1934 twin engine rebuild

[Tony Fearn]

Here's the 'alone' photo to go with my post below (or above if you can't log in).

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Tony.

[Keith Clements]

With many modern cars you have to replace the studs as well each time you take the head off because they stretch to provide the correct clamp on the head.

[BarryCambs]

Thanks Tony. I had no idea there were more than one type of head for these engines! Mine definitely have the removable plugs on them. Can I assume the combustion chambers are all the same, as I assume all the 7hp engines were the same capacity? I was going to change the studs,along with the nuts, as a matter of course, but it's all a bit academic at them moment, as I don't have any barrels to work with.

Paul B kindly had a look at JCS for me, but it looks like they only have the early ones with the mounting lugs underneath. He did make a couple of suggestions. Michael Cavanagh had suggested making up mounting brackets for my spare barrels. I'm a bit nervous of doing this given I am so tight for space and I'd have to reassemble the engine and box for a test fitting before I felt confident to spend out getting pistons and paying for a rebore.

He wondered about using 8hp cylinders. Is this a common conversion? I think someone said you have to open the crankcase bores slightly, but that should be quite straightforward if it's going to a machine shop anyway. Would my heads and manifolds be compatible?

He has a 1935 stationary engine with a damaged crank case that "could be sacrificed". Would these barrels be the same as the car engines? I guess I need to check the manifolds are interchangeable.

The most obvious thing would be to have my existing barrels re sleeved. I've had this done before on motorcycles with great success, but i get the impression people are not keen on this option with these engines. Clearly on the bikes, you don't have the entire weight of the engine and gearbox hanging off the barrels! Have people had problems with them breaking after sleeving?

A final thought occurred to me on the way to work this morning and I'd need to have a good think and a proper measure up, but is the idea of milling 2 flats onto the front of my spare barrels to effectively convert them to the mountings I have completely laughable??

Barry

[BarryCambs]

My confusion deepens. I went to the workshop to have another look at the mounting lugs wondering about fabricating mounts. In my disappointment of realising the spare barrels weren't going to be any good, I had only really looked at one and I now see they aren't even a matched pair. Chatting to John Box this afternoon about the parts he has sorted out for me, he described the 8hp barrels as having a "fish belly" underneath. Looking at the second barrel, I'm wondering if this is in fact what it is?

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What it does seem to have is the correct flat face for my mounting brackets. John said everything else (heads, manifold, valves etc) is the same as 7hp, so maybe this is the best option? Is there anything else to consider? He did say he has 2, both for the same side, but I can't remember which side he said, as I didn't think they'd be any use to me at the time! If not, I think JCS may have a pair.

In the meantime, I have sent the dynamo field coils from the one Tony kindly let me have and the armature from the original off for a rewind to cheer myself up.

[Tony Fearn]

Hello Barry.
Once again I have 'a feeling' that the 'fish belly' cylinders are from an 8hp engine as John suggests.
I have some in my spares, and they do have the sort of tubing under the cylinder, unlike the 7hp ones.

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Tony.

[BarryCambs]

Thanks Tony. Whenever I see your photos, I'm always reminded of the old Unipart TV advert - "Thousands of parts, for millions of cars!"

To cut quite a long story short, the rebored 7hp barrels that John was advertising in the Jowetteer have now become available again, so I am going with those. A colleague will be picking them up from him in a couple of weeks, along with all the other parts , so I should have pretty much everything I need and hopefully, it can go back together quite soon. I'll donate the spare 7hp barrel to JCS, but I'll hold on to the 8hp in case an odd one comes up and I can keep them as a spare set. John has found the sleeve and spring from the oil thrower set up, but not the disk. I think that's all I'm missing, so if anyone has one, or an accurate drawing, so I can try and fabricate one, I'd be very grateful.

The barrels from John have been bored out to take 8hp pistons. He said he's not heard of them breaking due to over boring, only when sleeved. He has though suggested I use some sort of flexible mount though, instead of having them bolted straight to the chassis. Looking at the 1934 parts list, there are no mounts shown, just what looks like rubber washers. My brackets are mounted on the bottom of the chassis rail, but I suspect the engine was originally mounted above the chassis? I'm thinking I could replace the roughly cut pipes and washers currently used as spacers with some proper rubber mounts, just to give a bit of flexibility. Something like this.

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[BarryCambs]

We finished stripping the engine this afternoon so the crankcase is ready for a thorough cleaning and repair of the timing chain trough. The rear main carrier was pretty well stuck on with some sort of sealant, but I eventually managed to free it by heating the whole lot up to melt it a bit and removing all the studs first. I still don't know why the cam has so much end float as there's nothing obvious wrong. When it came time to remove the sprocket, I was mid way through explaining the advantages of impact socket guns, when I noticed my 9 year old daughter had already unscrewed the nut. This might suggest it wasn't particularly tight! John is sending the bearing carrier along with the CA cam, so hopefully, the problem is solved anyway.

