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+--- Thread: Three bearing crank....strange middle bearing issue (/showthread.php?tid=8515)
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Three bearing crank....strange middle bearing issue - A7novice - 11-04-2023
While removing pistons from crank shaft, I was surprised to find underneath the middle bearing housing an empty female threaded hole. I was expecting to find a copper pipe oil feed etc.
The engine has covered many miles in this state without any apparent problem (the reason for current strip down is a porous block).
Anyone any idea why the middle bearing should have no oil supply.?
RE: Three bearing crank....strange middle bearing issue - Chris KC - 11-04-2023
Does it by any chance have a little blanking screw - 5/16" or so - right next to the oil filler spout, in between the two jet screws?
RE: Three bearing crank....strange middle bearing issue - Reckless Rat - 11-04-2023
Photographs would help...
RE: Three bearing crank....strange middle bearing issue - A7novice - 11-04-2023
I will try and get a photo on Friday. I will also check for blanking plate.....what's your thinking?
RE: Three bearing crank....strange middle bearing issue - Chris KC - 11-04-2023
Some three bearing engines were modified to take Reliant crankshafts. Part of the mod is usually to drill down through the main oil gallery at an angle to provide a pressure oil feed from above the centre bearing, via the old centre cam bush feed. In this case you would most likely find the two splash feed oil supply jets blanked off. As Reckless suggests, a few clear pictures should quickly clear things up.
RE: Three bearing crank....strange middle bearing issue - A7novice - 12-04-2023
That's interesting, I will try to get some photos tomorrow. I guess if it is no longer splash fed, that might explain why when hot on tickover oil pressure is 8 psi or so, while on my RP tickover oil pressure is the more usual 1 psi or so.
RE: Three bearing crank....strange middle bearing issue - Chris KC - 12-04-2023
8 psi would be very low for a pressure fed engine, more like 25 - 50 when running.
RE: Three bearing crank....strange middle bearing issue - Ruairidh Dunford - 12-04-2023
Three bearing engines have smaller oil jets so as to raise the pressure to feed the centre main and centre cam bush appropriately.
They normally run at about 9psi warm.
RE: Three bearing crank....strange middle bearing issue - A7novice - 12-04-2023
It's got a 0 to 10 psi gauge, anything above a tickover sends needle on gauge full scale.
It DID have a 0 to 100 psi gauge fitted, . But in my ignorance I replaced it because I EXPECTED oil pressure like my R P
RE: Three bearing crank....strange middle bearing issue - Ruairidh Dunford - 12-04-2023
Those type of engines would originally have been paired with a 0-20 gauge.