1.5 vs 1.6 rockers

-
Along with that, if a lobes specs (duration at the various lifts) are based on a 1.5 ratio and you use 1.6 instead, what would the duration specs increase by then, typically, in general, or roughly... short of actually measuring.

Not much !
 
I have had longer push rods on one side of my motor and i can hear a difference lol im pretty sure you will feel a difference maybe 200-400 rpms more in the topend on the camshaft power band im guessing? on my cam card with the same camshaft with 1.5 rockers Intake .410 lift Exhaust .425 but with 1.6 rocker ratio intake .437 exhaust .453 That same camshaft just got a little nasty with 1.6 ratio not a huge difference but something you can hear.
 
I do know there was a guy from Davenport that ran a demon at the strip, he had 273 rockers and would tighten up the lash almost half of what Mopar suggests on their chart...he would pickup a couple tenths...
 
Can't say if this has any value for a V-8, but some slant six racers (not me) have done back to back at the track on the same day, comparing 1.5 stock rockers to 1.6 roller rockers, and reported little to no gain. It seems like the benefit of roller rockers on a slant, is consistent ratio, and strength for a full boggie high revin engine.

PS: on the type of engines I build, I can think of better ways to spend $1000 (like another complete engine). It is less expensive to change the cam, and can get bigger gains.
 
Last edited:
Here's the whole ball of wax with 1.6s or other higher ratio rockers. They are used for one of two things. Putting on a "smallish" cam to give more lift, OR fine tuning such as how some do with 1.5s on one side and 1.6s on the other. Thing is, if you choose the right camshaft to begin with, you won't need a higher ratio rocker.
 
This seems like a good tread to ask this question-

Can you use adjustable rockers to make a 1.6 ratio?

I've always wondered this.
 
This seems like a good tread to ask this question-

Can you use adjustable rockers to make a 1.6 ratio?

I've always wondered this.

No. The ratio is raised by moving the pushrod cup closer to the rocker center. This puts the pushrod closer to the pivot point causing more lift.
 
Not much !
Yup, I've read it increases duration as measured @ .050" about 2°-3° I know I'll never do it, but seeing a valve lift curve drawn for any particular lobe using both ratios is something I don't recall ever seeing, lines would be on top of each other for the most part, but I'd like to see it.
 
I ran into a good deal on some hughes 1.6 rockers and made the swap from 1.5 to 1.6. Car picked up .1 and gained the hp up top, 1-1.5 mph gain. The wipe pattern moved from centered to slightly up, toward the intake side.
My Comp XS274S SFT is to small for my head flow and the swap improved performance. The motor also revs quicker.
 
Hi,

i did the change from 1.5 to 1.6 Rockers some years ago, crane ductile iron 1.5 to mancinis version of the Harland Sharps. Car was significantly faster, two tenth. Could be influenced by track conditions or weather, so i think it was worth a solid tenth.

Michael
 
I asked this question over on Moparts years ago. The general consensus was it was not worth much...I heard stories from a tenth to maybe a few hundredths...and a few with no change. It probably depends on your combo (i.e. is your current combo optimal).
 
I ran into a good deal on some hughes 1.6 rockers and made the swap from 1.5 to 1.6. Car picked up .1 and gained the hp up top, 1-1.5 mph gain. The wipe pattern moved from centered to slightly up, toward the intake side.
My Comp XS274S SFT is to small for my head flow and the swap improved performance. The motor also revs quicker.

Hi,

i did the change from 1.5 to 1.6 Rockers some years ago, crane ductile iron 1.5 to mancinis version of the Harland Sharps. Car was significantly faster, two tenth. Could be influenced by track conditions or weather, so i think it was worth a solid tenth.

Michael
thanks guys! hearing your personal experiences is awesome.
:thumbsup:
 
Absolute duration, that is zero lift to zero lift wont change. Closed is closed.
But, as I understand it, because it has further to open within a given amount of time, it will be at .050 to .050 ever so slightly longer. The closer you get to fully open, the more the duration will "increase".
By any amount that means anything, I doubt it in a street car, and as previously said, on a race machine, probably going to depend heavily on where your combination is already.
 
