The Cal-look Lounge

What is people's experience with how rocker ratios actually measure compared to stated figures?

I measure lift at each cam lobe on the lathe then all valve lifts on each motor.

As examples I had a set of CB 1.4s which measured at 1.45.  My Berg 1.4s measure at 1.51.  Scat 1.25s measured at 1.30.  So it seemed like generally they work out higher than stated.

However I bought a used set of CB 1.4s which worked out as 1.39.  Unless they were actually a set of 1.3s.

Cheers
Phil

CB , Berg and Pauters are close to what they say . This is what i found out

Udo

I had a set of CB 1.4s that measured out at 1.52:1. Pain in the ass.

I run a set of older Scat 1.4's purchased in 2007 that measured out to 1.41:1

BP4019-21 from Pierside turned out to be 1.4

Just tested a set of VW 1.1 rocker on a bolt together shaft and they came out at 1.13.

Seems like generally rockers tend to be a higher ratio than stated.

I have got the new cb 1,3 ratio, in about two days will have them to my hands, I'll check and let you know

Friendly

Dimitrios

O.K. as I thought initially, I measured the 1,3 ratio rockers, they give me 1,373 actual ratio, so on a 10,3mm cam lift I end with 14,14mm on the valves. As someone might think, is relative probably the setup on which the rockers are used, so those are used on a std vw mexico head (casting 043101375H) directly on the stud blocks, no shims beneath and std length valves with lash caps

So if you wish for some reason to get 1,4 ratio rockers maybe the 1,3 ratio is the best match as its far better than the 1,55 that the 1,4 measure, hope it helps a little. Anyway I'm covered for this specific engine!

Friendly

Dimitrios

I guess it's safer for the rocker makers to go over the quoted ratio, so you are "getting more than you paid for", imagine the neg if they came out under the spec'd ratio. Quite large variations can occur just from casting irregularities in the slight rocker pedestals positioning on the head in relation to the valve centre line, even valve angle/inclination will have a tolerance, but no body EVER checks this value, taint a given in my book, I see variation often after fitting new guides, if the guide is tight and harder than normal to press in, it's guaranteed something will move, it shows up in the re substantial cutting of the valve seat required to re establish the 'new' angle just for the valve to seat.
Regards.  Spanners.

That's not it.
Put your thinking caps on.  
The ratio is the distance between the rocker pivot and the contact point at the valve, divided by the distance between the rocker pivot and the point of contact of the pushrod.  Both of those distances are changing as you turn the cam, so there's no way to state a single fixed ratio.
On top of that, if you put the same rocker on the same engine but with a bigger cam, you will get a different ratio because as the cam lifts the lifter more, the contact point of the pushrod moves closer to the rocker pivot faster than the contact tip at the valve moves away.
You may now ask, "how does the manufacturer measure their lifter's ratio?"  Since the result varies so greatly depending on the cam, many of them measure against the stock cam.  That way you can compare brand xy rockers to brand yz.  I know about 10 years ago SCAT de-rated their rockers so they would measure closer to advertised on a cam you're probably using.  Others may now be doing the same.
If you want to post the ratio you measured, you also need to specify the cam or it's lift.  Otherwise the info isn't much use to someone with a different cam.

Hello

I actually did that, I mean I got the measurements all the way from 1mm lift, the amazing thing is that the "ramp" of the rockers if I can say this way its very well done -probably cnc- I mean all over the lift the ratio is maintained the same, so in any given cam lift the valve is lifted with a true 1,37 ratio, not less no more. Same happened with the 1,4 ratios measuring like 1,5, I lifted at 8,5mm which is about the std cam lift and the valve lift was 12,75mm and on the max lift of 10,3mm was 15,40mm so you see the ratio is maintained very close,hope this helps on some thinking

Friendly

Dimitrios

must feel a little like christmas getting an unexpected 20 or 30 thou lift!

Well yes to a point, :D but only if you KNOW the piston/valve clearance is workable and even then, you can't know the ACTUAL lift until the rockers are installed and clearances checked, easy at the build stage, not much fun if up grading rocker lift with an installed engine.

Thank you for this info Dimitrios.
I need to buy some rockers for my project, and I'm closing in fast on a true maximum lift figure before coil bind.
Very much appreciated!  :)