Performance camshaft.... wont start!!!

[picky]

I was unaware they were a lightened set.. I bough them off ebay as standard MG Metro turbo rockers. The cylinder head had double valve springs on when I got it, so I kept them. Would I release a bit of power by swapping to single springs? When would I get valve bounce if I did that??

[Cam]

Would I release a bit of power by swapping to single springs?

No. It will be a very tiny amount of power that is not measurable using a dyno. Using double springs allows you to turn more RPM which produces more power without the rev-limiting valve bounce. Assuming of course that everything else is OK.

I use double springs with no problems as do a lot of people. They remove nasty valve bounce at high RPM. If you are reving up to about 5500 then don't bother with them, but if you are going near the 7000-8000 mark then they are essential! If you have them already then keep them. Just get a good set of rockers!

They DO load the valve train a bit more, but if you have good quality parts fitted you should have no problems. Most of the head modifiers use and recommend the double springs, MED etc.

[bmcecosse]

Double springs on Minis getting the nuts revved off them - YES !! But single springs will be fine to 6000 rpm - especially if you have fitted higher lift cam which compresses the spring more. If you are going over 6000 you need extensive rotating assembly strengthening and balancing. I wouldn't bother to take them off now - but next time the head is off consider removing them if you don't need the revs.

[Cam]

What have Minis got to do with it?? An A-series is an A-series and it does not matter if it's in a Mini or Minor or even an Allegro as to getting the nuts rev'd off them!! My 1380 regularly sees 7000+ RPM and the double springs stop the valve bounce which is why they were fitted in the first place!

Of course of you are turning high RPM then you will need a bottom end to take it.

[picky]

Well the crank pistons and rods etc are all standard so I wouldnt like to rev it too high really... Next time I come across a good ported 12g940 head I will consider using only single springs, as oppose to the double springs I currently have on my 12g295 head. Im thinking a set of forged rockers from a cooper S would be adequate?? I dont think that 1.5 ratio rockers would be a good idea on a 1098.

[Stig]

I dont think that 1.5 ratio rockers would be a good idea on a 1098.

Eh, why not? It depends what lift you've already got from the cam you're using. I'm happily running a standard cam and head with 1.5 ratio rockers and I rather like the increase in torque.

I seem to remember that Mr. Vizard suggested 1.5 ratio rockers even with some performance cams to get the best power. Wasn't there something about it being better to use the rockers to get the lift rather than the cam as the pushrods don't have to accelerate so much...?

[rayofleamington]

I dont think that 1.5 ratio rockers would be a good idea on a 1098.

certainly not if you plan to use a 12G940 in future!

[Stig]

certainly not if you plan to use a 12G940 in future!

Oh yeah, different head. D'oh!

[picky]

well with the 12g295 I have fitted at the moment clearence would be ok, but as I have a "road/rally" camshaft, would the higher ratio rockers make the engine very "cammy"??

[picky]

also in the advertising stuff that came with my camshaft it said 1.5 ratio not reccomended on engines smaller than 1275cc

[picky]

I'm melting.. what extra BHP would I get from the 1.5 rockers??

[bmcecosse]

Recent test in a Mini mag produced exactly 1 extra bhp - and that on a 1275. They are a big waste of money unless you are looking for the very last HP on a big capacity full race engine. They also introduce additional stress and wear on the valve train.

[picky]

bmcecosse, was that a standard 1275?