Quote:
Originally Posted by steve25
The real purpose of that spring is to allow the passenger side Head to warm up just as fast as the driver's side.
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That is very true because IF the heads had different thermal conditions during the first 505 seconds of the EPA Emissions Cycle it would have been much harder to pass the dyno emissions test which was standardized in the early 70s.
Ideally you want all of the cylinders to cool the heads the same so that the carb calibrations could be the same bank to bank and not have one side of the engine making more emissions vs the other side.
The 1/4" orifice in the heater line was a fix many years ago that was done by the Ford Engineers after the Heater Cores were being damaged by high speed accelerations on the Mustang Police Cars. That orifice may still be available from Ford.
Some heater manufacturers bent the inlet side heater tube inward in 4 places and made a 1/4th inch "Square" flow area to reduce their warranty issues.
Tom V.