Rover V8 oil pressure cause and effect

[100SRV]

I have a 3.9 litre Rover V8 which had an oil pressure problem where when cold and idling you could hear the tappets rattling. The engine has covered about 12k to 15k miles since a full rebuild (rebore, +.020" pistons IIRC) and once run in has been lubricated with Fuchs 15w40 synthetic oil.

My first port of call was the oil pressure relief valve - I removed the filter housing and found that the plunger was stuck in the bore. A little work to polish out the scoring and the plunger travels freely. The rattling tappet noise is all but eliminated now.

Now to the cause / effect question:
A while ago (maybe 2k miles) I changed from SU carbs to EFi (14CUX) which on start up runs to very fast idle before working out where it should be and behaving normally. I don't think that this startup procedure is particularly good for a cold engine and wonder exactly what engine speed I should expect when the idle bypass valve is fully "in" (need to take some measurements)?

Could this cause to the pressure relief plunger sticking open? - Oil pressure spike, plunger opens to regulate oil pressure, engine speed drops to normal but PRV plunger is stuck open and low oil pressure at idle until things warm up and the plunger is free to move.


As an aside to this I decided it would be useful to fit an oil pressure gauge so I could keep an eye on things - the electric sender I have appears to have an unusual resistance / pressure relationship in that when idling the gauge shows more pressure and as the engine speeds up the pressure drops...

[Steve_D]

100SRV said:

I have a 3.9 litre Rover V8 which had an oil pressure problem where when cold and idling you could hear the tappets rattling. The engine has covered about 12k to 15k miles since a full rebuild (rebore, +.020" pistons IIRC) and once run in has been lubricated with Fuchs 15w40 synthetic oil.

My first port of call was the oil pressure relief valve - I removed the filter housing and found that the plunger was stuck in the bore. A little work to polish out the scoring and the plunger travels freely. The rattling tappet noise is all but eliminated now.

Now to the cause / effect question:
A while ago (maybe 2k miles) I changed from SU carbs to EFi (14CUX) which on start up runs to very fast idle before working out where it should be and behaving normally. I don't think that this startup procedure is particularly good for a cold engine and wonder exactly what engine speed I should expect when the idle bypass valve is fully "in" (need to take some measurements)?

Could this cause to the pressure relief plunger sticking open? - Oil pressure spike, plunger opens to regulate oil pressure, engine speed drops to normal but PRV plunger is stuck open and low oil pressure at idle until things warm up and the plunger is free to move.


As an aside to this I decided it would be useful to fit an oil pressure gauge so I could keep an eye on things - the electric sender I have appears to have an unusual resistance / pressure relationship in that when idling the gauge shows more pressure and as the engine speeds up the pressure drops...

If the valve is sticking it needs to be fettled, as you have done, or replaced....The high revs/high pressure at start-up will not in themselves cause the valve to stick.

The high revs then backing off is normal. If this concerns you then you could fit an Accusump which will pre-oil the engine at start-up.

Steve

[blitzracing]

A sticking valve is a know issue on those oil pumps, its caused by bits in the oil scoring the soft alloy of the pump body around the valve. You can get a ball shaped valve (called a tadpole valve) that is supposed to be less inclined to stick and fits in place of the stock cylinder valve.

[100SRV]

Thank you for the responses Steve, Blitz,
IIRC JE used to supply the tadpole PRV, I'll have a look on the interweb for suppliers.

Any comments regarding oil pressure gauges?
I am not sure whether to use a capillary (via aeroquip hose) or electric for pressure.

Also I have an odd pressure sender but the characteristic is inverse to the smiths gauge - more pressure gives more resistance! No makers mark on it sadly and a search using the stamped on number didn't help much either.

[chedder]

15-40 synthetic, probably not the best oil for the venerable V8, better off woth a quality mineral oil such as Valvoline VR1 20-50.

Tried the fully sythenthetic route myself with Mobil 1, engine rattled a lot on start up and was noisier that normal when warm, swapped to VR1, no more noises and better oil pressure too.

Chedder

[tr7v8]

chedder said:

15-40 synthetic, probably not the best oil for the venerable V8, better off woth a quality mineral oil such as Valvoline VR1 20-50.

Tried the fully sythenthetic route myself with Mobil 1, engine rattled a lot on start up and was noisier that normal when warm, swapped to VR1, no more noises and better oil pressure too.

Chedder

This, 10/40 too thin for a RV8. I ran the VR1 bought in 4 x 5L packs from my local factors & it was fine.

[100SRV]

Further developments on the engine problem, first a timeline:

1. Didn’t like rattle when starting with EFi so decide to fit oil pressure sender (electrical) to port in filter housing, sender works backwards (more pressure gauge reads less and vice-versa) so will use capillary gauge (aeroquip) instead.
2. Oil leak from filter housing, suspect that there is a very small hole in the filter so replace with Bpart filter, eventually find leak and replace copper washer on unused sender port plug.
3. Green laning on 1 Jan and notice that at idle when hot the oil pressure light flickers. Oh dear, hope engine OK. Turn idle speed up a little in mean time.
4. Notice again that engine now rattles badly on startup. Oh dear – new gearbox and now engine F%^ed.
5. Suspicious though of things as engine looked after with good oil and so on so fit a borrowed oil pressure gauge and find that 27PSI cold idle and 40PSI around 2200rpm which within specifications. Will recheck when hot.
6. Alarm sounds in head so retrieve old filter from bin and compare with Bpart filter – Bpart item has no non-return valve so when engine off or hot idle the pump loses its prime (because pump above oil level and filter is horizontal rather than pointing down).

