Oil Pump mod to increase pressure

[davejake]

I'm rebuilding the oil pump. I've heard that by adding extra washers to the relief spring the pressure will increase. Would any of you have details or old posts to share? How much thickness should I add? What else should I be doing to the pump now that I have it apart and all cleaned up?

 

[Dr.Jeff]

A couple of suggestions:

Remove the screen from the bottom of the pickup. You will be amazed at what has collected under it.

Check for wear by measuring the gaps, as shown in the factory workshop manual (available on Xweb for free).

In general adding one additional stock shim under the spring seems to be about right for me. A thick washer can be used if you don't have any extra stock shims - just be sure to carefully measure the thickness and compare it. But how much you shim it depends on your specific application; the engine build, the intended use of it, the oil you run, the climate you are in, etc. You really won't know until the engine is reassembled and the operating pressure tested. Also consider what the pressure was before, which depends heavily on the condition of the rest of the engine; if you are rebuilding the engine then the pressure will be very different from what it was before.

There was a related thread about how adjusting the bypass valve (which is what you are really doing when you add shims under that spring) affects flow volume in addition to pressure:

Oil pumps for performance engines

The topic of "performance" oil pumps has been discussed, here's a good example: https://xwebforums.com/forum/index.php?threads/oil-pump-design-changes.37599/ The bottom line is there isn't a "performance" pump available for the X. By "performance" I mean high volume and/or high pressure...

xwebforums.com

 

[ArtBasement]

I'm rebuilding the oil pump. I've heard that by adding extra washers to the relief spring the pressure will increase. Would any of you have details or old posts to share? How much thickness should I add? What else should I be doing to the pump now that I have it apart and all cleaned up?

Adding shims increases the relief valve pressure, so it increases your top end pressure. If you are building a race motor that will see lots of high rpm, then that's appropriate. But for a standard motor there is no need. Cleaning the screen and checking clearances will better assure plenty of oil at lower pressures.

 

[Dr.Jeff]

Adding shims increases the relief valve pressure, so it increases your top end pressure. If you are building a race motor that will see lots of high rpm, then that's appropriate. But for a standard motor there is no need. Cleaning the screen and checking clearances will better assure plenty of oil at lower pressures.

There is some evidence that increasing the bypass relief spring resistance will divert more oil flow to the main galley and therefore increase oil volume to the engine's lubrication surfaces, even at lower RPMs. However I don't know to what extent. But the volume of oil is what's important, not so much the pressure.

 

[Dan Sarandrea (Phila)]

I seem to remember it being mentioned here that with the SOHC, in a rebuilding scenario, attention paid to the proper bushing clearances of where the aux shaft rides in its bores will pay dividends in satisfactory oil pressures. If you look at the FSM specs, the clearance range cited for the aux shaft is actually a scoush tighter than for the mains.

 

[DanielForest]

Probably more than 20 years ago, PBS was selling a stiffer spring for that use. But I can't say no more.

 

[MikeHynes]

Probably more than 20 years ago, PBS was selling a stiffer spring for that use. But I can't say no more.

I think I remember Clark telling me that they used a cut down 850 inner spring.

 

[fiatfactory]

I'm rebuilding the oil pump. I've heard that by adding extra washers to the relief spring the pressure will increase.

Oil pressure won't increase throughout the range, i.e. you will not see more oil pressure at idle, you will only see a higher total pressure before the relief valve opens...so it is not a fix for a worn pump or excessive bearing clearances.

One of the first ports of call after the oil pump is the aux shaft bearings and the oil pump drive gear bushing, if these have excessive clearance then it will bleed pressure off regardless of any relief valve spring / shim differences.


SteveC

 

[davejake]

Adding a 2mm thick washer. Fingers crossed!

 

[davejake]

Torque? Am I really tightening to 61ft lbs? Feels like I’m going to strip the bolt!

 

[fiatfactory]

A copper washer is a bad idea, it's too soft, and the sealing/crush washer you've chosen is softened to seal... find a hardened washer.

61 ft/lb is the bolt that secures the oil pump shaft drive gear, I.e. the gear the timing belt runs on which turn the auxiliary shaft.

SteveC

 

[davejake]

@fiatfactory do you happen to know what the torque spec is for the oil pump?

 

[fiatfactory]

Not off the top of my head, but an M8 bolt threading into cast iron I'd expect about 22ft/lbs torque would be sufficient.

SteveC