PHILIP8N
Veteran Member
The weak spring is only on the exhaust and the conversions I've seen were Model A and Chrysler flathead 6 so they weren't terribly high speed engines. I suppose if you had a high enough reving one, it could be a problem but as you mentioned, they run at about 2400.
I remember I had a 283 Chevy in a Jaguar XK120 roadster and had to go over 6000 before it started breaking down, which we attributed to valve float, but never new for sure that's what it was and didn't want to push it any further to find out the hard way. Of course a weak spring would aggravate the problem.
The weak spring is always on the intake of a hit-and-miss engine and the discahrge valve is controlled by the governor and eccentric, and these engines only run a few hundred rpm. The two way concentric valve used on a high speed (1800 - 2400 rpm) compressor is quite sophisticated. Total lift may only be 2.5 mm and typically contains one seal ring, 6 lentoid springs, and 1 backing ring. Philip.