Oil Pumps

[Legal Bill]

From what I read on line, the Denis Welch oil pumps seem to be of a higher quality than others that are available. But this conclusion comes solely from reading the provider's own websites. I was wondering if any of you have direct experience with some of the available oil pumps that you would be willing to share. I am disappointed with my oil pressure at idle when hot (a common complaint, I know) and wonder if my British Victoria (remember them?) oil pump could be improved upon.

 

[Bob_Spidell]

The significant factor with Healey oil pumps is the type of pump: rotary or gear. Earlier cars came with the rotary type which, in theory, can deliver greater flow (conceivably, greater pressure). Later on, BMC started using a gear-type, with gears made of sintered iron (basically, pressed metal filings). The rotary type can move more oil at low RPM, but it was found the increased pressure on the cam gear could cause premature wear at higher RPMs, so BMC started using gear-type in the later 6-cyl cars. I don't know exactly when or on what models this change occurred; I also suspect the gear-type was, er, more 'economical.' IIRC, an 'extra' tooth was added to the shaft gear to reduce the load as well. Manufacturers, at least AH Spares and DWM, do point out the different applications.

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Low indicated pressure at hot idle is common; first thing to do is check your gauge; when I had my safety gauge rebuilt and calibrated I 'found' another 15PSI of oil pressure at hot idle (OP should never read above about 60PSI, that would indicate a defective relief valve). Also, check for a worn rocker shaft and/or bushings, that can cost a few PSI. I bought a DWM rotary-type when I last rebuilt my BJ8's engine, expecting at least a small increase at hot idle, but got none; on inspection, I found out the previous pump I'd installed was rotary--back then, I don't think the sellers distinguished; they sold what they had on the shelf.

I'm sure Doug or Richard can add to this, or correct my recall of events.

 

[John Turney]

"Low oil pressure" can come from various things:

• An inaccurate gauge - If you have a good gauge, an air supply and a 1/8" female BSP to 1/4" male NPT adapter, you can check the gauge.
• Worn relief valve or relief valve spring - you can put a #10 washer (IIRC) between the spring and valve piston if the spring is weak.
• As Bob said, the rocker shaft - open the oil filler cap with the engine running. If oil is spraying everywhere, it's time for a shaft rebuild.
• After going through those, my friend bought a County oil pump from one of the usual suspects. I had heard they were not good and opened it up. The clearances wore worse than on his old oil pump. Both pumps were the gear-type pump.
• Since we had the sump off, we pulled #3 main bearing (the one without the thrush washers) cap to check one of the bearings for wear. Unfortunately, that told us the news he didn't want to hear - the main was shot, so a rebuild was in order.

Bob is also correct on the oil pumps - they started with a rotary-vane type, which will pump more flow, but at higher RPM they tend to break. So, if you want to rev the engine, go with the gear type. According to Clausager, the switch from rotary-vane to gear happened in April 1959, one month after introducing the 3000 in March.

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[Healey Nut]

You can also remove the base of the oil pump then on a sheet of glass with valve grinding compound lap some of the wear grooves made by the gears away to make it smooth again .

 

[Legal Bill]

Thanks for taking the time to share all that information. I’ve already been through all of those steps. I’m just really focused on the quality of the available pumps, thinking the old Vicky Brit unit may be a low quality item. The engine had low pressure at idle when hot from day one. I had my gauges rebuilt at Nissonger before they closed shop. The rocker assembly is all new, but I took off the valve cover and ran it and noticed the oil pipe from the head to the rockers was leaking a bit. I replaced all of that, and then installed a new spring and pressure relief valve and exchanged the factory oil filter for a spin on filter. But the hot idle pressure is still sitting just at 20 most of the time and can still drop as low as 18. My engine idles around 800 rpm, so it really should be no lower than 20. I just suspect the quality of my oil pump and wonder if a better quality oil pump would make a difference. But maybe not.

 

[BoyRacer]

18 psi hot at idle is exceptionally good.

 

[dougie]

Richards correct, 18-20 psi hot at idle is great.