What do you think of these compression figures?

Those are fine readings, leave it alone.

Gauge inaccuracy will give readings far from what you might expect, but your readings are quite consistent, showing the engine is ok. Oil pump and a set of shells would be a good idea though.

mrcheerful

Agreed - it's possible one cylinder has a slightly pitted valve, or a sticking ring, but I wouldn't worry about these figures. The pressure that a given engine produces depends on its compression ratio and how much leakage there is (the two factors that everyone thinks about) but also on the efficiency the cylinder fills with air (which is why you test with the throttle wide open), and how close the engine gets to adiabatic (no heat loss) compression. The faster it spins, the closer to adiabatic, so the higher the pressure.

The Range Rover manual quotes 135psi min - but that's for an 8.25 CR engine, and yours will be much higher, I'd guess.

Hmmm. The Rover V8 is a very low oil pressure engine. Quoting the Range Rover manual again, 30-40psi at 2400 rpm with a warm engine - and this is the "new" figure, not the minimum permissible" You might find you need to do a lot of work, besides shells, to get your pressure up much. Many Rangey owners would be delighted to get 20 psi hot running and 5 at idle. The electric oil pressure senders are notoriously unreliable, too.

It won't be up at full temperature in 5 minutes idling. Or driving, either. On an average day it might take more than 10 minutes of town driving for just the water temp to get to normal.

When you say overheating, do you mean signs of running weak?

Treat the fitted gauge with suspicion.

They're fine. The hydraulic tappets are decidedly iffy at cranking speeds. Could also be a worn camshaft - notorious on a gently driven or poorly maintained engine.

Yup. If there's no sign of bearing rattle at cold start up then leave well alone. My SD1 shows zero on the gauge in town when hot at idle. ;-) Can't be though because the warning light doesn't come on. And only just above

Oil pressure doesn't matter, as such. What matters is fast circulation of the oil to cool and lubricate. Of course if pressure is low against that of a new engine then it indicates wear.

Thanks Dave et al.

"When you say overheating, do you mean signs of running weak? -"

A couple of the plugs looked a bit on the white/glazed side. I don't think its running weak, I'm not losing any power, even under hard acceleration. I haven't tinkered with the carbs at all, it seems happy enough once it warms up.

I changed the thermostat today, the old one looked fine though - I'm not sure why, but now the temp is up to where it should be after 10 minutes idle. A consequence of this is the oil pressure is down to 5-10 psi at idle and 15-20 at 2000 rpm and 30 at 3500. Still people seem to think thats not a worry, so I won't.

I did change the oil pressure switch - the replacement had 3 connector points and the one I took out only had one, I'm not sure what to make of that. I stuck the connector on the middle one (dont even know what the oil switch does! what I thought was the sensor was not) What's the difference between the switch and the sender?

I'm not worried about this stuff, it would have been nice though to get to know the engine a bit more running before I took it out.

The engine is coming out on Friday, and the rests going on ebay - just got to work out how to fit it to the engine stand. The bell housing bolt holes in the block don't go right through, I'll need to find some identical but longer bolts than the bell housing ones.

The extra connections on the pressure sender are the ones that feed the fuel pump, no oil pressure equals no fuel!!

mrcheerful

Ooo! The one I took out only had one - it still seemed to work though even when I plugged nothing into any of the 3 connections?

I can't work out what they do from the wiring diagrams either (being a bit more mechnaical than electrical by nature). I had assumed it is one of those redundant things you occasionally find on cars, which must have a purpose but dont seem to do anything at all.

Picture the sender as a switch with its contacts closed when you have no oil pressure, and open when you have. If you disconnect the wires, it is the same as running the engine with some oil pressure. So of course everything works without anything connected. What you lose is the fail safe conditions when there is no oil pressure and the circuitry is supposed to prevent you wrecking the engine.

Personally, I would want the warning light to work, but I am uneasy about the car's circuits killing the engine regardless of what I want. I might be in a situation where I would rather wreck the engine than have it cut out on me in a situation where the loss of power might cause a crash.

Jim

My EFI was company owned before I got it, so I assume dealer maintained. It had a similar oil pressure operated system, but with an electrically operated valve in line next to the fuel filter. And it was disconnected. ;-)

Is it not a way of not adding fuel to the fire in the event of a crash? Mind you, the crash would have to stop the engine...

Ron Robinson

SD1s have an inertia switch to cut off the fuel in event of a crash. The oil pressure one is just to try and prevent damage to the engine if the oil pump fails or you run out of oil.

Where is the inertia switch Dave? If I'm transplanting and engine it would be nice to have that with it.

Most crashes do. Before solid-state multi-axis accelerometers an engine-stop detector was seen as more reliable than an inertia switch. Anyone who suffered an XJ6 with central locking and a (lucas) inertia switch will probably agree.

I can imagine ;-(

It's not always Mr. Lucas to blame though. A few weeks back we parked near a whole lot of radio-type masts on top of a mountain near Albuquerque and the remote locking of Mr. Hertz's Chevrolet (yes, you read that right - surprised me too) wouldn't work. Quite OK down the road a bit though.

Ron Robinson

On mine it's close to the foot pedals. You have to remove the glove box to get at it.

I have heard similar stories of the Volvo 440 being difficult to start if you are unlucky enough to arrive at Dover from Calais and are positioned where a radar beam sweeps part of the deck. Push the car to a different part of the deck and it starts first time.

Jim