Erratic to no-existent oil pressure - diadnostic help wanted

[Roy Gillett]

UPDATE:

Parts have arrived but so has the rain, so I am waiting on the weather.

I have been experimenting with re-sizing pictures I have been taking so if I have mastered GIMP I will include the illustrations to go with my story.

I hope this works, if so it might be interesting to all those who have helped me ( assuming we now have a solution!!).

I will try one first and if that works I will upload some more. This is the damaged sump with two clear witness marks from the strainer One is light scuffing (presumably the normal positioning and the other much more pronounced where the sump floor was driven into it, knocking it off its spring-loaded mounting plate

Roy

[Roy Gillett]

More pics:

I seem to have duplicates which I can't find a way of deleting - sorry

Roy

[StoatWithToast]

Yeah, I can see a clear crease in that top photo. With the 2.8mm clearence needed, mentioned before, I think that crease would be enough to block the pipe. Interestingly on the other sump it looks like there's a bulge about where the pickup pipe is.

Not had the sump off my twink yet, but from your pictures they look thicker than most I've dealt with before; I think it could be carefully beaten out without causing fissures or fractures and provide clearance again. It would obviously be to a worse tolerance. Maybe ok on an engine without the higher performace pump?

Hope swapping to the other sump works!

[gerrym]

Roy, you seem to be on top of this now bt a couple of observation in any case:-

1/ To measure internal clearances as assembled, I have used lumps of plasticene in the past and then measure what the squashed dimension is. This is easier and more reliable than measuring protrusions and then estimating the clearance.

2/ Having been affected already by pump suction issues and seeing how critical they are, why don't you go the whole hog and get your sump modified with full baffles (to prevent cornering problems). You seem like an enthusiatic user of the Elan so this will be a worthwhile mod for the future. Lots of details on this forum. See especially the Aussie designs (remind me they sell the design and/or a kit of the parts?)

Regards

Gerry

[Roy Gillett]

Roy, you seem to be on top of this now bt a couple of observation in any case:-

1/ To measure internal clearances as assembled, I have used lumps of plasticene in the past and then measure what the squashed dimension is. This is easier and more reliable than measuring protrusions and then estimating the clearance.

2/ Having been affected already by pump suction issues and seeing how critical they are, why don't you go the whole hog and get your sump modified with full baffles (to prevent cornering problems). You seem like an enthusiatic user of the Elan so this will be a worthwhile mod for the future. Lots of details on this forum. See especially the Aussie designs (remind me they sell the design and/or a kit of the parts?)

Regards

Gerry

Hi Gerry

I had thought of using plasticine but wondered about the strainer spring squashing it and therefore giving a false reading. What I have done is offered both sumps up without gasket and cork inserts and you can feel / hear the dented one contact the strainer on end of the pipe as you push it home against the crankcase skirt. I then noticed that the corner of the sump in question will not lie flush with the crankcase skirt . I can still get a 40 thou feeler gauge between sump and flange when pressed home as far as I can. With the undamaged sump there is no sound of connection with strainer and it goes up flush onto the crankcase. . I reckon it is 7 or 8 mm deeper than the damaged one under the strainer measured from a straight edge across the top of the sump and measuring vertically down from that. So, as I am coming to find out things are mighty tight at that point..


Both sumps already have a baffle running front to back along the deep section . I really don't think even at my most enthusiastic I could get oil surge enough to leave the dip tube high and dry (could I?)
Thanks again to everyone for their interest in my problems.
Roy

[bcmc33]

Both sumps already have a baffle running front to back along the deep section . I really don't think even at my most enthusiastic I could get oil surge enough to leave the dip tube high and dry (could I?)

Roy,

With the standard baffle that you have it is easy to get the oil pressure needle to drop on right hand bends. I found this easy to achieve even with my pathetic speeds at Gerrards (Mallory Park) and even round the top bend at Curborough.
I had intended to make the Rohan design, but instead opted for a swinging pick-up by partly copying the John Clegg idea.

One thing that has always puzzled me, and for which I have never found a satisfactory answer -- why is the Twink pick-up not central in the sump? Being positioned on the RH side promotes starvation on fast RH bends. Someone please enlighten me.

For the tall block I plan to build over the winter, I am thinking of modifying a Twink sprung pick-up to place it in the centre of the sump - does anyone think this is a bad idea?

