Inliners International

My research up until now shows meaningful intake flow improvement on the 235/261 series engines primarily comes from using the 1.94” diameter valve and improved geometry near the seat. Now that I have a set in hand I will submit them for seat machining and flow testing and will find out how much they show as a stand alone improvement. Can anyone tell me why this valve was only used on 1950-1952 powerglide equipped engines? Thanks for any insight.

Curt, just imagine all inlines at that time being manual straight shift with three gears, and then switching to a two speed tranny. It probably felt like a snail in comparison to a straight shift car. They probably felt the larger valve gained low speed HP/torque to offset the lack of gear multiplication factors absent in a planetary type tranny with only two gears as opposed to the previous three gear manual trannies....maybe.

My guess: it was the cheapest thing they could do to pick up power a bit.
Didn't do very much, since they didn't change the port.

Chevrolet must have decided that the 1-15/16" intakes did not provide much of a payoff as they went to the 1-7/8" valves in 1953 and all later 235 and 261 engines. However, the ports in the 50-52 Powerglide head were larger than in the 216 head. I've never seen a direct view, as Curt prepared for the 848 head, but the 50-52 PG head used the larger intake-to-head rings, and the Chevrolet Specifications indicate that the throat diameter above the bowl is larger for the 50-52 PG than in the 216.

It still seems that going to the 1.9375" valve can't hurt, especially on a 261 or larger engine.