BMC 3/42 2.8 JCB issues

[Jeremy Rowland]

The valve springs sound like they are shot to me you should not be able to simply open the valves by hand. I would remove the valves and check the seating of the valves and replace the springs.
I would also remove the pistons because it does sound like you could have a collapsed ring, if possible I would also get the head lightly skimmed, that depends on how deep any damage is on the face? If there is no deep damage to the face then you can simply clean it up with emery cloth.

Jeremy

[martyn williams]

I would pull the pistons and re ring and deglaze the bores now you have gon that far.
Martyn

[Stormin]

I would pull the pistons and re ring and deglaze the bores now you have gon that far.
Martyn

I think at least one new piston and probably a liner is going to be required, if that is a piece of ring that's escaped to the top. If the other pistons and bores arent in A1 condition it's probably worth doing the lot.
Fortunately the full engine kits are often cheaper than buying individual parts.

[FOWLER MAN]

I think at least one new piston and probably a liner is going to be required, if that is a piece of ring that's escaped to the top. If the other pistons and bores arent in A1 condition it's probably worth doing the lot.
Fortunately the full engine kits are often cheaper than buying individual parts.[/quote]

Hi,
I agree, also the valves on No.3 look too deep in their seats, probably need new valves and seats, or at least seats re-cut and new valves.
Has No. 3 piston been hitting the head
Looks in the pic. like the imprint of the piston crown on the head.
Fred

[martyn williams]

I would strip down the head , check valve seats and valves.get injectors tested,one looks gummed right up on the nozzle.Looks like something has been inside the cyliner,broken piston ring perhaps. ? Pull the pistons and check for damage,wear in piston grooves.Inspect bottom end shells for wear.It will cost time and money but you will have peace of mind when its all done and good for a few years service.From you video the engine looks in poor health and in need of TCL.
Keep us all updated on your progress
Martyn

[NickH]

In addition to the snapped valve springs, I found the previous owner had replaced the big end on number three cylinder with the shim material shown in the attached image (TW*T).

Having measured and checked everything, it looks like I can salvage the situation...just.

One thing I can't work out is whether there should be a seal on every valve stem. Could someone let m know if possible?

[FOWLER MAN]

Hello Nick,
That shimming probably explains the imprint of the piston on the head.
There are stem seals on all valves but they are fitted differently on exhaust and inlet.
There's an excelent download for the workshop manuals for the 3 & 4 cylinder Leyland, (BMC),engines on here.
Go to downloads and you'll find all the info. you want under JCB or Nuffield Tractors, the engines are much the same.
Fred

[NickH]

Thanks Fred. Will have a look