ajscomboman wrote:As for your crankcase drain plug, I thought about this and decided that your engine is a mix of years. The stamped half must be the original 56 case but the other half with the drain plug must be earlier with the smaller 1/4" BSP thread.
Yes, that makes sense. Hopefully there aren't many other surprises for me!!
Do you have the right tools to do that fix with the bolts, Rob? I could get the bolts out and over to you...
I haven't changed the final two bolts as I didn't want to disturb the rocker box and tappets, but I can do if I find someone willing to adapt the bolts for the headsteady.
I would have taken it to the local engineering company but sadly that is no longer trading, my mate has moved to Portsmouth and with lockdown I can't get to him.
Maybe someone in the club is an engineering wizz?!
I think Mick D is right (again). Get a bolt made to suit the thread that is now in the cylinder head if that thread is good.
It is interesting to see that the space between the bottom of the head of the two bolts and the point at which the thread ends differs quite a bit. The rogue bolt doesn't seem to engage as far and with the head steady in place it will be even less. These bolts take a bit of strain and I would think that more engagement in the head than what's there would be needed. On the other hand, some caution and careful measurement may be required before extending the rogue bolt thread into the head as the rogue bolt is quite a bit wider than the correct bolt.
I suppose (and here IKBA) that a length of hex bar could be turned and threaded to make a bolt to substitute for the rogue bolt? As for running without the head steady, personally I wouldn't.
Hex bar would be a good shout. Are those two holes blind? The shorter thread on the bodge bolt makes me wonder if they cut the thread deep enough into the block. Not a major problem to cut a new one but I don't want to strip the engine and /or get a load of swarf in there.
I had exactly this problem on my engine (stripped Head Steady bolt hole). The hole had been drilled and re-tapped at a greater size, which meant the rocker box hole was also drilled out to match. And no head steady.. The correct solution (which took 30 years to put in place) was to helicoil the head bolt hole back to standard size, which also meant getting another rocker box as the old hole in the rocker box was bigger than standard... One change makes another, which causes another problem and so it goes.
Two choices, fix it back to standard, or live with no head steady. A helicoil is not that expensive (£25-35?) and most machine shops could do it and that would solve the problem for good.
I'm going to make an oversized version of the correct bolt with the thread for the headsteady as well. I don't have the funds to try and source a new cylinder head. Hopefully this will at least get me in the road for a few years!
I've taken the rocker box off to get a better look at the bodge in the cylinder head.
From people's helpful comments I have a couple of options: straight forward option is to make an oversized bolt out of hex bar and enable me to fix the headsteady on, my mate with a lathe can turn this up for me. Option two is to screw down and loctite the oversized bolt in place, cut off flush with the top of the cylinder and drill/tap through it to take the 5/16 bolt. The problem I think with this is that there is very little difference in size of the oversized and correct bolt. Option three, I try and source a decent secondhand cylinder head.
I don't have any experience with helicoils, would a properly inserted helicoil take up the difference in size? I want a proper fix, something I can live with permanently!
In my opinion the best 'fix' from an engineering point of view is to manufacture a new stud with the correct thread to screw into the modified head and the correct thread to accept the head steady, this will also 'fit' the modified rocker box correctly.
It's very unlikely that a helicoil insert would work as you need to be able to tap the head to accept the insert and the already oversized thread probably wouldn't allow this.
A new head is an extravagance and would not address the oversized hole in the rocker box.
Get in touch with your mate - I notice in a previous response I made a typo - I meant to say Stainless grade 302 or 304 would be suitable - both are free cutting.
