Low Oilpressure At Tick-Over

[Nick B.]

My engine were rebuild some 10.000 miles ago, and has after the rebuild always suffered from oilpressureproblems. The main problems are:

 

1: Appr. 5 seconds to build oilpressure. I have tried different oilfilters without result

2: Low pressure - less than 10 psi on hot tick-over. About 40-50 psi @3000 rpm when hot

 

After completing 10CR last week, I decided action must be taken. Therefore I am pulling the engine this winter (if time permits) and hope I can escape by changing the shells. A NOS oilpump has been purchased and will hopefully help a bit.

 

Any suggestions for what to check for when the engine is open?

 

Cheers

 

Nick

[oldtuckunder]

Couple of things to check before you open it up (if you haven't done them already)

 

Have you tried a different oil pressure gauge (always worth knowing that what you are looking at is correct)

 

Pull and check the oil pressure relief valve, I have see these stuck open, the plunger can jamb open on the spring.

 

Alan

[Darren Groves]

The slow building of oil pressure at start up is probably an oil filter with a rubbish anti-drain valve. If you can get an oil filter adapter that is 3/4UNF rather than the standard 5/8UNF it opens up a massive choice of filters you can use. I was getting 4/5 seconds of the death rattle on start-up on recently rebuilt engine, but got an 3/4UNF adapter and fitted a Mann W724/1 filter and I now get nothing, even if the car has been standing for a few days.

 

You can read more about it here: http://forum.tssc.org.uk/index.php?/topic/2670-oil-filters/

 

Darren 

[Nick Jones]

I would say that the oil pump fitted now had crap clearances.  Fit a decent one.

 

You can drop the sump and change the pump with the engine in.  Not a very nice job but less work than pulling the engine.

 

Nick

[oldtuckunder]

Is this the Spitfire or GT6?

[Nick Jones]

Spitfire.

[Nick Jones]

Nick,

 

To add detail, alot of the repro pumps have very crap tolerances.  The critical ones are the gaps between the lobes of the inner and outer gears which are easy enough to measure with feeler gauges and also between the end of the gears and the faceplate.

 

You can't do anything about the gap between the gears - out of tolerance = bin food.  However, the gap between the end of the gears and the faceplate can be fixed by lapping the pump body on a sheet of glass with a piece of 400 grade wet of dry paper laid face up on it.  You can go down to 0.001" on a cool day.  You can also reface the faceplate in the same way if it is scored

 

like this

http://tr6.danielsonfamily.org/OilPump.htm

 

Also check bearings.  It's possible to change all with the engine in the car though the front main is a real PITA due to the bridge piece so I usually leave that one unless the rest are bad.  The bottom shell on the centre main wears worst (most thump on it) followed by the rear main and the front wears least.

 

If you find problems with the oil pump then there is a good chance the bearings are fine. The pressures you give should not lead to problems yet though the long wait for pressure after starting might.  Does it knock before the pressure comes up?  If not then it's pretty likely the bearings are still good.

 

Nick

[spitfire6]

Hi,

 I bought the Witor "Blueprinted" pump a while ago. Will get it fitted soon.

Taking it into work on Wednesday to get it pro measured and will post results Thursday.

A tight pump is much better for pumping oil.

I have a gallon of M1 FS 0W40 ready to go in.

[Nick B.]

On 14/9/2017 at 4:08 PM, oldtuckunder said:

 

Hi all

 

Thanks for the very good feedback. It was caught in the middle of the server-changeover, so unfortunately I had not had the possibility to reply. Anyway - here goes

 

Quote

 

Couple of things to check before you open it up (if you haven't done them already)

Have you tried a different oil pressure gauge (always worth knowing that what you are looking at is correct)

Pull and check the oil pressure relief valve, I have see these stuck open, the plunger can jamb open on the spring.

 

Alan

I trust the gauge as very low pressure corresponds with the green light (fortunately I only witnessed this light flickering once, and killed the engine immediately) . My thoughts were initially with the oil pressure relief valve, and I have been working my way through a combination of different plungers and spring without this affecting the low pressure unfortunately.

On 14/9/2017 at 7:11 PM, Dazman1360 said:

The slow building of oil pressure at start up is probably an oil filter with a rubbish anti-drain valve. If you can get an oil filter adapter that is 3/4UNF rather than the standard 5/8UNF it opens up a massive choice of filters you can use. I was getting 4/5 seconds of the death rattle on start-up on recently rebuilt engine, but got an 3/4UNF adapter and fitted a Mann W724/1 filter and I now get nothing, even if the car has been standing for a few days.

