AH 3000 Oil Pressure Relief Valve - Spring Length

[twas_brillig]

We have a 62 BJ7 that has about 65000 miles on it and has been stored since the mid-70s. Oil pressure is a bit below 20 psi at idle (using 20-50 Penrite, if memory serves).

I ordered a replacement relief spring and relief spring cup from AH Spares in the UK, based on the possibility that the engine was losing pressure due to oil bypassing the spring cup (due to a weak spring or worn cup). Order placed Dec. 15 and received the 23rd (via air letter).

The Haynes "Austin Healey 100/6 and 3000 Owners Workshop Manual" (date of publishing unknown) that I have advises that the minimum length for the spring is 2.87 inches. THe Bentley reprint of the original Healey workshop manual doesn't mention this dimension.

My 'old' spring is about 2 11/32 (2.344) inches long; the new one is about 2 5/8 inches long (2.625), so I've gained a bit more than a quarter of an inch, but am still a quarter inch shorter than the Haynes reference.

The angle of the 'cone' on the new cup appears to be slightly more tapered (ie more shallow; less blunt) than the original; the base on the original has a slight chamfer that is missing on the replacement - I think I'll smooth the resulting 90 degree edge a bit with a whet stone.

I'll install the new bits and advise if there's any change in my oil pressure.

And hopefully I haven't betrayed any etiquette by mentioning brand names.

Later,

Doug

 

[RF Thom]

Doug Had a similar problem. Utilizing Shell Rotella 30HD, at 180F after a long run I had 45 PSI, but the delta at idle was too great dropping to 15 PSI. Bought a new spring no measurable change. Sorry but I didn't measure the free length. What I did do was take the brass end cap and drill & tap a 5/16-24 thread in it. Then I took a 5/16-24 set screw and silver soldered a spring pilot on the end and reinstalled. Now with a 1/2" wrench and allen key I can turn the screw in to gain idle oil pressure - progressively three [3] turns brought the idle pressure up to 23 psi, and slightly raised the running pressure closer to 50 PSI. level. Also inspect the relief valve for wear and measure the clearance in the hole. This is to prevent leakage past the valve which returns oil into the sump, not the by-pass circuit. Mine had wear and some scuffing on the O.D. so I measured the hole and machined up a new one with 0.003" clearance.

Regards, Bob

 

[GregW]

Hi Doug,
Check this old thread out. It may have the information you're looking for. OIL_PRESSURE_RELEIF_SPRING

 

[twas_brillig]

Eureka!

Installed the new spring and cup last night; re-installed the spin-on oil filter assembly (had removed it to ensure that the gasket lined up etc; had to use the tap and die on the bolts and the block; used a magnetic pickup to pull some of the debris out of the block bolt holes); fired her up with some paper over the rad to get the temperature up (we've got about a foot and a half of snow on the ground and temperatures to match) and...

oil pressure at idle of 600 rpm and temperature of 195 to 200 F was 45-50 psi; at 2500 rpm, it was 55 psi.

Looking forward to confirming these numbers this summer.

Quite happy about this pretty cheap fix, as I don't have the skills Bob has. Greg -thanks for the note regards the other thread also.

Doug

 

[britman]

just a thought. I did not replace the bearings in the rocker shaft when i rebuilt my BJ7 and I have the same low oil pressure readings at idle after being at speed.
bd