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MG TD TF 1500 - Oil Pump Pressure - Shim or Helper Spring

Installing new rod bearings in my early model TF next week, so sump is off and no oil in engine. Time to check a few things under the engine ...

Today, I noticed that I can move the WASHER that is under the COVER PLUG of the PRESSURE RELIEF VALVE on the oil pump, even though the COVER PLUG is as tight as I can get it.

A couple of years ago, I put a penny in the COVER PLUG to add more force to the SPRING and raise the oil pressure. (Maybe because of failing rod bearings.) It worked and I was happy. The COVER PLUG had the obligatory drop of oil hanging from it, but no gushing leaks.

I removed the COVER PLUG and removed the penny. Then, reinstalled the COVER PLUG. It sealed tightly against the oil pump.

So, it looks like the penny pushes the GUIDE up against the oil pump and prevents the COVER PLUG from seating against the WASHER and oil pump body.

John Walton, New South Wales, Australia, noticed the problem in his post in 2016. "Washers were no good under the spring as they bounded on the bottom of the ball valve guide." John machined a plug that fit inside GUIDE to push the SPRING up and increase pressure on the BALL.
https://mg-cars.org.uk/cgi-bin/or17?runprog=mgbbs&access=&mode=archiveth&subject=8&subjectar=8&thread=201608191518505217

>> So, here's my question: Should I ...

1) Continue to use the penny and SPRING (no helper spring). This will prevent the COVER PLUG from fully seating ... like it's done for the last two years,? The threads on the COVER PLUG seal against leaks, not the WASHER.

or

2) Should I remove the penny and use a helper spring inside the SPRING and take a chance on too high / too low oil pressure? This will allow the COVER PLUG to seat fully against the WASHER and oil pump. I have a helper spring from Abingdon Spares.

Thanks for your help,

Lonnie
TF681
TF7211


LM Cook

My recommendation is to go for the adjustable spring that Moss sells. I have been using one for years. Probably did not need it but it was in the motor when I rebuilt it. It allows me to adjust the pressure.

https://mossmotors.com/435-550-adjustable-oil-pressure-regulator

I also think it would be rather easy to build one of these.
Bruce Cunha

helper spring or a washer the same diameter as the spring to adjust pressure.
The adjustable set up is just an expensive piece of ornament.
Use a brass drift and hammer (tapping only) to seat the ball, Use just the spring at first and if pressure is low then adjust , it only takes 5 mins to change.
Remember oil flow is more important than pressure,
I worked on high speed steam turbines that had low pressure but high flow oil supply on plain bearings.
Ray TF 2884
Ray Lee

Please correct me if I am wrong. My understanding is if changing the spring, or shimming it, will only really impact the blow off pressure on start up when cold and maximum pressure is generated due to thicker oil. In my experience (with multiple older English cars) when once fully warmed up the pressure at any RPM is somewhat less than the blow off pressure so a stronger spring, or one that is shimmed, really has no effect on increasing oil pressure.
John Quilter (TD8986)

Ray - You and John Walton say about the same thing … the shim under the spring should be about the same o.d. as the spring. That will raise the spring, but not change the position of the guide.

The U.S. penny that I used was larger than the o.d. of the guide, so it raised the position of the guide and prevented the cover plug from seating.

I made an executive decision to remove the penny and to add the helper spring inside the original spring. The cover plug is tight to the washer and the washer is tight to the oil pump.

We will install the rod bearings next Tuesday. Hope we will have time to start the engine. Look forward to seeing the oil pressure with new bearings in the engine and helper spring in the relief valve.

John - the penny added to the cover plug in my TF increasedoil pressure at idle and at speed. Went from 12psi idle / 30psi speed to 25psi idle / 45-50psi speed. (This is an early model TF with the gauge pickup on the head instead of the block like later models.

The penny didn’t help oil pressure at startup. Must crank with ign off for 15 seconds before the gauge needle flicks. Hope the new rod bearings help.

Bruce - the adjustable spring sounds like a nice solution. However, I need to start and run the car on Tuesday. If I don’t like the oil pressure (high or low), then I may look into buying one.

Thanks for all of the help and answers to my questions the past week or two. We’ll see if I followed your suggestions correctly next Tuesday.

