Rv_performance

What is the difference between 1.7 and 1.8 rocker arms? and what gains in horsepower in aftermarket rocker? any info will be great thanks

Rv_performance

And I forgot there also adjustable rockers which is the best?

02*C5

iTrader: (1)

There is no gain in HP per say you lighten up the valve train. Secondly most after market off the shelf cams are ground to run with a 1.7 rocker ratio and what happens you will raise your final lift numbers. If you just want that get a cam with the lift numbers you want and it will be a lot safer and your chances of valve train failure are going to be a lot less. If your going to run 1.8 rockers I would advise to get a cam that is ground for it and build your valve train to run with that rocker ratio IMHO.

If you are still looking to get roller rockers go 1.7 and Yella Terra.

ae13291

iTrader: (8)

^^^ well said. dont bother upgrading rockers unless its yella terra, the stockers due just fine and they have been designed very well by GM

vettenuts

iTrader: (4)

Been there, done that, have the T-shirt. Don't waste the money.


For the 1.8's you need to upgrade valve springs. For a cam, you need to upgrade valve springs. That part is a wash.

Depending on the rockers, if it is a kit, it will include a lot of parts including pushrods. A cam will likely require new pushrods. That part is a wash.

In the end, if you figure it out (without labor), a cam is not a lot more money but the pay-off is much larger.

Rv_performance

There was in a gm hightech was. A gto upgrading comp springs 918 and slp 1.85 rocker and has shown on da dyno increase about 15 to 17 horsepower gains

02*C5

iTrader: (1)

That's because of the lift it is higher but realistically the damage that can be incurred is not worth it. Listen to the people who have made the mistakes and wasted the money and had to start from scratch. Ultimately the choice is yours but like i say advice is free not taking advice can get expensive.

Good Luck

Rv_performance

Thanks for da info, now I understand about rockers, no iam not buying the rocker just wanted to know how they work and if there worth buying

Vic Nalbandian

increase in rocker arm ratio not only increases lift, but also increases duration of the cam. if you’re looking into full roller rockers… most likely You already installed a performance cam and valve springs hardened push rods, maybe even aftermarket performance heads. The full roller shaft mount rockers will increase valve train stability and horse power. 1.8 ratio even more so but Keep in mind you’re gonna need taller valve covers or valve cover spacers. Longer ignition wires… yup stars getting expensive nickel and dimed to bankruptcy lol.

showdog75

iTrader: (8)

My 1.8's didn't require longer spark plug wires... it wasn't a afterthought rather the plan from the beginning to go with 1.8 rockers. I used the thicker valve cover gaskets provided with the Yella Terra rockers.

G Atsma

Duration is NOT increased.
Lift is, but the time from valve leaving seat to hitting the seat is NOT increased.
Plus, longer wires are usually not needed.
Not only that, you are replying to a 13-year old thread.

grubinski

Seat to seat duration is unchanged, but .050” duration *does* go up.

G Atsma

Agreed, but he did not make that distinction.

grinder11

iTrader: (1)

I agree seat to seat there's no difference in duration. Easiest way I've found to explain it to newbies is this: If the 1.7 rockers gave .575" lift, and the 1.8 rockers increase the lift to .600", I tell newbies you now have duration at .600" lift, where you had no duration at .600" lift with 1.7 rockers, because you never had .600" lift with 1.7 rockers!! Hope this makes sense. Most of them pick up on it right away.......

Che70velle

iTrader: (6)

Duration numbers at the valve change 2-3 degrees with a 1:1 increase in rocker ratio. The changes will start immediately after valve lifts off seat. As grinder implied, it’s hard to explain, but you have to look at acceleration rates. Acceleration rate increases so duration numbers designed for a certain ratio rocker are moved forward a couple degrees. It’s a matter of manipulation. The camshaft has no idea there’s been a change made, but the valve sees a faster ramp rate, although it’s not faster. Another explanation of this is time. Duration is time. As ratio increases, lift increases. The valve sees a new higher lift and gets there faster than the previous ratio at the previous given lift. Because of the faster movement of the valve, at the same given degrees of crank movement, duration has increased. I’ve seen that in a solid roller application, I could change this with valve lash, because valve lash will alter the actual seat to seat timing, regardless of ratio. Interesting topic here.