Difficulty installing oil pump driveshaft (7m)

[kemicalx]

Hi all,

Am in the process of putting together my 7m bottom end, The machinist along with doing the machine work also installed new bearings for the oil pump drive shaft. Problem is, that when i went to install the shaft the bearings and the shaft journals seemed to be basically the same size, so it wouldn't slide in. I went and spoke to him about it, and he said that due to a slight chamfering on the edges of the bearings sometimes shafts require tapping in to place with a plastic mallet. He said that due to the bearings being a different composition white metal to engine bearings this wasn't a problem.

So i got home, gave the bearing edges a light going over to ensure they didn't protrude inward. Slid the shaft in and with the assistance of a plastic mallet, It went in reasonably easily however it's a tight fit.. Feels too tight.. I removed it and reinstalled it a couple of times ,though now just by pushing on it firmly while rotating it with the drive sprocket on the end for twisting leverage.

The outer larger bearing and journal measure up fine according to TSRM,
bearing - 41.02mm
journal - 40.97mm

The inner bearing is too far out of reach to measure, and with the crank and rods in the way too it's a bit of a prick.

So basically, how tight should it feel? i imagine after 10mins running at operating temp, the bearings will change in shape anyway?

Anyone with an idea on this please give me let me know, i want to work on it tonight.. but i'm held up with this.

[kemicalx]

anyone able to shed some light on this while theres still a couple of hours working time in the night

[amichie]

My local engine reconditioner measures each bearing inside diameter when installed and then grinds the journal on the shaft to give the correct oil clearance. When I had my 7M done the crank was ground but the aux shaft and bearings were just removed checked and refitted.

My guess is if it feels too tight then it most likely is too tight. Biggest worry is it might bind up.

[kemicalx]

yer thats the concern, don't want it spinning a bearing or seizing... like i said, the oil clearance for the front bearing/journal is in spec according to my measurements ( i will take those again when i get home) but i can't get down to the rear one to measure it.. Do you know if when your auxillary shaft was installed (without the pump) if it would spin freely on the film of oil between the bearing and the journal, like the crank does?

[amichie]

Yes mine did spin freely but as I said the bearings wern't replaced they were just checked so it had about 150,000kms on it.

[kemicalx]

Ok.. thats the same as mine used to be before the bearings were replaced. gahh. I wish i had a little more engine building experience so i could be confident in making a decision, i want to finish off the bottom end and move on to the head and head gasket installation..

[cambelt]

A bit tight is ok but if yr worried just linnish the shaft till its a nice fit .
Dave

[kemicalx]

Cheers mate, could you give an example of how tight is acceptable? as I won't be able to linish the shaft at home.

[jimmmayyy]

Hmm well when I got my built short block back, I tried spinning the oil pump shaft and it rotated easily enough, but it wouldn't spin 'freely', if you know what I mean. Does that give you any idea?

[kemicalx]

yup i know what you mean, ie, not like a turbo impeller. I'm going to remove the oil pump again tonight.. remeasure the front journal's oil clearance. With the oil pump installed the shaft was quite tight, and could only really be turned with the gear on the front.. without the pump gear engaged it might spin more easily.

[cambelt]

Thumb and pointer finger hurting when shaft starts turning without the cam belt gear on the end but once turning a bit freer.
Dave

[kemicalx]

hmm cheers mate, that sounds about the same to be honest