Oil pressure too low...

In my quest to fix the thrust washer problem on my TR6, I decided to take my "new" oil pump out and check it's tolerances. Well, the rotor blades have triple the allowable maximum clearance as measured with a feeler gauge. Could this be a source of less than great oil pressure? I max out a 50+ when hot. Needless to say, I am installing a new pump. My old pump was new 20K miles ago and of the later style. Do these babies go out that quick?
And, does it ever end? (This is a rhetorical question)

Bill

Large clearances would definitely lead to larger oil bypass and limit the oil pressure the pump could generate.
What was the heritage of the bad oil pump, was it a Taiwanese job or a "rebuilt" unit and where did you get it?
Did you check the pump clearance when it was brand new? Trying to figure out if it's from wear or just poor manufacturing tolerances. It' good to learn from problems like this.

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And, does it ever end? (This is a rhetorical question)

Bill

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Bill -

To borrow from Robert Earl Keene, "The road goes on forever, and the party never ends."

It IS a party, isn't it? /ubbthreads/images/graemlins/thumbsup.gif

Mickey

I was just about to order a new oil pump for the 1500 Triumph-based engine in Spridget. It looks very similar in design to the one used in your TR6. My parts guys (a friend) advised me not to bother, because (in his words) "They're terrible!". Apparently he's had some bad reports on them. The rotor clearance on my pump is right at the limit, so I guess I'll keep it.
One thing you can do: the end-plate on these pumps gets worn by the rotor rubbing against it. You can take some 200 grit emery paper, put it against a nice flat piece of glass, and smooth down the end-plate. This can make a measurable oil pressure difference if the end-plate is pretty worn.
While you have the pan off, have you measured the rod bearing clearance? (with Plastigage) It's cheap and may help verify the cause your lower oil pressure (and for the record, your pressure's not *that* low).

By the way, these little "mechanical adventures" won't end until you end! Best to hope that these problems keep coming! /ubbthreads/images/graemlins/wink.gif

Graham,
The pump I pulled was installed by the fella that built my short block. It has the letters "MCDI" moulded inside somewhere. I have no idea where that one came from. All I know is the guy that did the original work would have used parts from WalMart if I let him. Had to lean on him to buy the best as I was paying the bill. At least we did put Vandervell bearings in as they were available at the time. The new pump came from TRF and has the word "county" or something to that effect moulded inside. What gets me about these pumps is there is no special surface for the rotor assembly to spin against in the cap. I would think that at least there would be a bronze seat inside the plate. Just soft aluminum, the devil's metal. Too, I have thought about Plastigauge-ing the crank at the rods. Am not sure if I want to know. PO'd that I have to wait another week for some more thrust washer sizes. I may have to install a large and a small (relative) size to get the tolerances I want. Am assuming that the larger one should go to the rear. Kept emailing the dude that advertizes the bronze thrust washers on the net, never got a reply. Oh well.

Keep on truckin'

Bill

Out of curiosity...

If you dress the end plate down to make it flat and remove the wear rings... can you also dress down the length of the body to minimize the rotor's axial clearance? If so, what (minimum) axial clearance should a pump have between the rotor and end plate?

Hi Bill,
I'ts not clear to me whether you have the gear type pump or the rotor type pump. In either case, some "blueprinting" of the pump could help. The end clearance between rotors or gears & the end plate are critical, should be uniform, & no more than .0015". You may have a choice of pump types. The rotor type may or may not be "better". The gear type is easier to work on.

If it is the gear type, the gears may not be exactly the same length - depth. The gears can be machined or lapped on a surface plate to the same length. The bottom of the housing itself may not be square to the gears or is located too far from the gear surfaces. Again, the housing can be squared & depth set by machining or lapping. Lapping can be done on a sheet of plate glass, but must be done perfectly square to the pump axis. This also applies to the rotor type pump. Remember, we are talking about .001" or less, differences.

Obviously the mating surface of the cover must be smooth & flat.

This "blueprinting" must be carefully done with very precise measuring equipment, such as parallels & depth mic, & slow, careful work. The difference between a "bad" pump & a "perfect" pump can be as much as 30 psi output pressure, especially at lower engine speeds.

The internal RADIAL clearances cannot be adjusted except by selective fitting which is usually not practical. However, adjusting the end clearances, as noted, can make a large improvement.

There can be a large difference in quality & internal fits between pumps of the same manufacture & between various pump "brands". If there is a "known" brand of higher quality pump it would help, but even this should be carefully checked for proper clearances.

