I'm planing on a FI/turbo engine build. I have come across an article about valves and most suggest using 1.70 in./1.44 ex. from SI. And someone said that SI made some inconel valves for turbo/supercharger applications because of the added heat produced. These are not cheap. MY question is... do I really need these valves? Will having them eliminate any possible problem I my encounter? Is there some part I can add on like a intercooler or maybe water-injection? Or will those have any effect on valve temp? I have an opportunity to get the SI valves for a good price with guides and keepers for under half the price of the inconel valves. Any advice will be greatly appreciated.

There are a lot of different grades of stainless steel. The SI valves are probably fine, but I would NOT take it for granted that they are. You need to find out what they are made of. I would not be afraid of running a decent grade of stainless with a turbocharged engine unless you plan on doing something extreme like endurance racing or marine use.

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Joshua

The intake valves are made of Martensitic steel and the exhaust valves are non-magnetic Austentic steel, and both are one piece forgings if that is any help.

I am using SI stainless valves in my na engine these are the same vavles I am going to use in my turbo engine

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http://www.cardomain.com/id/lncognito

Inconel is /not/ stainless steel. It's a nickel alloy, that has heat tolerances much higher than those that can be obtained with any common steel alloy, stainless or otherwise. Iirc, it's heat resistants actually borders on that of most ceramics, but without a book in front of me, I wouldn't swear to that. As Joshie said, the SI valves are probably going to be ok for anything but the harriest engine build.

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Used to own:
'82 Dodge D150
Erson 270 Cam, O/S valves, mild port work, ~9.5:1 compression

Currently fighting with an '85 VW Cabriolet

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