Road test results in and our panel finds:
Hot idle – 5 to 7 PSI and 2000 RPM upwards – 20 PSI

That isn’t good.
Will check tightness of timing cover (as that is where oil pump lives) then...
Next thing is rockers, sump and timing covers off to check:
Oil pump to housing clearance
Big end and main bearing shells
Rocker shafts

ETA:
miles / event
0 engine rebuild +020" rebore and new bearings
15000 change to 10w40 Fuchs XTR (recommended by their website)
25000 fit EFi
30000 oil pressure woes

Oil and filter changed between 3000 and 4500 miles

Comments please...

Edited by 100SRV on Monday 16th January 11:08

[Steve_D]

I would start by replacing the pump as they are known to wear. I believe you can also get an uprated version.
I believe the pressure relief valve is also in the pump so will get replaced at the same time. These are also prone to sticking open.

Steve

[Pumaracing]

Your simplest test is to put some 20/50 in it and see what happens to the pressures. I suspect the combination of thin oil and sticking PRV has started to wear the crank and shells. It only needs the briefest of metal to metal contact to start this happening. Thicker oil might either cure the problem or at least stave off a rebuild for some time. It's certainly easier to try first than stripping it down.

You might also try shimming the PRV spring up a bit with small washers between the spring and plunger. I used to do this on race engines with known oil pressure problems. A 1mm shim can make quite a difference to a spring that's a bit on the weak side.

[100SRV]

Steve_D said:

I would start by replacing the pump as they are known to wear. I believe you can also get an uprated version.
I believe the pressure relief valve is also in the pump so will get replaced at the same time. These are also prone to sticking open.

Steve

Hi Steve,
uprated pump is under consideration, first line of attack is as per Pumaracing.

A Milner oil filter adaptor has been fitted so the PRV is now remote from the oil pump, in a previous in this thread I changed from the cylinder type PRV plunger to a tadpole with some improvement.

[100SRV]

Pumaracing said:

Your simplest test is to put some 20/50 in it and see what happens to the pressures. I suspect the combination of thin oil and sticking PRV has started to wear the crank and shells. It only needs the briefest of metal to metal contact to start this happening. Thicker oil might either cure the problem or at least stave off a rebuild for some time. It's certainly easier to try first than stripping it down.

You might also try shimming the PRV spring up a bit with small washers between the spring and plunger. I used to do this on race engines with known oil pressure problems. A 1mm shim can make quite a difference to a spring that's a bit on the weak side.

Thankyou Pumaracing, I had wondered about trying a more viscous oil but thought I was clutching at straws, I will try the shim trick too...do you think that the EFi start-up cycle may have accelerated the damage?

[davepoth]

100SRV said:

Thankyou Pumaracing, I had wondered about trying a more viscous oil but thought I was clutching at straws, I will try the shim trick too...do you think that the EFi start-up cycle may have accelerated the damage?

Very unlikely I should think - it would be standard for that EFI system, and Rover were usually quite good at stuff like that.

[Boosted LS1]

My turbo engine suffered the same thing. After a hot run the oil light would sometimes come on but I know I had 7 psi of pressure. I had shimmed the pump and oil pressure matched revs if you know what I mean. I used 20/50 Kendall synthetic back in those days. I once burst an oil cooler upon a very cold winter's startup which wasn't very amusing.

When I eventually stripped the engine the shells were fine so I'd say it's more about volume of oil being circulated then the actual pressure on the guage. I think plenty of oil gets pushed round the rv8 engine. An independant guage might be useful.

[100SRV]

Boosted LS1 said:

My turbo engine suffered the same thing. After a hot run the oil light would sometimes come on but I know I had 7 psi of pressure. I had shimmed the pump and oil pressure matched revs if you know what I mean. I used 20/50 Kendall synthetic back in those days. I once burst an oil cooler upon a very cold winter's startup which wasn't very amusing.

When I eventually stripped the engine the shells were fine so I'd say it's more about volume of oil being circulated then the actual pressure on the guage. I think plenty of oil gets pushed round the rv8 engine. An independant guage might be useful.

Interesting opinions regarding the oil, I think now that I will drain the present lube, refill with this:
Halfords Classic Oil 20w50 5L or similar and a new filter and see what happens to the pressure. I have another two gauges which I can use to validate the present gauge readings.

Thank you folks! Always good advice on here.

[Boosted LS1]

I did eventually find a ford dealer offerring a 20/50 mineral oil at a very reasonable price so switched to that instead of the synthetic and things were fine.

[100SRV]

Not good news I'm afraid - I changed the oil for Comma 20w50 and the filter too. I collected a clean jam jar full to let it settle so I could see what bits fell out of suspension but whe pouring the oil from the collecting tray into the can you could see it sparkling (a bit like J20 glitterberry eek!). When warm the oil pressure was the same as with the 10w40 and I could here the rearmost tappet tapping under certain conditions (higher engine speeds) so the next step is to remove the covers and see how much damage there is.

I am pretty sure that the cause of this is fairly recent as previous oil changes have resulted in dirty but not sparkly oil, not happy but at least I found the evidence before it caught me out.

Now to the rebuild: I am contemplating using a different (4.2) crankshaft and maybe a Crane H-218 camshaft - comments please?
I have some data on various cam grinds on another PC so will review before deciding, that said I may just rebuild it to present specification (minus the oil particles).
thanks for your help and advice!
100SRV