803 oil pressure worries AGAIN

[JOWETTJAVELIN]

Hi all, what are your thoughts on these figures:

Good cold start-up pressure of 70 psi.

Hot figures:
At 30 MPH - barely 20 psi, often just below.
At 50 MPH - 35 - 40 psi.
At idle - 5 psi.

It's the idling figure which worries me. I cannot adjust tick over any more or the engine might take off!! (or at any rate increase the risk of overheating whilst stuck in traffic).

It's worth saying that the engine is in good overall health but does smoke a little. Duckham's 20/50 oil used.

What will be the effect of this on the bearing surfaces, especially when I'm getting like zero oil pressure at idle?

[mike.perry]

How is your pressure release valve?

[David53]

Those figures really are low - Def check the pressure release valve but I fear it will be either the oil pump or general wear in the engine. How's the compression? Should be 120-130 across all four pots on the 803. When you say "smoke a little" are we talking blue smoke or white?

[JOWETTJAVELIN]

It's blue smoke but oil consumption isn't excessive. At the next service I'll drop the sump and check the pressure release valve.

I have no idea of compression as I haven't got a gauge. Keeping my eyes peeled at autojumbles for one.

The mileage is around 40,000 but the original owner in one of his letters says 80,000. If that is correct (all the MOTs from 1971, btw, point to it being 40,000 miles). I think he must have made a typing error, but if not the engine will have done 90,000.

[brucek]

You don't need to drop the sum to check the oil pressure relief valve - it's located to the left of the distributor and is housed by the large nut you will see in the block. Once out of the block, check the quality of the cup and, if possible, thoroughly clean the seat in the block where the cup sits. Something like a good pipe cleaner should do the trick. The pressure exerted by the spring needs to be 60lb/sq.in (4.2kg/cm3) - to do this the spring must be the correct length - 7.3 cm. If necessary renew the cup and spring and see if this improves the pressure. Good luck

[bmcecosse]

It's not the relief valve.......it IS a worn oil pump and bearings. The original pump on these engines is a sad wee thing with sliding vanes........ As long as it's not rattling too much - just keep using it. But - I would be looking for a replacement engine (preferably a 948!) to recondition and have on stand-by.

[David53]

Hate to rain on your parade but a pre 1956 803cc engine will have done a LOT more miles than 40,000 or even 90,000! Even if rebuilt at some stage the general wear in a small engine this age means it needs to be handled with care. I had my block completely rebuilt when restoring my car with all new rings, caps, bearings etc but there is no way it performs like it would have in 1953. I keep my speed to 45 mph, occasionally 50 mph if I need to. The 803 is a car to potter around in, not attempt to keep up with modern traffic. I very much fear if you have been bowling along at 65-70 and popping radiator caps you have probably got a very worn little engine which is on it's last legs

[JOWETTJAVELIN]

I will check the relief valve anyway. Some new evidence has come to light to suggest the unit has indeed covered 80,000 + miles.

It just sounds 'sweet as a nut' though and actually, for an 803, I would imagine performs very well. Sure it is slow but it is still a very willing little engine and pulls very well, no fatigue at all.

There are no worrying noises coming from any area of the engine and it is as quiet as a mouse on cold start-up, so I am content to just keep using it and keep my eyes and ears on things.

Maybe I should just fit a new oil pump and it will go on for another 80,000 miles?

Thanks.

[bmcecosse]

Indeed - but unfortunately it's engine out to do so.

[JOWETTJAVELIN]

Oh.

[MikeNash]

A couple of thoughts. Its 40 years since I've had an 803 engine out but (although much younger and not doubt stronger) I remember it as quite easy, and the main bearings and big end bearings being fairly easy to change. But that's only worthwhile if their ovality is no more than, say, 2 thou. Roy'll have a few ideas on this.
Re oil pressures I've just replaced my old 1098 engine (with one bought from Roy!) which had done well over 100K. It was then doing well below 200 mile to the pint of oil (Asda 20/50) with most of it being blown out the rear main bearing down out of the hole in the cliutch bell housing and covering the underside of the car. However, the engine was quiet and if I kept the valves in good order so I had good compression it went like a train. But cruising at 60-65 mph (true) for a couple of hours up the A1(M) on a warm day the oil temp would climb to 210F and the oil pressure would drop to 40 psi. Tick over would then be about 8 psi, but still no rattles. So I'm with Roy here - use it if there's no rattles, take care but don't worry and look out for another engine! Regards, MikeN.

[JOWETTJAVELIN]

Well, I had the relief valve out today and the spring is 1/8" shorter than is recommended.... so a new spring will be ordered.

In the meantime I slightly stretched the existing spring to see what effect this has, although it'll probably make it lose more tension.

[bmcecosse]

It's nothing to do with the relief valve.....or it's spring....

[JOWETTJAVELIN]

I feared as much but thought I'd check it anyway. It hasn't made any difference so I'll just have to accept this 88,000 mile unit is reaching the end of its life.

It's the original engine though and I don't think its ever been rebuilt. Are parts still available for an 803 rebuild? I want to keep the car with 'matching numbers'.

[David53]

I would suggest it is probably 188,000. But yes parts readily available.

[bmcecosse]

But not inexpensive...... Are oversize pistons available for that engine? And I doubt you will get a service exchange crank for it although I 'think' oversize bearing shells are available, but at a price.

[JOWETTJAVELIN]

There is no rust on the body or underneath though. Sure it's had some welding repairs but these have been done properly, not 'patched' to get it through an MoT. The sills are like the day it left the factory.

88,000 miles is quite an achievement for an engine of that age; bear in mind the odometer only reads up to five digits. Still, if I can nurse it up to 100,000 I will do and will be well pleased.

[bmcecosse]

Indeed! Some folks swear by the restorative powers of a can of STP - never tried it myself - but can't see it doing any harm.

[MarkyB]

With an oil pressure gauge fitted you will be able to see if STP makes any difference and for how long.

[Neil MG]

Hate to rain on your parade but a pre 1956 803cc engine will have done a LOT more miles than 40,000 or even 90,000! (

My 1956 803cc has a genuine 70,000 and has never been out of the car. It's not uncommon to find a low mileage Series II here.