Any Difference Between 1.6 & 1.7 RR?

['88Cobra]

I have 1.7 ratio roller rockers on my car and while reading many other people's mods have noticed that most of them used 1.6 ratio roller rockers. The parts store gave me the 1.7's without asking me and I didn't know that I had more than one option. Is this a bad thing? Does it matter? Should I switch them? Thanks for any advice!

 

[KamiKaziDK]

Instead of having a 498 lift on that E cam, you have around a 529 lift on it now....technically

 

['88Cobra]

Instead of having a 498 lift on that E cam, you have around a 529 lift on it now....technically

So does that mean its almost like I bought a bigger cam, like the FFRP X cam (similar lift)? Is that a good/bad thing?

 

[KamiKaziDK]

Sort of, but the Cam is doing the same lift, the lifters are compensating the extra lift for the rockers.....someone correct me if I'm wrong, it's been a while. And you're not getting any more duration.

 

[Foxfan88]

*i deleted this becuase it will confuse people*

 

[DMAN302]

What in the name of #@# are you talking about??

 

[KamiKaziDK]

Yeah, that just confused me.......

 

[FourG63 97GST]

1.6 and 1.7 refers to the ratio on the rocker arm

the e cam has .498 lift. now with 1.6s
its take the .498 lift the cam gives alone mulitplies it by 1.6 which puts it around .515 or something

the 1.7s will lift it more to the above stated .529

I dont get this math, is that the formula?

 

[PrimerdFury]

the total lift of the e-cam is already figured using a 1.6 rocker ratio...so lift at the lobe is actually only .311
To come up with a total lift of 1.6 x .311 = .498
If you are using 1.7s you calculate 1.7 x .311 = .529
In this case I would say more lift = good.

 

[KamiKaziDK]

Yeah, don't listen to foxfans cracked out math. For all of you thinking....how do they figure that crap out...easy...find out what rocker ratio is used with the cam profile..... 1.6s make .498 lift with the E cam.....divide .498 by 1.6 and you get .311....then multiply it by the 1.7 rockers you're putting on....and you get .529 something

 

[95COBRA241]

Like KamiKaziDK said the larger ratio rocker arms give the same cam greater lift but no added duration. Is it bad, no, if it was you'd know by now. The added lift could haved caused a problem with piston to valve (PTV) clearance. It obviously didn't. Another problem with more lift is the potential for valve float. This occurs when the lift is greater than the valve spring can handle. For example some heads have standard springs which can handle a max lift of .540. Upgrade spring kits allow more than that e.g. .600. At this point you'd already know if there was a PTV issue. Check for the max lift of the springs and upgrade if needed. You don't want to drop a valve in the motor.

 

[Foxfan88]

ok i see now, i didnt understand how it worked so my first post is messed up... i erased to prevent further confusion

i didnt know that the cams were listed with 1.6 rockers, i learn something everyday

 

[stang8urimport]

Max lift doesn't really play a big part in p to v clearance. Duration does. MAX lift happens when the piston is all the way down in the cylinder. The duration (aka the length of time the valve is open) causes the p/v problems.