TR4A engine oil usage

[RogerH]

Hi Folks,

here is a simple question (ho ho ho).

Since I rebuilt the engine last year or so it uses a fair amount of oil - probably 1 Ltr / 500 - 600 miles.

 

The engine has no external leaks (honest).

 

So where is the oil going.

Three areas to investigate -

1, valve guides. These were renewed at the engine rebuild.

2, Piston oil control rings. Again these are new.

3, The engine PCV from the rocker. This is not new.

 

So, how do I progress.

Valve guide seals would need the head removing to cut a groove OR is there a better/easier way.

I could remove the PCV and simply hang a pipe overboard to see how things develop.

The oil control rings look difficult to play with. Are there any tests that can be done to check this area.

 

Is 1Ltr/500 miles too much

 

Roger

[Guest ntc]

Roger

Way to much is the rear of the car keeping clean? and yes you can fit seals without the head coming off

[RogerH]

Hi Neil,

the back of the car is reasonably clean.

No blue smoke out the back when driving.

 

Occasionally (not often) on a warm start up there may be a puff of light coloured smoke (not steam).

 

Have you any information on what seals to use etc.

 

Thanks Neil

 

 

Roger

[Guest ntc]

Roger

Under threat of ban so send me an email

[stillp]

What are the compression figures?

 

Pete

[timhum]

Could it be that the cylinder bores have glazed and that the rings are not sealing due to over cautious running-in of the rebuilt motor. That assumes prisons, rings and liners were changed during the rebuild.

I suggest this after a similar experienvce with a Jaguar XK motor.

Tim

[Rockie51]

Hi Roger

 

I had/am having a similar problem. My 4A with about 25k miles on a rebuilt engine suddenly started to use copious amounts of oil. It used 6 litres in 3000 km (i.e. a litre per 300 miles). It was mainly coming out of the dipstick hole and rust proofing the entire underneath of the car.

 

Eventually tore the engine down and found that the rings had a gap of about 48 thou at the top of the stroke so the combustion pressure was whistling past the rings and into the sump at a greater rate than the PCV valve could cope with. So in went new liners and pistons. The car is not fully run in, but the problem persists albeit at a lower rate of leakage.

 

I put a vacuum gauge on the engine this weekend. It was pulling 50cm (20") of vacuum from the manifold at idle which according to my gauge is in the normal sector for a good engine. However, on the rocker cover side of the PCV valve, it is only pulling 30cm (12"). I am not sure what reading I should be getting there.

 

It still seems to me that the problem is insufficient vacuum. Does anyone have any figures on the vacuum levels that should register through the PCV valve?

[RogerH]

Hi Folks,

everything should be newish (20K miles since rebuild0.

 

I'll test the compression today.

 

Roger

[Motorsport Mickey]

Hi Roger

 

I had/am having a similar problem. My 4A with about 25k miles on a rebuilt engine suddenly started to use copious amounts of oil. It used 6 litres in 3000 km (i.e. a litre per 300 miles). It was mainly coming out of the dipstick hole and rust proofing the entire underneath of the car.

 

Eventually tore the engine down and found that the rings had a gap of about 48 thou at the top of the stroke so the combustion pressure was whistling past the rings and into the sump at a greater rate than the PCV valve could cope with. So in went new liners and pistons. The car is not fully run in, but the problem persists albeit at a lower rate of leakage.

 

I put a vacuum gauge on the engine this weekend. It was pulling 50cm (20") of vacuum from the manifold at idle which according to my gauge is in the normal sector for a good engine. However, on the rocker cover side of the PCV valve, it is only pulling 30cm (12"). I am not sure what reading I should be getting there.

 

It still seems to me that the problem is insufficient vacuum. Does anyone have any figures on the vacuum levels that should register through the PCV valve?

 

Depressingly for you I'm pretty sure your excessive crankcase pressure is nothing to do with excessive piston ring gaps but located somewhere else on the engine,

Just harking back to Piston ring wear, gaps and how to measure them this article from the Institution of Diagnostic Engineers (first published 1995) may give you food for thought, and it's how I've approached piston ring fitment through the years.

 

 

 

Ring Gaps vs Knowledge Gaps

 

Frequently I hear in court that when an engine is dismantled it is discovered that the ring gaps were not staggered when they were installed. Frequently I read workshop manuals that go into great detail on the necessity to stagger ring gaps. Frequently these manuals specify ring gap limits – which is yet another myth we can bin before we are finished.

 

Piston rings are free agents and can rotate or not rotate as they see fit. They are not in touch with the base of the groove and neither are they trapped between the upper and lower faces of the groove. The rings are entirely free to rotate – except where a stop peg is fitted – so what's the point in staggering the gaps on installation?

