Double valve springs???

[TNT ANDY]

When is it necessary to install double valve springs?

How do you do it?

[Red October]

I picked honda civic type r double springs and had custom titanium shims to bring them up to the piper pressures. You'll need a custom retainer cap to accommodate both springs and stop them bouncing around. Pick the spring you like and shim accordingly. I liked that spring because its proven at 7-9k daily and are bulletproof.

[turbo ted]

if you plan to rev to 8000rpm or more and run crazy boost 2bar looking for big power yes other wise not needed,
ford crossflow engine inner kent springs fit inside piper 5 gt turbo springs just need to machine the spring seat bigger.
works well stops valve bounce and drop valves but this setup will wear you camshaft out and followers.
I would just fit piper uprated spring and keep the revs under 8000rpm turboted

[Scoff]

It's an RPM thing. Glenns engine had catcams retainers and some center springs I specced to add 25% rate over piper springs alone. I didn't want to go too far in fear of killing cam lobes and constantly bending pushrods. Eventually Glenn had to have some pushrods made in the USA to cope with that extra 25%. The standard rods would often bend. It was better than dropping valves though.

[TNT ANDY]

Interesting

I think before doing this I'll see how we get on with mapping with the new turbo after Christmas as ol' Fluff has never been a particularly good breather top end. I think that will be the deciding factor, I never dreamt that I'd be looking at 8K+, I might be wrong.

Thanks for the input chaps.

Stotty

[DaveL485]

Valve float, Valve bounce.... basically double springs close the valve faster and help it stay closed....for example in high rpm situations the cam lobe may rotate off faster than the valve can shut with an OE spring and the rocker loses contact with the lobe. In theory/an extreme the piston could come up fast enough to clip the valve before it springs shut.

Double springs is a handy way of increasing the spring rate without increasing the size of a single spring which I guess would be thicker and coil-bind easier.

I had some made for the 21, I had to have seats made to match and the retainers modified to fit too. Just the seats and retainer mod hit me for £200! then another £120 for the rocker hardening to cope with the increased spring pressure and the billet high-lift cam.

Double springs




Hardened rockers with a 2:1 rocker ratio:



Le sexy billet cam (£750 worth if you include the 5-bolt vernier LOL)

[DaveL485]

To add...all this can be made bespoke by suppliers in the UK. Well, kind of....the cam and pulley were made by catcams in Belgium but I dealt through Matt who is the UK Rep.
The valves were made by G&S Valves from Nimonic 80A (£84 each, +VAT)
The springs were from Isky (I think!) they were about £200
The seats and top retainer mod was done by Julian Godfrey Engineering (£200)

I had the cam caps shortened and then the cam runners were line bored and honed to give an as-new finish for the billet cam by Paul Gardias Engineering in Oxford, he fitted the double springs too so I didnt take my eye out trying to do it myself. Very talented chap, a veritable genius with stuff like this. That was another couple of hundred quid.

Best of luck mate, I hope this gives you some reference on whats involved with parts, suppliers and costs!

[TNT ANDY]

To add...all this can be made bespoke by suppliers in the UK. Well, kind of....the cam and pulley were made by catcams in Belgium but I dealt through Matt who is the UK Rep.
The valves were made by G&S Valves from Nimonic 80A (£84 each, +VAT)
The springs were from Isky (I think!) they were about £200
The seats and top retainer mod was done by Julian Godfrey Engineering (£200)

I had the cam caps shortened and then the cam runners were line bored and honed to give an as-new finish for the billet cam by Paul Gardias Engineering in Oxford, he fitted the double springs too so I didnt take my eye out trying to do it myself. Very talented chap, a veritable genius with stuff like this. That was another couple of hundred quid.

Best of luck mate, I hope this gives you some reference on whats involved with parts, suppliers and costs!

Wowzers Cheers Dave, that's quite tech, and expensive, lol. My first thing to do is see if I'm going to need to Rev that hard, but this is invaluable info for future use. Thanks for taking the time bud.

[TNT Tricky Nicky]

I'd doubt you'll need to rev that high. Can't remember at what rpm Ross' started to drop off on the rollers, it was a lot lower than what he would go to so all the map was written within that range. ( his afrs at high rpm weren't great but you wouldn't have that problem with efi, Clive said even with them sorted it wouldn't help make power but would obviously be good to get them right )

[DaveL485]

Wowzers Cheers Dave, that's quite tech, and expensive, lol. My first thing to do is see if I'm going to need to Rev that hard, but this is invaluable info for future use. Thanks for taking the time bud.

No probs. Don't forget the harder your cam profile, the lower the revs this will potentially happen. It can also, I believe, be altered with high boost pressure behind the valves but this might be something I heard that applied to way higher boost than we will ever use, like the 150psi boost some of the tractor pullers use...I cant remember now lol!

[TNT ANDY]

I'd doubt you'll need to rev that high. Can't remember at what rpm Ross' started to drop off on the rollers, it was a lot lower than what he would go to so all the map was written within that range. ( his afrs at high rpm weren't great but you wouldn't have that problem with efi, Clive said even with them sorted it wouldn't help make power but would obviously be good to get them right )

ATM I'm at peak about 6k, so I expect that to shoot up with a big boy on there. Time will tell.

[michael tierney]

the old Volvo 340 had the same engine and 2 springs on each valve........probably wont be able to source them now though