 

You can read more about it here: http://forum.tssc.org.uk/index.php?/topic/2670-oil-filters/

 

Darren 

I have been through different filter without any change in start up pressure. The latest incarnation is a K&N filter with the  3/4 adaptor.  I am ashamed to admit I never got around to fit this as the original 5/8 stud is hopelessly stuck in the block, and I could not get it out.

On 14/9/2017 at 7:39 PM, Nick Jones said:

I would say that the oil pump fitted now had crap clearances.  Fit a decent one.

 

You can drop the sump and change the pump with the engine in.  Not a very nice job but less work than pulling the engine.

 

Nick

Oh Nick - I trust you are right. I hope the NOS pump I have on the shelf has better clearances.

On 15/9/2017 at 12:20 AM, Nick Jones said:

Nick,

 

To add detail, alot of the repro pumps have very crap tolerances.  The critical ones are the gaps between the lobes of the inner and outer gears which are easy enough to measure with feeler gauges and also between the end of the gears and the faceplate.

 

You can't do anything about the gap between the gears - out of tolerance = bin food.  However, the gap between the end of the gears and the faceplate can be fixed by lapping the pump body on a sheet of glass with a piece of 400 grade wet of dry paper laid face up on it.  You can go down to 0.001" on a cool day.  You can also reface the faceplate in the same way if it is scored

 

like this

http://tr6.danielsonfamily.org/OilPump.htm

 

Also check bearings.  It's possible to change all with the engine in the car though the front main is a real PITA due to the bridge piece so I usually leave that one unless the rest are bad.  The bottom shell on the centre main wears worst (most thump on it) followed by the rear main and the front wears least.

 

If you find problems with the oil pump then there is a good chance the bearings are fine. The pressures you give should not lead to problems yet though the long wait for pressure after starting might.  Does it knock before the pressure comes up?  If not then it's pretty likely the bearings are still good.

 

Nick

This will be interesting to measure out on the new pump - just as well as measuring the old pump once removed.

14 hours ago, spitfire6 said:

Hi,

 I bought the Witor "Blueprinted" pump a while ago. Will get it fitted soon.

Taking it into work on Wednesday to get it pro measured and will post results Thursday.

A tight pump is much better for pumping oil.

I have a gallon of M1 FS 0W40 ready to go in.

I just checked out the Witor pump. It seems only fit for the large engines - not dspitfire. Am I correct on this? Would be a sublime solution if it could be adapted to a spitfire. But now - at lreast I know where to find a pump for my GT6 :-)

 

Cheers

 

Nick

Edited September 20, 2017 by Nick B.

[Nick Jones]

The 6 cylinder pump is different.  There are those who claim it can be adapted to the 4 cyl, but I don't know if it's true or why you'd want to do it.

Same principles apply when measuring and adjusting the end float to either type.  It will be interesting to see what you find.

Nick

[spitfire6]

Hi,

Two measurements on Witor GT6 Oil pump at room temperature:

1. Outer Rotor and Body= 6 Thou or mills.
2. Inner rotor tip to Outer Rotor= 5 Thou or mills. (Max should be 4!!!)

A bit disappointing. 

The Rotor end float was not measured as I only found out what to measure tonight. I have been told that the equipment at work can work to sub .05 Thou/Mills.

Is there a problem reducing end float to less than a Thou? 

Cheers,

Iain.

 

[Nick Jones]

I reduced mine to 0.001" IIRC.  This measured at ~ 10ºC.  I didn't go lower because a). I was bored with lapping and b). it occurred to me that it might end up too tight if I ever wanted to start it at negative no. temperatures.

Oil pressure is still unimpressive but I don't think it's the oil pump.

 

Nick

[rogerguzzi]

Hello Nick

                   I also think it is important to get the end cover sitting over the rotor to form a seal as i have done on several pumps and peg to maintain position while fitting as blueing shows(all the re pro pumps have holes to big to control this!)

Roger

[rogerguzzi]

Hello All

better photo

[spitfire6]

Hi,

 I was using the below to check my pump:

With reference to below, my Witor pump on Fig 35 and 36 is actually OK. 

How do I reduce Fig. 37? Put the oil pump true in a "machine" and machine until I have 1 thou? I'm guessing metal will be removed from body and or outer rotor to achieve this?

Cheers,

Iain.

[Nick Jones]

Ian, see the link I posted above.  You can lap it by hand using a sheet of wet/dry paper (400 or 800) face up on a sheet of glass.  Do the taller of the two gears first to get it to match the shorter one (usually they are almost the same anyway) and then the body of the pump to give the desired clearance.  Great care needed to keep it flat.  Keep shifting your grip point to minimise the effect of uneven hand pressure.

Nick