Inliners International Forums General Discussion Engines Hardened Valve Seat Inserts and unleaded fuel . . .

Well to be real, out here in Calif. most vehicles post '75 have "cats" on them to pass smog test.

Is the smog pump diluting the exhaust gasses or cooling the exhaust gasses?

I was under the impression it was cooling the exhaust gasses which tend to be a little higher on a smog motor that usually has the carb leaned out causing higher exhaust temps.