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I don't get it, with VS CAM stock springs are fine, but rockers need stiffer springs?

S

Schwuppes

New member
G'day from Australia,

I hope I'm allowed to post here.

So I've been looking into cams and rockers recently. My car is a GM Holden VT Commodore with L67. Just has basic mods like extractors (you guys call them headers I think lol) twin hi-flow cats and 3.4 inch pulley.

Anyway, so I was looking at ZZP and saw their VS cam, apparently it designed to work with stock valvetrain components. Yet the lift from that cam (.512/.507" is much higher than the lift that would be obtained from 1.9 rockers on a stock cam (~ .490"). Yet everybody always says 1.9 rockers need new springs.

Does this make sense or am I missing something? Over here we have many people using YT 1.95 rockers (they're not available in the US) with stock springs with no problems.

My shift points will not go above 5400rpm, which is redline on our Holdens here... so im wondering are stiffer springs really needed?

cheers guys
 


I'm running stock springs on my 1.9 rockers. I'd replace the springs while everything was apart if I were you.
 
cheers mate,

Yea, its just that replacing springs is pretty labour intensive and expensive, and not something i can do myself, dont have the skills or time.

Eventually I will be getting a cam package with DR chain and 105 springs... just want to know if I can get by with stock springs for maybe a year or so.
 
about 160.000km... I think thats around 100.000 miles.

I bought the engine second hand from wreckers, so I'll have to trust them on that lol
 
While yes, you would be safe with stock springs.

I would replace them with gm l76 springs. They will be a happy medium for springs. Or you could just get 105 springs to give you a window if you ever want a larger cam
 


Yea I'll get that done along with double row timing chain when I get the cam I think.... Ive spoken to a performance shop here and getting DR chain, springs and rockers fitted ends up costing more than their cam package lol.

I guess Im stuck with just the rockers for now, Ive thought about going the 1.8 ratio to be extra safe.... but the performance gain probably isnt worth the cost with those/
 
Do the stiffer springs make more valve noise? seems after I replaced my springs, the engine seemed a little noisier.
 
Yes, ZZP says it's ok to run stock valvetrain with a VS cam. But, you a loosing power when doing so. And, people do break stock springs with the VS. That's why it's suggested to upgrade them.

With a VS cam, I wouldn't even think about putting a double timing chain. It's not worth the extra vibration. Get a new stock timing chain, a new chain dampner, and throw on a set of PBM 110# springs.
 
Swapping in some upgraded valvesprings on a stock timing chain is pretty simple. Any rocker/cam upgrades will gain from them although "required" is a strong statement. On bigger cam setups you are going to need extra room in the valvespring area to allow the cam to lift.

Also, lift does not play as big of a factor on the required spring strength as duration does. The more duration you have the steeper the cam lobe will be and the more succeptable to floating it is.
 


darkhorizon said:
Also, lift does not play as big of a factor on the required spring strength as duration does. The more duration you have the steeper the cam lobe will be and the more succeptable to floating it is.
Click to expand...
Not entirely true. The lobe geometry is affected by the total lift in relation to the duration. The higher the lift, the further the valvetrain has to move. The shorter the duration, the less time the valvetrain has to move the distance set by the lift.
 


No. Reuse your stockers. Only way you'll be having to buy rockers if you wanted something more then the standard 1.6 that come stock. Basically increasing the lift. You go with either a CAM or rockers..not both.
 
REDCOMPG said:
No. Reuse your stockers. Only way you'll be having to buy rockers if you wanted something more then the standard 1.6 that come stock. Basically increasing the lift. You go with either a CAM or rockers..not both.
Click to expand...


you can do both with milled heads....:th_king-evil:
 
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