4 replies to this topic

[petehuws]

Hi folks, as the topic suggests when is it best to use double valve springs?  Some suggest 'always' others say 'never', others,  'when one is running a ported head' others when you're running larger inlet/outlet valves, & others suggest when only running roller tipped increased lift rockers.

 

Many thanks Pete

[Cooperman]

The answer is when you want to use very high revs without risking valve bounce. Valve bounce happens when the cam rotation speed and the strength of the springs combine to prevent the cam follower keeping in contact with the cam lobes.

For example, if using a really high-lift cam the spring rate required at high revs, say over 6500 (as a guesstimated figure) will be such that stronger springs are required. These can be up-rated singles or doubles, it depends on the engine spec.

Tell us what you are running and the revs to be used and we can advise. Or look at the Kent Cams specification sheets.

[petehuws]

Many thanks Cooperman!  I've got a standard 1990 RSP 1275 that of course has the metro cam.  I have fitted the new Cooper Car Co' / Minisport 'S' conversion kit which is a stage 2 gas flowed head 36inlet/29exhaust valves & double valve springs, twin HS2 with AAP floating needles.  the kit comes with some 1.5.1 lift roller rockers of which I DO NOT want to fit preferring the standard original Rover A+ rockers.

I guess my query is whether the double valve springs would work OK with this setup running the standard rockers in respect of the slightly reduced lift of the original rocker ratio or whether the single valve springs will be safer on the cam lobes.

Many, many thanks.  Peter

[Cooperman]

Double springs will give absolutely no advantage and will cause higher wear rate on the cam & followers. Stick with new standard springs. They will be good for up to around 6500 rpm with no risk of valve bounce.

[petehuws]

Many thanks Cooperman, you're a star!!  All the best