I personally "blueprint" or verify all new pumps before installing them. Even the 'best" pumps sometimes have less than optimum internal fit. The oil pump is too important to the engine's welfare to just install "something" & hope.
D

Hi all,
I used a "County" brand pump on my last rebuild with reservation. The pump I took out was the original with over 100,00 miles on it & was out of spec. After close inspection I noticed the port design on the County was very restrictive compared to the original , other than that it was decent. After matching the port design with a dremil I felt alot better about using it. So far I have over 20,000 miles on it with no problems ( I'm going to regret saying that ) no funny stuff in my oil changes or drain plug.

Unfortunatly there isn't much of a choice other than a race pump prepared by racetorations or others, but be prepared to mortgage the house. As suggested by "D" , if you want to make sure, have the part blueprinted first.

Hello Bill,

there is nothing at all wrong with 50lbs\sqinch + on a Triumph engine. I would also be quite happy with the white metal thrust bearings, bronze is not needed. The only extra I have done on my car is to pin the thrusts to the block so they can't drop out.

Alec

Piman....
I've not been into the lower end of my TR6 but it's only a question of time before taking a look at those dreaded thrust washers. I'm curious about how you "pin" them in place to stop 'em falling in the pan. I'm assuming that can only happen with a lot of wear which I understand can have a fairly sudden onset when the washer bearing metal wears through.

Dave,
Thanks for the info on pump clearances. The GT6 oil pump hasn't been available for years so when I last replaced it I had to use a TR6 pump from TRF. I also had to cut clearance in the windage tray of the pan to get the pickup tube into the sump. I saved the old worn pump... I've often wondered if these can be revived by building up the lobes by flame spraying or plating. Do you know if this is possible?

Like all LBC owners I keep my old parts "just in case" but I've often thought that parts like used oil pumps really were junk and I frequently ask myself why I keep them.

Hi Doug,
The rotors don't usually wear much. I don't know if they could be built up. The housing may wear, but again, I don't know of an economical way to save it. Much of the pumping effeciency loss comes from end plate wear which can be corrected. The pumps are about as well lubricated as anything can get & even the ones with aluminum housings usually last a good long time, unless the pump has been in an engine failure which put metal particles through it.
D

If you're getting a 50 lbs of pressure in your car, I wouldn't worry about the pump. I have a rebuilt pump with tight tolerances and I still get 50psi.

I wonder if the fact that I have a rather large oil cooler with no oil thermostat and the auxiliary oil line to the rockers might have a tendency to keep my oil pressure at the 50+ range. Having to push over six quarts of oil through all those different channels. Possible?

Bill

Hi Bill,


First of all, 50 lbs ain't bad in a fully warmed up engine, although a little higher pressure might be nice, but 50 lbs is probably quite safe.

The oil cooler should not effect oil pressure within the engine, other than helping by keeping oil from becoming overly thin due to high temperatures.

However, you really should consider installing a thermostat. Oil coolers are rather fragile by nature and shouldn't get the high pressure on them that often occurs with cold oil at startup.

It's also possible to *overcool* oil, which will keep it from ever heating to the point where moisture and other contaminants are properly "cooked off". A thermostat will insure that oil temps are correct, not too cool or too warm. It's not a big deal to add a thermostat. In fact, if you are using a sandwich plate at the oil filter as a take-off point for the oil cooler lines, Mocal now offers one with a built-in thermostat, making for very easy installation. I recently bought one of these from www.racerpartswholesale.com

The auxiliary line up to the rockers *could* be reducing oil pressure in the bottom end. That auxiliary feed is also sometimes marketed for 4-cylinder cars, where it is considered by many to be a serious mistake to install it because it can lead to a lot of oil burning. On the other hand, I've always heard it's a good thing on the 6-cylinder TRs, where there is a definite benefit from some extra lubrication to the valve gear.

However, if it's flowing a lot of oil away from the more critical bearings below, maybe you should think about putting a restrictor of some sort in the bypass, reducing the diameter of the feed by inserting something inside the hose, for example. Or, it might be possible to make a restrictor from brass plumbing parts bought at a local hardware store, depending upon the threads and connector sizes used.

You could test the theory pretty simply. Just temporarily removing the bypass feed line, plug the holes it's fitted to, drive the car for 20 minutes to fully warm it up and check your oil pressure readings.

Have you mentioned pressure at idle/warm, or what motor oil you are using?

I'm more knowledgeable about the 4-cylinder cars, but would guess you should get about 15-20 lbs at idle, fully warmed up.

Someone correct me if I'm wrong, but isn't 20W50 motor oil called for? (BTW, I'm not a fan of synthetic oils in these older motors, either.)

