UKPaul

I've been loocking at various different heads & have noticed that some have single valve springs while others have dual valve springs. Having a choice, wouldn't dual springs be the way to go every time? With a single spring fitted, if it were to break (over-revved, bad luck, etc) then there wouldn't be a lot to prevent the piston hitting the valve. With dual springs then at least you've got the security of another spring. There's also less chance of a weak/worn spring causing float, etc.
Why have a single valve spring? Just curious :)
:cheers:
Paul

BeaterShark

I'm not going to pretend that I know much about valve spring design, but I believe that the inner spring is mainly used as a damper. The main thing to look for when choosing valve springs is to match it to your cam. Every cam I looked into had a recommended spring (or spring pressure specs) to be used with that cam.

71coupe

You want to use what the cam manf. recommends. Dual spings will cause unnessessary wear on a flat tappet cam that could get by with single springs.
:chevy





[Modified by 71coupe, 9:38 AM 11/26/2001]

gkull

You rarely see a true single spring. It's usually a single outer with a flat coil damper to cancel out harmonic distortion. I have never personally broke a spring. durring drag & circle racing in the pits I have helped change out broken springs. It only happens on extreme lift and rpm motors like nearly .800 lift small blocks doing 8800+ rpm or big blocks with .800+ lift doing 8000 rpm.

You are right dual and triple springs have a built in safety factor. all you have to worry about is closed seat pressure. 125 lbs. closed is about as high as I would go for a hydro flat tappet cam.

Valve float with weak springs is what kills more motors. Springs rarely break. Over rev. a motor and your right into the pistons every time.

UKPaul

Thanks for the replies. I was wondering because I once had to fix a 100cc Honda for a girl. She thought the red area on the tacho was there so that she could clearly see the white needle against it at night!! :lol:
It had 2 outer valve springs broken & the only thing stopping the valves dropping into the piston was the inner springs. I just like the thought of having a bit of a safety margin with dual springs :yesnod:
Paul

Ingar, Norway

I broke a spring, but the valve was not damaged. With a stock engine L48 that is.