Tappet block replacement

[John Jarrett]

I need to knowledge of those who have been there before... I have tried twice to insert the tappet blocks into a 1950 AJS 16MC crankcase and I cannot get them fully home into the crankcase before they heat up and lock solid. The first time using a gas torch to heat the exhaust tappet block area only the tappet block went in other than the last couple of mm's and no matter how much I bashed the top with a drift and hammer it wouldn't budge. So I had to extract the tappet block and start again.
The second time I heated the crankcase the same way and put the tappet block in the freezer but tried the inlet side. Broadly the same result not quite so far in before it locked up.
The third time I heated the whole crankcase in a gas barbecue and the tappet block only went in about half way before I hit the same problem.
There aren't any obstructions in the crankcase and the old tappet blocks have just been removed. The new ones have come out from another set of crankcases. Do I just need to get the crankcase much hotter?
Any thoughts?
Many thanks in advance.
John

[clive]

John I have only moved tappet blocks that had dropped at some stage. This only required heating the cases in the oven until spital fizzled on them. They moved easily. I have a vague recollection somewhere of reading about a special tool for getting the blocks into place but it may be unreal. Have you accurately measured the diameter of the blocks you took out and the ones you are trying to fit in case there is a significant difference? I wonder if your barbecue is getting hot enough. John B has a baby belling cooker in his garage so he does not have to use the kitchen cooker. I have to wait til Hilary is on one of her walking days and air the kitchen heavily afterwards.

[John Jarrett]

Hi Clive,
I have measured the OD both the tappet blocks I removed and the replacements I am trying to fit at 2 thousandths over 1 inch. I cannot find any specification of what the measurement is supposed to be.
Roy sold me a home made version of the tool to remove the tappets and that works a treat... a bit slow but very satisfying.
It sounds like I might just need to get the crankcases hotter... but if there is a tool to replace them that would make life easier.
John

[jackstringer]

You can put the tappet blocks in the freezer to shrink them ever so slightly.

[clive]

John maybe what I am remembering is the removal tool. I think your crankcase would fit in John B's baby belling. He said my twin case without the studs for the head would. Sounds like a good Xmas day activity i am sure he would thank me for suggesting it! The ones I moved did so easily but the case was pretty hot. It was a very long time ago but I think I just tapped them with a wooden drift.

[John Jarrett]

Success!!!
I am pleased to report that after taking a break over the past few days to enjoy the Christmas festivities, the tappet blocks are now successfully installed. In the end it was very simple... I just had to heat the crankcases for much longer (hotter) than I expected and the tappet blocks dropped right into place. I am not entirely sure it was necessary, but I placed a buffer/stop in the timing chest to avoid the tappet blocks dropping too far.
Cheers,
John

[clive]

Good news John

[56G80S]

Pleased for you, John

Johnny B