[gerrym]

Roy/Brian,

I'd be going down the road of the proven fixed baffle system rather than re-inventing the wheel with shifting the point of the standard pick-up. See Elantriks system http://www.elantrikbits.com/about.html

Roy, as Brian says, it takes very little to get transient oil starvation. While you have the sump off and the motivation to fix the problem. The plasticene would be best used across the end of the fixed pipe. Check the clearance between this and the sump bottom and then used the end of the pipe as you datum. Whatever you do, remember the old dictum to measure twice and cut once. Even better if the two measurements are from different methods

Regards

Gerry

[GrUmPyBoDgEr]

Both sumps already have a baffle running front to back along the deep section . I really don't think even at my most enthusiastic I could get oil surge enough to leave the dip tube high and dry (could I?)

Roy,

With the standard baffle that you have it is easy to get the oil pressure needle to drop on right hand bends. I found this easy to achieve even with my pathetic speeds at Gerrards (Mallory Park) and even round the top bend at Curborough.
I had intended to make the Rohan design, but instead opted for a swinging pick-up by partly copying the John Clegg idea.

One thing that has always puzzled me, and for which I have never found a satisfactory answer -- why is the Twink pick-up not central in the sump? Being positioned on the RH side promotes starvation on fast RH bends. Someone please enlighten me.

For the tall block I plan to build over the winter, I am thinking of modifying a Twink sprung pick-up to place it in the centre of the sump - does anyone think this is a bad idea?

Starting from scratch the centre of the Sump is the best starting point to place the Oil pick up Pipe.
Why the Elan Pipe ended up where it is is really anyone's guess.
Today an Engine being developer would be initially have the Lubrication System tested on a tilting Test Bench.
The engine being run at max. Revs & the amount of Air in the circulating Oil measured.
Major adjustments would be made at this stage if necessary.
Final testing in a car on a Handling Course would be the last step before handing the engine over for Durability testing.
I don't think that Lotus in the 60's would have undertaken so many tests.

FWIW I am not aware of any Production Car that uses a swiveling Pick up Pipe.
The 4 x 4 Vehicles that I have been involved with all fulfilled the required 45? Longitudinally & 35? Sideways Tilt with a fixed Oil pick up Pipe
Errm, after a lot of work

A note to whoever calculated the 2.8 mm Gap from the previously given Formula.
That is the absolute minimum before you start strangling the intake.
Preferably it is better to add up to 3mm to that figure if you've measured everything on the Components involved.
If you're not sure of the Tolerances, play safe & add 5mm.

There was mention of a local deepening of the Sump in the region of the Oil pick up.
This is a good thing as it does provide a Sump within a Sump permitting the Oil pick up Pipe to be positioned even lower in the Oil.
The deeper the Sump, the better it will be!

Cheers
John

[gerrym]

Roy/John, you are aware of course that a high flow pump will make the suction conditions even more critical than with a standard flow pump. Both in terms of required submergence depth and end effects/ clearance from the sump base (or end of the basket). What is the suction velocity for the high flow pump?

Roy, is there any particular reason that you need a high flow / high pressure pump or is that just what is easily obtainable.

John, the Zetec sump pan that RetroFord provided for me had some pretty trick baffling. Apparently well proven across many applications on the track. I needed this because I elected to go for a shallower broader sump than the Ford OEM sump, complete with wings. In terms of cost this is not a major item, just a matter of implementing a good design.

Regards

Gerry

[bcmc33]

I'd be going down the road of the proven fixed baffle system rather than re-inventing the wheel with shifting the point of the standard pick-up.

Gerry,

It seems to me that all of the successful alternatives move the pick-up to the centre of the sump. This also makes life a little easier when fitting a windage tray.

[oldelanman]

A note to whoever calculated the 2.8 mm Gap from the previously given Formula.
That is the absolute minimum before you start strangling the intake.
Preferably it is better to add up to 3mm to that figure if you've measured everything on the Components involved.
If you're not sure of the Tolerances, play safe & add 5mm.

John, Very good point. I was merely trying to clear up the confusion that seemed to have arisen over the calculation itself and did the maths with Roy's pipe diameter in the formula. I did not mean to imply that the 2.88mm was a suitable working clearance. Thanks for making that clear I would not want to mislead anyone.

