[Healeys] Oil Pumps

Bob Spidell bspidell at comcast.net
Wed Jan 1 11:24:07 MST 2020

Vewwwwwy interesting ...

Would oil pressure be at least an indirect indicator of how much load 
the pump is putting on the cam and driveshaft gears?  IIRC, the nominal 
proper pressures for a Big Healey engine are 20psi at hot idle--which, 
per the book, is 600RPM--and 40-45 at speed?  When I bought my BJ8 the 
safety gauge would indicate zero pressure at hot idle; obviously some 
oil was flowing or the engine would have seized in a few seconds.  When 
I finally got the safety gauge refurbished, by West Vally Instruments, I 
'gained' 15-20psi at hot idle and still showed 45psi or so at speed.  I 
got the exact same readings after installing the DWM 'High Capacity' 
pump but I figure the gun-drilled camshaft is effectively a large 'leak.'

I'm not a fluid dynamicist, but wouldn't, say, 45psi from either a 
vane/rotor type pump put the same load on the cam gear and driveshaft as 
45psi from a gear-type pump, all other factors--oil viscosity, 
etc.--being equal?  Or, is there some other factor(s) at play?  Do the 
gear-type pumps produce lower pressure (seems to me that's the only way 
they'd reduce the load on the gears and the cam thrust plate)?


On 12/31/2019 9:03 PM, Larry Varley wrote:
> As a matter of interest the rotary oil pump is from the Austin A70 2.2 
> litre engine, same rotor. Then when the 2.6 litre engine was produced 
> for the Healey 100 Austin changed the pumps to the gear type. Probably 
> because the gear type pumps less oil and they knew the cars would be 
> revved harder. In an A70 and 100 engine the rotary pump will produce 
> up to 80 PSI oil pressure and around 3000 engine revs, where the gear 
> pump will produce about 60 PSI with the same bypass spring. This shows 
> the rotary pump has a far greater output. Austin may have changed the 
> pump running speed when they fitted the rotary pump to the six 
> cylinder cars, I don't know. Austin A70's have no problem with 80 PSI 
> oil pressure, but then we all know the 6 cylinder engine was an 
> inferior design :))
> Cheers
> Larry Varley

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