Oil starvation / sumps

[gingerpaul]

This is my first post so first of all hello everyone. It looks like you've got a great site here. Sorry for asking a question the first time on here but I suspect that's how most people end up on here in the first place.

I recently finished building a Dax Rush. It's running a Rover P6 engine with a Weber 500. Internally the engine is stock and fairly worn out but it runs ok for now (I'm planning on building a replacement engine over the summer and installing it over the winter).

As I've got more used to the car I've found I'm pushing harder and I have started to explore the performance of the brakes a little. I have found that when braking hard from about 60mph or higher the oil pressure drops very low and on one occasion, plus once more to confirm it wasn't a dash fault, it dropped to 0. I also noticed the engine was struggling to idle for a second or two.

Would I be right in thinking that this is an oil starvation issue due to oil surge in the sump? If so, is there anything I can do to fix it short of fitting a sump with more internal baffling? Could it be that I don't have enough oil in there? It's topped up to the maximum on the dip stick, but could the engine being level in the Rush and being on a slant in its original configuration (Rover P6) mean that I have infact underfilled it?

I haven't explored the limits of the car during turns so I don't know whether this issue manifests itself under hard cornering but I do know that so far it has only been an issue under hard braking so far.

Some people on the Rush owners club have come up with some interesting suggestions, including a few pictures of a DIY trap door sump which seems like a good place to start once I've sourced a Range Rover sump, but I was wondering if anyone on here might have some suggestions for me along the lines above.

Thanks in advance for any advice that may appear.

[IainB]

I also noticed the engine was struggling to idle for a second or two.

Welcome
Have a search for topics regarding sumps and fixes, but for the above it will be the fuel being pushed to the front of the bowls. For the Holley 4150/4160 you can get jet extensions that are supposed to help with this (as the same thing happens with a drag car on launch) I would assume that Edelbrock also do the same?

[RoverP6B]

Hello Gingerpaul,

From what you have explained, it certainly sounds like oil surge to me, and you have also answered your own question is that the solution is a suitably modified sump to prevent such an occurance.

I don't feel that the change in angle of the engine from being slightly up at the front to horizonal would realise such a variation in oil level, sufficient to contribute to the problem that you have discovered.

Best of luck,
Ron.

[ian.stewart]

You mean a bit like this one I made earlier,






Dunno if its going to work as the engine is still in bits, but I dont see why not, and i think the capacity is a bit larger than I originally envisaged @ 7 litres

[sidecar]

I also noticed the engine was struggling to idle for a second or two.

Welcome
Have a search for topics regarding sumps and fixes, but for the above it will be the fuel being pushed to the front of the bowls. For the Holley 4150/4160 you can get jet extensions that are supposed to help with this (as the same thing happens with a drag car on launch) I would assume that Edelbrock also do the same?

I agree, it's going to be a fuel serge issue.

My sumo (Fake snake) also misfires if it is cornered very hard. (Or at least it did do until I started fiddling with the carb, it might have improved a bit now).

I'm not sure if there is any jet extensions available for the edelbrock carb or any other gizzmos that could help, hopefully someone will know.

One thing you should be made aware of is that the standard needles in the carb will badly overfuel your engine and this will cause bore wash. It may even be having an effect on the problem that you've got.

The 67 x 55 needles will get your fuelling closer to what it needs to be, they cost about 10 quid from John Woofe Racing and take about 2 minutes to fit. You don't even get covered in petrol!)

I've just bought an LC1 lambda probe and it shows my 4.6 fuelling to be around 13.5-14:1 with the above needles. (A little lean for max power but not dangerously lean) My mate has a 3.5 and the AFR is about 13-13.5:1 on the same needles.

I'm going to try to get the fuelling to about 12.5:1 under WOT and under hard acceleration and keep it the same on cruise but it looks like I will have to modify some needles to do this!

One last thing, the probe has shown that the carb is very sensitive to the pilot screw settings, going from too lean to too rich within 1/2 of a turn!
My carb is set to 2 - 2+1/4 at the moment.


Don't let me put you off modifying the sump, it can only improve the lubrication which is a good thing , especially with the "G" that you can pull in your Rush

HTH,

Pete

[v8alex]

Hi Gingerpaul,

You've probably seen my posts on the DSC forum....

I have a baffled sump, though not yet got the Rush on the road to benefit from it. Seems a sensible way to go, especially when throwing the car about. There's a trapdoor in the middle too.



Alex

[gingerpaul]

I saw your efforts after searching the site Ian. Looks quite impressive! This is what a guy on the Rush owners club has done:



It looks like you've gone another stage further fitting that oil tank down there.

Interesting what you said about the Weber carb Pete. I had assumed, wrongly it seems, that the screws on the front adjusted the amount of fuel going in. Does it change the the air going in then? I think I'll order the needles and give them a go. For £10 it's worth a pop.

What would you expect the figures to look like on a gas analyser? I can get access to one for a bit of a tune up if it'd help.

[sidecar]

The screws on the front setup the mixture srength when the engine is ticking over. Infact they supply the mixture regardless of the revs when the throttle is just starting to be cracked open.

They are set with the engine ticking over, get the engine up to temperature and have the screws open maybe 2+1/2 turns, slowly wind one of them in, the revs may rise a bit if the inital setting was a bit rich. At some point the revs will just start to drop or a slight misfire will happen, I then open my screws 1/4 turn from that point. Do the same with the other screw then re-set the tickover if needed.

The edelbrock website explains how to setup the carb, their method for setting the screws ends up with them a fraction too lean in my opinion!

If you are running a 180 manifold such as the edelbrock performer don't be fooled into thinking that one half of the carb does one cylinder bank. The two outer cylinders from one bank and the two inners from the other are fed from one half of the carb.


The standard needles have overfueled every RV8 that I've ever seen by quite a lot. The needles that I suggested seem to work very well and only take 2 minutes to fit.

I'm planning to go a lot further with my carb as I now have a lambda probe (I will modify or make my own needles if needed!) but you will be fine if you just whack in the ones that I suggest!

Good Luck,

Pete

[kstrutt1]

A simple short term fix that may work is to keep the oil levelat the max mark on the dipstick or just above(also check the dipstick is accurate). This certainly works on my other toy (Lotus Elan).

Kevin

TR7V8