I am looking at potentially switching a couple of engines (that are currently pressure fed phoenix systems) over to a splash fed arrangement.

The reason I ask is the splash fed phoenix system in my trials car has been (touch wood) rock solid for 11 years of trialing almost every trial, where as these two race engines I've acquired have both seem to have had major failures on No.4 big ends that seem to be as a result of oil starvation. Both are pressure fed systems.

I understand that pressure fed systems are of course fine in principle and many fully tuned race engines/and trials cars use this system, but as I'm at the stage of forking out for two new cranks and rebuilds, I am wondering if maybe the simpler system is worth choosing overall?

They two cars will be used for sprints and hill climbs, not track racing.

Is it a case of scones and sconz, or are there distinct advantages with one over the other?

Any help would be appreciated.

I'm not, I feel qualified or have the knowledge to comment on weather or not one is better than the othere, but what I can tell you is that the splash feed engine in my special has been ultra reliable ( touching wood at this point) having covered many hundreds of miles and done three sprints this year. It's thrashed mercilessly and will Rev to well over 7000 rpm although not much point as it makes peek power at 6250 rpm.Is keeping it simple possibly a good thing ?
Regards Ian.

Location: Work (sheffield)

Ian, out of interestare you running with shells or white metalled rods?

Location: Farnham

Shells david

Location: Worksop notts

Thanks Ian, and a filter I presume?

Location: Farnham

Most definatley an external oil filter
Regards Ian.

Location: Worksop notts

Splash or more accurately oil mist fed engines are definitely as good as or better than current pressure fed engines. When Austin pressure fed in in the 20's and 30's they used circumferential pipes to avoid centrifugal forces.
If you use pressure feed make sure that sufficient oil pressure and flow are available to overcome pressure drop down the tortuous route to No4 bigend.
If splash is employed I would recommend oversize pump and jets. I would also recommend careful jet alignment. I am not sure how important this is but better safe than sorry.
Full flow Filtration is also in my opinion very important on either system.

Location: gatwick

A good number of years ago I took some advice from Tim Myall, Alex's father, he insisted I would be better off splash feeding my crank. As mentioned in previous posts I followed that advice, my car has done many hard road and race miles over the years and I have never had a problem with the big ends.

Location: New Zealand

I just got all new pressure fed stuff.

A couple thoughts:

7's have done really well on splash systems. All over the world and for many many years.

I think there are special set up necessary for pressure fed set ups.

First fit a proper large pump. Gear rotor pumps do a better job at proper oil temps than gear pumps.

Oil lines REALLY NEED to be 1/2 inch ID min. Especially if you fit a filter and oil cooler. This is important if you are doing long hard driving. The pressure drop across small ID lines may no matter in sprints or climbing. If you plan to drive hard for hours it's just a good idea to not take a chance restricting flow. I'll "lead and trail" the oil holes as well.

Once the oil in inside the crank it needs to get to the rear. Something people forget is the oil needs to maintain a wedge and get out. Number 4 con rod needs a few more thou SIDE clearance….. to let the oil out freely maintaining the oil wedge ….. this is where the high volume pump and non-restriction lines, filter, ect really comes to play.

There are many factors involved. If your set up and use of the car is correct I have no doubt splash can work and it is simple and trouble free.

Our Rosengart Van will be driven my wife. She has a very heavy foot! For this reason I've gone to the extra effort and expense of a pressure fed system.

Clean oil at proper temp and pressure just make me feel like I am not going to have to strip and rebuild this little engine often.

And if your wife didn't go 287 MPH at Bonneville (50mph+ on the previous record) you may not need to consider any of these things I must. I don't even want to mention her "Brake at the last moment" driving

Just my .02 PLN

Location: Poland

Many Aspects

Some years ago there was an article in the NZ VCC mag about an early Miller engine imported here. Suffered repeat rod failures. It was rigged to be fast rotated and the crank observed. The Austin type starvation problem applied. (Many racing rod failures are attributed to seized bearings.)

As pressure drop to the crank axis is regained after the axis is crossed, so a reasonable pressure in the 2/3 gallery to feed 4 seems a logical expectation. Presumably it is oil loss from and on the way to the gallery and the flow restriction inside the crank which saps pressure. But this would apply also with circumferential gallery of the same diameter.

