pettrix

On an Olds 455 does changing the rocker arm geometry from 1.6 to 1.7 cause and negative effects on the valvetrain?

The advantage of a 1.7 would be higher lift on a cam vs 1.6 which would have a lower lift.

Duh

If your heads are set up correctly probably not. I say probably because I don't know why you want to make the change.

chadman

A 1.7 ratio basically makes the cam act more aggressively in all aspects than a 1.6 ratio. You gain both lift and effective duration. It doesn't have any more negative effect than having a cam ground with the additional lift and slightly more aggressive lobes.

olds 307 and 403

I did it on an under cammed Olds 350. I went from 1.6 Comp roller tips to 1.72 Scorpion SBF full roller rockers. They were quieter under the aluminum valve covers. The motor was still tempermental on 91 octane. I plan on trying them with the iron heads on my current build,will see how the geometry looks.

Tederra

Were their any modifications done to use sbf rockers if so please elaborate, thanks in advance.

olds 307 and 403

Yes, you need the Comp cams 5/16" to 3/8" studs and guide plates, along with the correct length push rods.

83hurstguy

You're definitely going to want to check pushrod to head clearance... to increase the ratio, the pushrod cup moves closer to the pivot. Not a big deal to clearance when the heads are off the car, but not something you really want to do with it in the car. I tried a Harland Sharp 1.7 many years ago as a sample piece (motor together in car) and decided against it since I would have to perform clearancing.

olds_freak

On my Edelbrocks, to go froma 1.6 to a 1.7 rocker the pushrod holes had to be elongated on the top and bottom of the holes. Like Luke said, the pushrod cup location in the rocker arm moves and you may have to make room.

brownbomber77

An alternative is using the PEDESTAL mount SBF roller rockers. Ford Motorsport made them years ago E351 (1.7) and B351 (1.6). Can usually get them around $200. Just be sure you're NOT getting the "Crane" rockers that came on the 93-95 Mustang Cobras as the roller rip is recessed for the longer Ford valve stem.

Just make sure when you buy, you get the rockers, pedestals, bolts, and slotted mounts.