uprated valve springs?

[Radar]

Hi,

I purchased a performance cam kit a while ago.. 264° cams, verniers and springs. Come to strip the head today and noticed the new uprated valve springs are quite a bit longer than the stock springs... Is this right? If so why?

Paul

[apache]

at a guess, I'd say yes, cos they're uprated to make the valve operate faster so a longer spring will have more kinetic energy than a shorter one

[danny hoffman]

The heavey duty rear springs on my wedge were shorter than the originals - I just thought I would drop that in to confuse the issue as I have no idea on valve springs!

[Captain Muppet]

Longer valve springs will have higher preload than the original items, reducing valve float at high revs/high lift but increasing the loads on the valvetrain (ie more friction and more wear).

[Radar]

Cheers fella, thats all I wanted to know.
If I go ahead and fit the springs I could be looking at pulling the head apart for new guides in a year or so, or longer?

[GavinPearson]

Springs are selected to control valve bounce but the critical part is ensuring that their fitted length is to design spec.

You need the details of this from the cam kit manufacturer. Install the springs and measure the fitted length. You should install shims under the springs or machine the seats to do this.

The best (most competent) company to do this is Chesman Engineering. (www.chesmanengineering.co.uk). They do a lot of machining for engine builders and used to do work for Andy Rouse Engineering. Ask for Jo Chesman or Steve Pearson.

[Captain Muppet]

Radar said: Cheers fella, thats all I wanted to know.
If I go ahead and fit the springs I could be looking at pulling the head apart for new guides in a year or so, or longer?

Guides? I wouldn't think so, they wouldn't see any of the spring load. It'd be the cams and cam followers that see the extra load and as your cams came with the kit they should be hardened to suit