Forum

[Flick5848]

Just doing a little research regarding our hosts performance cams by looking at the data and concluded that they are essentially retarded by 10 degrees compared to the data on my own standard cams. The only notable difference is the lift is a little higher. I can only assume I've missed something because adjusting my cams by a tooth would give a similar result so perhaps somebody can offer their comments ? I should add that my bike is a 1959 350CC.

[Tim NZ]

The sports cams for the 350 have a significant difference in Open Area, as well as Duration and Lift. Along with different lobe centers to reflect the anticipated rev range where they provide optimal breathing.


Fitting the cams with out also raising the compression ratio negates much of the 'benefit' of the sports cams.




Randomly changing cams, and or their timings, with out actually double checking on WHAT timings exist already, can be a real 'Can of Worms'. Check your existing timings to start with...


If you are considering fitting sports cams and NOT reconditioning the head (valves, guides springs etc) AND raising the compression you could be wasting money.

[Flick5848]

Thanks for your reply. The engine has been fully reconditioned with a high comp piston and performance valves etc so I'm confident I have the necessary equipment to benefit from the cams. My confusion is in the data from our host and the data in the manual. They show the same duration but just 10 degrees out. I appreciate there are other variables in ramp and lift so I was intrigued as to where the main benefits are gained.

[Bullet Whisperer]

Even just retarding standard camshafts can give sportier performance in some cases, particularly Indian 500 Bullets, 350's don't really respond that well unless the compression ratio is raised at the very least. I have found with the 350's that they will really wake up with a compression ratio between 9 and 10:1 and a retarded inlet timing - this will help keep the cylinder pressure at a sensible level and help avoid pinking, while also enabling an engine to rev a bit higher [subject to decent valve springs if hotter cams are fitted] and produce a bit more top end power while sacrificing a small amount of bottom end 'grunt'. An engine will often feel smoother at lower RPM's with a retarded inlet timing because of the lower cylinder pressures and it might even help the bottom end bearings' life. It makes sense that the Hitchcocks cams run a later timing than standard, they will also probably have a good bit more lift. Here is my 350 Indian Bullet, which has some slightly [not much] hotter than standard cams and 10:1 compression. It also has a lot of piston slap, thanks to my recycling of an old Meteor Minor Sports piston from one of the 350 racer's engines! ... https://youtu.be/RBPg_Xj2X04

[PeteF]

Bullet Whisperer knows best but I'm sure I have a slight increase in performance on my 350 just by retarding the inlet.
I find a bit less power at low revs but quite a bit more at higher revs. I have to ride it differently but it does seems perkier.
I've always been loth to change the compression but I might have a go this winter.

[Bullet Whisperer]

PeteF, you are correct with what you say about your 350 with retarded inlet cam, but I found a relatively small gain at the top end with standard compression ratio, along with a loss of some bottom end 'plodding power'. Lots of people don't like this, but the 500, being a bigger engine copes better in standard trim with this adjustment. People who like 'chugging' or 'plodding' [I don't care for it much] don't like a retarded inlet cam. Also, I think many Indian machines seem to have a more advanced inlet cam timing than their Redditch counterparts, but I suppose something that performs like an old traction engine may be what the Indians [and many of us] want! Regards, Paul.

[PeteF]

Well, I don't like to plod much either BUT it does seem to run smoother at 30 in top gear than it used to.