Two threads about rubber bumpers in one digest!
Early RB cars had the license plate hung under the front bumper on the
kerb side (US spec). 1977 & later had the plate in the middle of the
bumper, with the backing plate screwed onto the bumper with large sheet
metal screws. Saved the cost of the hang-down bracket & the captive nuts
found on the lower back edge of the earlier rubber bumpers. Improved the
cooling.
Why RB cars run hotter at highway speeds- I had this problem, & it
became worse after inserting 4 more cylinders in my 1977, trying to
solve it with a bigger radiator, more fans, etc. Conventional wisdom is
that above some stated speed, usually around 55 mph, no cooling fan is
needed, the incoming air will be sufficient. Problem is, as I found
quite by accident, because of the very streamlined shape of the rubber
bumper, air passes over it, & does not go into the radiator. With a
chrome bumper, the grill area is larger, & flat, ingesting much larger
quantities of air.
Driving some muddy roads one day in the rain, at various speeds, mostly
over 55 mph provided the "wind tunnel" answer. The next day after the
car had dried off, you could see heave streaks of mud running from the
bumper to the windshield, & then over the front portion of the top. The
inside of the bumper openings leading to the grill were mud free, as was
the black expanded metal grill & the radiator. No air inflow.
On the other hand, if you are having the overheating problem with a CB
car, it is because your car has been cursed. Or you have a slipping fan
belt, or your radiator is not flowing water through out the entire core
due to crud. Or you have been cursed.
Just my opinion.
Jim Stuart
Of course it could be timing.....
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