Honda 1300 Coupe Forum

General Category => Workshop => Topic started by: RobertP on May 06, 2020, 10:13:44 PM

Title: Camshaft trivia
Post by: RobertP on May 06, 2020, 10:13:44 PM
As most would know there are a few engine components that are different between the 7 and the 9  apart from the obvious induction system, one of those is the camshaft, below is a photo of both a 9 and 7 camshaft. The difference at first glance is that the 9 shaft is slightly thinner and measuring them at a non-machined point the 9 has a diameter of 21mm and the 7 is 25.4mm, the weight of the 9 is 2.67kg and the 7 is 2.81kg, one has to ask why would Honda go to the trouble of using 2 different castings to machine the same item, the weight difference in negligible. One possible, but unlikely, reason is that the 7 could have an optional a/c compressor connected and more strength was needed, the 9 shaft has 'A-1' cast on it and the 7 has 'C-3'. You would also expect the 9 cam to be 'hotter' but my observations and measurement suggest otherwise, the distance from the heel to the nose of the lobe is 38.4mm and is the same on the inlet and exhaust on both shafts, so lift is identical, I was able to reasonably accurately compare(not measure) the lobe separation angle and they are the same. Looking closely at the asymmetric lobes they appear identical on both shafts, not very scientific I admit but if there is subtle differences to the lobes then I can't see it