Had the same problem with the 182. Sent the muffler down for overhaul and
more important, sent the shroud down for overhaul.

25 RPM drop before; 200 RPM drop thereafter. $500 fix.

Jim



"figurado" wrote in message
...

I just bought a 1973 Cessna 172. During runup at 1700 rpm there seems
to be no noticeable drop in rpm when carb heat is applied. We
inspected the operation of the cable, and flapper and inspected the box
and everything looked fine. We inspected the ducting for blockage and
found nothing. What might explain this? Thanks in advance for your
help.


--
figurado