The Classic Machinery Network

Hi All

A farming forum member has had trouble with his AEC since a rebuild after years of lay-up. It has blown a head gasket and also bent a push rod and an exhaust valve. The 2 perhaps are unrelated but it ran OK for a bit. There is no evidence of the piston striking the valve. Any ideas?

Peter for Pete

stuck valve is what I would be looking at

Paul

Yes it probably is that but i think the guy fitted new guides. I wondered if it were possible for some sh!t could have been dislodged in rebuild and got to the guide??

Hi Pete,
The problem could well lie with the fitting of the new valve guides.
When fitting new guides valve stem to guide clearance should always be checked. It only takes a burr or a bit of cr##p in the head and the guide can distort and go out of round when being pressed in.
You may just press in new guides and get away with it most of the time but you can get caught out.
Typical guide to stem clearance for this type of engine would be .003 in. for inlet valves and .004 in. for exhaust.
I remember having to ream the guides on one Gardner engine.
Fred

Thanks for the replies I will pass on.

From Pete with the Mercury:

Good morning, thank you very much for your message, it's much appreciated.

I suppose that's entirely possible. Thinking back, Matt thought we had a very slight mistime burble on the engine, but that could have been a valve sticking maybe?

If we ream out the guides that may help. I'll put it to Matt and see what he thinks.

Thanks again and please pass my thanks on to Fred!!

Cheers, Pete.