Wondering if anyone has put these RRs in a 5.3 and tested them? LS1.com has 2 threads. One gained 9 h.p. and the other lost 13 . He got it back when he put the 1.7s back in.

 

I don't see how you could lose that much hp. They probably didn't set the valve lash right or something. 9hp gain seems realistic. I've never messed with them on LSx engines, but with my Camaro, and gen 1 SBC's you typically see 1.5-2mph gain in the 1/4, which is about 10-20hp (rough estimate) most likely 10-15hp with our trucks.

IMO if you don't have a cam, then do that, because it would be more cost/performance effective. You'll get more lift/duration, and better lobe profiles/ramp rates with an aftermarket cam than you would with 1.8's. I'll probably be about the same price too. JMO.

 

I put 1.85's in a 5.7 with a .522/.529 cam. Don't have any new numbers, but SOTP was considerably more than I expected.

 

I put 1.85 rockers on my 5.3. At the same time I also put on Gibson shorty headers on. Nver dynoed before or after, but I could feel a pretty good difference, especially at part throttle.

 

I have some '98-'00 LS1 cams available to me for $25 but don't want to lose any low end power. By my calculations 1.8 - 1.85 puts me in the same lift range but sith less lobe separation and duration. ON PAPER I would end up with top end gains & no low end loss. (The dude that lost h.p. lost it above 4000 rpm.????)