Lonnie
TF681
TF7211
LM Cook

Hi John,
As I said flow is more important than pressure, cold oil = low flow and high pressure.
Early engines took the oil pressure readings at the head later at the block.
This always shows a higher pressure at the block one but there has been no actual change in the system. It made people happier when they did it themselves though.
Ray TF 2884
Ray Lee

I made a spacer from a bolt. It has a step so it inserts into the spring.




Steve Simmons

Steve - that’s perfect. Similar to the one that John Walton made, that I mentioned in my original post.

It raises the spring about the same amount that my penny did but it doesn’t affect the guide and cover plug.

Lonnie
TF681
TF7211

LM Cook

Neat part Steve! Lonnie, I have the adjustable deal if you want it. Won at a GOF and never used it. Let me know- I can send or brave I4 and meet half way. Make sure you are replacing rod bolts! And I’m 99% sure only early TDs had the gauge at the head, never on TFs. George
George Butz III

Thanks for the offer, George. I may take you up on the deal if I'm not happy with oil pressure after we replace the rod bearings and with my helper spring added to the relief valve. (Actually, I'm afraid of too much pressure with the fixes.)

Yes, new ARP rod bolts. The bolts aren't drilled for split pins and the nuts are flanged without castellations. I investigated ... looks like all ARP rod bolts are the same.

RE: oil gauge pickup. Hmmm, you may be right. Perhaps a previous owner switched the position of the pipe during an engine rebuild. Photos of TF554 which was built before Jo Ann's TF681, show the gauge pickup at the block.

Thanks,

Lonnie
TF681
TF7211
LM Cook

Yep all TFs connected at the block as far as I know. Early TDs at the head.
Connected at the block shows pressure to the bearings, at the head pressure to valve gear.
Altering position only shows pressure at that point.
Ray TF 2884
Ray Lee

Hi Lonnie. Some good comments from Ray and John. I would first shift the oil gauge connection down to the block to get the real pressure reading. (Also try the standard arrangement of relief spring.) You might be pleasantly surprised at the reading on the gauge. Maybe you don't need new rod bearings?

If you modify things to raise the pressure to 50 or 60 on the gauge with the oil gauge connection still on the head, you might be getting dangerously high pressure at the block. I say dangerously because more oil pressure means more load on the oil pump/camshaft gears which have been known to fail.

Check the spring. My notes say standard specs are 1.476" length, .5" diameter, 13.5 coils, 7 lb load at 1.073". If you must increase the oil pressure, why not stretch the spring instead of using washers/spigots or pennies?

I have a friend who shifted his oil gauge connection down to the block on his TD and immediately got 10 psi increase. The more worn the rocker gear, the more inaccurate is the gauge if connected to the head.

Bob
Bob Schapel

Bob. He got a 10 psi increase on his oil pressure gauge. It did not change the actual pressure the pump is putting out.

I am of the opinion that the reason they moved the line from the head to the block, was due to complaints about the low oil pressure with the early TD.

By moving the line, the public was happy with a reasonable oil pressure. Even though the pressure actually did not change.
Bruce Cunha

Hi Bruce,
Agreed. I should have written, He "immediately got 10 psi increase reading on his gauge". I know that shifting the connection point does not change the actual pressure.
Bob
Bob Schapel

I removed the penny from the cover plug on the oil pump a couple of days ago and installed a helper spring.

Today, we installed new rod bearings, front and rear seals, and installed the sump.

We pumped oil into the priming plug on the oil pump and spun the engine with spark plugs out to build pressure.

Inserted spark plugs and started the engine.

YIKES! 100+ pounds of oil pressure. New bearings plus helper spring plus regular spring plus cold 20w-50 oil were too much.

Shut off the engine and removed the helper spring. Restarted engine ... 45-50 pounds of oil pressure at 2500RPM -- cold. Great!

I'll drive the car for a while to watch the oil pressure and check for leaks. And I'll probably switch the pick up for the oil pressure gauge from the head to the block to see if that raises the indicated pressure on the gauge to match other TFs.

Thanks for all of the advice that you gave to me regarding bearing installation, seal installation, gasket "goo", and oil pressure. This is a great forum.

Lonnie
TF681
TF7211
LM Cook

This thread was discussed between 03/02/2024 and 06/02/2024

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