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| SABB valve job |
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| AdeV:
When people know you've got machine tools, the damnedest of jobs start popping up... A friend of mine recently bought a boat, complete with a rusty old nail of a SABB 10hp single cyl diesel engine. The engine turned OK, but required a new exhaust system and - when the head was pulled off, well... : The head is quite badly pitted. The inlet valve was shut, so at least the seat of that has more or less survived. This should only need lapping in: Unfortunately, the exhaust valve was left open, and the seat has entirely corroded away. The valve itself cleaned up nicely, but of course it has nothing to seat on: There's no way I can simply cut a new seat into the metal, as it will have recessed far too far; so, the only option that I can see is a valve seat insert. Therefore, my questions are: - What material would be suitable for a valve seat, for a low-revving diesel engine? - Should I try to make the seat myself, counterbore the head, fit, shape & grind it all in myself :dremel:, or is this a job best left to the experts :hammer:? I'm thinking of using an ordinary medium carbon steel (such as EN8 - because it can be hardened) to make the insert; which would be an interference press fit. I'd like to make it as close as possible to shape in the lathe, then harden & fit it, then lap the insert & valve together for a good fit. So.... Am I on the right track? Any advice/ideas welcome... |
| DavidA:
An engine re conditioner may have a valve seat of the correct material in stock. Remember that the aluminium heads have steel seats. Also they will be geared up to do this kind of work. No offense meant, but if you screw it up then the head, being old may be irreplaceable. You could lose a friend easily; and get some bad press. Dave. |
| lordedmond:
I totally agree with DaveA Ade to do the job your self you would need a piloted cutter to cut the seat , shrink in a new one , then use a piloted valve seat cutter , as you know it has to be concentric ,no compromise allowed Stuart |
| AdeV:
£350+ for a piloted valve seat cutter set :bugeye: Hmm... The head is cast iron. The combustion chamber is heavily pitted, there's lots of slop in the valve guides... I think this head is already essentially scrap; so I'm not to worried about having a go, because there's almost nothing I can do to it that'll make it worse. However... I would like to be as accurate as possible anyway... even if I have to make/adapt my own tooling... (I'd wondered about using a T-slot cutter, except I don't have one the right diameter... yet... |
| krv3000:
HI on thes old engines the valve seat is cut strate in to the casting ther is two wase to do this job 1 is to weld up the damiged parte then recut the seet or mack up a scruw in replasment as for recuting the seet you need a valve seet cuter see pic i have rebilt meney old engines with both metherds with no problems regards bob |
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