 

We used to work on a minimum of 0.020" back clearance on radius or, to put it another way, the inside diameter of the ring when installed in the cylinder must be at least 0.040" bigger than the groove root diameter. Minimum side clearance was generally held to be 0.0015" and if you could fit a 0.006" feeler gauge in the groove along with the new ring then the groove was "goosed" so the piston was replaced.

 

The piston ring was manufactured with a tangential load – the force with which the ring presses against the cylinder wall – but apart from that it is completely uncontrolled. There is no way, under these circumstances, that you could prevent the ring from turning so, to repeat the question, why stagger the ring gaps on installation?

 

Equally mislead are those who expect ring gaps to stay staggered when the engine is in operation. When there is clearly nothing to prevent the ring from rotating, why should the gaps stay staggered?

 

More than one county court judge has fallen for the hocus pocus that because the gaps were in line when the engine was dismantled, they must have been in line when installed. Absolute poppycock! Yet the inclusion of such rubbish in workshop manuals does admittedly give it an air of authority.

 

When you think about it, you don't need me to tell you – but I will anyhow – that rings do rotate in operation. Every now and again the gaps do line up – and once lined up there is a tendency for them to stay lined up at least until the vehicle hits the next pothole in the road when one or other will rotate and break the line. Staggering ring gaps when installing rings is a myth that we can bin forthwith.

 

Even worse is the preoccupation with the size of the ring gap. Yes, there is a minimum but this varies considerably depending on the material used. Normally 0.003"/0.004" per inch of bore size is given but where, for example, low expansion SG (spheroidal graphite) iron is used, it can be considerably less, so what about rings with gaps that are too big.

 

Well, the answer to that was that you melted them down and started afresh – until AE research asked the question, "What is too big?" and set out to quantify that. The results were interesting – very interesting – and what you are about to read was kept quiet because it bestowed an enormous commercial advantage on AE. This is probably the first time the information has been published although the research was undertaken in the late 1970's – almost 25 years ago.

 

A Ford Kent engine was stripped and fitted with compression rings which had end gaps of 0.015" when fitted in the bores. The engine was wired up with the usual telemetry to measure blow-by and oil consumption and then run in one of the test cells. After making due note of the blow-by and oil consumption, the engine was stripped and fitted with new compression rings with gaps of 0.025" and the test cycle repeated.

 

These rings were subsequently replaced by ones having end gaps of 0.035" and the test cycle repeated again. It had been planned to stop at 0.035" gaps ----------> but the results were so interesting that it was agreed to proceed to 0.045” and then not to 0.0055” but to 0.0625” – 1/16"!

 

Whoever heard of rings with 1/16” gaps – a ridiculous figure – but the interesting thing was that the increase in blow-by and oil consumption at 0.0625” was only marginally above the figures obtained with 0.015” gaps.

 

Practical tests established that the gap was not the villain of the peace. To all practical purposes the size of the gap didn’t matter. It is important to stress at this point that we were dealing with compression rings that were brand new when fitted to the test engine.

 

The gap was specially manufactured for the tests. So how come all oil burners and heavy breathers have ring gaps you can back a bus through? Well, the tangential load that the ring exerts onto the cylinder wall is a direct function of its radial thickness.

 

As the periphery wears in contact with the bore, the radial thickness obviously decreases, as does the tangential load. Peripheral wear means a smaller ring o/d and this manifests itself as an increase in the ring gap, it's not the gap but the reduced tangential load that is detrimental to the performance of the engine. The ring gap is a complete red herring.

 

Imagine four top compression rings all with 1/16” gaps. The total gap for all four would be 1/4”. Now imagine the seal provided in an 80 mm diameter bore. Pi x Diameter = Circumference, so we have 3.14” x 3.15” = 9.891”. Multiply that by four cylinders and we have 39.564” – over a yard of contact seal between piston rings and bore. Now visualise the many litres of blow-by and consider whether all the gas is squeezing through 1/4” of total gaps or passing through 39½” of reduced pressure contact seal!

 

But even this ignores one important facet of the argument because there is not just the one compression ring on a piston – there are usually at least two and that is because rings work as a team to form a labyrinth seal.

 

For gaps to be the villain of the peace, the gas would have to find the gap in the top compression ring and pass through. It would then have to circulate to find the gap in the second ring and pass through that and so on. Now this may be possible if the power stroke lasts for 10 minutes but it doesn't, does it?

 

At 3,000 rpm the power stroke duration is a mere 1/100second. Quite simply, the power stroke does not last long enough for the combustion gas to find its way around the maze – or labyrinth seal, so the villain of the peace has to be the reduced tangential load of the ring on the bore caused by peripheral wear or reduced radial thickness of the ring.