I know George recommends manhandling the entire engine onto the gas stove to loosen the oil pump, but sadly we have a halogen hob. I did however discover last time it was out that a heat gun works superbly, especially when it's still in the car and you are working below the fuel lines and carb!

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[Tony Fearn]

John has found the sleeve and spring from the oil thrower set up, but not the disk. I think that's all I'm missing, so if anyone has one, or an accurate drawing, so I can try and fabricate one, I'd be very grateful.

Barry,
Have you tried Jowett Car Spares, or placed an advert in the Jowetteer magazine to see if you can get one?
If all else fails, I have one that I can lend to you to have it copied, but I need it back as it's from a complete engine, so can't let you have it.
Let me know.
Tony.

[BarryCambs]

Hi Tony

Thanks for the offer!

Sorry, I should have updated this. Dad came round last weekend with an old cantilever toolbox that was in the garage when we originally collected the car, wanting me to check through it before it went for scrap. It just had a load of old box spanners and bits of scrap in it, but there right in the bottom was the complete oil thrower assembly! I'm not sure why someone thought it was better off there rather than in the engine. The thrower has a slight dent and given the broken oil trough in the crank case, I do think it probably broke a timing chain at some stage damaging both. Maybe someone just forgot to put it back in when putting the new chain in and given it didn't leak oil, never got round to putting it back? The chain on the engine didn't have many miles left in it before the same thing happened again.

I looked at the valve springs from the barrels John sold me and the originals and none of them really match in length and some show signs of corrosion. JCS had them in stock and they have just arrived along with a timing chain, so I think we have everything we need to start building it back up. I have replacement studs for the rear main carrier as I had to removed them with mole grips to help un glue it from the block without damage, new screws for the baffles, exhaust studs etc. I'm still a bit puzzled by the head studs though. The ones on the heads from John are the same length as mine and once I put a washer on, there's only about 3/8" of thread showing. They don't look bad, but I'm tempted to replace them with slightly longer. John's came with new nuts.

I spoke to the chap who has the dynamo parts and he's just about finished the field coils, but hadn't checked the armature yet, so hopefully it won't hold things up.

Barry

[Tony Fearn]

Hello Barry,
Glad the oil thrower is sorted.
The original pattern nuts were only threaded internally for about 3/8" on both the short and long ones.
So 3/8" protrusion of the stud didn't leave much stud thread to rust, presumably to help on removal of the nut.

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I have more modern examples, from JCS in the past I think, that have a much longer internal thread, although the overall lengths were the same.
Tony.

[BarryCambs]

Hi Tony

I'd not looked closely at the nuts, but that does make sense. The JCS ones are threaded right through I think. I guess they are not tightened to the sort of huge torque I am used to on more modern engines, so I'm probably worrying about nothing.

As an aside, I should maybe lower my expectations and more modern engineering anxieties. I did take a trip to the local engineering workshop to see about getting hardened seats put in the exhaust valves. I'm not so bothered about running it on unleaded fuel and I think it still needs additive for ethanol protection and halve stem lubrication, it just seemed worth doing while it was apart. As it turned out, when we looked at it properly on the bench, the thickness of the material between the seat and port is only a couple of mm more than that of the insert, so it was a non starter. John had the seats professionally recut when the boring was done anyway, so hopefully with the fuel additive they will last a good few years - possibly longer than me.

Barry

[BarryCambs]

I spent a thoroughly unpleasant hour doing an initial clean on the crankcase this afternoon. Although there was a reasonable layer of sludge in the bottom of the sump, the rest wasn't too bad and mercifully, not coated in tar like a lot of older engines I've had apart. I also spent some time trying to sort some of the oil leaks, the irony being that the only place it didn't leak was the timing case bush, where the thrower was missing.

All the brass plugs for the oil ways had home made washers cut from copper sheet and I had replaced these with new ones which improved things. Looking at it properly out of the car, it looks like they had been wound in very tight without washers at some stage, so I have faced them all off to try and help. One is so mangled it's going to need a filler repair. The oil pump face had the threads pulled slightly proud, so I suspect it wasn't seating right down. Looked like it had been overtightened at some stage.

The rear main bearing carrier has been pretty butchered with the faces on both the carrier and crankcase having various dents and gouges where screwdrivers have been hammered in to free it - not me! The threads were proud here too. I was a bit puzzled by a small hole in the top of the casting, which had something loose in it when poked. I could feel it moving from behind when I put my hand in the crankcase.