As I understand it oil will flow across the axis provided pressure there does not drop to 0 absolute, when a void forms (as in a barometer). An absolute pressure in the 2/3 gallery equal to centrifugal pressure ensures flow to the 3/4 axis. This does not seem to need a whopping pressure. Just how the flow and pressure in No 4 is affected when the pressure at the axis is low but the oil is not actually disrupted is beyond me. Again, once past the axis the full centrifugal pressure presumably can develop again.

Perhaps someone can clarify exactly what occurs, if it has not all been done before.

The original Austin b.e.s in my My RP car had an oil groove in the top of the b.e. I gather earlier cars just had the drilled holes. These all seem to be in theoretically the wrong place, but presumably pick up some oil from the jets (even if it is promptly thrown out again at the top of the stroke!). Austin must have considered them necessary. Am curious as to the arrangement the jet feed racers adopt? With and without shells? Are the holes in the conrod dispensed with? Without, would need a generous clearance and side clearance somewhere for oil to exit.Did the shell bearing Rubies retain the holes?

on old rods there is often ridges on the trailing side of the oil trench. This either indicates reduced film as per theory, or dirt forced in through the oil holes!

Bob Culver

Location: Auckland

Thank you so far to all the advice that has been offered. This has opened up an interesting thread, and it's given me plenty to think about. Any further expert/experienced advice is only going to help make my decision easier.
Kindest regards
Tim

So why bother with pressure fed engines and the extra complexity? It would be good to hear from people with pressure fed engines and the reliability of such engines.How many big ends run over a few years of competition use?
Dave.

Location: Sheffield, the home of Hendersons Relish.

Well, I've used a pressure fed engine for almost 30 years. In that time I've done something like 250 sprints and hillclimbs. Never run a big end, in fact the engine comes apart regularly and there is never any sign of distress on No4 big end. It's not a lot more difficult to build a pressure fed engine. There's a few things to be done, but these days most of the bits you need are easily available.
The key thing is supply of oil. Quarter inch pipes and a standard oil pump won't do.
Just for the record, nose fed cranks are not that unusual. Notable examples include RollsRoyce Merlin and some modern formula one cars. So, Bob Culver might not understand the physics of oil flow through the crank, I'm not sure I do either, but my old boss Stanley Hooker clearly did, so that's OK.
Note to the uneducated. S. G. Hooker- Merlin design team.

For anyone curious

Centre end fed cranks have an advantage in that the oil does not have to battle against centrifugal force to get to and past the axis of a main bearing before carrying on to the b.e. In fact such engines should draw oil at all speeds. The distance involved in a large conventional modern is near 1 1/2 inches and, at least at high rpm, some input pressure is necessary to gaurantee a flow.

Bob Culver

Location: Auckland

Re some of the discussion above it is interesting to read that apparently in 1936 the early production RR Merlins under the design leadership of Alfred Cyril Lovesey suffered from excessive wear to the crankshaft main bearings.
Reportedly Lovesey later commented that the major technical improvement to the Merlin was the improved supercharger designed by Stanley Hooker.
It appears that Lovesey and Hooker were recalled from retirement in the 70's to assist with development problems in the trouble plagued RR RB211 turbofan engine used extensively in the Boeing 747.

Tony.

Location: Malvern, Melbourne, Victoria, Australia.

For any one interested there is an excellent book about his work and engineering achievements.
Not much of an engineer, Sir Stanley Hooker. Isbn 1-85310-285-7.
Well worth reading.
Steve.

Location: South East Cornwall

It would have been 1972 or 73. SGH (or Hkr in Rolls Royce reference terms) was recalled along with quite a few retirees. They also called upon the services of a string of graduate apprentices, inc. me, as gophers.
The book title is a reference to comments made about his degree in mathematics when he was interviewed for a job at RR.

"Not Much of an Engineer" is an outstanding book and should be essential reading for anyone interested in Engineering.

Location: Melrose, Scottish Borders

Does the extra load when using a more powerful oil pump for pressure feed cause rapid wear of the pump drive gears? The skew gears look a bit weedy to me.
Dave.

Location: Sheffield, the home of Hendersons Relish.

I wonder that too.
What modern pump are folk modifying to fit these days?

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.