Seats and guides

[fiatfan]

The seats in my 850 RH4 head from -73 are in some yellow material, and need changing because of a bad cutting job. I´m thinking stainless steel because of the fuel of today, is that the way to go? And is it an absolute "must" to use Kibblewhites own guides when using their valves? My guides are cast iron and so are theirs, and I need to fix the outlet guides, the inlets are fine. If it means anything I´m not talking racing here.

 

[Fast Eddie]

Look like bronze seats to me. AFAIK bronze is the best material for seats, it’s self lubricating, it work hardens, it has a closer expansion rate to the alloy head, and it does not ‘micro weld’ to the valve, which is a cause of wear and seat recession.

I can’t quite tell from your pics, but are you certain those seats cannot be re-cut to your satisfaction, after all, you‘re not racing, etc.

 

[ashman]

Seats look fine to me but a bit of damage around the guide hole.

 

[850commando]

you do not have to use kibblewhite guides for kibblewhite valves. HOWEVER, if you are replacing the seat and have a significant number on miles (KM) in the engine, you need to check to valve guide wear. i just replaced a set of stock iron valve guides after only 14,000mi and they were worn sloppy, I like the kbblewhite products, but they do cost a chunk of money.
the one advantage of the kibblewhite valves is the hardened contact surface on the end of the stem.

 

[fiatfan]

Look like bronze seats to me. AFAIK bronze is the best material for seats, it’s self lubricating, it work hardens, it has a closer expansion rate to the alloy head, and it does not ‘micro weld’ to the valve, which is a cause of wear and seat recession.

I can’t quite tell from your pics, but are you certain those seats cannot be re-cut to your satisfaction, after all, you‘re not racing, etc.

Well, they are all pretty deep down, hard to get that in the pics. Plus the strange cut job, also hard to see in the pics but if you follow line around the seat in pic nr 2 you see that it is totally off center and almost touches the head material at one point. And in the first pic you see the narrow extra cut all around which makes the surface that the valve seats against too narrow. The exhaust guides needs to be replaced also but the inlets are fine.... I made contact with a very well renowned small company here in Sweden today and I´m sending the head there for the appropriate jobs needed. About the bronze seats, do they stand up well with this new crap petrol? Should I have them put new bronze seats in instead of the hard steel ones they usually put in?

 

[Fast Eddie]

About the bronze seats, do they stand up well with this new crap petrol? Should I have them put new bronze seats in instead of the hard steel ones they usually put in?

I’d take their advice and go with it. I know experts today who fit bronze seats, and also some who fit hard steel seats. Dunno who’s right !

 

[mean gene]

Are Bronze seat compatible with Titanium valves?

 

[mdt-son]

Well, they are all pretty deep down, hard to get that in the pics. Plus the strange cut job, also hard to see in the pics but if you follow line around the seat in pic nr 2 you see that it is totally off center and almost touches the head material at one point. And in the first pic you see the narrow extra cut all around which makes the surface that the valve seats against too narrow.

I guess someone tried to re-angle the inlet valves (and guides) in order to fit lager valves and avoid valves clashing when using an agressive camshaft providing a significant valve overlap. This is probably why there appears to be missing some alloy next to the guides.

As a first step I suggest you measure the valve guide angles. Reverting back to a standard configuration may not be advisable.

-Knut

 

[lcrken]

Are Bronze seat compatible with Titanium valves?

Yes. The preferred bronze for titanium valves is a beryllium copper alloy, but other alloys also work well, including the old standard Ampco 45 and similar nickel aluminum bronzes. I had beryllium copper seats and titanium valves in the heads in my Ron Wood rotax-powered road racer, and they seemed to last forever under some serious abuse.

Ken