Hi,

i did the change from 1.5 to 1.6 Rockers some years ago, crane ductile iron 1.5 to mancinis version of the Harland Sharps. Car was significantly faster, two tenth. Could be influenced by track conditions or weather, so i think it was worth a solid tenth.

Michael

I agree and it’s what I have seen although it is purely combination dependent.

My question is, is there a cheaper budget set of 1.6 rockers? The harland sharps cost nearly a grand that just seems ridiculously expensive to me.

Mancini racing has a excellent deal going I now with sets labeled under there own name made by Harland Sharp. Under $500. Pay attention to what your getting with the set.

Why would the duration change ?

The duration changes because the higher rocker ratio is lifting the valve off the seat sooner and quicker. Even though both rockers are being activated at the same time, because the cam says so, the quicker movement at the valve is due to the increased ratio.

This quicker and more aggressive lifting of the valve acts like the cam is approximately 2* larger overall except the actual start of the lift with a quicker, more aggressive ramp. The overall curve of the cams lift is increased and becomes more aggressive.
 
It's obvious the change of rockers is going to be very dependent on the current combination. If the cam and the 1.5 Rockers are already producing the max amount of flow the heads can support adding extra lift ain't doing nothing.
 
What rumblefish says, there wont be a change at .000 lift what so ever, but the more it sweeps through the cam ramp, the lift spec at each measured interval is achieved sooner on the opening ramp and later on the closing ramp, hence making the profile ever so slightly more longer or "aggressive" . For eg .050 occurs earlier in degrees of cam timing (as measured at the valve) because of the ratio change, therefore a not longer at .000 but longer at any other measured position profile of a cam.
100_2362.JPG
 
Here's the whole ball of wax with 1.6s or other higher ratio rockers. They are used for one of two things. Putting on a "smallish" cam to give more lift, OR fine tuning such as how some do with 1.5s on one side and 1.6s on the other. Thing is, if you choose the right camshaft to begin with, you won't need a higher ratio rocker.

Or you could be moving from 273 rockers to roller rockers and say what the heck, I might as well get the 1. 6 s and add some cam they're the same price...
It happens ask me how I know...
 
The NASCAR engines run lower lift stuff... Like 1.2 with no adjusters. They adjust the valves with different length pushrods.

Maybe that's the next hot set-up....
 
The rocker is also longer behind the shaft at the valve so u probably need a correction kit from Mike at B3Racing. Kim. 1.5 crane gold, 1.6 Procomp, and 1.7 Sharps.

90D4D41A-523E-4F3C-94E6-E8500D43D09E.jpeg


710C1102-7D34-4D11-AC38-96D80648E683.jpeg


1AA34964-0C2B-475B-8514-E381339561D9.jpeg
 
Here's the whole ball of wax with 1.6s or other higher ratio rockers. They are used for one of two things. Putting on a "smallish" cam to give more lift, OR fine tuning such as how some do with 1.5s on one side and 1.6s on the other. Thing is, if you choose the right camshaft to begin with, you won't need a higher ratio rocker.



Close Rusty, but not always. In my case, to get .600 net lift, I had to use a 1.6 rocker. If not, the lobe would have been to aggressive. I'm already 281/255 with a .3875 lobe. I would have needed .414 lobe to get where I'm at with a 1.5 rocker and that would be a mushroom lifter lobe. Maybe. I'd have to call Jim and verify. You may not be able to do that even with a mushroom lifter.
 
My question is, is there a cheaper budget set of 1.6 rockers? The harland sharps cost nearly a grand that just seems ridiculously expensive to me.

Having gone through a few sets and ended up with HS rockers that get adjusted once a year, I would HIGHLY recommend not putting your rockers on a budget.
 
-
Back
Top