Modern day Pre-war Sporting Jowetts

[Tony Fearn]

In the 'Jowett Sport' post, on 11 August 2019 within the Library discussion section, Bruce Girvan wrote:

...I was fearing that my ramblings on trialing etc Eddie was seen poorly by the club members

I'm sure this isn't true Bruce.
Reading of your exploits brings back good memories of past times of Jowetts being used for such purposes.
We just wish we had the enthusiasm, drive and time to do the same with our cars.
Keep up the good work, and letting us hear about 'Eddie's' outings in the Jowetteer.
Tony.

[Brucegirvan]

Thank you, Tony. Given the huge wealth of sporting Jowett knowledge in the club....are any members able to provide a few hints as to ways they found of coaxing more from the little engine with the big pull? With Eddie, I would say the that engine runs well, only todate on trials we have found the rear needs a little more weight to help the grip. Some cars I note have moved the seating backwards...particularly notable for short chassis sports. Are there other mods/ tricks out there other than “practice makes perfect” and of course “the drivers right foot makes the biggest difference”?

[Keith Clements]

Power comes in many forms. Hill climbing can either be brute force and big tyres like the Icelandic version or low revs and relatively high torque on skinny tyres like the vintage version.

Revs give power so balancing the engine and fitting stronger valve springs makes getting it safer. CR ratio gives power so reducing combustion chamber volume or increasing bore size acheives this. Gas flowing heads, valve opening and exhaust and inlet ports as well as tuning the inlet and exhaust pipes will get more charge in.
How you do this within the competition regs is the discussion.

How about a big battery over the back wheels with a dynamo switched in to give a hybrid boost?

[PJGD]

Reducing friction in the engine thereby converting more of the fuel energy into shaft power is always a good move. Modern engines all have graphite coated piston skirts and piston rings that are coated with a hard and low friction surface such as DLC (Diamond-Like Carbon) coating, running in a smooth bore, i.e. a "deep hone" having few peaks but deep valley's for holding the oil (a low Rpk number [p = peaks] but a higher Rvk number [v = valley] in metrology terms).

As Keith notes, improving breathing is helpful. Consider having your inlet manifold and inlet & exhaust ports extrude honed (where they force through an abrasive-laden media in a process properly called abrasive flow machining) and it leaves the passages super smooth with all the corners rounded off. It can be done by this company in the UK: https://www.deburring.co.uk/about-us/

Optimizing valve events and their timing is another option. Find someone that has "Lotus Concept Valve Train" software and have them design a new cam profile for you. With the right inputs, it is the work of a few minutes and is bound to be streets ahead of the original Jowett cam profile. Plus, if you use the single cylinder engine simulation freeware from Lotus, here: http://www.lesoft.co you will be able to optimize the torque curve to suit the sort of motoring that you have in mind; low speed torque for mud plugging, or torque at higher speeds for greater power.

I also recommend increasing the compression ratio, but the problem with side valve engines is that at higher CR's there can be a breathing bottleneck between the cylinder and where the valves are. This needs careful analysis otherwise you can go backwards on power, particularly at high engine speeds.

Philip

[Keith Clements]

Very interesting Philip. I really wonder how accurate the simulation would be , how much effort is involved in even getting close to the Jowett configuration and also how you would go about implementing and testing anything you would find out.
Have you or could you show how this might apply say to the Jupiter?
I see that suspension simulation is also available. I would love to know what the optimal shock absorber settings and spring rates should be.

You also pointed out my omission of the camshaft as being crucial in gaining the desired performance and I would add the ignition advance curve also. Both these could benefit firstly by fitting unworn components and then to tweaking to suit a different rev and gas flow configuration as well as modern fuels.
Accurate setting of valve timing also comes into the equation.
If you have not a new camshaft and followers fitted it is likely the valves are only opening half as far as they should.
If you have not a refurbished distributor profiled to a modern curve it is likely you are many degrees away from the optimum firing point.

[Srenner]

Thanks Phillip!. Now I haw endless hours of playtime on the computer. The coatings you mention (and others) have been around for some time, but few want to spend the additional money. Modern tech is good; remember when getting 100k miles out of motor was an achievement?

Man, I want to build a motor, get a dyno and thrash through all the variations. Oh, wait, maybe I should finish my pile of projects before that.

[David Kemp]

If you want to go faster, read Tuning for speed by Phil Irving. It has a fare bit on side valves & is easy to read.
The last people to race side valves was Harley Davidson, their combustion shape design is available online, & may be a good start.

[PJGD]

In terms of engine simulation, nowadays the Industry largely use GT-Power which is part of GT-Suite, but that is priced way out of our league. I have never used the Lotus software, but physics is physics so I am confident that it will provide accurate projections if given accurate inputs in terms of component mass, stiffness, and spring preloads.

With respect to AFM [abrasive flow machining], here are some short movies on my website showing a truck cylinder head and inlet manifold being processed:
http://www.philipdingle.consulting/page ... r_Head.MP4
http://www.philipdingle.consulting/page ... nifold.MP4

Philip

[Keith Clements]

It seems to only take a few seconds to do the manifold. What pressure is involved and what is the abrasive goo?

[PJGD]

Keith,
Normally, just two or three passes through is all it takes to leave the surface smooth and bright with no sharp corners.
The goo is a paste that is laced with an abrasive of your choice, eg. carborundum etc.

