valve sealing

johan

johan

New member
Location
sweden
Hi
I have a question! another topic.
Got back my head today from porting.
The guy who has done the job is world champion in dyno shoot outs 712 bwhp :-X
Have safely ported over100 head And his job is a combustion engineer for a car copany.
He uses a mira cutting tool that is only in some 0.86mm in sealing (both in and ex)
I have discussed this with him, "no problems," he says
What say you? The green book says inn 1.5mm as 2mm.
Aim shore its  Flo nice
Johan
 
Hello Johan
It is true that a narrow valve seat helps improve gas flow.  In my experience, a narrow seat like yours is not very practical for road use - the valve & seat contact area starts to wear noticeably after 1500 miles (no air filter) and this reduces any performance advantage.  My engine only had narrow inlet seats - the exhaust seats were kept wider to assist with heat transfer.

Will be interested to see how your motor performs!
 
I use .75 inlet and 1.25 exhaust 3 angle cutters on the Serdi. Narrow seat should not wear any faster than a wide one if your valve to guide clearance is good.



  Keith. 
 
Narrow seats not only aid gas flow, they also aid sealing.

Hardened seats won't change much within 80000km, a bit of wear on the valve will be evident by this time though.  As Keith states, valve/guide relationship is all important for seat life.

For road triples, I use 1.00/1.20-1.30mm for inlet/exhaust, more for safety reasons than anything else.  Race engines can go a bit narrower, does sacrifice heat transfer a bit though.

piet
 
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