It doesn't appear that these have any kind of heat riser valve to manage the heat going to the intake manifold. Could be why the design was changed as continuous heat to the intake would have the same effect that a stuck flapper on an original manifold would have, causing poor engine performance. headscratch


~ Dan
1951 Chevy 3 window 3100
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"My Grandpa Carl's Truck and How it Became Mine"
1966 Chevelle (Wife's Hot Rod) | 2013 Chevy Silverado (Current daily driver)
US Army MSG Retired (1977-1998) | Com Fac Maint Lead Tech Retired (1998-2021)