 

This was our hypothesis based on the results obtained in the engine test cell but it took a very clever American to prove it. This genius invented telemetry that measured gas pressure between the piston rings in a working engine.

 

Use of his brainchild revealed that some gas did get through the top ring gap sufficient to generate a hell of a pressure between the top and second rings – so it clearly was not finding the gap in the second ring. The labyrinth was working well. Caterpillar and IHC must have thought it was working too well because they increased some second ring gaps to 0.050” and 0.070” thought to be beneficial.

 

Come to think of it, the exception proves the rule – as usual. Two stroke engines would not need stop pegs to prevent the end gap from crossing a port if the ring didn't rotate. The people who allege that ring gaps were not staggered when installed just because they are in line when the engine is dismantled don't need stop pegs.

 

The very presence of a stop peg also proves my point about the size of ring gaps. Where a peg is fitted, the end gap has got to be 1/8” to accommodate the peg. There would be one hell of a draught through that if the 0.015”/0.018” boys were correct.

 

This knowledge was commercial dynamite because, instead of the '0.015”/0.018” spec., it meant that new rings with gaps over 0.018” could be used without any detriment to the engine's performance. The gap was only detrimental when it was the result of peripheral wear. Customer acceptance was the only problem.

 

To re-educate the customer would let the cat out of the bag, thereby losing the distinct commercial advantage. It was decided, therefore, to accept rings with gaps of up to 0.030” in a nominal bore but even then there were arguments. 0.030" in a nominal bore is 0.045” in a bore worn by 0.005” – and it's normally engines with this sort of wear that get new rings.

 

It made diagnostics a lot harder too because when all rings set off in the 0.015”/0.018” area gaps of .040” meant something but now, when you don't know what they set off at, what they measure is meaningless.

Well, now you know. All rings are free agents to rotate as they like, making staggering of gaps on installation a joke and ring gaps are not a problem provided that the gap is not the manifestation of reduced ring radial thickness caused by peripheral wear.

 

M H Booth F.I.Diag.E

 

 

Interesting eh... for what it's worth I always fit my Piston rings staggered it just makes me feel better, having confirmation that it doesn't matter a damn is just insurance...I can't possibly get it wrong !

 

As for Piston ring wear as stated in these posts previously it could only be estimated by confirmation that the bores were in a good condition in the first place and the piston rings had been accurately gapped. Where this information is not known measuring the piston (remember they are not round) and the cylinder dimensions will show how worn the cylinder is in comparison, remembering that on Pistons up to these sizes the engines will still work ok with wear up to as much as .005 (Complete Automotive Engine Rebuilding by Robert Scharff ).

 

As long as the piston and liner fitments are the correct clearance and the piston rings are the correct size and type fitted then as the article above describes because of the labyrinth ring seal (the various layers of rings) and the miniscule time the compression is applied in the process it's impossible for enough compression to be passed through the piston ring gaps, even if they are in the order you have described.

Search elsewhere for the problem, it sounds as if the crankcase compression relief has been compromised trapping any gases within.

 

Micky

[ianc]

Try this to see whether it effects any change:

1 - Remove the sucker which takes oil vapour from the side of the rocker cover into the inlet tract.

2 - Seal the hole in the inlet tract.

3 - Attach a length of heater hose from the rocker cover's outlet, route it over the top of the rocker cover to the left-hand side of the engine and either dangle it down the side of the engine past the fuel pump to about the level of the bottom of the sump, or stick the end into a container (catch tank).

 

I have an alloy rocker cover on my TR4 and have used this crude method for the past several years in addition to the crankcase breather which is standard on TR2-TR4. As far as I can tell, next to nothing comes down the rubber hose.

 

Afterthought: like many others, I never fill the sump beyond about 2/3rds up from the bottom of the dipstick towards the FULL mark, as the top 1/3rd will disappear quite rapidly. Thereafter, oil consumption is quite modest, even when driving quite hard.

 

Ian Cornish

[stuart]

Like Ian says we always recommend running approximately half way on the dipstick for oil level as for whatever reason this does seem to be optimum level for these engines.

Stuart.

[RogerH]

Hi Stuart,

that is how I normally fill the sump.

There is probably a simple answer to why the top 1/3 of the stick disappears so quickly.

 

I have my thoughts on it.

 

Roger

[Quicksilver]

Roger,

 

Did you have tried another brand / type of oil?

 

Marcel

[RogerH]

Hi Marcel,

I have used Halfords Classic for a long time and have just recently started using Silkolene.

 

Both give similar usage.

 

Roger

[Quicksilver]

Hi Roger,

 

is the lose of oil the same with cruising the small roads or drive like an Italian? Or on motorways cruising 70 mph or pushing hard and do 85 mph and more on the right side of the way like on a circuit?

