Race Engine Forum UK

Hello Guy,

i own a Fiat coupe 16v cylinder head which I like to use later for a conversion on my strada.

During disassembly I noticed that the inlet valve seat inserts had a big mismatch, about 1 mm step.

My question is, is it possible to open the throat by 2mm to eliminate this mismatch? I guess opening the throat by 2 mm results in a loss of gas velocity?

Guy, you said, opening the throat 0.5 mm gives no gain in terms of flow for this valve size!

Suggestions greatly appreciated.

Regards

Daniel

That's called an undercut - in this case leave it alone, generally you should not increase the throat bore - you might find there is no metal left for the valve contact face. A purely practical perspective. What influence on flow? Dunno.

G

Thank you very much, Guy. I'll leave it like that.
I will remember the technical word "undercut", thanks.

Daniel