Hi Chaps,

I compete in hill climbing in the UK with a NA S2000. About 18 months back I refeshed the OEM motor with a few upgrades including OEM JDM pistons, URGE Bumpstix cams and head built by Clockwise Motion in the UK. The head has OEM valves with the Clockwise Beehive Spring set, built by the man himself. These are built for duty and in that respect the URGE cams are mild.

At an event a year ago I found a cracked roller bearing (non-VTEC lobe). Intake side, cylinder one, valve one. After several discussions and inspecting everthing else, determined it might fatigue on that bearing. Replaced the arm and got it running again wihtout issue. A year later and I've had another roller bearing crack. Suspuciously, its the exact same bearing position (intake side, cylinder one, valve one). This leads me to believe something is wrong on that valve and not fatigue. My thoughts so far are the following,

1 - Coil bind - I would expect this to have consequences elsewhere. If it's due to lift, I don't understand why it's cracked the non VTEC lobe as it wouldn't be in contact. Additionally, the springs are rated well above the lift of the cams.
2 - Cam lobe issue - Off center lobe or miss shaped. Placing undue stress on the roller. This would be position specific. Its known that the Bumpstix don't perfectly align on the rockers or caps, with some variance across the board. Wear marks in rocker arm show offset.
3 - Piston to valve contact - No witness marks on the bore scope for the top of the piston, or signs of bent valve.
4 - VTEC dropping out - Nothing felt or in the logs. Running a Haltec Elite 1500 for around 5 years now without issue. Would also expect damage in other places.

Currently I've put in OEM cams and left the Beehives insitu. There's nothing out of place or looks off with the springs. They are rated for 15mm of lift intake side, and Clockwise mentioned I would make more power with more aggressive cams.

I was wondering if anyone else has experienced this issue? Advice moving forward etc?









Thanks in advance.

 

Thought i have read grinding is needed on some parts with these cams,but cant find any info,reach out to URGE or clockwise.

as notched in post 12
Which cams are currently top of the pack? - Page 2 - S2KI Honda S2000 Forums

 

My opinion on this is long.

To start, do you think there was a noticeable/worthwhile gain with the aftermarket parts?

 

That's honestly a great question. I've been competing succesfully in hill climbs and sprints for a decade now. A good number of wins and different venue class records set. The best times I've achieved at the main UK hills (Shelsley Walsh, Loton Park, Prescott), were all from a scrap yard used motor after the orignal motor let go. Gernpipe cat failed, turning sideways which block air flow, super heated the exhaust valves which eventually fatigued and fell off. That damage was imense, as it radially split the block and set fire, taking out a signficant amount of wiring and ancillaries.

Overall, the cams have presented good figures and you can certainly feel the additional torque. Ultimately, that has not transfered into a faster car.

I can almost predict the response inbound.......

 

No recomendation of grinding. This was questioned at the time, as I know TODA cams certainly require it.

 

The roller is nothing more than a needle bearing. Bearings wear out. That is what is happening here. This is becoming a bigger problem that does not yet have a solution other than finding a low mileage set or buying pairs from honda.

I'm in the process of having new rollers/needles/ and center sections manufactured. They will not be available until at least mid next year though.

 

Charper, I know you're attachment with URGE and all the good work you are doing with reviving these motors. I'm a thin film coating specalist, tenured in years of developing functional coatings &engineered solutions. In my formative years, I earned my PhD in development of bespoke coating systems so understand the difficulty in your builds. I find this work really interesting and you're approach is superb, which is a excellent way forward for the F20C. With that said, you're wrong about fatigue in this case. Its twice now on the same valve / cam profile, which I've narrowed down to the cam itself. The rocker arms were a good low milage set and crack tested & inspected prior to install, fatigue twice is not likely. The discussions I've had with Patrick have already highlighted that these camshafts don't work with well with other spring setups (several failures noted on other springs). That's telling me the shaft isn't made correctly, with suspicion being around the deceleration of the lobe causing bounce. Given that these camshafts don't sit central to lobes or in the caps, reinforces the concern shaft design. I know of multiple other UK S2000 running the same springs set ups as mine with significantly more aggresive cam profiles, with 14-15mm lift VTEC & 11ish mm non-VTEC without issue.

As I've said to Patrick, the intention is to get time with my QC inspector to have the camshafts CMM inspected. This is for curiousity to try determine the issue at hand and put rest to any other concerns. Realistically, despite the support from URGE, I can't help but feel I've been sold a pup. If these cams can only work with the URGE spring/retainer combo, its a bit gash tbh.

 

It would be nice to get a super slow-motion video of that valvetrain in action, and compare it to the OEM setup. All you'd need is an extreme-high-temp clear plastic valve cover and high-speed digital video setup. Hmm....

 

When I first heard of computer science terms many decades ago the first thing they told you was - " garbage in - garbage out " . Secondly, my father always told me "when you sleep with pigs you will wake up with fleas"

That sums up my opinion and recommendation. I suspect Billman has the same thoughts.

 

Now that’s an interesting set of phrases to hear. Typically we would coin it “shite in, shite out”, which is neigh on the money.

Forgive my ignorance and lack of clairvoyance, are you intimating that the camshafts are fools gold?