Ok, first off why do you guys sometimes run 1.6's on the intake and 1.5's on the exhaust? I think I've heard people say this retains bottom end power more? But I thought usually our cars could use the help on the exhaust side with stock heads, that's why we use dual pattern cams alot. So doesn't the 1.6 rocker on the exhaust just offer more lift and therefore more power? Some body please explain this to me, because I'm gettin a set of Crane Energiser 1.6 full roller rockers to use on my motor to bring my lift up to around .500, since with 1.5's with my cam it's only at around 480, and I don't wanna lose any power. Do the rockers actually add some duration too? Don't you want the lowest duration(within reason)and the highest lift you can, and isn't that the reason for using higher ratio rockers? And my second question is, is there anything wrong with the crane energisers, why are they so much cheaper than the gold race rockers, I'm guessing their not as strong or as high of quality obviously, but are they still better and/or stronger than stock rockers? I don't want one breaking on me. Thanks everyone, and sorry bout all the questions.

 

Increased ratio does not change duration. Only the lift.

Energizer rockers are mode from the same extrude aluminum as the Golds except they have a bit more metal in them. If you have very oversize valve springs (I doubt it) then you'll have to use the golds since the springs will contact the rockers. Other than that they are basically the same rocker. I use the Energizers on my race car.

Blazers are cheaper because they are made completely different. There's nothing really wrong with them but they're not as good as Energizers or Golds.

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and check out the race car

87 IROC-Z Pro ET Bracket Race Car
383 stroker (carbed) with double hump cast iron heads and pump gas
461 Big Block installed and ready for the 2001 racing season

Best results before the 383 blew up
Best ET on a time slip: 11.857 altitude corrected to 11.163
Best MPH on a time slip: 117.87 altitude corrected to 126.10
Altitude corrected rear wheel HP based on power to weight ratio: 476.5
Best 60 foot: 1.662

Racing at 3500 feet elevation but most race days it's over 5000 feet density altitude!
Member of the Calgary Drag Racing Association

87 IROC bracket car, 91 454SS daily driver, 95 Homebuilt Harley

 

So why do people run 1.5's on the exhaust side? I think I've even seen these people say it's because it gives them more low end power, why would that be, when the more lift you run at a given duration is almost always better?

 

I think that all goes back to some testing TPIS did and is in their book for TPI's. As far as the came, the more duration the more power. You want a came with the most duration that will keep your computer happy and your engine in the powerband you want. As far as lift, every set of heads is different but at a certain point your heads cannot flow anymore no matter how much lift you have. So you want enough lift so you max out flow on your set of heads. That said, by going to a higher lift it actually increases the time that the port is at it's best flow and minimal flow which also acts like giving it more duration. The same for higher ratio rockers, though it doesn't actually increase duration it allows the port to spend more time at it's best flow and minimal flow which has the effect of increasing duration without actually increasing duration.

 

Nobody answered his question about why 1.6's on the intake and 1.5s on the exhaust. I'm curious as well about this.

 

People do it to balance the flow on the 2 sides of the heads.

Most GM SBC heads are weak on the exhaust side, which is one of the reasons for dual-pattern cams in the first place. But, if you get the exhaust side to flow really well by porting, it can outflow the intake side; if that happens, then the higher ratio rocker on theintake side will increase the flow without affecting the duration very much.

The higher ratio rockers do increase the measured duration slightly, but it is only a very tiny amount, not enough by itself to affect the way the engine runs.

It has nothing to do with TPIS. People have been doing that for decades, before TPIS was even a gleam in its founder's daddy's eye. TPIS may use the technique, but they didn't invent it. In some motors, people even mix rocker ratios by cylinder, to compensate for different flow in differently shaped intake or exhaust tracts. It's a very common NASCAR tuning method, for example.

 

Take note that changing to 1.6 rockers will increase your valve lift
to .512" from .480". You may run into a coil bind situation
or at least over tax your stock springs. The push rod my contact the root of the push rod guide slot nearest the rockers stud with 1.6 rockers as the pushrod seat on the rocker is moved closer to the stud.
Energizers rockers are quite a bit heavyier than the stock rockers and should use a better than stock valve spring to control this extra mass at high rpm to avoid valvetrain float.

1.6 rockers on the intake side allow the valve to open faster
per degree of rotation with-in the same seat duration.
(More intense valve motion). This seems to benefit the intake side more than the exhaust side on SBC's. Especially with dual pattern cam timing.