bad to me either.

I am not a mechanic, I've never even taken off oil pan before so proper diagnosis is iffy at best. I didn't want to run it further and cause damage to crank.

What I would like is for someone to help confirm my diagnosis that the connecting rod bearings are the cause of issue. I have the video I can send to phone or even better if someone is around Elizabethtown, KY area and is willing to come look at it for a few bucks.

Then I would like to attempt to replace the bearings if the crankshaft looks ok with rock auto .001 undersize (Not .01)

I know it is a hack job, but I'm doing it to learn more and also to see if/how long it works. Please don't tell me to overhaul the motor properly, the internet is full of that advice on forums. It's this or scrap the truck and purchase newer, so might as well give it a shot.

Advice or anyone willing to listen to videos?

[SunSoaked]

Bearings and journal don't look bad, especially not bad enough to cause a noise. I would inspect the valve train before doing anything with the bearings. Could be nothing more than a plugged lifter. If the bearing was bad it would be more of a deep knock- not a tick, no matter how loud. Is this an automatic transmission? A cracked flexplate makes a similar sound. It can be hard to pin point the location of odd noises sometimes. Also, if the noise started after this water incident you may well have got cool water on hot metal somewhere. Look for cracked exhaust manifold, leaking gaskets, etc.

[homemade87]

How hard did you hit the water . You dont suppose you ingested some water into the engine and hydraulic a cylinder and bent a rod . Could have bent a rod or cracked a piston .

[Trent_McAllister]

The truck is a manual 4 speed.

Engine was still cold when hit water, it had flooded here and drove .6 miles across the road to help my tenants move some of their things to my house. This water was not deep enough to get in engine, about 8" deep at deepest. Air filter was dry immediately after I parked it. I hit the water faster than I should of, maybe 15-20 mph.

Did not see exhaust leak, which seemed like a real possibility since it happened in water. I looked at manifold gaskets and where they bolt to pipe. After that, it is undamaged straight pipe.

Someone local suggested it might be a wrist pin based on a loud ticking/knocking.

So at this point, since the pan is off and I have ordered some new connecting rod bearings and main bearings, one set .0001 and one set standard each. Also some plastigauge and I'm replacing my 40 year old micrometer with a new digital. The oil pump intermediate shaft bushing broke, so that and new pan and cover gaskets.

I plan to roll the appropriately sized bearings in since I am already this far along. I have not broken all the caps to inspect mains and 1-6 since I do not yet have the parts. I know this is a backwards hack job, but I am learning a lot.

After they go in, I will turn over the engine with rocker covers off and take it from there.

I do not know about plugged lifters so I will do some more research. I'm not confident adjusting valves other than one at a time with engine running.

The springs were not broken. The rockers appeared to me were straight on push rod and valve with no damage. The exposed inch or so of the push rods are straight.

[Trent_McAllister]

Or I could replace the 7 & 8 with standard.

Button it up, add oil and look for problem in the top/exhaust/elsewhere before I got deeper into replacing bearings.

I hate to cause damage that would be unrepairable without rebuilding engine, and without inspecting all the rod and main bearings I wouldn't know if its a problem somewhere other than 7&8.

btw, there was no metal in pan and oil was at normal level with no noted sludge or contaminants.

[Dead Parrot]

Did you look in the clutch area? There was a thread not long ago about a similar ticking noise that turned out to be a combination of cracked flex plate and rubbing on the converter housing. Could be the water splashed a small rock past the starter gear and into the clutch plate area.

It's a little late for this test now since the pan is off but I learned that a dying PS pump can sound a lot like a dying engine noise. Was relieved when the noise disappeared after I removed all the belts and ran the motor.

[Trent_McAllister]

It’s a manual transmission so it has flywheel instead of a flex plate. The way the starter is mounted, I don’t see opportunity for any rocks to get in and this was on asphalt road.

I did not inspect because I wouldn’t know what to look for?

The noise sounded more to the rear of the engine. I wish now I had ran it longer, but at the time I was very concerned about chewing up the crankshaft badly.
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[Trent_McAllister]

Plastigauged and replaced connecting rod bearings with standard. Everything looked ok so it was pretty much a waste of time. I didn't even bother doing the mains.

Turned over truck until I got good oil pressure and started and ran without valve covers. I observed every pushrod going up and down.

I pulled plug wires to each cylinder one at a time and noise never stopped. Is this a firm rule that rod knock on a cylinder can be diagnosed in this manner or just a trick that might work?

Is a compression test for each cylinder useful to diagnose anything?

[jkk]

Good Luck with that

[andyh1956]

For future reference brgs worn beyond their serviceable limits will be worn thru the babbit & be showing brass.

[Trent_McAllister]

ok, so I did a compression test and found out that I have approx. 100 psi every cylinder except #6 which is 25 psi. I sprayed in a little gear oil and got it to 35 psi.

So I think that this means I have catastrophic failure of piston rings or a valve is not completely shutting. I'm researching online to see what information is available to be able to further diagnose the situation and how to fix valve if possible without tearing it down.

[andyh1956]

It COULD mean the intake valves are not opening to allow the cyl to fill w/ air to be compressed.
Moot point now as you are about to get your hands dirty...

[Trent_McAllister]

I took off the brake vacuum hose and poured in a can of seam foam which made it sound more like valve noise and less like rod knock. I've got one of those valve compression tools from a friend and I'm planning to put engine TDC on 6, hook compression gauge to air compressor and remove and replace that valve spring. I might also hook the valve to a cordless drill and try to spin it in case its just a big piece of carbon.

[andyh1956]

It won't matter what stroke the engine is on once you remove the rocker arms.
Be advised though that when the compressed air is introduced to the cyl the engine will rotate to put the piston at BDC so be careful & don't get wound up in the fan blades!

[Trent_McAllister]

Replaced valve spring, did not make a difference.

The engine did not spin over to BDC when shop air was applied, it might be because I put regulator on @ 15 psi.

Leaked the whole time that I was doing it unless I pressed the valve DOWN approx. 1/2" into engine (no audible leak over compressor running)

Also found some weird pieces of metal further down on the valve's shaft when I removed the collets from it and pulled the spring. I guess they are the valve seals so it might really start burning oil.

I hear that Ford 305 CI are good motors. This is one better as it is a 306 CI (7 divided by 8 cylinders * 350 Cubic Inches)