Regards,

[GrUmPyBoDgEr]

Roy/John, you are aware of course that a high flow pump will make the suction conditions even more critical than with a standard flow pump. Both in terms of required submergence depth and end effects/ clearance from the sump base (or end of the basket). What is the suction velocity for the high flow pump?

Roy, is there any particular reason that you need a high flow / high pressure pump or is that just what is easily obtainable.

John, the Zetec sump pan that RetroFord provided for me had some pretty trick baffling. Apparently well proven across many applications on the track. I needed this because I elected to go for a shallower broader sump than the Ford OEM sump, complete with wings. In terms of cost this is not a major item, just a matter of implementing a good design.

Regards

Gerry

Gerry,

the point that I made about the deeper the better, refers to a perfect World.
In the past I've been forced to make some pretty crappy looking Sumps work & it was hard going.
Like yourself I had to forfeit a lot of depth on my Zetec Sump, mainly in order to obtain good Ground clearance. I posted a series of Photos not too long ago.
To regain some lost capacity I added "Wings" to both sides of the Sump but baffled them to reduce surge.
Those Mod's were not tested at all but everything works extremely well in the Car.
Regarding your mention of Oil Flow velocities.
The limiting factor will always be the internal Diameter & Length of the Oil pick up Pipe so provided the gap between the Sump bottom & the Pipe end equates to that or more there should not be a problem.
High capacity Pumps will always have their drawbacks & there is no point in using one if a standard Pump does the job of putting Oil in the right places at the right time.
A bigger Pump will put more energy into the Oil, resulting in higher Oil temperature.
Pumping more Oil around will give the given amount of Oil less time to de-aerate in the Sump.
The bigger Pump will draw more energy from the Engine, resulting in higher fuel consumption & lower amounts of energy at the back wheels.
A high pressure Pump will also have similar detrimental effects.
Again in an ideal World, an Oil pump should be positioned as low down in the System as possible, Ideally down in the Oil.
Also the suction side of the Pump & its pick up Pipe should be as big as possible in order to reduce the effects of Cavitation.
Neither of which do the Twincam or the Zetec fulfill.

Well there you go, I blathered on once again
Have a good Weekend
John

[Roy Gillett]

Gentlemen I have oil pressure!!

Wether it is the new pump. new sump, new oil or new filter is at present conjecture, but I think the scenario we ended up at is about right and I strongly suspect the pump I have taken off is actually fine. One day I might substitute it back and see. Then I can use it on my spare twin cam when I rebuild that.

Thank you all for your help and interest.


Roy

[gerrym]

Roy, glad your oil system is working fine. It goes to show that the margins between success and failure can be small. And that such a primitive device as an oil pressure gauge can be very useful (and how many moderns have this).

John, if I can dig out some old photos from a laptop I retired, I'll send you some shots of the baffles for the Zetc sump.

Best regards all

[Roy Gillett]

Hi

I didn't answer the point earlier of why I opted for an HC HP oil pump. When I stripped this engine to rebuild it my engine fettlers, Sutton Rebore, measured the crank journals and found them at a minimum size for the bearings fitted, minus 40thou's as I remember. They thought it unwise to regrind again from there (though minus 60thou bearings were available the suggestion was that cranks ground that far can break even in normal use) and I did not want the vast expense of a new crankshaft so he suggested that they would be fine with a high capacity oil pump to ensure that pressure was maitained even if leakage past the mains was at the high end of normal. As I was going to fit a new oil pump anyway this seemed very reasonable and logical to me. It certainly seems to have worked.

I take the point also being made that having a high capacity pump will increase the suction pressure and I have a mental image of of the dip tube hoovering up the strainer basket if it gets too close, as Aussie John's post described earlier on.


I am fairly sure from my offering up of both sumps that the dented one was holding the solid base of the strainer against the end of the dip tube, maybe even off-axis so that not even the tiny hole in the centre of the plate offered up a flow (it had fallen off remember).
If that was the scenario then I reckon there is now about 7mm clearance with the undamaged sump. Pragmatically and theoretically that seems to be enough.

The only mystery remaining is why I suddenly and fleetingly got full oil pressure back when I took the oil pump off to inspect it and refitted it in Wales..

But I won't lose any sleep over that. I agree with the comments about the usefulness of an oil gauge . It is astonishing how quickly you notice a change even if you don't think you are looking

Much relieved,

Roy