rocker arms 1.5 vs 1.6

[RICHARD CHARLES]

what is the advatage in geomatary of using the 1.6 rocker compared to the 1.5 standard rocker ? does it increase lift deration on the cam ? thanks rick

[Duke W.]

Re: rocker arms 1.5 vs 1.6

First, rocker arms are not constant ratio, but vary throughout the lift cycle.
OE rocker arms start out at about 1.37:1 and increase with increasing valve lift peaking at about 1.44:1 in the range of maximum lift for most OE cams.

I've don't know the detailed ratio behavior of aftermarket rockers because I have never measured them, but I can assure you that, like OE rockers, they are not constant.

Higher ratio rockers will not effectively increase duration, but at any point in the cycle they increase lift slightly. They also increase valve train loading so they could cause "float" at lower revs than the OE rockers.

They will increase top end power by a percent or two, with lessening effect at lower revs, and IMO are not worth the price. The biggest way to improve Corvette engine performance. regardless of engine option, is to pocket port/port match the heads and grind a multi-angle valve seat and top cut on the inlet valve.

Duke

[Mark #28455]

Re: rocker arms 1.5 vs 1.6

Racing teams spend tens of thousands of dollars dyno testing various rocker arm ratios for each cam they use to gain a few horsepower. On any street driven (reasonable RPM, mufflers, etc) motor, you're likely to see only a few horsepower difference at best. In addition, many times the best horsepower is produced by using different ratios on the intake and exhaust.
If you want to come out ahead, contact the manufacturer of your camshaft and see what they say. If you already have .480 or more lift with the stock 1.5 ratio arms, you may need to check for clearance between valve guides, seals, retainers, rockers, etc and may need to step up to better springs as well. Not likely to be worth the hassle for the amount of power you'll gain.

[John H.]

Re: rocker arms 1.5 vs 1.6

Even the hot-rod magazines finally agree that changing to 1.6 rockers is a waste of time, money, and effort; one of them ran a series of dyno tests in the last few months (can't remember which mag) specifically to answer that question with several different cams and both ratios of rockers, and the results were statistically insignificant. Jeg's and Summit probably didn't like the article