1934 twin engine rebuild

[BarryCambs]

We've had great fun in the Long Two over the summer covering a few hundred miles with 100% reliability and bar a new seal on the fuel cap, not a spanner on it ............. until yesterday afternoon. Planning to go across town to collect the eldest son and a couple of friends from a Cub Scouts day, I found the car reluctant to start. Eventually it fired up on one cylinder accompanied by a horrendous knocking and backfiring, scaring the life out of me, a passing neighbour and her dog. A quick investigation showed the ns exhaust valve being held slightly open. The engine has always been very noisy compared with the others I've heard running, and it did have an intermittent knock. I originally thought this might be excessive crankshaft end float, but having read other threads taking about the subject by Tony and others, it seemed more likely to be camshaft shimming or bearings. I now suspect the rear cam bearing has broken up and the valve spring on the opposite side is pushing the cam across far enough to keep the ns one off its seat. This probably explains why we had a problem getting any clearance on the os valve in the beginning. I was going to have the engine out this winter to address the other issues, but was waiting as it's booked in with a car upholster to fit a new hood end of November.

Anyway, I hope to get the engine out ASAP to strip for inspection. The known issues are:

Hairline crack in os cylinder head which weeps when hot - temporarily sealed with filler

1/16th inch play on all valve guides - there does seem to be a new set of valves in the spares and I'll have the seats replaced by modern ones while it's at the machine shop.

Bad leak on the oil pump, probably due to damage to the sump mating surface

Exhaust studs too short and pretty much stripped.

Timing chain and sprockets completely worn out. The chain is running bone dry due to the back of the oil trough being broken off.

The engine has good oil pressure at all times and I've not seem a whiff of smoke, so there's a chance the crank and pistons are ok. I will check condition and clearances while it's apart.

I need to get a parts list together, but I have a couple of initial questions. I read in an old thread that a couple of people have used Bradford CA/CB camshafts in these engines. Given mine is probably worn and/or damaged, would there be any reason not to go down this route? I think Tony's flying fox runs one?? Were the cylinders and heads painted when they left the factory, or left bare? Are there any other useful modifications or pitfalls I need to think about? Given the carb, distributor, exhaust, radiator, wiring loom etc are either new or rebuilt, I hope to end up with a pretty near perfect engine at the end of it all, ready for anything in the coming years!

Barry

[ian Howell]

Barry:-

Sorry to 'hear' of your problems but you seem at least to have the measure of them.

The excessive wear on the valve guides could have been caused (not by you!) by lack of lubrication in the past.

On my car, and I think yours too, it is necessary to apply a few drops of oil externally as there is no oil feed from the crankcase. This was partially rectified by fitting valve spring covers on later cars.

My engine also seems to rattle more than I would like but that will have to wait for now.

Keep us posted on progress!

[BarryCambs]

Thanks Ian

From what I read, the valve guides should have drillings in them to help with the lubrication and I know there is a warning in the manual about fitting the followers the correct way around. I wonder if someone, not knowing this, has had plain guides fitted at some stage. It could be just wear due to high milage of course! I know JCS hold the correct ones in stock. I'm more worried about finding some good timing sprockets. There was asggesting in an old thread that new bradford cams were available from JCS whic could be a result. I also seem to be missing the spring covers, so hopefully I can get a set of them too.

Barry

[Robabineri]

Hi This is my first posting.

I have a 1934 long for saloon and I understand the engine was rebuilt approx 5000 miles ago. I have very worn valve guides I have checked the orientation of the oil feed holes as per the manual and they are all correct I have noticed the the subtle doming on the adjustment nut has a significant flat spot and was thinking as different parts of the engine warms up the angle between the cam followers and the adjustment nut is bound to evolve as these parts expand at different rates.

With two effectivley flat faces between the worn valve stem nut and the cam follower then any movement off true will shift and the moment will not be central on the valve stem and this could explain the wear pattern I can see.

Also the noise evolves as the engine warms up which fits with this diagnosis.

I need to replace the valve guides and valves and adjustment nuts at some point as the rattel is quite noticable.

I am interested if anybody is aware of this explanation for the apparent rapid wear of the valve assembly or if there is another idea I can persue... with winter approaching I think its time to put the engine on the work bench ...

[ian Howell]

Rebuilding the engine with new guides and valves correctly installed should sort that problem.

You will probably get quite a bit of advice - mostly cautionary tales or based on bitter experience!

One thought to consider - these cars were built at a time before the high precision of today's engineering. Care may be more important than precision.

Discuss!

[BarryCambs]

Hi Rob

I was wondering after we waved at you coming the other way near Bottisham, when the last time 2 pre war Jowetts passed each other outside an organised meeting! It will be interesting to compare notes once you take your valves out given we have excatly the same age engine. I've can't say I've looked that closely at my adjusters as I knew it was all needing overhaul. It could be JCS have new ones in stock, as they do seem to carry a pretty impressive number of parts. As an aside, I have always used Cambridge Rebores for machine work if you need new guides and you could probably walk there! If there is any question on condition, I will have modern seat inserts put in mine, as they are so cheap, I don't see any reason not too.

