4L Con rod bearing oil hole question

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Fred3
Posts: 2
Joined: October 17th, 2022, 12:13 pm
Vehicle Year: 1994
Vehicle Make: Jeep
Vehicle Model: Cherokee

4L Con rod bearing oil hole question

Post by Fred3 »

I'm currently rebuilding a block from a 92 cherokee for my 94 cherokee (blew up the 94 Block... oops). Both engines have 544 casting rods with the stock bearings (f112 std. Stamps). The replacement bearings I've ordered don't have oil holes while both stock sets do. I've asked both my parts guy and the tech line for the manufacturer of the replacement bearings why this is and they told me that the bearings from 84-93 are all the same and never had oil holes. The tech line even pulled up the oiling diagrams. I guess im going to send my replacement bearings in or file a hole myself. I'm just wondering why jeep has oil holes stock from the factory but I can't seem to find replacement ones that do or even anyone to acknoledge that they did. https://photos.app.goo.gl/DWFJzCMLsigzAPKG7
Randy Bobandi
I made it to triple digits!
I made it to triple digits!
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Joined: December 22nd, 2020, 8:50 am

Re: 4L Con rod bearing oil hole question

Post by Randy Bobandi »

Ya, I'm not sure if this is an oversight by aftermarket manufacturers or something that they deemed unnecessary. The FSM notes that the passages in the rods are for lubrication of the cylinders and the camshaft. Yet none of the aftermarket rods or bearings have this feature. I know a few other engines of the same era have this feature in the connecting rod.

I welded oil spray jets into the oil pan on my engine. I'm running a line tapped off of an oil filter sandwich adapter which goes to a motorized ball valve. The valve is controlled by a switch. When open, oil runs to the three jets and sprays oil up at the cylinders. That doesn't lubricate the camshaft though. I think I might clamp the rods together, with their bearings in place, and drill a small 3/32 hole straight through that main thrust side. Then chamfer the top of threads for the bolt to get the oil flow. That should accomplish the same function of the factory rods.
Mr_Roboto
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Stroker Displacement: 258CI
Vehicle Year: 1982
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Re: 4L Con rod bearing oil hole question

Post by Mr_Roboto »

So, pardon me for asking a dumb question are you saying/inferring that these are in effect oil squrters to keep the cam lubricated?
Randy Bobandi
I made it to triple digits!
I made it to triple digits!
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Re: 4L Con rod bearing oil hole question

Post by Randy Bobandi »

Mr_Roboto wrote: October 24th, 2022, 9:53 am So, pardon me for asking a dumb question are you saying/inferring that these are in effect oil squrters to keep the cam lubricated?
This is quoted from the 2000 Cherokee FSM.

The pump draws oil through the screen and inlet
tube from the sump at the rear of the oil pan. The oil
is driven between the drive and idler gears and
pump body, then forced through the outlet to the
block. An oil gallery in the block channels the oil to
the inlet side of the full flow oil filter. After passing
through the filter element, the oil passes from the
center outlet of the filter through an oil gallery that
channels the oil up to the main gallery which
extends the entire length of the block.
Galleries extend downward from the main oil gallery
to the upper shell of each main bearing. The crankshaft
is drilled internally to pass oil from the main bearing
journals (except number 4 main bearing journal) to the
connecting rod journals. Each connecting rod bearing
cap has a small squirt hole, oil passes through the
squirt hole and is thrown off as the rod rotates. This oil
throwoff lubricates the camshaft lobes, distributor drive
gear, cylinder walls, and piston pins.

The hydraulic valve tappets receive oil directly
from the main oil gallery. Oil is provided to the camshaft bearing through galleries.
Fred3
Posts: 2
Joined: October 17th, 2022, 12:13 pm
Vehicle Year: 1994
Vehicle Make: Jeep
Vehicle Model: Cherokee

Re: 4L Con rod bearing oil hole question

Post by Fred3 »

Randy Bobandi wrote: November 1st, 2022, 10:49 am
Mr_Roboto wrote: October 24th, 2022, 9:53 am So, pardon me for asking a dumb question are you saying/inferring that these are in effect oil squrters to keep the cam lubricated?
This is quoted from the 2000 Cherokee FSM.

The pump draws oil through the screen and inlet
tube from the sump at the rear of the oil pan. The oil
is driven between the drive and idler gears and
pump body, then forced through the outlet to the
block. An oil gallery in the block channels the oil to
the inlet side of the full flow oil filter. After passing
through the filter element, the oil passes from the
center outlet of the filter through an oil gallery that
channels the oil up to the main gallery which
extends the entire length of the block.
Galleries extend downward from the main oil gallery
to the upper shell of each main bearing. The crankshaft
is drilled internally to pass oil from the main bearing
journals (except number 4 main bearing journal) to the
connecting rod journals. Each connecting rod bearing
cap has a small squirt hole, oil passes through the
squirt hole and is thrown off as the rod rotates. This oil
throwoff lubricates the camshaft lobes, distributor drive
gear, cylinder walls, and piston pins.

The hydraulic valve tappets receive oil directly
from the main oil gallery. Oil is provided to the camshaft bearing through galleries.
Thanks for posting this. This is precisely as I see it in both blocks I have apart. I guess "squirt hole" is more semantically correct then "oil hole". I ended up fileing a V shape with a triangle file on the bearing edge to match that in the con rod and then polishing with some crocus cloth being carefull not to bend or chip the shell.
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