 

 

Marcel

 

ps i use Kendall GT-1 HP 20W 50 Liquid Titanium

[RogerH]

Hi Marcel,

all speeds from 0 to 70 +++

 

I have never assessed it for one speed or one style of dsriving.

 

Roger

[Guest ntc]

It will be valve to guide clearence

[AlanG]

It will be valve to guide clearence

 

Either that or rings. Mine used what I thought was excessive oil consumption at around 500 miles per litre. Following new rings, bore de-glaze and new valve guides now about 2000 miles per litre after 7000 miles use. I always keep the oil at the full mark and do not experience any excessive oil consumption.

Alan.

[BarryG]

Hmmm interesting.

 

I have just done a 1200 - 1300 mile trip and used about 2 - 2.5 litres of Halfords Classic.

 

Since getting the car about 2 years ago i have been working at fixing the many oil leaks it had, sump gasket, timing case seal and oil filter adaptor. The only oil leak i think i have now is from the rear crankcase seal. I have a PCV valve fitted with new spring and diaghram.

The engine was rebuilt about 15 years ago and from what i can make out has done very low mileage since. My cylinder pressures are 192 and the highest 198 which seems ok.

I have often pondered about where to fill up to on the dipstick. Gut instinct is to fill to the max mark but as has been said it does seem to drop very quickly to about 3/4 full. I think i am going to try ditching the valve and fitting the crankcase breather pipe down below and see what the differences are.

Ho hum.

 

Barry

[Rockie51]

Progress report.

 

I ditched the MX5 PCV valve that had been fitted when the new liners and pistons were installed and reinstated a new standard (or is that Standard?) PCV valve. I still had a vacuum of 20" between the inlet manifold and the PCV valve, but a reading of zero between the valve and the rocker cover. I noticed that the new valve had an extra spring and plate in the bottom presumably to prevent backfires from entering the system. I did not recall seeing this on the original valve which was on the car for many years. I still had this one, so I fitted the new spring, plate and diaphragm from the new valve to the old one. Lo and behold, I now have 4"of vacuum between the valve and the rocker cover and I can feel vacuum at the oil filler instead of a small hurricane.

 

I drove the car to work and back yesterday and there is NO LEAKAGE from the engine!! Bliss!

 

Until I noticed the gearbox oil under the car. The mechanic claimed to have renewed the front and rear seals..... He will never darken my door again.

[Mark1965TR4aBRG]

Like Ian says we always recommend running approximately half way on the dipstick for oil level as for whatever reason this does seem to be optimum level for these engines.

Stuart.

 

Exactly what I do..

[stuart]

Progress report.

 

I ditched the MX5 PCV valve that had been fitted when the new liners and pistons were installed and reinstated a new standard (or is that Standard?) PCV valve. I still had a vacuum of 20" between the inlet manifold and the PCV valve, but a reading of zero between the valve and the rocker cover. I noticed that the new valve had an extra spring and plate in the bottom presumably to prevent backfires from entering the system. I did not recall seeing this on the original valve which was on the car for many years. I still had this one, so I fitted the new spring, plate and diaphragm from the new valve to the old one. Lo and behold, I now have 4"of vacuum between the valve and the rocker cover and I can feel vacuum at the oil filler instead of a small hurricane.

 

I drove the car to work and back yesterday and there is NO LEAKAGE from the engine!! Bliss!

 

Until I noticed the gearbox oil under the car. The mechanic claimed to have renewed the front and rear seals..... He will never darken my door again.

With regard to the gearbox oil leak, when you replace the seals try and find double lip seals as they are much better in this application.

Stuart.

[RogerH]

With regard to the gearbox oil leak, when you replace the seals try and find double lip seals as they are much better in this application.

Stuart.

Indeed. If it is leaking from the selector rods then the 'Q' or 'Quad' seals appear to work well. A typical number would be Q112 or 4112.

 

Roger

[Ade-TR4]

+1 on the dipstick level: The first third disappears quickly, then stabilises approx 1/8th" below "max"

 

Ade

 

PS: when they stop leaking, they've run out of oil...

[Rockie51]

We have just had a week away at the Triumph National Rally. We did some nice trips in the Victorian Alps as well as 25 laps of a local racetrack. Only spun once...... It ran beautifully and used NO oil! So it seems that my theory that a certain amount of vacuum is needed in these engines might be correct. The speedo ceased operations after 178 miles this time. Last time it was 30 miles out of Melbourne.

As one wag suggested on another site, the system was carefully designed so that a faulty speedo unit would cause the angle drive to fail ($$$$) before the cable (¢¢¢). Oh well, what are weekends for?

 

Rockie