Barry

[BarryCambs]

The engine and gearbox finally came out this morning and we can hopefully start the autopsy tomorrow. I have already had a bit of a shock though - the gearbox seems to be in near perfect condition, so this could be the first component of the car we have found that's not been comprehensively bodged or otherwise wrecked! The oil came out as clean as it went in a few hundred miles ago and lifting the top off shows it all to be spotless inside. The bearings all seem nice and smooth, so I'll leave it well alone.

i do have a question though. When I took the timing cover off to refit the oil pump, I noticed there weren't any washers under it's nuts. I spent some time knocking the cover flat again and refitted it with washers. I noticed today however that nothing I can see has washers on including the studs holding the barrels to the crancase, propshaft bolts, bell housing bolts, gearbox top cover and everything else, apart from the manifold studs. Was this normal practice, or has a previous owner deemed them unnecessary and binned them?

I also noticed when I had the timing cover off before that looking at the 1934 parts list I seem to be missing 3 components from the from of the crankshaft, labeled as:

Crankshaft oil thrower washer
Crankshaft oil retaining sleeve
Crankshaft oil retaining sleeve spring

I am assuming these got lost or damaged at the same time as the back of the oil trough got broken off. I wonder if a timing chain snapped at some stage. It doesn't leak oil, but that could be due to the fact the trough isn't holding any. I do need to repair that, as the chain was bone dry and completely worn out. My question is, do I need to source some new parts, or do they normally remain oil tight without them?

I also seem to be missing the tappet covers. Do people normally run with these on, or leave them off to provide regular access for an oil can?

Barry

[BarryCambs]

Our team of highly skilled technicians has swung into action and we have some progress. The cylinders are off and timing gear out of the way. It's not pretty. The nearside bore has some pretty serious water damage. I suspect this occurred a long time ago as it wasn't using any water when we were driving it and the gaskets looked fine. I was a bit surprised, as given the state of the bore I'd have expected it to be a bit smokey, but it seemed to run very cleanly. The offside bore is fine, or it would be if someone hadn't broken the skirt off at some stage! In some ways I'm relieved as it does save having to make a decision about reboring or not. For some reason, one little end bush feels a bit rough, but I couldn't detect any play at all. Both exhaust seats were pretty ropey, so I'm just amazed it ran as well as it did.

The really good news is that while visiting friends over Christmas, I took the opportunity to collect a couple of cylinders and an oil pump I won on ebay which look to be in much better shape, with less corrosion on the cooling hose stubs. They don't have pistons, so I just need to have a measure up to check they haven't gone over maximum size and hope JCS have a set to suit. If the flywheel's not on too tight, I should be able to get the crank out this week and form a plan of action. It's just a shame it's going to need running in a bit before it can hopefully tackle the run to Peebles!

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The car originally had a petrol pump, but this seemed a bit of an over complication as the tank is on the bulkhead, so it now has a blanking plate.

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[BarryCambs]

The sad looking cylinders. Both these and the heads were completely full of loose scale to the point some channels were pretty much blocked.

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[ian Howell]

Barry (and others with similar views!): -

Its great to see the next generation joining in the fun. I have commented previously on the need to 'catch 'em young'.

Last weekend I went with my son James to see about a replacement Mustang for the one he bought BRAND NEW DIRECT FROM AMERICA LAST YEAR (Yes I know!).

In the garage alongside the prospective next purchase - an immaculate '69 Mustang - the owner's son, age about 8,was busily dismantling a Ural motorbike recently imported from Latvia and looking as if it had been driven there from Mongolia.

What also caught my eye was the fact it has a flat twin (but air cooled) engine and 19" wheels.

Now if Jowetts had ever made motorbikes = other than Scotts = would this have been the shape of things that never came?

[Tony Fearn]

Hello Barry,
What a lovely set of photos. Are they posed, or do you actually get some help?
Back to the engine. I have always used washers under nuts, wherever they are on the car. it's probably sound engineering practice.
I do remember I was told that the washers under the nuts on the cylinder flange must be flat steel washers and not spring washers. The nuts should be tightened 'dead tight' (and then a bit), and perhaps Loctite would be useful.
Somewhere there might be a list of torque settings for the pre-war engine nuts etc., but I've never seen one. I wonder if George has one.

Oil retaining bits - crankshaft front..jpg

The three missing bits from the crankshaft front all lie inside the timing cover at the front of the crankshaft as you say.
It's self-evident how they work. The the flat face of the sleeve bears on the inside of the brass starting-dog hole riveted to the timing cover.
It's a rather crude type of seal, but it must have been deemed necessary by the engine designers.
As for the tappet covers, perhaps they should be present to allow an oil mist to form.
I have drilled two holes in the cover at the cylinder end over each valve stem to allow occasional oiling of the stems going into the valve guides. I don't know if it's of any use though.
Finally - that cylinder bore!! If it was running as well as you say it was before dismantling, just think what performance you'll get after refurbishment.
One of the slogans for the pre-war Jowett was: 'With spurs it could climb trees'.
Tony.

