Rocker shaft bolts

Right, bit long winded this but stay with me! I had a bent rod replaced, fuel pump rebuilt, new cam belt, woodruff key and head gasket, all going well though it always sounded slightly noisy on one tappet, fast forward a couple of thousand miles and I start to get a bomp bomp noise from the air intake, reading up I found that this could be valve clearances, I checked and sure enough they are all pretty big, well over 1mm, worse is that 2 of the M8 rocker shaft bolts have backed out and both the small rocker shaft locating bolts have gone, I find one in the oil on top of the head, I call company that did the work and they recover it after advising me not to use it with missing rocker shaft bolts as they may be in the oil feed.
They tighten down the M8 clamp bolts and replace 1 rocker shaft locating bolt, they say this engine only has the one locating bolt, they reset the tappets and I'm away again, still sounds tappety especially on one tappet but runs well.
Now after another 1000 miles I check the tappets, engine is warm, all are uniformly large, one being worse as the valve stem has lost its cap, I reset them, even though one is missing a cap and order the parts, a week later I come to fit the missing cap, the valve clearance on the capless valve is pretty big again but I fit a new valve cap and reset all the tappets spot on to 10 thou with the engine cold.
It now runs like never before, quick (ish) and smooth, what's bugging me is why the gaps had opened up in the first place? Are the rocker shaft location bolts in an oil feed? Has me using the engine with them missing starved the followers and lobes? Is the garage right, should this engine only have 1 locating bolt? They say they set clearances both times to. 25 mm. Since I've set them 2 days ago the engine is nice and quiet, responsive as well, just hoping it stays that way!

Doesn't sound right to me. When I rebuilt the head on mine I think there were three. There are also two different types - metric and imperial. You could come up against the imperial ones if an early head has been fitted at some stage. That doesn't quite explain the gaps opening up though - were the tappet adjusters loose when you fond the gaps had increased?

zeaphod said:

Doesn't sound right to me. When I rebuilt the head on mine I think there were three. There are also two different types - metric and imperial. You could come up against the imperial ones if an early head has been fitted at some stage. That doesn't quite explain the gaps opening up though - were the tappet adjusters loose when you fond the gaps had increased?

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No, all the tappet lock nuts were tight, that's what makes me wonder if the followers are worn? Could be of course that the gaps were set wide by the garage but the bomp bomp noise from the induction was not there when I first picked the truck up?

Have you read the post before yours by Downsy? Worn rollers would give you same issue with tappets changing

One of my cam followers had a dish worn out of it, I had set the clearances ok but when I removed them it was easy to conclude that if the follower had rolled further it would have dropped into a location where the clearance would have been massive. This could have happened here but unfortunately it's not something that you can tell until the cylinder head is off.

I did read the other thread, that's what got me wondering, I'm hoping I don't need to remove the head as it's not long ago that it's had gasket, stem seals etc, I've already put far too much into it already and would have preferred to put money towards a 300tdi or Mercedes 606 conversion, when it's right it's a happy little engine and I can see its plus points to a degree, it's even OK at keeping up with traffic when it's right.

When you reset the tappets, did you notice if all of them had the same length of thread showing above the locknuts. If one had more than the others that points towards a worn follower. It is unlikely that all of them Would be worn to the same degree. If you need to get the rocker cover off again, measure the protruding threads.

Col

Pretty sure they were all about the same, I'll take the cover off again and check, that's a good idea measuring the lengths. It sounded tappety both times the garage re did it, especially on one tappet, after I checked I was so convinced they couldn't have got them wrong that I actually bought new feeler gauges! I'll check the clearances again soon, see if there's any change.

It sounds as though they have managed to get some oil down the rockershaft bolt holes which will not allow the bolts to remain tight as the engine gets hot!
I love the 10 thou in and out settings which are given almost everywhere, which is why mine are set to 10 thou inlet and 12 thou exhaust with the engine cold.
Try it, you might find it improves the performance.