redtail2426

iTrader: (10)

as it states

speed_demon24

iTrader: (6)

Why would you want 1.5 rockers instead of 1.6's.

LiENUS

The important thing is to make sure you get rid of the stock stamped ones because they cant take the lift, and if you're upgrading you may as well get 1.6s rather than sticking with 1.5s.

redtail2426

iTrader: (10)

im looking for facts not statements

LiENUS

FACT your stock stamped rockers CANNOT handle the lift of the new cam
FACT the cost to go with improved 1.6 rockers is not much higher than the cost of improved 1.5 rockers
FACT 1.6 rockers result in a more aggressive cam profile
FACT a more aggressive cam profile results in more power
4 facts hows that for you?

Boodyrider

iTrader: (2)

AND full roller rockers will make more power, but cost exactly the same whether you go 1.5 or 1.6.

But if cost and max power stay out of it, feel free to get 1.5 roller rockers, but don't use the stock rockers.

3pnt4maro

iTrader: (2)

seems like 1.6rr would be a natural no brainer

firebird6786

i think he means on ported stock heads?

jninan2k2

iTrader: (6)

EXACTLY

firebird6786

theres a ton of people that run 1.6rr on ported stock heads why is that. they can only flow about 265cfm

-PEPE-

iTrader: (10)

Especially on stock heads, even unported heads. The 1.6rr RollerRocker is a much better upgrade over the 1.5 stamped steel rocker with any cam, not just the 847 and obviously the the 1.6s will give you a more substantial lift which your future upgrades will benefit from, headers, better heads, etc.

firebird6786

yeah i know but stock ported heads cant flow enough to support a 1.6 rocker(for the gm847 it would be .575/.595 lt1 ported head cant support that). wouldnt you loose power?

LiENUS

Your cam profile would be more aggressive and reach higher levels of lift faster.

-PEPE-

iTrader: (10)

Good point and your on the right track of thinking, I too was concerned but When I spoke with Crane about the 847 & the Crane 99893 springs they recommended 1.6rrs based on the cam specs relative to stock LT1 heads, let alone ported heads. I bought Comp ProMag 1.6rrs and also talked to them about the same thing, they also agreed for this application 1.6s were best. So that being said I tried the 1.5 stock steel stampers, was badass, then went to 1.6s even moreso and then I bought the Comp stainless 1.7 promags and woke it up even more. I did go back to 1.6s and with stock heads it put down 373rwhp on a DynoJet. TONS of people have and are still using this cam with 1.6s on stock heads and have great performance...

Your choice though, your car, feel comfortable about your build, if all else at least use 1.5 roller rockers for better wear on your valvetrain.

...still recommend 1.6s though, promise you'll love em ...

LT-x7

Why did you get rid of the 1.7 promags?

-PEPE-

iTrader: (10)

huh? ohhhh why? The 1.7's I ran for about 8 months actually, but after breaking a 99893 Crane spring and then collapsing a piece of **** CompR lifter, decided to calm down a little. Ran just as good. Only reason I done it to begin with was there were just a few of us willing to do it. The geometry can be checked if you know how to do it right.

seawolf06

iTrader: (8)

1.6 RR will make more power, just make sure you get a spring that can handle that lift. I doubt the 918 on the LT1 head will.