Javelin head stud

[TedAllen]

I hadn't intended to remove the heads on this engine recently acquired from JCS as the whole ting was, at least, water tight. Unfortunately 3 of the exhaust valves were stuck open. 2 of them responded to the copper mallet on the collet end but the 3rd wouldn't budge. So off the o/s head had to come.
While dismantling, I saw that the stud above no. 4 pot had a stripped thread. No prob, I thought, I've plenty of spares. So, with the head off, my trusty stud extractor removed the offending stud very slowly and carefully. Oh dear...this stud had an end about 12mm with a coarse thread. At first, I thought it was a helicoil that had come out but it looks to be part of the stud. Cutting a new thread on the head end and putting the stud back in was no good as the maximum thread I could cut was M8 and it wouldn't torque up......water dripped out along the stud and through the nut.

A bit stuck now, did the factory use these bigger threads when re-conditioning or is it a later bodge by someone ?. If it's factory then a replacement will sort out the prob, does anyone have a spare ? Perhaps helicoiling will do it and as a final chance, changing the casings would sort it but I don't want to go that route due to getting the liners out.

[David Morris]

Hi Ted,

Oh dear! Sorry to hear about your head stud. I have never seen an oversize stud being fitted by the factory, although it might be possible? I assume that the tapped hole in the block is ok and clear? I reckon that it must have been a bodge by a previous owner of the block? A lot of things can happen in 65 years! My suggestion is to replicate the stud that you have extracted. It will take some careful measuring and probably thread gauges to ascertain the right threads. Someone else might suggest having the tapped hole in the block filled with weld and then re-tapped with the correct thread, but too many blocks have been distorted by welding. Don't be tempted!

If the tapped hole in the block is crisp and clear, just work with what you have and either make up a new oversize stud or have one made. It sounds as if the tapped hole in the block is larger than the original, so you may have to have a piece of bar ( silver steel? ) the right size for the threads in the hole and then turned down to suit the original OD size of the head studs.

Hope it all goes well,

David

[TedAllen]

-Thanks David. My own thoughts were a replacement which is why I wondered if it was a factory bodge when reconditioning cases. In which case someone here might have a stud. The thread in the casing seem to hold the stud well, it's the head end that's the problem. The hole in the case is about 11.75mm and the regular stud seems to be about 9.5mm...or 5/16 of course. Looking at helicoil sets, they all seem to be metric now. As you say, it might be a case of having one made.

Now, I believe there's a guy in West Lothian who has a fantastic lathe and might like a challenge.....now what was his name....?

Heaven knows how anyone has managed to damage both ends of a stud of this thickness. Maybe savage overtightening has ripped it out of the block but it can't be easy to damage the head end !

[David Morris]

Hi Ted,

Thanks for your email. It was strange that both ends of the original stud have been savaged! Perhaps in the past, someone was using the 'old' head nut torques? We never go beyond 35ft.lbs. now and always use NZ gaskets. I just had another thought. How about using the stud you have extracted, cut off the damaged cylinder head portion and butt weld the 'top' portion of a spare stud onto this 'root' ? Might not work, but perhaps worth a try? It would be tricky to get the stud concentric and the assembly would probably need some careful jigging before welding. I would have a go if you like?

All the best,

David

[TedAllen]

-
David, I had thoughts along the cut and weld lines last night so thanks very much for your kind offer. My welding days are long over now.

However, the problem has resolved itself in one simple word...Scrap ! I had a closer look this afto to see how much the enlarged hole in the block had reduced the face between the stud hole and the liner. There isn't any, the bottom of the hole has been broken away. This will be the reason why water is getting into the stud hole through the head and out into the rocker cover. Possibly the reason why the outer thread has stripped due to someone overtightening to try and rectify the leak.

I guess that means digging out a spare block and transferring all the liners and moving bits over...bums !

Whilst on here, can you let me know how to obtain the NZ gaskets please. I have two of Bill Lock's copper/steel in reserve at present.

Thanks for the advice and input
Regards. Ted

[David Morris]

Hi Ted,

Thanks for your email, and my commiserations about the block! It's a s*d!! You can order the NZ gaskets from JCS. They come with very specific instructions about fitting, warming the engine and then finally tightening, which I really recommend you follow to the letter. Our experience is that these work well, but after a thousand miles or so, I recommend you check the head torques again. We have found they ease off after a while and can lead to subsequent problems.

I know that I have 'banged on' about checking a block set before you re-fit everything to it, but I can really recommend you rig up an air pressure test on your replacement block set, before doing a lot of work. So many of these old blocks are hiding cracks and frustrating subsequent problems. Really happy to advise?

All the best,

David

[TedAllen]

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Thanks for the reply, David. Sorry for delay in responding...been away with no interweb. Thanks for the information you gave.

Would you mind me emailing you direct as we seem seem to be the only two interested in this subject and I'm sure I'll need a few more hints and tips.
Regards Ted.

[AmilcarJohn]

Ted,

If the block is otherwise sound, without too much corrosion in the water jackets please don't scrap it. I need to get one of my crankcases welded, and yours may be better than the one I have, so I could be interested.

John

[TedAllen]

-
Hi John.

I won't be scrapping it just yet. I'm just stripping down another engine so will let you know.

I have a photo of the damage but I'm having trouble posting pictures on here. Perhaps send me your EMail address. I can do it on there no problem..

Regards
Ted

[AmilcarJohn]

Thanks Ted.

My email address is john-dot-chevers-at-yahoo-dot-co-dot-uk

(please replace -dot- and -at- with the appropriate symbols!)

John