Rocker ratio, 1.5 or 1.6?

[TexasRoadRunner68]

With a fresh build, would you go with 1.5 or 1.6? I will be looking into t&d rockers.

Is the bigger ratio mainly used to get more lift for those not wanting a cam swap? Or are there other benefits? It seems some just say to buy a bigger cam if you want that.

Being as they are $1300+ a set, what do you think?

The trick flow 270s on a 512 can use the lift.

 

[440Coronet500]

The 1.6 ratio just gives slightly more lift. Duration won't be effected. Personally, I use the 1.5 ratio rocker arms. 440'

 

[diesel_lv]

Multiply the base lift by 1.5 and that's usually what you see on a Mopar cam card. Multiply by 1.6 and you get just slightly more. More lift does zero good if your heads don't flow enough in that range to use it. Hypothetical 234° duration w .525" lift w 1.5 rockers has a .350" base lift. With 1.6 rocker arms you'll have .560 lift. If your heads don't flow any different between .525" n .560", then you are getting nothing by using them.

 

[Moparguy59]

I.5 if your bracket racing
1.6 if your turning big rpm& and want to wear out stuff
Most guys are nt faithful to monitor valve gear geometry Its crucial

 

[diesel_lv]

Are you doing dyno drags for bragging rights or driving the car? If your just looking to say my car put out "X" horsepower, then install the 1.6 w the TF 270's dyno it, get the sheet n then install 1.5's.

 

[BSB67]

I dont know why you would not consider a 1.6 rocker. Seat timing (duration) may or may not change depending on the style of cam. The duration where it matters (i.e. at the valve) does increase with higher rocker ratios. The motor sees it as a larger duration cam.

If I was buying a set of rockers, it would be 1.6. Then select the cam accordingly.

 

[67MPRFAN]

Andy F did a rocker arm swap on his TF headed 470 build, and if I remember correctly he saw zero gains. Might be worth looking it up

 

[Photon440]

Even a good set of 1.5 rockers will be advantageous over stock, which often measure as low as 1.42. But I'd still go with the 1.6 if I had to buy new ones anyway.

 

[sam65]

Just make sure the heads have clearence for pushrods with1.6 rockers. Meaning pre assemble and checking and not assembling then find out heads have to come back off for pushrod clearancing.

 

[Geoff 2]

Increasing rocker ratio may or may not result in more HP. All depends on the combo. The butt-meter is NOT going to feel the difference between 1.5 & 1.6.
The duration that the valves are open does not change going from 1.5 to 1.6 but the effective duration @ 050 increases about 2*. Hardly worth the expense with an unknown outcome.

 

[BSB67]

The duration continues to increase with lift.

There is no additional expense.

 

[Geoff 2]

There is if you already have 1.5 rockers.

 

[66Satellite47]

Uless you are building an all out killer motor with all the parts that go with it, can't see why to go to a 1.6. With some cams you may gain some power if you have heads that will want the lift. The whole combination needs to be figured out.

 

[BSB67]

There is if you already have 1.5 rockers.

Obviously.
But not on point with the OPs question

 

[diesel_lv]

The duration continues to increase with lift.

There is no additional expense.

No, duration does not increase with lift. 234° is 234°. Lift only opens valve more, and rocker arm ratio allows lift to be slightly higher based on ratio. But does not, in any way, change "how long" valve is open, just "how much" valve is open.

 

[Geoff 2]

Diesel,
I am assuming your 234* figure is at 050 tappet lift, the industry standard as [a] a method of comparing cams giving some indication as to it's performance/rpm range.
Yes, net valve lift is higher with higher ratio [ HR ] rockers, but the HR rocker also increases the lift everywhere. So a cam with 234 @ 050 & 1.5 rockers will have more open area under the lift curve when used with 1.6 rockers & will behave like a 236 @ 050 cam with 1.5 rockers. [ all else being equal ]. So as I said earlier, 0.1 increase in rocker ratio adds about 2* effective duration, to the 050 duration.

 

[Geoff 2]

Sorry, bold was unintended.

 

[66Satellite47]

The increase in lift applies across the board. It does create an "effective" increase in duration by a small amount. More lift at a given cam position is more duration, you get more area under the curve. Does the motor want that? That's the question.

 

[diesel_lv]

Sorry, bold was unintended.

No problem. And yes, 234° is a hypothetical at 0.050 lift. Yes, it does create more lift throughout the entire duration and may cause it to "act" as though it has more duration, but no matter what, it does not "add" more duration. I'm just literal, a grammar nazi.

 

[eldubb440]

bigger = better....... just ask the wife