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[bobqzzi]

I am working with a small 5 valve cylinder head and we are considering installing larger valves.


Intake Valve 1.062” (want to go 1.102”) stock seat OD 1.129"
Exhaust Valve 1.181” (want to go 1.220”) stock seat OD 1.260"

Head is aluminum, seat some sort of pretty good steel (it's an Audi). Engine is highly turbocharged

I had a question that I hope the experienced engine people on here could take a shot at:
Describing a valve seat like a piece of tubing, how much wall thickness is required? We are currently at about 080" on the intake and .100" on the exhaust- can we go thinner so as to maintain the seat id/valve diameter ratio, or should larger OD seat be installed?

If we were to go with cuBe seats on the exhaust, would that change the required wall thickness?

[McGuire]

There are a number of issues in play here. You probably want to contact a vendor directly... for example Del West for copper beryllium seat inserts (for titanium valves) or LE Jones for sintered or stellite inserts.

I can't tell you what you can or can't get away with regarding inserts. In some applications running high boost you can run into troubles with the stock valve and insert diameters... anything that affects the insert's ability to stay concentric (like a reduction in wall thickness) is a very bad thing: that is really all that is holding it in the cylinder head. Imagine an insert coming loose at high rpm and what it would do.