17 replies to this topic

[ACDodd]

No, not the best, the last set I had in got 1.22:1 after mods! However very strong and hard wearing/long lifed.

 

 

AC

Edited by ACDodd, 23 May 2014 - 09:43 PM.

[Captain Mainwaring]

Isn't the SW5 supposed to have been designed with hi lift rockers in mind? Though that's probably more for large bore A's. You can't really have too much lift, though it will waste a little bit of power compressing valve springs, then higher ratio rockers require less spring poundage to start with. The issue is the faster rate the valves will open, this is basically a good thing, but it also has the effect of increasing the effective duration of the cam.

 

The SW5 doesn't have much duration (244 degrees), so I don't think you'd end up with anything undriveable.

 

Not really...that same power less losses gets given back to the cam on closing.

[Ethel]

I see your point, but compressing the spring further is work and that takes energy, even if you get some of the elastic potential stored in the spring back. Increases in friction will permanently rob you of some power.

 

As an aside, performance cams need stronger valve springs because they mostly make their power through increasing the engine's rpm. Higher revs means you need more force to accelerate the valve train faster as the valves close to keep the followers in contact with the cam lobes. Hi lift rockers give the springs more leverage, so the don't need to be as strong to accelerate the follower side of train. The best springs will be just a fraction stronger than is needed for your engine's red line.

 

Perhaps that's one practical use for flash roller rockers, getting a better match than you can with the limited choice of valve spring poundages.