I did my pressure fed engine first in (?) 1986, from a very early batch of Phoenix cranks. The crank and rods have outlasted almost all of the rest of the engine! 1 x No 4 failure, about 15 years ago due to a faulty replacement nose from Phoenix. Oversize A7 pump bored on same centreline, with stronger springs in vanes, 10mm copper oil lines throughout. Mocal filter head. Mag crankcase with home made nosepiece using O rings as the seals. No rev limit, ever, 7000 whenever possible, 6000 often. Probably 50000 miles. Touching wood.

If anyone has a spare pressure fed crank/rods kit i would be interested as i'm just piling up the bits to build an Ulster with/for my son..............

W

Winston, that's interesting. My Phoenix crank in the Ulster is similar age. It's not done a huge mileage but it's done lots of events. Oil pump is two standard pumps mounted back to back- double capacity- (if anyone is interested I'll tell you how it's done but hardly worthwhile now you get get better pumps )
I'm intrigued by your use of O rings to seal the nose - am I right in thinking it's where I use lip seals?
A

Yes Alan. I simply made a new oil seal housing to replace the standard item on the mag timing cover. It has a gallery with an O ring each side and a side drilling for the feed. At the time i approached the tech dept at Dowty Seals with a ********** sketch and their man said Orings would be more suitable than lip seals for a number of reasons, including space and price. So far he has been right. I became nervous about the wear on the Phoenix nose 15 years ago so replaced it with a new one in a panic rebuild before a Lands End, this nose, it turned out had a brokrn drill bit in the botton of the drilling, partially blocking the flow. I was very pleased with the new oil pressure on the engine for about 15 miles till No 4 started rattling! The only failure so far. No longer worry about the wear marks. W

I've not built an A7 oil pump but several others in the past. I like the gear rotor pump. They seem have better pressures when oil is up to temp. AND they are easier to make/machine housings for. Replacement gear rotor sets from MGB are easy to get 5 main is a but taller than 3. If you have room I prefer 5 main.

Location: Poland

I am looking at oil pumps at the moment,and have a new MGB one and a Don Rawson one here.
We seem to have an oil pressure loss on my car for no apparent reason,Having checked everything I'm considering making another pump for it.
Bluto,did you shorten the rotor length on the MGB based pump or leave it full length?

In the case of my prewar BMWs I use 5 main MGB. You can use a pump rebuild kit @US$15 a bargain

I've seen others use Ford and Mini pump rotors but it think the larger O.D. pits a strain on the drive gears off the cam

Location: Poland

So as not to upset either of you,could I have both to play with,please.Happy to pay for either/both
Thanks Dave

hi Alan

If you have an understanding of what exactly goes on I for one am curious. Certainly
if the flow disrupts and no 4 drains, that adds 15 psi to the pressure reqd and certainly at 7,000 rpm the figure is then very considerable, although I am not over confident of my arithmetic. Presumably engines are arranged so there is absolutely no risk of momentary oil disruption due to surging.

Impact pressure with jet feed would seem not to be astronomic. At 4000 rpm like riding a motorbike in the rain at 70 mph with your mouth open. I have not had the experience at 120 mph!

Bob Culver

Location: Auckland

Charles P

Steve Jones

Austin in the Shed

So as not to upset either of you,could I have both to play with,please.Happy to pay for either/both
Thanks Dave

Might cost you a pint in the Wheatsheaf at some point over the weekend Dave

Steve

Typical Yorkshireman!

Location: Brittany

Bob,
I think this subject can become as complicated as you wish to make it, but, to me, there are two separate aspects:
First, as I’m sure you know, we need to get away from the idea that the oil pump pressurises the big end bearings. It doesn’t. The big end on a pressure fed engine is lubricated in exactly the same way as a splash fed one. That is, by the hydrodynamically induced forces in the bearing. All the oil pump has to do is ensure a sufficient flow of oil to do that. If you think about it, on a splash fed engine, the oil may squirt out of the jet at 2psi, but the force at which it hits a crank rotating at 7,000rpm is very much more than that. As far as the bearing is concerned, that’s not a lot different to pressure feed. Think about the raindrops hitting your face at 70mph!!
The second aspect, as we’ve discussed, is the pressure required to overcome the centipetal forces acting in the crankshaft. This will tend to increase pressure as the oil travels away from the centre and reduce it as the oil travels inwards. The net effect is if the rotational speed is high enough (and the input oil pressure low enough) the oil flow can stall at the crank axis. All this is calculable, and all you have to do is ensure you have enough initial pressure to overcome the losses.
You can make it a lot more complex, if you want. For example the oil isn’t travelling in straight lines but along a curve described by the crank rotation, then there’s viscosity to consider, and whether the oil is compressible or not, and then the travel across the crank pin. The list is endless, but one thing is sure, it’s about Flow not Pressure.
More empirical engineers, like me, however will go by the old rule of 10psi per 1000revs, and probably get away with it.
Oil surge isn’t really a problem. It’s usually solved with deep sumps to give more oil capacity, baffles and a drilled aluminium plate in place of the normal sump oil strainer mesh.

