The new Project

[paul_turner]

Good progress Paul. I noticed on the cylinder head between the exhaust ports there is a hole cut in the fins . Is this a Healey mod ?

[paul.jameson]

The hole is something of a mystery. It is about 2 inches diameter and goes through the outer 2 fins midway between the exhaust ports. There is a hole on each side of the head. Perhaps it was someone's idea to improve air flow. Tim Healey was looking at my head during the summer and saw the hole. He remarked that he had seen a head with a hole like that in it before, and wondered why it was there. The head he was looking at is the one for my swinging arm Square which will use Healey engine No 5. The engine I dismantled today is Healey engine No 4. Until I took the left side exhaust manifold off I had no idea the hole was present on this head as well. So perhaps it was a Healey modification which Tim forgot about. Or has anyone else got the holes in their head?

[paul.jameson]

Even the Healey bothers had difficulty getting the coupling gears on without the crankshaft keys moving, apparently. I rotated the cranks to put both keys to the top for photographic purposes, by the way. I was amazed when the cranks turned after I took the cylinder off because it does look as if the main bearing whitemetal has melted. I shall find out shortly....

[nevhunter]

There's a fair bit of wear on the engine mainshaft spline Paul. Is that common? Nev

[paul.jameson]

Spline wear like that is common on Squares. I think I will be using the rear crank from my other engine unless I can get the splines welded up and recut. It looks as if the crankcases were NOS when fitted to the bike but the cranks had seen plenty of use, although only newly reground to -0.010. The timing side bushes had melted the whitemetal as I thought but the bushes came off easily enough once warmed enough to melt the whitemetal again. This revealed newly reground timing side journals.
I took the sludge trap screws out despite evidence from mutiple centre punch marks that they had been out fairly recently. Each of the four traps had some debris in it. Whilst some was undoubtedly running in debris from the 100 miles or so done before the bike left the factory, I think some was from imperfect cleaning of the cranks. There are bits of carbon visible on the cranks which will wash off with detergent oils in time, I believe. Before the cranks go back into use I will remove the balance weights and flywheels so I can get the whole crank spotlessly clean.
Then I got out my rear crank from my spare engine (spare at present but destined for my swinging arm Square Four once I finish the Healey). This crank has been ground to -0.020 and might need a further grind before use, although the splines are very good. But the sludge trap screws did not appear ever to have been removed. So I took them out and sure enough, the traps were well blocked. Why on earth someone would regrind the cranks without looking at the sludge traps I cannot imagine but this could have been done twice on this crank. The cranks on my 1936 4G had also been recently reground but had totally blocked sludge traps. Perhaps crank grinders are better machinists than they are mechanics and perhaps the mechanics left everything to the crank grinders.

[simon.holyfield]

It's not as though cleaning those traps is difficult once the cranks are out...

[roger.fellows]

True, but if you haven't met 'staking' and how to deal with it, it's easier just to leave it.

[nevhunter]

If they stake the threads, you have a problem. Why they do that beats me. I doubt they would ever come out if just tightened reasonably. A small dremel bit, Sil carbide and grind the staked threads out to the base diameter. If you have a tap to the right thread run it through the shaft and remove any pieces of burrs, slivers of metal any where in there. The design of many plain slipper bearings doesn't allow swarf to get out of the bearing so it will stay there, build up right at the bearing and damage the bearing surface. Engines like a SQ4 should be scrupulously clean on assembly. The sludge in those crankshafts is centrifuged out and forced to the outside of the oilways, where it adheres quite firmly. (until you start the engine up years later). Nev

[Bob.Murphy]

I don't understand . . The sludge traps on a Square are large-diameter countersunk-headed machine screws. There is a shallow hole drilled into the countersunk recess on the crank and the screw head is staked into it - the threads are not involved.

Unless this is a general comment about 'staking' anything.

Or my Square was different to others .

Bob.

[nevhunter]

It's a general comment. Staked into the thread means the damaged part damages the thread as it's unscrewed unless all damaged thread is removed (eased away) before unscrewing. People do it an many parts of motors. Nev