Finally, the earlier 4-cylinder cars have an adjustable pressure relief on the oil filter head, making it pretty easy to increase or decrease pressure a little. Do the 6-cylinder cars have an adjustment there, too? I think not, but it doesn't hurt to mention it.

Cheers!

Alan Myers
'62 TR4 CT17602L

For starters, anything above 20 psi at 2000rpm is just bonus. If you've got 50psi warm at 2k, your engine is doing great.
Actually though, an oil cooler is usually detrimental in anything but a full race prepped TR6 engine. Oil needs to reach at least 180 degrees in order for it to properly lubricate, clean, and cool, and oil coolers will overcool it. The oil is too thick to do its job.
I'm going to disagree with Alan for a minute, though. Synthetic oils are good for older cars. I have tried both types, synthetic and not, and the synthetic oils will not break down as quickly, maintaining their viscosity and giving a higher pressure. 20W50 is best for summer, 10W30 is good in the winter. And no, the 6 cylinder engines do not have an oil pressure adjustment.

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Oil needs to reach at least 180 degrees in order for it to properly lubricate, clean, and cool, and oil coolers will overcool it. The oil is too thick to do its job.

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Agreed, Webb. That's exactly why a thermostat is so important. The Mocal stat I just installed is preset to open at 180 F.

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I'm going to disagree with Alan for a minute, though. Synthetic oils are good for older cars. I have tried both types, synthetic and not, and the synthetic oils will not break down as quickly, maintaining their viscosity and giving a higher pressure.

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You are welcome to your opinion about synthetic oils. I've had two bad experiences with it, and won't use it again.

Another important consideration, are we talking about a recently rebuilt engine here? Synthetics should *never* be used in an engine with less than 3000 miles on it. The rings will never fully seat and the bearings won't bed in. The stuff is too slippery to allow proper engine break-in.

And, despite the clear advantage of maintaining consistent viscosity at temepterature extremes, most full synthetic oils have way too much detergent for these old engines. Older engines were designed to run with some carbon deposits, that actually help rings seal, for example.

I do use Valvoline semi-synthetic oil in a couple modern cars. But, not in the old Triumph. I just have to change it's oil a little more often.

Cheers!

Alan

I agree with the folks that 50 pounds is good pressure. Remember that (on the TR3 and TR4 at least) the oil bypass spring is set to 70 pounds so you will not get any more then that.

On my TR3A that has not had anything done to the oil pump I see (once I have a hot engine) 20 pounds at idle and 50 pounds at speed. I have been driving the TR3A since 1985 and this has been constant all along.

On my TR4A which I blue printed the pump and took the end clearance down to as close to nothing as is safe (I would have to look in my lab book to give you the exact number if you want it) I get with a warmed up engine 55 pounds at idle and 65 pounds at speed.

All this to say, at 50 pounds you are doing just fine.

Alan,
I was speaking from the point of view of a broken in engine, though your point about new engines is good and one I hadn't thought of. What non-synthetic oil do you use and how often do you change it?

Hi again Webb,

In the TRactor motor I use Valvoline 20W50 year around, especially here in Calif. with winter temps seldom as low as freezing.

Castrol 20W50 is fine, too, IMHO. Most of the major brands are fine, I'm sure. I'd just avoid high-detergent and I'm not too keen on cheap/unknown or recycled oils.

(Note: In more modern cars, I use Valvoline semi-syhtnetic blend: 5W30 mixed 50/50 with 10W30 in a Pontiac 4 cylinder with 126K miles, and 10W40 in a Land Rover V8 with 52K mi.)

In the TR gearbox I use Valvoline 20W50 Racing oil, non-detergent. I have no plans to use anything different now that there's an A-type overdrive on the gearbox. Again, Castrol Racing oils would likely be fine, too (just not "Type R"!).

I used 90W gear oil in the stock diff, which has never been rebuilt and is in perfect working order. 90W often is impossible to find these days, so 85W95 or similar seems fine. But, I'll need to change to a different type of oil after the Quaife limited slip diff is installed.

Engine oil changes in the TR probably average less than 1000 miles, although I'd feel safe up to 3000 mi. if it were driven more often (it's currently getting rebuilt with an estimated 120K mi. on the engine, which was re-ringed and got new bearings about at about 80K mi.). Time is more often the oil-change determining factor with the TR, rather than distance. I don't like to leave oil in any car for longer than 6 months, even if it's only done modest mileage.

Cheers!

Alan Myers
'62 TR4 CT17602L