Topic: Anyone have experience with a RC327 cam in a 736-836 engine?

[gschuld]

I’d guess the RC327 cam, with its lift and duration, would push an 736-836 engine up pretty far in the rpm band, assuming the head, compression, exhaust, carbs etc could support it.

Both MEC and Riccardo and others have had good success with the RC315 cam.  MEC at 1000cc and 1100cc and Riccardo at 762cc(both road racers). I’m sure there are others...

The RC327 has the same lift(assuming late revisions of both cams) as the RC315, but a bit more duration. 

In bigger bore motors where these cams are more commonly used, it seems the 327 sacrifices a bit of lower rpm torque in favor of higher rpm power, with the peak usually pushing upward about 500rpm over the 315 on average.  Sound about right?

FWIW, the application would be a road race engine. 762cc, 11.5-12.5:1 compression(140-150 gram pistons), ported head, light crank/rods, CR31 carbs, no charging provisions, possibly a close ratio transmission.  Aiming to push the higher limits of rpm range.  Let’s assume the planned cam/primary chains and tensioner systems (Let’s not get off on that tangent) will not be an rpm limiting factor.

It’s mostly about matching cam specs to carbs(CR31s are the max allowed) head/exhaust flow/balance for best results.

Thoughts are welcome😉

George

[gschuld]

I ask as I have a cam out of a 70s 749cc (61.5mm RSC 2 ring slipper pistons) road race engine with all major parts dating from 1972 or earlier(Other than perhaps the cam)

The engine had a lightened crank, looks like early RSC prepared factory rods, ported head, no kickstart, no electric start, etc.

The cam is from a 70s CWC billet blank(like RC, Kenny Harmon, and pretty much everyone else used back then), but there are no markings.  Not a single spec besides perhaps a small center punch dot at the end of the cam(visible in the pics)

Of the two cams shown, one is an RC327 cam, the other the mystery cam.  As you can see, by my caveman style  lobe “comparison tool” (just carved the shape of one lobe of the mystery cam into 1/4 marine ply and saw how it fit on other vintage race cams of mine) it matched up rather well on the 327 cam.  It wasn’t even close on the other cams.  The lobe centers (based on another equally caveman style measuring method) appear to be a match, yet the profile is ground about 3 degrees advanced on the cam gear compared to all 3 of my RC327 cams.  The base circle is also slightly bigger on the mystery cam. 

It just seems to be a rather aggressive cam for a 749cc road race engine. The 315 seems to be a safe choice as the open/close on the lobes are identical (advertised) as the Yoshi Daytona cam.

[Jerry Rxman Griffin aka MuthaF'er]

Caveman bring big sticks to the party!

Wasn't Bill running a 327 in his Calendar Girl 836?

[gschuld]

Caveman bring big sticks to the party!

Wasn't Bill running a 327 in his Calendar Girl 836?

You funny.  I’ve got bigger cams😁....but for a “little” race engine this one appears to be pretty aggressive.

Bill ran a Yoshimura Daytona cam in Calender Girl early on with Yoshi 810 pistons.  I don’t recall an RC327 cam going in the bike until the engine got bigger(could be wrong)

George

[Jerry Rxman Griffin aka MuthaF'er]

My Yoshi Daytona and the 810 but with stock head started coming on STRONG at 7000.