1.6 rr's vs 1.7 rr's

[bailey_57]

my car's current set up is a set of ported e7's, edelbrock performer rpm intake, e-cam, 1.6 rr's, 65mm tb, and adj fp regulator. my question is if changing my roller rockers to a 1.7 would help me squeak out a couple more rpm in my powerband. my heads and cam are nicely matched but my intake is designed for 1500-6500 rpm. i chassis dynoed my car and had 241 whp at 5200 rpm. if i change to the 1.7's will it bump up the power band or not. thanks.
jay

[lx mike]

I wouldn't think it would help at the top end. if you had a goood set of heads it might but with those ported e-7's thats probly about as high as your powerband is gonna be.

[Unit 5302]

I really doubt 1.7s are going to do anything for you. Those E7s may flow worse at max lift with the 1.7s than they would with 1.6s. The heads are just not designed with high valve lift in mind. Also, if you haven't changed the valvesprings, the 1.7s will exceed the maximum .500 lift your springs were designed to accomodate.

[Coupe50h]

True, unit, but i will say i had 1.7's on my stock setup, i did notice a pretty good gain on the street, and track, but then again that was going from stock stamped.....

[Gearhead999]

Don't think you'll see much difference.

[rwhite65]

Some of the guys will argue the added stress of the 1.7's to the valvetrain is not worth it. I have 1.7's, but put this all together from scratch, so cant tell ya how it did with 1.6's or anything like that.
Ryan

[Rev]

Originally Posted by rwhite65

Some of the guys will argue the added stress of the 1.7's to the valvetrain is not worth it. I have 1.7's, but put this all together from scratch, so cant tell ya how it did with 1.6's or anything like that.
Ryan

Glad to hear that those 1.7 RR's are doing OK, Ryan.

I actually went from 1.7 RR's back to 1.6 RR's when I changed cams. My application is for a flat tappet rather than a roller cam. I changed cams going to .509/.512 lift. I really didn't want much more than that with a flat tappet, so I sold the 1.7's to Ryan.

With roller lifters, you can tolerate steeper valve lifts without stressing the valve train as much as long as you have adequate piston/valve clearance and as long as you have adequate valve springs. "Adequate" is the key word here.

My belief is that a little over .500 valve lifts is OK, and does not compromise longevity of the cam/valve train for a street driven car. "More's law" states that "more is not always better" and may apply here.

Rev

[bailey_57]

thanks alot guys, you just saved me a couple bucks that i can put toward lca's and drag radials.
jay

[rwhite65]

As Rev pointed out, he had the 1.7's and helped me out when I needed some rockers for the new set up. The 1.7's might help a little, but I personally would say use the moeny in another area of the car, or better yet, save that money towards a better set of heads.
I have yet to run my new combo, but I will tell you the "seat of the pants" feeling has gotten me wanting even better heads now!
Rev - Sure did work out, thanks again!Hoping to get it tuned good, had a stumble off idle last year when I put it up. I think with the boards help I may have it figured out.
Ryan

[skiwesser]

I had them on my car that was bolt-on'd out except for intake and I think it at least reved faster and had a little more power, I did put in new valvesprings when I swapped rocker arms.

[tmoss]

Originally Posted by skiwesser

I did put in new valvesprings when I swapped rocker arms.

There is the key - the valve springs have to up to the job. the 1.7s lift the valve faster and increase valve duration (as opposed to cam)and can add some HP to a combo.