• Hi Guest!
    If you appreciate British Car Forum and our 25 years of supporting British car enthusiasts with technical and anicdotal information, collected from our thousands of great members, please support us with a low-cost subscription. You can become a supporting member for less than the dues of most car clubs.
    There are some perks with a member upgrade!
    **Upgrade Now**
    (PS: Subscribers don't see this gawd-aweful banner
Tips
Tips

Oil Pump Question

Share this page

R

Ray Smith

Jedi Hopeful
Offline
I have two questions:

1. Can the rotor type pump be used in a BJ7 engine?

2. Which is more desirable, the gear type or the rotor type?

Thanks,

Ray
 
[ QUOTE ]
I have two questions:

1. Can the rotor type pump be used in a BJ7 engine?

2. Which is more desirable, the gear type or the rotor type?

Thanks,

Ray

[/ QUOTE ]

1. Yes

2. Depends on who you ask; the factory updated to the gear type, but the guys at Southern Carburettors (now SC Austin-Healey) recommended the rotor type for my modified engine.

Given the pump being in good condition (no excessive clearance issues), either is good for a street engine.
 
[ QUOTE ]
I have two questions:

1. Can the rotor type pump be used in a BJ7 engine?

2. Which is more desirable, the gear type or the rotor type?

Thanks,

Ray

[/ QUOTE ]

Call me a cynic, but I strongly suspect that BMC changed from the rotor type pump to the gear one as it was cheaper to make.

I was suffering low hot oil pressure on my BJ8 - I pulled the gear pump, and apart from very marginal scoring on the pump cavity walls it measured 'good' to the workshop manual spec using feeler gauges. I replaced it with a rotor type, and all my oil pressure issues went away.

I think that the rotor type actually displace more oil per rev than the gear type, but the gear type displace 'enough' for a new tight engine. I have no idea how many miles my engine has done since a rebuild but it must be well run in by now.

/ubbthreads/images/graemlins/england.gif /ubbthreads/images/graemlins/england.gif /ubbthreads/images/graemlins/england.gif /ubbthreads/images/graemlins/england.gif
 
My 100 has "suffered" from low hot oil pressure since I put it together thirty years ago. On a hot engine at 2500 rpm or so, it runs about 25 psi, give or take a few. At idle it drops to below 10. I use 20W 50 oil in it most of the time.

My engine has an original gear type pump that I checked for wear and it measured up as I recall. The main and rod bearings were new on this car 30 years ago, with nominal clearances on a newly ground crank. The rocker shaft is in very good shape.

I have driven this car thousands of miles in very hot weather with this low oil pressure with no problems at all that I can see. I am sure that a higher capacity pump would increase the oil pressure, but is it necessary? Remember that higher flow of oil through the bearings will also increase runoff from the bearings, especially the rear main which tends to leak like crazy from a 100. Ditto for flow up into the head, which has limited pathways for return back into the case.

I know it feels good to see 50 psi on that gage all the time, but is it really necessary? I would be reluctant to fool with a high capacity pump unless I was racing or had some sort of lubrication problem that was known to be caused by low oil flow.

Good luck!

Bill.
 
Back
Top