6 replies to this topic

[cobblers]

Having heard conflicting opinions I'm unsure which to use. I'm rebuilding a 1330cc Pre A+ after it span a big end bearing 3k miles after a professional rebuild. I'm replacing the oil pump, crank, rods and obviously all gaskets etc. I've got some new oilway bungs and will thoroughly clean the oilways out (Most of the crank bearings are scored due to debris).

When it comes to the Oil pressure plunger, I've read 80% of people who say "Get rid of the plunger and fit a ball and spring" and a couple of people say "Keep the plunger!"

I've ordered a ball and new spring, I'll probably fit them, but I'm unsure.
Professional builders are recommending using a ball, so they must work alright?
My engine had plenty of oil pressure to start with, but the arse fell out of it on the drive home from buying it!

[dklawson]

If you use the search feature here, you'll find a thread that ran just last week where Martin suggested that the plunger was better than the ball at maintaining more uniform oil pressure. However, I have not heard a discouraging comment about the ball conversion prior to his. I have the ball conversion on my car's engine and have no complaints.

[bmcecosse]

I found the ball to be excellent - but you may have to play around with the spring until you get the desired pressure - it is deadly accurate at holding the pressure, although like the plunger, it can be overwhelmed with thick cold oil if you rev too hard then! make sure the cold pressure doesn't go above ~ 90 psi. Aim to set the spring for 70 psi when hot - should be fine.

[Waffs1984]

I was looking at the ball bearing conversion a while back - i assume its a good idea to fit the variable oil pressure screw whilst i'm at it to get the desired pressure?

[bmcecosse]

Certainly no harm in that - I just cut a turn off the spring and it worked fine for me - with the full spring the pressure was too high.

[Waffs1984]

Great, thanks.

[Ethel]

The idea of the ball is that it's less susceptible to sticking because it has less contact with the side of the drilling. The plunger should work better as a valve because the seat will have a larger contact area.