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GT6 MK3 Oil Pressure


Dolomitejohn
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Hi All,

Managed to drive 30 miles today in the GT6. Bit of an issue with a misfire (corroded contact in the Dizzy cap - so easily sorted),  but when really hot the oil pressure at idle was about 15 PSI as per the SMITHs gauge.

When driving at 50, PSI was just over 50 PSI.  

Is 15 too low ?    I seem to remember from my Dolomite 1500 days, it was possible to increase the oil pressure by changing the oil pump relief spring.

The Engine appears to have done about 109000, doesn't smoke and doesn't rattle on start up now the non return oil filter has been fitted. 

I don't want to damage the oil pump drive or pump, so what would your recommendation be?  Leave or increase the pressure by changing / modifying the spring ?  Where would I get a modified spring from ? Part number ?

But loving driving the beast.....

Cheers All.

John

 

 

 

 

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That seems reasonable pressure "at speed"; what weight oil are you using?

Also, with that kind of mileage on the engine, you might consider changing big-end bearing shells...or at least checking them for wear. Checking and, if needed, changing them can be done without much difficulty from underneath without disturbing anything else, and it might be worth doing?

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As Mark said, the idle oil pressure was never specified, only the 2000 RPM figure.

Bigger relief spring will not help with idle pressure, just make the pump and seals work harder when you don't want to.

As Andy said, if your oil pressure is low, treat the cause, not the symptom. Check your big ends as they're normally the most worn. It's also possible to change main bearings with the engine in situ (ish) but it's a fair bit harder.

Also, use good quality oil. I use Penrite 20/60 on the Vitesse but not the GT6 because mine had a new oil pump when the engine was rebuilt and it still gives rather higher pressure than it needs, so that gets Millers 20/50

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Hi all

Thanks for your replies. 

I am using halfords classic 20/50 as all I could afford. Its green like the old duckums oil. 

Rattle on start up was minor and only about 1 to 1.5 seconds prior to the new oil and non return valve adaptor and spin on filter.  With spin on there is no rattle. 

Bizarly no oil leaks either, unlike the incontinent dolomite that leaks from every seal despite new seals everywhere... 

OK I will leave the pressure spring alone. I have never seen 20 / 60 oil.... 

Thanks all. 

John 

 

 

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the low pressure warning is set around 6 -8 psi  and you have double that at idle  .

the only spec is 40-60 psi  hot   at 2000rpm , there is no 'minimum at anything' spec. 

you are well above the warning so smile and ride

you could up the idle by a few rpm that will raise it if youre that worried 

but as all others have said leave alone its fine 

pete

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I would recommend listening to the engine though as at some stage, depending on the mileage you do, it will benefit from a bottom end refresh. Mine had big ends at 40k and then recently at 70k my brother heard my mains so it had those and a new oil pump fitted with engine in situ. Both times the shells were just going through to copper....

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I'm no expert on the subject but I did read what seemed like a very sensible article recently that said that oil flow was the important thing, not pressure which though easier to read, can be misleading to most of us, including me, having previously assumed that high oil pressure is a good thing.

If your oil galleries were blocked with crud, starving your bearings, then the oil pressure would be reassuringly higher as the pump couldn't force the oil through the obstructions. Likewise if the oil is too viscous.  High pressure but low flow.

Makes sense to me.

The author suggested that as a rule of thumb, 10psi per 1000rpm was a healthy reading.

 

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Hi Dolomitejohn,

your oil pressure looks good If this is with 20W50. I would not put thicker oil in it in the belief that it will increase the already good oil pressure to a better figure. It will not.

I would avoid Penrite 20/60 mineral oil as it is substandard for a Triumph Engine. The Penrite 20/60 syn is a better choice but in your case not required.

Cheers,

Iain.

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John,

I'm a great fan of gauges, I've got loads! However, people misunderstand their purpose. My oil pressure gauge tells me I've got 80lbs at start up, do I believe that? No! Calibration on these things is...…...not good. The point is, "is the gauge reading different from yesterday". if the gauge reading drifts over time something might be up, but what the gauge reading is, doesn't actually matter.

Doug

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I really can't see the point of synthetic oils in our engines, apparently the average annual mileage of a classic is 900 and even if it does more the scheduled changes are much more frequent than moderns which is what synthetics are best for. Our old low tune engines contaminate the oil much more rapidly than a modern so a normal oil changed frequently is ideal.....

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Sounds to me like the oil is thinning too much. Which would be about right for the Halfords 20-50. 

In reality not an issue if the car is driven like most, and not thrashed. 

The reason synthetics are good is that they maintain their qualities much better than old oils, they are just better.... but not always necessary.

Simple solution is to use a better oil. Not sure the castrol 20-50 will be much different. I found VR1 to be a little better, but the real change came when I used Millers CSS20-60. Certainly not a cheap oil and probably overkill for many.

 

Doug, I believe your 80psi on startup, especially on a cold day. I have had nearer 100 on a couple of my cars after refreshing the engines, but the oil thinned a bit pretty quickly once running, and the pressure dropped to sensible levels. (another advantage of modern oils, the first number is the cold viscosity, so a 10-50 would flow better when cold than a 20-50 but with a bit less pressure)

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John, treat yourself to some of the Pennine 20/50 that the club sells, especially if you catch it when on special offer.

It has been good for me recently.

I also use Millers CSS20/50 and Valvoline VR1.

the VR1 consistently gave 10PSI less at 3000rpm, and that was seen by multiple other people as well, but never faltered however hot the engine.

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Indeed. My spit just had a 1200 mile thrashing (should have been nearer 2k, but a prop UJ failed so got recovered home...)

That is on mobil 1 oil in a modern engine. You can just about see the colour of the oil on the dipstick now.

And tonight leaving for another 1000 mile round trip to spa. The oil will last a year, probably about 6-7K. But it does get a very hard life. Poor thing. Which is why it gets treated to a very good oil. 

 

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Zetec/st170. It goes well! (plus pretty economical, averaging about 35mpg on the trip, half mileage was a "steady" (ahem) motorway journey up, where the satnav was very handy, most of the rest was enjoying the largely empty scottish roads. Right up until the car started shaking itself apart.

(yes, the engine obviously contributed to the demise of the UJ, but when I took it apart, it had NEVER been greased. The other had. The prop was new 2 years ago..)

 

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