high ratio rockers

[troykinsvt]

can someone tell me or link to me what the difference is with the rockers , i know bigger lift lets the engine breathe better i just want to understand it more , how they work and stuff...in plain english thats simple LOL

[FATMOE]

www.google.com.au

[troykinsvt]

hahah, i wanna find out by someone who knows how they work personally....

[ari666]

its like a seesaw. if you both weigh the same amount and the pivot is in the center, then you will both balance off the ground at the same height as the pivot. if you move the pivot closer to one side then the short side will have less leverage and the person sitting on it will go up in the air at the rate you moved the pivot from center.

i.e. a regular rocker pivot ratio for a holden V8 is 1.6, yella terra do 1.65, which means their arm is slightly further away from the pivot point (0.05%) so when your cam shaft lifts up to 300 thou, the short side of the rocker goes up 300 though, but the longer side goes up 480 thou (300X1.6) and 495 with yella terras.

there are many down sides to doing this. everyone thinks of it as "free lift" when in fact it isnt really. one thing it does is steepen your ramp rates dramatically (the rate your valve opens and closes) which puts undue strain on things like pushrods, springs, collets and retainers.

the other thing to remember is that on a pretty much stock setup, its going to do FK ALL. all it does is move your powerband slllliightly further up your rev range. there is a company advertising a gain of 20-30RWKS which is the biggest bunch of arse rape i have ever heard. on a stock engine, something else will restrict you before you see any benefit to the extra lift (stuff like restrictive induction systems, low compression, poorly flowing heads etc etc etc)

so in summary, if you have a mild cam, got the induction system flowing well, a nice exhaust setup all your ignition is working as it should, then maybe play with a 0.05% increase in lift. but dont be surprised if it does nothing at all except wear out your valve train faster.

[troykinsvt]

thanks ari that helped a heap...not getting those any time soon

[monkeys437]

I got YT 1.9 rockers and found them a great mod. Seat of the pants feel was almost as much as the 10PSI pulley with no bottom end loss and plenty of gain in the mid range. Based on the research I did I wouldn't go any higher ratio than 1.9 and I wouldn't raise the rev limiter without changing valve springs.

Its a great bang for buck mod and I'd say go for it if you got a spare $500

[ari666]

i dont mean to be "that guy" but have you got any dyno proof of the improvement? seat of pants improvements usually are also "placebo" improvements. you want it to be a good mod so much you make it one in your head. when really all it achieves is lowering your bottom end torque and raising the top by a smidge.


thats not to say dont do it! no, not at all. i have 1.6's on my impala (usually 1.5) and i had 1.65's on my VK (usually 1.6) BUT after i had done everything else to the point i was happy. i.e. headers, intake, carby, cam.

also the rolling affect from the bearings DOES have an impact on oil temps, by removing a frrrraction of amount of friction. from the trip of the valve and the old oil lubed fulrcrum.


im just saying do everything else first.

[ari666]

hey monkey, whats the original ratio and lobe lift?

*nevermind googled it:

so stock ratio is 1.6 and stock intake lift is .258 so valve lift is 412.8

lol, 1.9.. anyway, that means your intake now lifts at 490.2 .. which is a mild V8 cam, pushing the limits of LT1 springs... except now you dont have the benefit of the slower ramp rate. your valves are basically just switching off and back on. mate. i reallllllly hope you checked your pushrod length to make sure your rocker is starting right at the back of the valve tip. there is gonna be some pretty significant side loading on the valves with that amount of extra lift

faaark thats like a 78 thou increase. nearly 2mm of extra lift.... wow. glad its your car. how often you need to adjust them?

[TI3VOM]

I've got 1.9/1.95's in my car and they were the biggest improvement on my engine apart from the supercharger, longer pushrods were included in my kit. I have had them in my car for 50,000k's and have had the rev limiter upped to 6000rpm which it has seen on many occasions. They were not a placebo effect as well.

That's why they say upgrading the rockers with this ratio, is the equivalent to a small cam upgrade.

The don't need adjusting unless they are the adjustable kind, which not many people buy.

[monkeys437]

Ari, they are definitely not a placebo effect, As I said almost as much difference as the 10psi pulley. They came from Yella Terra with longer pushrods and have been pumping away for 70,000k's now on the old girl with no issues. There's heaps of guys kicking around with 1.95,1.97,1.98 and even a stupidly high 2.2 ratio. I've seen a couple of cases of failures mentioned on forums but they were all 1.95 and higher ratios. YT advised me that 1.9's were ok with stock springs and stock rev limiter and so far so good, no sign of bent valves or pushrods

[ari666]

They were not a placebo effect as well.

yeah i gathered that. an extra 78 though of lift is basically a cam swap.


i stand corrected then

[troykinsvt]

so are they worth it , my car a standed v6 vt has no mods and want something , i dont want an exhaust i want it quiet so i thought about rockers...or should i get a cam first ?

[The1]

Probably already been done elsewhere but if this helps keep an eye on this thread, will be fitting 1.95 YT's with new springs soon, still stock apart from intake and exhaust and will be dynoing after, already have a dyno run in current form.

delcohacking.net • View topic - The1's Daily

[ari666]

Probably already been done elsewhere but if this helps keep an eye on this thread, will be fitting 1.95 YT's with new springs soon, still stock apart from intake and exhaust and will be dynoing after, already have a dyno run in current form.

delcohacking.net • View topic - The1's Daily

Yeah man, I would be really keen to see a before and after. I'm curious what that kind of lift would do to dynamic comp/low End torque

*edit: bah, you've done throttle body, headers and exhaust.

Op, do those mods first. You shouldn't get rockers or a cam until you have sorted induction and exhaust imo

[troykinsvt]

i want it quiet ...how can i upgrade the exhaust but keep it quiet ...more so police stay away

[Trayner]

i want it quiet ...how can i upgrade the exhaust but keep it quiet ...more so police stay away

Dont get one with only 1 muffler ?