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Posted: Tue Jul 05, 2005 9:02 pm
by Gosling1
spot on Hemi, too much tension will accelerate wear / work the engine, camchain etc , the need for super-strong springs ( in a street motor) is hocus pocus. What is far better is (a) using hollow cams if at all possible ( less reciprocating weight), lightened valve followers ( buckets) - the RC racing buckets for the old Z motor look like swiss cheese mmmmmm yummy - lighter springs, all this will help a top-end work good and last long.
Gizmo - those are always options, bit exxy but will work
cheers
z9Dave ( waiting for the day the world gets a Pope Dave the 903rd....)
Posted: Tue Jul 05, 2005 9:59 pm
by AussieZed
The HPC on valve springs would make 'em look nice, but wouldn't much else for the cams.
Nitriding the cams is probably an option, but if the cams have too brittle a surface, higher-than-stock tension springs will still accelerate the wear rate on the lobes.
Most cams are treated to reduce surface scuffing and once burnished by the follower, just do their jobs without too many problems so long as the oil supply is kept up to 'em.
The matching of valve spring rate and tension, cam rate and lift is a technical affair. Too heavy a spring rate can cause excessive wear on a lobe on the opening side and too low a tension can cause hammering on the closing side. Add in the everpresent issue of valve float and spring harmonics..... and it gets even more technical.
I used to build race motors for the speedway in a previous life, we always had to match valve springs and camshaft profiles. Luckily Crane Cams produced a matrix that gave a recommended tension but things like lightweight valvetrain components could change the need for spring characteristics on a particular camshaft or profile.
If the valve lifts off the front angle or at max. lift on the cam lobe and crashes back on the back angle of the lobe it will eventually hammer the lobe into submission.
Stuffed followers will also accelerate lobe wear.
I still believe that this problem was an isolated incident - once the cams and followers are replaced, the oil and filter changed, it should go like buggery and do it for a long time.
Posted: Tue Jul 05, 2005 11:17 pm
by AussieZed
Been sniffing around on a US zzr1200 board. Seems that some 2002 and 2003 bikes ZZR's have reported pitting. There is a mixed opinion as to the cause - most report no change in performance for pitted cams.
Given the number of ZZR's made by K.... and the number of posts actually reporting the issue.... it is still a relatively small number.