Philip

[BarryCambs]

Hi Bruce

The performance of our Long Two with it's rebuilt engine is a revelation and at times quite scary. A member who followed me back across the Cambridge Fens on the way home from Grantham said it was out accelerating his Jupiter between 30-40mph. I'd estimate it has around 3 times the power it had before the rebuild of what was in fairness, a pretty knackered engine. It has a later detachable head engine fitted, which I assume you have if it is 1930? The improvement in performance is way above what I'd expect from a simple engine rebuild, but it's not as it left the factory.

I managed to get some already rebored barrels and heads from John Box, who had then as spares from his trialing days, so it is running with 8hp pistons and slightly skimmed heads. I fitted new valves and springs.

I was advised by him and a couple of members here to fit a Bradford CA camshaft, as these give a useful boost, but I have no idea by how much. I've rejetted the carb to cope with the increase in capacity, different cam and rather free flowing exhaust I ended up with from Ian Priestly. John Box did tell me they always seem to run better with a Bradford distributor, but as I had the original rebuilt and calibrated, I've not tried this and the car in now well powered anyway, so I'm not looking for any further improvement.

One thing I have noticed is there does seem to be a marked difference in performance between identical pre-war cars. I wonder if this is due to poor valve timing. There are no timing marks in the engine, so it's a bit tortuous to set it up and my feeling is, a significant number of the engines that have been rebuilt decades ago were put back together "about right". It also occurs to me that any wear on the rather flimsy single row cam chain could shift the timing significantly. Mine looked about ready to break and damage to the crankcase showed it wouldn't have been the first time. While it's a pain to set up, it is very easy to check without dismantling anything and there are good instructions in the Pre-War Technical Document you can download from the library.

I know when I spoke to John Box he'd used lightened flywheels, polished con rods and all sorts of things in competition, but I was looking for a reliable road engine, so decided to quit while I was ahead! I do remember he told me they had used an additional cross member to mount the engine on the crankcase to avoid breaking the barrels in trials use, but I think this was only due to using 8hp pistons in 7hp barrels.

All the best
Barry

[Brucegirvan]

Gentlemen - thank you very much. I have been away in a family holiday and came back to this wonderful list of pre-war Jowett know-how. It all seems sensible and reminds me a lot of my karting days, though frankly there I always felt going to the toilet before the start was a bigger benefit than silicon inserts in the con rod little ends! Fortunately trialing is less about grams saved or lost.
Interestingly I was reading Noel Stokoe’s sporting Jowetts book on holiday - and the paragraphs from W.S.Canney ring very close to what you have all have mentioned, bar direct application low friction coating. He mentions CR of up to 10:1, which would be great if I had throw away engine parts at the ready. So something well energy engineered comes to mind.

Eddie is a 1930 detachable head design.

A few questions:
Gas flowing the manifold - was this off of a new manifold? Or put it thus way, how thin can you go before thinning becomes an issue with these old Al cast units? Has anyone tried a flow insert to help the mix flow into the head port? Or should one just go twin carbs, one on each head? This latter solution to me seems to remove some problems and provide more tuning room....admittedly with tuning headaches too.

How machinable are the heads and valve seats? Does age make them more suspectible to machining dangers?

Cleaning up the head inners seems a no-brainer and is something I will look into. It will also allow a volume comparison check cylinder 1 v 2.

I can certainly vouch for seemingly same Jowett cars performing very differently. Eddie goes pretty well as is and can out power similar Jowetts. I have also just acquired a 1929 Short (non detaches head) that has been rebodied into a Sports type body with engine move back etc. A complete engine rebuild too, of which I am trying to ascertain the details. She seems to need some engine tweaking after being laid up for some years and we are just making sure all works ok for now before delving into re-engineering - ie knowing our starting point. She goes OK.

Best regards and thanks again.

[k. rogers]

I am very interested to read about your latest acquisition. I too have a '29 Sports replica which I've owned for nearly three years. Its engine has been positioned 18 inches further back in the chassis than a standard Jowett. It is on a 7ft wheelbase chassis and has none of the 29 attributes, so only rear wheel brakes and right hand gear shift, etc.

[BarryCambs]

I remember being surprised by the generous size of valves and their tracts against my Moto Guzzi 1000 twin (so similar capacity per barrel) which puts out about 4 times the power at twice the revs. What I did have an issue with was the exhaust valve seat. While everything was apart, I thought it would be a missed opportunity not to have hardened seats put in. Without really looking at them, I took the barrels down to our local machine shop, but when we looked at them on the bench, it was clear there wasn't enough meat under the seats to put the inserts in, without breaking through into the exhaust tract. As there wasn't anything wrong with the seats, I wasn't really bothered and if the seats were to far gone, I'm sure a specialist engineering shop would have ways and means of repairing them

[Brucegirvan]

Ours had an outing at last weekend’s 2 day VSCC Welsh trial. Bar a frustrating charge (or lack of) issue on the Saturday, which resulted in only 2 hills be tried (or was that hills forded...given the amount of rain), Sunday was much better.
7’ chassis - yes
18” engine shift - yes
We have 4 wheel brakes
Gear-lever has been moved in board....though I suspect it was there anyway as it was originally a light 2.
Has headlamps...but not the right ones. If anyone knows which Lucas set the 1929 and/or 1930 Jowett should have I would be very grateful.

3E17DF0E-3C4B-4478-A765-26FBA2E37141.jpeg

Regards