oil starvation symptoms

[123-jn]

On a run to Aberystwyth and back from Bromsgrove, hills up and down and some long tightening bends this is a problem I get.
As you can imagine on this road she spent alot of time nose up/ nose down or under high G one way or the other, in these situations especially after a long tight bend I start to hear dry tappets like an angry wood pecker (like when you start up after a lay up but all the tappets not one or two.) After 5-10 seconds all suddenly goes quiet again. I've checked the oil level and its 5mm below the max on the stick. The oil is 20/50 and is new!!! The effect is more likely in a tight bend but also happens on uphill stretches. On a bend it happens when I throttle up as I straighten out, on a hill it happens after throttling up to climb. If I slacken off the throttle it shuts up only to reappear if I throttle up again until after about 5-10 seconds when it all goes quiet again.
It seems to me that in all these circumstances the oil will have been flung to the rear of the engine away from the pick up tube, does anyone have any thoughts? Has any one had this or do I just drive madly.

[MidLifeCrisis]

Well - I've certainly never heard the phrase "high G" used about a T25 before!!!!

[itchyfeet]

Pinking?

Id describe it like a can full of ball bearings rattling around in the engine ,...always under load

it sounded like stones pinging against the floor pan

And my favourite...

sounds a bit like a skeleton w*"king in a biscuit tin

.
All from...
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[123-jn]

well i though pinging first but why would it suddenly stop with no change in load at the time, I thought spark knock but again no c hange in load and it will do it on petrol too. Normal driving around bromsgrove and it doesnt do it only the big hills and long tight bends seem to bring it on?
oil pressure is 25 psi at tickover when hot and 65 psi at 2500 rpm.

[marlinowner]

If it was oil starvation then the oil pressure warning light and/or buzzer would come on. My old van used oil and when the level was low the light would come on on roundabouts, then I knew it was time to top up.

[123-jn]

No warning light or buzzer comes on when this happens could it be that pressure is high enough for most parts but not to properly pump up the tappets?

If it was Pinging why would it only do it just after a tight long bend or in a long up hill stretch? When I originally thought it might be pinging I fitted a brand new dizzy, leads spark plugs,etc, plugs are clean no sign of carbon, inside cylinders is completely clean looks just like when I put it together using a mini camera in the plug holes. Timing is set at 7 degrees btdc vacuum disconnected. Mixture is lambda controlled. Plug gap is 0.7 which is a good size for lpg/petrol. Ive tried it at 0.5 but it can miss on petrol at this. I did wonder if the heads were overheating but water temp is good no where near overheat, temp gauge runs on led centre point. Thermometer (infra red) reads no more than 87 degrees anywhere hottest where it leaves the head.
Are there any other theories out there or ideas for finding out what it is?
The van runs great it is just abit annoying, it did this about 5 times on the way and similar on the way back but not at all on the flat roads of England!!
P.S you know when you cross the border into England from Wales as the road surface degenerates into a moon scape.

[itchyfeet]

Lambda controlled can still be lean flat out if the powervalve or bias is not set right (or perhaps if you have tried to trick the controller by not following the correct setup procedure ) do you have the test lights permanently connected?
Around a corner and up hills means your engine has to work harder than in a straight line, its going slower and running hotter.
its the more likely, you really need to find a local hill where you can repeat it, drive the same route on petrol and see if it happens, oil starvation wont change if its that, pinking will.

[ghost123uk]

Unusual to get pinking on LPG though as it's 113 Octane rating. But reading the fault conditions, it does point to pinking I have to agree, even though it shouldn't be.

The easy way to test if it is pinking is, do as Paul says, find a hill and deliberately labour it up the hill to get "the noise", then back the timing off a tad (marking where it was of course) and see if that cures it. Or, do the same hill on petrol and see if it pinks. It will pink much more readily on petrol.

Does it ever do it on petrol, as said above, petrol is much more prone to it.

[California Dreamin]

I have to agree that any dramatic loss in oil pressure (enough to cause excess engine noise) would bring the low pressure oil warning light on.
The 'pinking' theory does sound the most likely and adding to the previous posters comment about LPG having high anti knock characteristics...I have seen cases where excessive oil consumption has caused pinking..even several diagnosis where carbon build up behind valves and on pistons have caused this issue (the carbon deposits 'glowing' leading to pre-ignition).

Martin

[123-jn]

if I drive it up a local hill I get no noise at all even with the throttle flat out, this is why I dont think it is pinking, usually you can get a pink on demand by slamming the throttle down up a gradient but I cant.
Its not weak as the 3 lights are cycling as usual

[itchyfeet]

It will pink much more readily on petrol.

Does it ever do it on petrol, as said above, petrol is much more prone to it.

air fuel ratio is also important, I suspect that's the cause which is why I suggested trying on Petrol where air fuel ratio can't be messed with like it can on gas.

I find the air fuel guage gives different impression to the lights, it will show lean when the green flickers more than the red, something you can't see with the eye on LEDS

Engine would be very hot up a long steep hill after a long drive

[kevtherev]

If you are getting tappet clatter at high rpm then the gallery is emptying due to low oil pressure.
0.3 psi will keep the oil light out but might make the tappets clatter IMHO

[123-jn]

On petrol it does exactly the same as on gas all is fine except in the outlined circumstances. I've just checked the plugs and all around them for burn marks or arc marks, there is nothing at all. Timing and plug gaps all as I set them originally no sign of carbon on the plugs or in the combustion chambers so I'm rather stumped. The tappets are all new, all I can think is that when the oil is hot and thin and the oil runs to the back and the sides of the sump perhaps the amount of oil picked up by the strainer is lower and the oil runs out of the tappet bores quicker leaving half charged tappets?
I will have to m ove the oil pressure gauge so I can see it when driving and keep a careful watch. (At present the steering wheel is in my line of sight.

[kevtherev]

Where are you taking your oil pressure reading from?

[123-jn]

The oil pressure gauge is in the same hole as the sender below the water pump, perhaps it would be worth trying it in the other hole inbetween the pushrods to see if the pressure is ok in the gallery there.