I'm in the process of dismantling my 1936 Model 18 and find the valve gear in a poor state. I'd appreciate some help on the following:
The inlet and exhaust valves fitted have differing diameters. Inlet 1.728 in. and exhaust is 1.706 in. Aren't they meant to be the same?
The inlet and exhaust springs differ as well. The inlet outer spring expanded length is 2.482 in. and the inner spring is 2.249 in. and the exhaust outer is 2.003 in. and inner 1.760 in. Can anyone point me to documentation that says what they should be?
Should I replace with phosphor bronze guides or stick with replacement cast iron ones?
The exhaust guide moves easily with the head cold. When installing a new one, is green loctite likely to be effective or should I install oversize valve guides?
Any guidance much appreciated...
Don't know about the valve sizes but....
- Log in to post comments
Thanks Ian, I'll be…
Thanks Ian, I'll be replacing the valves, guides and springs as they are clearly past it. The NOC shop has valves for pre war singles which are the same diameter for inlet and exhaust so why mine are different sizes is a mystery. The exhaust seat is a mess; unless I learn otherwise I'll get valves of the same length and diameter and get the seats recut. I'll take your advice and stick with cast iron.
- Log in to post comments
Normally inlet and exhaust springs are the same lengths. I'd be looking for replacements anyway. I believe that normally the inner springs are longer but could well be wrong on that.
With respect to valve guides I would definitely go for oversize ones as a guide moving in the head could wreak havoc..... Cast iron is self lubricating to an extent so especially with your engine having minimal lubrication up there I'd stick with it.