Oil Pump Relief Valve

[Mike Allfrey]

Sadly I have become involved with a Javelin engine that has suffered instances of more than 90 psi engine oil pressure. A consequence of which, a spin-on oil filter (mounted on a flimsy adaptor, it seems) burst twice (!) and dumped oil all over the engine and car port floor. The pump features the Series III adjustable relief valve. It has been reported that the valve spool is 'pitted' or, maybe, rust affected.

On checking the spare parts catalogues, it is noted that the Series III valve spool and spring are different from the earlier items. Can anyone advise the differences between these parts - better still, how to tell them apart? I will have a look in my technical files.

I use a homemade test rig for setting relief valves and, for this pump, am considering a garage day so that others in our Club can be educated by a small amount. I would very much like to have examples of the two types of spool/spring combinations. In the past, I have successfully used these items that came with the pumps, however, I do not know what went on when the pump being worked on was previously assembled.

Regards and thanks to all of you,

Mike Allfrey - Melbourne, Australia.

[David Morris]

Hi Mike,

I was also involved in a Javelin engine where we had a stuck oil pressure relief valve. At the time, we didn't realise this and the engine, on initial start up after a rebuild, burst the gasket under the rear timing cover, and on subsequent, burst the flexible oil transfer pipe. The oil pressure must have been off the scale, let alone 90lbs ft!

I know John Airey has made a rig to test the relief valves and probably can advise on the differences. From my experience, I have only come across just the one type of adjustable valve fitted to the later pumps, which has a locking nut at the end. The previous oil pumps had a non-adjustable valve, recognisable by a roll pin or split pin across the end of the valve. Basically, both types use a spring-loaded plunger, which, as I now painfully realise, can get rusted up, causing the oil prssure to rise to dramatic levels!

The lesson I learnt is to get the valves checked over for correct function during an engine rebuild. You cannot see the inside of the valve and if you dismantle it, it needs to be reset correctly on reassembly.

Hope this helps,

David

[Forumadmin]

Bulletin Issue Date: May 1951
Is it possible the spring is seizing in the piston if the old and new are interchanged?

Item No. 50. Oil Pump Release Valve Spring
From Engine Number E1 PC 15098 a modified release valve assembly has been fitted to the oil pump. This will have
the effect of increasing the maximum oil pressure from 60 to 70 (413 kPa to 483 kPa) pounds per square inch. The
assembly consists of the following modified parts:
Release valve spring, Part Number 54388
Release valve piston, Part Number 50680
Spring retainer, Part Number 50864
The part numbers for the retainer and the piston remain the same. The release valve piston and spring retainer are
interchangeable with the type used prior to the above engine number, but the new release valve spring has been
increased in diameter and can not be fitted with the old type release valve piston or spring retainer. It will be necessary
therefore, when fitting the new type spring to engines prior to Engine Number E1 PC 15098 to fit the complete
modified assembly consisting of spring, piston and retainer. It should also be noted that, due to the diametral
increase, the new type spring is not interchangeable with the camshaft thrust spring, Part Number 54388, as was
the previous type.
For parts information please refer to Bulletin Spares Note Number 71.

[Mike Allfrey]

Thanks David and Keith,

I have looked through the information I have, but the only dimensions I could find were two different spring lengths. No data on the spool dimensions. Your mention of the rear timing cover gasket blowing is another worry, but not for my Jupiter's engine, it has an aluminium 'gasket' with 'O' rings.

I wonder what the difference is between spool (piston) Part Numbers 50680 and J54720? I have a couple of spools here that are probably scrap, but appear to be the same. The parts catalogue I have, lists J54720 in an amendment glued inside the front cover, which relates to Javelin PE and Mark 1 Jupiter models. 50680 is a Part No. from early in the series, the J-prefix came later.

I will not know much about this until the pump cover assembly is brought here.

I also have a test rig driven by a drill. Sadly, I lent it to someone and it has gone AWOL. It made checking relief valves very easy and man valves have been properly set.

Regards,

Mike Allfrey.

[Keith Clements]

The difference is a wider bore to take the wider spring? Or are there three piston types?

[Mike Allfrey]

Thanks Keith,

So far, I have not found any reference to different diameter springs. I have assumed that the bore in the spool for the last version of the spring is, maybe shallower so that spring tension could be increased to increase oil pressure from its original setting.

Will measure any spools that are still here and report findings.

Has anyone made new spools to match cover body bores that have been reamed slightly oversize?

