sheared cylinder head bolt hole - i dont know what it is called

[billdn]

having had some helicoils replaced i tried to assemble rocker box apart from some helicoils coming loose (i'll deal with that guy later!).
however one of the rocker box bolts would not tighten. taking the rocker box off (again) i found this (see pics). i think the phrase according to James May is "oh cock" although i used stronger! and before anyone says it, yes i did have the torque at the right setting!
i guess find someone who does alloy welding and have it rebuilt or any other ideas?

[PatM]

Id buy this-     https://www.ebay.co.uk/itm/Honda-CB-400-4-Four-Engine-Cylinder-Head-and-Rocker-Cover-Restoration-Parts/172995768697?hash=item284759f179:g:mWoAAOSwX9FZJCVT

By the time you 'cock' around having it repaired- another cylinder head and then if you fancy, get yours done and build a spare engine?

Its what Id do...

Criminal, i know, but back in the day i dustbined a few 400/4 engines- but back in the day, the breakers were full of 'em...

[billdn]

Not what I wanted to hear Colin! Obviously it's cost a bit to get this far, but my inner voice is telling me you're right. Bugger bugger bugger.

[Tomb]

Will it drill and tap deeper and use a longer screw?

[Trigger]

Not a easy repair to do, it needs welding up and then you need to take two points on the surface for a milling machine to grind it flat, before drilling and tapping. Can be done but, I would charge about £150 for this type of job. 

[Nurse Julie]

What a shame that's happened. Onwards and upwards...........

[Clem2112]

Welding would be risky but machining the journal back to the right diameter in the cirrcet position would be a specialist job. Still don't know how Honda managed to cut those.

[billdn]

Thanks all, the cost of the repair works makes it cheaper to look for another head i guess. ho hum that's the joys of our pastimes i suppose. but having had it vapour blasted/sprayed /new valves/ lapping in and helicoils fitted it really hurts. i guess i can remove the valves and valve guides,valve springs /cotters etc as they're new and reuse on another head, providing i can get the guides out without damaging them!

[Tomb]

Will it drill and tap deeper and use a longer screw?

The reason I ask is I would be using that head but sorting out the threads, there are some helicoils hanging out near the break. The broken part of the head will not affect the running of the cam in the head. I've used worse on race engines.

[K2-K6]

The cost for replacement at about £80 doesn't taken into account other work you'd need to do to get it to the std you've got now.

That estimated cost from Trigger looks quite a good solution to get your head back into service.

The journal can be refinished by scraping and using engineers blue to check for clearance with the cam that you'd use.

[royhall]

To be honest that heads scrap. The journals don't look too good, it's full of loose helicoils, it's broken right through to the journal etc. I would just buy the head that Pat suggested. That's just a paperweight IMHO.

[matthewmosse]

Ho humm, not good. I would be looking for a spare head in better order myself, but that would be going in a box in the furthest corner of the loft, it's still fixable and one day might save someone's resto where theirs is worse. Values are fluid, today's beyond economic might be tomorrow's bargin bit. 4 years ago I had a slightly better head needing a bit of fin welding to fix, took a year to get shifted, only got £10 in a car boot in the end. Helicoils are a bit delicate and can wind themselfs back out. Not entirely the best thing in the world but they do save a few things. Apparently timesert are an alternative that have serrations to stop them wind out. Mostly I find helicoils ok as long as you carry a few spares in case one winds out.

[kevski]

I'm with Roy on this one, replace with a decent second hand one i'm sure someone on here will be able to come up with the goods, i am not a helicoil fan, much prefer time serts if applied with the right tool they lock in a lot better, another thing with both systems or should i say with some people that do them is the hole is rarely tapped out deep enough to allow the original bolt to go down to it's full depth without meeting  the original thread in the part, this then creates more problems, i.e heli coils/time serts backing out or being forced out.

[matthewmosse]

It is odd the way its broken up, maybe it is as Kevsky said, not drilled out far enough so the old thread pushed the helicoil out as the two met. Not seen that before but then I've only helicoiled things that had the old thread totally stripped out.

[Bryanj]

You cant transfer guides from one head to another with any sucsess