Helicoiled at birth?

[Chris B]

Yesterday I removed the head from one of my WSPCLs, in order to inspect the water galleries and cylinder bore.

I haven't had the head off this engine before and as soon as it came off, I noticed that the plug hole had been helicoiled.

I gather that some (many?) Seagulls had the plug hole helicoiled in the factory, in which case perhaps the example I have here is one of those. To help resolve the question, I'm hoping that one of you knowledgeable gentlemen with your mountains of painstakingly compiled BS data, can tell me if my WSPCL was fitted with a helicoil in the factory, or if it's an aftermarket repair.

The engine number is WSPCL 986 HH8, and as far as I'm aware, the crankcase, cylinder block and head are original - i.e. they've always been together as part of the same engine.

Any information re. the helicoil's origin will be most gratefully received!

Chris

[Chris B]

I posted the original question back in the summer but there have been no takers.

So I dug a bit deeper - fortunately I didn't have to dig very far - and for those of you who collect and file Seagull data, here's an update.

It's recently transpired that the thread insert (Helicoil) in the plug port on WSPCL 986 HH8 was almost certainly fitted by British Seagull when the engine was built. Apparently Seagull routinely fitted thread inserts to some of their engines' plug ports. This Silver Century Plus appears to be one of those.

It wasn't difficult to research because it turned out that I'm only the third owner of the engine from new. So the chain of ownership is short and the two previous owners (who, like myself, are knocking on a bit now!) live in the village where my boat is moored. Both chaps are technically savvy and neither of them knew that this engine's plug port had a helicoil. So it seems fairly safe to assume that the insert was almost certainly installed in the factory. Incidentally, the original owner told me he still has the cobweb festooned remains of the engine's original packing case sitting on the rafters in his garage!

Perhaps worth mentioning that although "helicoiling" is often regarded as a makeshift repair, some makers of high-end cars and light aircraft engines routinely fit thread inserts to their spark plug ports during manufacture.

So that's that loose end tied up.

C

[Oyster 49]

I've also seen several centuries with helicoiled plug threads, I suspect you are right, they were done at the factory.

[Chris B]

Oyster 49 - thanks for the confirmation.

So it seems increasingly likely that all the heads were helicoiled in the production run which created my WSPCL. And no doubt there were many others too. I like that - shows good attention to detail.

C

[Charles uk]

I think you'll find that 1960ish all Seagull aluminium heads (64 & 102cc, 14 & 18mm) had heli-coils fitted by the manufacturer.

The change happened when the LLS/CP's moved to the bowl shaped combustion chamber.

[Chris B]

Thanks for your input Charles. Information much appreciated.

The WSPCL in which I found the helicoil was made in August 1978. As my other WSPCL is only a few years older (I don't have the engine number to hand), your information tells me that I should find a helicoil in that one too.

C

[andrew]

I have 2 model 170s from different years in (I think) the early 1980s, and both are helicoiled with what appear to be original heads. I’ve always assumed they were done at the factory since both were helicoiled and I acquired them from different sources.

[Horsley-Anarak]

Here is a picture of one of my featherweights, first posted 2008 when it was discussed in depth, not sure what the conclusion was.

H-A