Regards,

Mike A.

[Keith Clements]

MIKE.
Reread the service bulletin I posted earlier!

[David Morris]

Hi Mike,

From the description in Service Bulletin 50, it sounds like Jowett's were introducing a different relief valve assembly, but before they introduced the relief valve with adjustment to the 'blow-off' pressure? I think this was fitted to quite late (PE?) engines. If Bulletin 50 was introducing the valve with the adjustment, surely Jowett's would have mentioned the need to have this calibrated? Or, at least, left alone if set at the factory?

Mike, you mention the aluminium gasket with 'O' rings for the rear timing gasket. Yes, this does solve a lot of the problems with the original gasket design, but needs to be 'tailored' for each installation. Tread carefully! This is a critical area.

All the best,

David

[Mike Allfrey]

Thanks Keith and David,

You are correct about Service Bulletin No. 50 and spring size change. Must watch out for different spools and springs!

When I made the 1.6 mm thick plate to support the 'O' rings at the rear timing cover. Dimensional checks for the oil galleries revealed bores were not directly matching, so when drilling the plate I averaged the dimensions that I had found. Maybe the rear timing cover was from another crankcase, who knows? However, after close to twenty years of being in place, there is no sign of oil leakage. Could that be a record?

The two 'O' rings at the left hand end are very close together, but are holding. The plate has a smear of Loctite 518 applied. I have often wondered if an aluminium plate alone would hold the engine oil in the right places - I think it could.

Will advise findings when I have seen the valved that jammed.

Regards,

Mike A.

[PJGD]

For what it is worth, a while ago I had made drawings based on measurements I had taken of the oil pump pressure regulator valve from a Series 3 engine, so I assume that these are to the latest and greatest specification. One difference between modern engines and engines of the Jowett era is that now the valves are configured differently and take their "signal" pressure from some distant point of the oil gallery network rather than right there at the pump outlet. Therefore in modern engines it accounts for the pressure drop through the filter, the cooler and the various drillings and intersections so that you get a more stable pressure at the bearings.

[PJGD]

I should also add that the Jowett spring design is very poor because the L/D [length over diameter] ratio means that the spring buckles when compressed (a shorter fatter spring would have been better) and as it buckles it rubs against the inside diameter of the adjusting screw and/or the regulating piston which wears the spring and over time will change its characteristics and could in theory lead to spring failure.

Have a look at your spring and see if it is polished on the OD where it has rubbed on the mating components. The friction related to this contact will also increase the control hysteresis implying less accurate control of pressure.

[David Morris]

Hi Philip and Mark,

Philip, that's a great explanation of the later oil relief valve! Thanks very much. A good point about the wear on the spring too.

Mike, good news that your 'O' ring gasket is holding up well. As you will know, actually making the aluminium gasket is tricky. This is due to the fact that while the oilways coming up from the pump and returning from the filter to the block are circular, they are cut through by the gasket at an angle. This creates the need for an elliptical set of holes in the gasket.

However, the 'O' rings need at least some remaining 'land' for support, and this is the tricky bit when creating the aluminium support gasket. We have found that each aluminium gasket needs to be individually hand crafted.

Personally, I strongly suspect that Jowett's, when assembling engines, had a pile of Rear Timing Covers, that they hand-selected for best fit on assembly. There are at least five production versions of the RTC's, some identified by differing part numbers and others being different, but carrying the same part number. This, in my view, was one of the weakest design areas of the Javelin and Jupiter engines.

A lot of heartache would have been avoided if the rear timing casing had met the crankcase through a flat junction flange, rather that a 'V'.

All the best,

David

[Mike Allfrey]

Dear Philip and David,

Thank you for all of that information. The good news is that we will be undertaking a pump test in a week's time. the not so good news is that I have been sent a photo of the pump cover's face that joins to the pump body, it is a bit fuzzy, but I can make out tracks where the pump element gears have worn the surface. Probably bits of the casting jammed the relief valve spool. Will take a photo with a decent camera and post here later.

With Philip's excellent drawings of the spool and spring, I now have a good base to start from.

David's comments are all very true, the aluminium plate was a 'just made it' result, but it is holding well. Maybe the Loctite 518 is the main support at the narrow wall between the two drilled oil galleries. The engine has 'R' prefixed Serial Number on a plate affixed above the starter Bendix, so it could well be a different rear timing cover from the original.

Will advise findings next week. all of the assistance is greatly appreciated.

Regards,

Mike A.