I must admit that I have never built or raced an Austin 7, although I have one waiting for a complete restoration. For over fourty years however I have worked on a lot of engines, mainly building them for serious racing.
The ongoing debate is very interesting, with people who firmly believe in the eficiency of the splash or non pressure fed engines.
What I can conclude from my experience with engines is that the way forward with ALL modern engines is pressure lubrication.
It does not take much either to see why. Pressure in the most elementary physics definition, is taken to be equal everywhere.
This does not change if at the main or con rod, BUT there is an ulterior consideration, that the con rod throws out oil by centrifugal force.
Although many swear by althernative methods, for me there is only one way to go.....pressure feed with good oil filtration.
Engineers have gone through great lengths in more modern engines to improve oil flow, including cross drilling and rechamfering of the oil holes.
I think that the considerations here should not be how much longer one system lasts over the other before overhaul, but if there should be any real need to open up the engine so often to check. A pressure fed system gives exact readings on an oil pressure gauge at given RPM and temperature, to judge an engine's condition.
Excuse me if I am wrong, but if I am, all manufacturers of modern cars are wrong too.

I agree Anton, however in most modern engines the oil feed to the crankpins is from the adjacent main bearing and in some there is a hole up the length of the crankshaft. However in an Austin Seven pressure fed crankshaft the oil is fed into one end of the crankshaft and it has been known for the last bearing to fail due to oil starvation.

As you say Anton you have no experience of Austin sevens. Nobody is saying that the theoretical reasons for pressure feeding an engine are wrong, however in an Austin seven engine many people, myself included, have proven with years of experience that it is not absolutely essential. In fact one prominent race engine builder in the 80's and 90's assured me that he had more problems and failures in pressure fed engines that splash fed. I run both types of engine successfully, but my race special is splash fed and has always been, the current phoenix crank has been in there for over 25 years and is still std.
The whole point of the discussion is to help those relatively new to the world of Austin sevens unravel some of the myths, and believe me there are a few! Obviously it is personal choice which way to go.

Location: NZ

I have spent a couple of months trying to figure out which to build. I have decided to go with the 1"1/2 splash crank and 45deg rods for ease of assembly. This will be my first engine to build so I think the slash system is the most simple to assemble. I was going to use an oversized pump and jets with an external oil filter.

Location: Ireland

Couple things:

Flow to the rear con rod is a problem in full pressure systems

I'm still trying to figure out what to do to get more flow thru the crank. I've a very large high volume pump. I will use at least -8 AN oil lines to the filter and from there to the front. Keeping the lines short is a good idea. Also I ""lead and trail" the oil holes and may grind a 360 degree groove in the front inlet again to help flow. Lastly I need advice on side to side clearance of the rods. That is the key to getting a proper oil wedge in pressure shaft. Too tight the oil puddles too loose it runs away reducing pressure and the wedge.

This heart bypass has taken time to get over but I starting back at is now.

Location: Poland

As I said before, I never worked on the 7 engine. Here I read about the difficulty of getting oil to the rear bearing. How about using an external feed pipe on a pressure system? I have seen this on some engine where all the oil is externally fed to the mains after filtration. Was a bigger engine though! Might be a big job, but for serious racing may prove ideal,

Just a comment on pressure fed crank oil systems.

Camshaft Front Bearing Oil feed!!!!!

When running pressure fed engines the front camshaft bearing has to be modified and the oil flow restricted to it. You will lose a lot of useful oil volume if you use the standard bearing.

I am using a 1980s Alan Crank I have two o rings on the outside of the front camshaft bearing and the oil groove has been filled, (a new custom bearing is an option)
I also have a flow restrictor in the oilway feeding the bearing.

I am now on my third set of shells since 1992.
One set needed due to front lip breaking and seizing oil pump breaking the drive gears the other two sets just changed while the engine was apart. Crank still not reground.

Hillman Hunter oil pump fitted.

Anton:
The only way to feed oil under pressure to the Austin Seven crankshaft is from the front. This is because the mains are not plain bearings but roller and ball bearings.
Provided that the oil jets are properly aligned the splash feed system is perfectly adequate for most use.

Now that I have learnt a little bit more about the Austin 7 engine, I will start the rebuild, overdue by some 30 years, with more courage. One can never know enough, even on stuff that has existed for nearly a century.
I look forward to receiving help during my rebuild. Thank you all.

Richard,

You say that you have a restrictor in the oil feed to the front camshaft bearing where is it fitted and what is the size of the restriction?

Location: Deepest darkest Kent

I restricted the flow to the front camshaft bearing by tapping the feed hole in the bronze bush M5 and countersinking it. I then fitted a countersunk M5 screw in the hole and drilled a hole through the centre of the screw. I had to file the screw flush with the bush. As the hole is at an angle it can't come undone.
It doesn't overcome the problem of leakage round the bush. That needs 'O' rings to prevent it.
I've also restricted the rear bush by rotating it 180 degrees and drilling a smaller feed hole.

I wholly concur withs Jim's modifications and carry out very similar myself. The o rings are well worth while, if you set a crankcase up with a reservoir of kero and run the oil pump it is amazing to witness how much escapes around the cam bushes. I is also well worth noting that as Mike Forest told us all those years ago the jets often do not squirt quite where they are pointing so the paraffin in your boots alignment method is very worth while.

Location: NZ

Thank you for the reply Jim,
what size hole did you drill through the m5 screw?

Location: Deepest darkest Kent

I reduce the hole to 5/32" with no ill effect to the timing gears or bearing, I would expect you could probably reduce further still.

Location: NZ

Location: Poland

This is a fascinating side-line that deserves a thread of its own with diagrams etc if any of the authorities who contributed to it are willing. Obviously guys like me just go for big pumps and hope for the best !

Location: Ferring, Worthing, West Sussex