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I popped it out with a small screwdriver and it turned out to be a piece of crumpled gasket paper. I can only assume the hole is a casting defect.

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The threads on one big end bolt were damaged, so I have bought some new high tensile ones as replacements. The only thing left before reassembly is the repair to the oil trough. I've used JB Weld successfully for this sort of thing and a friend recommended acetone for cleaning. I soaked the oil pump in it and it seemed to literally leach the oil out of the casting.

[BarryCambs]

I had another session cleaning the crank case ready to repair the damage in the timing case. I remembered George talking about modifying the oil trough by drilling a small hole to allow some drain back to the sump. Now it's cleaned, I see there are two holes. Putting an straight edge across from the side hole shows the oil level would be a few mm up the chain which seems reasonable. However, the second hole is below the main bearing is below the level of the chain (though might not look like it due to camera angle), so even when the trough is repaired, the chain could well lack lubrication. I'm assuming the first hole is correct unless anyone can tell me otherwise? Given the chain I took off was bone dry and looked to be close to breaking and all the sprockets are worn out, I think I'd rather risk a bit of oil weeping, so I was planning to block the lower one.

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[BarryCambs]

With the crankcase cleaned and repaired, I have started reassembly. Checking my cleaning job with a bright light, I noticed the engine must have had something pretty catastrophic happen at some stage as there are several nasty gouges and a lump broken off the end of one of the holes the followers fit in. I guess it broke a con rod or the crank. I'm about to fit the cam, but something doesn't seem right with the one that came out, so it put doubt in my mind, even though I wasn't planning to refit it.

The picture below shows the cam that came out of the 1934 engine on the top and below, what I am told is a Bradford CA cam I'm planning to fit. Though it might not be clear on the photo, the width of lobes on the CA cam are around 5mm less than those on the old cam. The lift on the CA cam does seem to be around 1mm less than the old one which I wasn't expecting. Though it's hard to measure, the duration seems a bit less too, which seemed odd for a higher performance cam, though I am aware cam design can be a bit of a dark art!

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What puzzles me about the old cam is the wear pattern. With the CA cam in the block, all the lobes look to be slightly off centre looking down the follower holes. This is what I'd expect, as it's normal practice to create some rotation on the followers. When I put the old cam back in it looks very odd. The inlet lobes are again slightly off centre, but the exhaust lobes are way over to the front of the engine so the edge of the lobe is almost in the centre of the follower. It was a bit difficult to try and get a decent photo.

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My question is, could the cam that came out be from a different engine altogether, or is this wear pattern normal for these? Can I assume the thiner lobes on the other cam mean it is definitely a CA cam?

Barry

[BarryCambs]

It lives!! All back in and up and running in time for our local Yesteryear Road Run tomorrow. I followed the advice of clamping down the manifold before the cylinder base gaskets, but both sides are weeping water. No oil leaks now though

I'd remarked to a couple of people that having stripped it down, I was unsure how it was running as well as it did. Clearly it was hardly running at all, as the increase in power is astonishing and took me completely by surprise! The performance seems more like you'd expect from a 1000cc in a car weighing virtually nothing. The other thing that took me (and several pedestrians) by surprise is the noise of the exhaust. There seems to have been a 10 fold increase in volume, presumable as there's now enough compression to actually burn the fuel properly. It might be a bit too much on longer journeys, especially with my side exit exhaust.

The engine is now mechanically silent like the one I heard running in another member's car. I guess it was a combination of cam end float, piston slap, valve guides, timing chain etc. I still need to sort the jetting. I'd always suspected the progression jet was a bit on the small side and after initial start up this afternoon, it wouldn't pick up well enough to be drivable really. The jet in it was an 80. I found one from my spare carb which is an 82 and it's a whole lot better, but there's still hesitation coming of idle and I think I'll try an 85. If anyone has one I could borrow, I'd be very grateful, otherwise I'll have to drill out one of mine and hope for the best.

I'll wait until it's run in before seeing if the main jet can be improved on, given it's now about 40cc larger capacity. Once off tick over, it revs very freely and I have to keep reminding myself it's running in! It has Morris running in oil in for the first 500 miles. After a run down the road, there was a pretty impressive amount of smoke from the exhaust, but I suspect that some of the gallon of oil it went through in the last 200 miles found it's way into the silencer, as well as out through the various leaks.

There are still a few little things to look at. I have swapped a set of completely worn out timing sprockets for some worn out set. While better, the new chain doesn't run smoothly. You can buy new with just a pilot hole through them ready for boring and a key way, so now I have a spare set I'll try and get some ready for next winter.

I still feel the cam that came out was wrong for the engine. It does have a cam on it for the fuel pump, so presumably it can't be out of an earlier engine??

Barry