Re: blood guts and the beer

Posted by BH On 2008/6/17 10:28:06

Heat riser valves were still in use up until about 1990 on GM vehicles but the name changed to "Early Fuel Evaporation (EFE) Valve" in the mid-1970s.

To burn efficiently, gasoline must be atomized, but condensation of the fuel vapor can occur in the intake on a cold engine - even above freezing. The idea behind the valve is to warm up the intake to prevent this, reducing HC emmissions and improving fuel economy. However slight that may be, but every bit adds up.

Up here in the Great Lakes area, I notice a difference in performance with the manifold heat valve after a cold-start in my V8 Packards as well as other SBC-equipped cars I've owned. Mind you, I don't race or hotrod 'em - just like to drive 'em.

Parts availability not withstanding, retaining/maintaining the valve or doing away with it seems like matter of personal preference.