[BarryCambs]

Thanks Ian and Tony. The photos are for real, but it really depends what you mean by "help". In truth, it would be a whole lot quicker and easier by myself and you need nerves of steel and the patience of a saint! The kids love the car and are keen to get stuck in and being allowed to "help" when I was a kid taught me a lot. Even if they don't develop an interest in things mechanical, hopefully they will not be afraid to try doing other practical things for themselves later in life.

Ian, the idea of the Jowett twin motorcycle is lovely, but I firmly believe there is only one correct layout for bike engines and that's the 90 degree v twin. If you look carefully, you will see the engine from my Moto Guzzi under the bench waiting for some tlc after 130,000 miles since I rebuilt it last time. The team won't be going anywhere near that though - some things are far too precious!

Your scan is a lot clearer than my rather tatty parts list Tony. I will have to put the call out to see if I can find some replacements. I don't know if the Bradfords have the same parts? I was pondering what happened to the originals and I do wonder if it did break a timing chain at some stage. That would explain the damage to the oil trough in the sump and if the flailing chain wrapped round these parts, I guess they would have been pretty mangled. The front of the timing case is bone dry, but that could be due to their being no oil in the trough behind it, so once that's repaired, I could be in trouble without them.

As for the barrels and valves - it never started well from cold and took some warming up, but once hot, it started first hit and idled nicely. It would touch 40 on the flat, but the last few times I drove it, the power was dropping off, more due to the cam problems than the bores I think. I never saw a whiff of smoke. Strangely, the pistons and rings are standard size and look perfect. As you say Tony, it should be very impressive with shiny new bores and working valve gear. Who knows, you might get a chance to try it for yourself as it should be nicely run in if it can make it up to Peebles

I have yet to have the cam out for inspection. Am I right in saying you have a Bradford cam in your Flying Fox? Is this something you would recommend? I have spoken to a Member who was advertising in the Jowetteer this month. He has a pair of rebored barrels with new pistons, valves, gaskets and refaced heads, which would save sorting my one cracked head. They are fitted with 8hp pistons, but is there any reason that's a bad idea? I think it gives you another 50cc capacity.

Barry

[BarryCambs]

Having had some conversations on the cost of regrinding the crank and metaling the bearings, I plucked up courage to check things out yesterday evening. Against all the odds, everything looks to be in great shape! Crank end float is 2 thou, whic is as listed in the service spec and both big ends are about 1.7 thou which I'm more than happy with. there isn't a mark on the white metal. Whoever did the machining obviously did a fantastic job, though whoever put it back together saw fit to reuse the split pins on the big end bolts and only use washers one side. I haven't had the crank out yet as I had the wrong size studs for the flywheel puller, but unless something has gone badly wrong, I don't see why there should be a problem with the mains and it spins very smoothly. Inside the crank case is very clean, though the oil that had only done a couple of hundred miles is very thick and black. I suspect this could be due to blow past the rings given the state of the bore.

The cam followers etc all seem good, but what I have found is cam end float at 23 thou. I could see Tony shaking his head and rolling his eyes as I measured it. I haven't pulled the shaft out yet, as the oil pump is still in, but it is not clear to me looking at the parts list, what controls the end float? The rear cam bearing feels ok too, so I'm not sure my theory as to the valve problems is right. I suspect the off side exhaust valve was sticking, which would account for it running on one cylinder, but not why we have had problems with tappet clearances closing up.

Anyway, it's all good news, so I now need to get the shopping list together, but hopefully it should be back up together sooner rather than later. and without having to spend several hundred pounds sorting the crank and bearings.

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[george garside]

I cant remember there being any shims or whatevers to control camshaft end float and no mention is made of any in the CA Bradford parts list. I don't think 23 thou end float is going to do any harm but would recommend that you follow Tony and fit a ''high lift'''' !! Bradford CA camshaft. It will do a great deal to improve all round performance.

If removing flywheel I would suggest gently heating it before applying a 'puller' as using a puller alone has been known to crack the flywheel

George ( who has come back to life after being locked out despite several attempts to get back via the somewhat overcomplicated procedure for so doing!)

[BarryCambs]

Welcome back George - your resurrection is very timely! I will go with the advice and try and find a CA camshaft then. I need a complete set of timing sprockets anyway, so maybe there will be a complete setup out there somewhere. My followers look in excellent shape, so can they be used with the CA cam?? That might well cure the cam end float problem too. The Service Spec says 1 - 4.5 thou and from what Tony and others say, it is probably the cause of my intermittent knock - I'm not sure what else it could be as the crank end float looks fine.

John Box has offered me a pair of rebored barrels with new pistons, skimmed heads, new valves etc, all ready to go, so I'd be a bit silly not to take them at the price he wants. He told me they are fitted with 8hp pistons. Is this a recognised upgrade? The skirts on the barrels look pretty thin on mine and they are at standard bore size. If not, he does have new oversize pistons, so I could have my spare set bored.

I'm told new valves are getting tricky to find. There are currently a couple of sets of new Bradford valves on ebay. I noticed the later ones have grooves for standard collets, but the early ones are threaded. Are they likely to be the same as the 34 engine? As I have a good spare set of barrels but no valves or pistons, I was wondering it it was worth overhauling them as a spares.

Barry