Rocker Arm Ratios

[Chad's Dad]

Is there a little or a lot of horse power gained by going from 1.5 to 1.6 rockers on a small block Chevy? Should all be changed?

[DanStokes]

I'll be watching this thread. On the 250 I'm running BBC roller rockers at 1.73 ratio while the OEM rockers are reputed to be slightly more - 1.75 IIRC. It's a pretty small difference but I wonder if it costs me anything. Of course, the BBC rockers are cheap while custom rockers with the correct ratio would probably be high dollar so I'll stick with the 1.73's.

Dan

[BigBlockMopar]

Going from 1.5 to 1.6 adds about 6% valvelift.
If anything there could be a slight increase in torque.

[squirrel]

If you gain a noticeable amount of power, you probably needed a bigger cam in the first place.

[Loren]

I'd have asked you a question like that.

.450 lift becomes .480 (for example and if my math is any good today), for what it's worth.

Really, I don't get why Chevy didn't just use the big-block ratios across the board.

[Barry Donovan]

If you gain a noticeable amount of power, you probably needed a bigger cam in the first place.

definitely.

going solid or low lift hydraulic lifter is another mechanically stronger route.

anyone ever see the rocker studs come right out? crazy ratio is good for that.

[TC]

Is there a little or a lot of horse power gained by going from 1.5 to 1.6 rockers on a small block Chevy? Should all be changed?

It'll add a 2-3 degrees of duration, and depending on cam lobe lift you can see anywhere from .035 to .045 increase in lift.......

Jim is right about if you gain power you need a bigger cam, But, if you are spinning higher RPM's going to the longer rocker will help keep the lifter on the cam lobe, due to the lift being created at the rocker and not in the added height on cam lobe that you would need to achieve with the smaller ratio rocker...............

[JeffMcKC]

Its not going to be something you feel, but you might gain a .10th and a little MPH its not going to knock off .50 and add 3 mph. With the added duration you will loose a little cylinder pressure along the way.

[Scott Liggett]

Is there a little or a lot of horse power gained by going from 1.5 to 1.6 rockers on a small block Chevy? Should all be changed?

Boy that short question is a big can of worms. You will get more lift, but almost nothing in duration increase. Noticeable power increase depends on the engine.

I've seen 1.6 rockers on all, the intakes, and on the exhausts. It all depends on the cam grind and how good the head ports are.

Some say that 1.6s will wear the valve guides, but that depends on a lot of stuff.

Maybe post up some specs of the engine you're thinking of installing these.

[CDMBill]

As others have said, if you run the numbers you'll get an increase in area under the lift curve, which has the effect of running a more aggressive lobe with the same rocker ratio. Also as already stated, if it goes faster you needed more cam for what you are doing with your particular combination. Changing one side at a time will provide more useful information.

Last but not least an increase in rocker ratio has an equal effect on the pressure seen at the lobe/lifter intersection. If that is marginal the increase in pressure ration at the lobe can result in increased wear or ultimately failure if the oil film isn't up to the task.

This is solid roller stuff, but it illustrates what can happen when the cam's heat treat and/or the oil supply etc. isn't up to the net effective pressure ratio acting on the lobe flank.

Three of these are on the closing flank and a couple are the result of grinding a too wide lobe separation spec on a narrower heat treated core. As you'll have noted these are all solid roller profiles. With solids the damage would be worse.

I'm not trying to scare you away form higher ratio rockers, these are all 1.8:1, but you need to be sure of what you are doing, what the component tolerances are, and what you are willing to deal with in terms of maintenance cycles.

[jcharliem]

I swapped to 1.6s... and picked up a tenth and one MPH in my SBC Chevelle (depending on the run). Obviously, the biggest change is lift and you do gain a few clicks of duration. (I have a pretty healthy stick for a mechanical tappet - with the 1.6 rockers - lift is .572/.591" with duration of 254/262* @ .050, and 112 LS.)

IMO... in a SBC... if you go to 1.6s... you have the wrong bumpstick. To do it right... stuff in the right cam with 1.5s (edit: as the 1.6s do increase the side load on the valve stems. Also... Google good ol' Smokey Yunick... as he did all sorts of testing/research on changing ratios on SBCs - IV and EV - with various results).

[Deaf Bob]

Springs stiff? That is some wear pattern...

[skullbucket]

If you gain a noticeable amount of power, you probably needed a bigger cam in the first place.

See I said this on another car site and they thought I was the devil, to scorn their bragging rights of adding 30 more numbers to their cam bragging rights without tearing the engine apart.
They would purposely put a smaller cam in their builds just so they could run 1.6s???

[anotheridiot]

and dont forget to consider your piston to valve clearance if you are running a big cam already and are gonna be bumping it a little further.

[TC]

I don't run 1.6 rockers for the added lift, I run them so I can run a smaller lobe on the cam..........