Modern_Muscle

iTrader: (11)

Last time I asked, I jsut got people telling me things to do instead.
I have already decided on my cam (200/203 .500/.500), and am not going with a bigger one.
Which ratio Rocker Arms do I need for my truck?
2003 5.3
1.7 (factory), 1.8, or 1.85?

I dont want people saying "dont get them", or " just get a bigger cam", or "they are worthless", or anything like that. I just want to know which ones to get. What are the benefits of 1.8 or 1.85 rockers?

Plus, my truck is 5 years old. It would be nice to have a few new parts on it, lol.

knuckles

iTrader: (9)

how much lift do you want. what is the lift on your cam? what springs do you have?

InchUp

iTrader: (2)

Keep in mind that rocker arms are nothing more than class I levers, and do nothing more than take an input from the cam lobe and pushrod and multiply that by the arm ratio to produce an output pushing down on your valve. Your cam was probably cited for the stock 1.7 ratio, so any rocker ratio more aggressive will change the camshaft's specs. Most camshafts only have .300-.325" lift, it is the rockers that turn such a camshaft into a .510-.550" cam at valve after being multiplied by the rocker ratio.

If you want new(er) rockers, find a goof ball who swapped his stockers out for a nice shiny new set of Harland's and buy his stock rockers with low miles on them. They are very well thought out by GM considering most Gen I "350" motors used stamped steel with no forethought to friction, then compare that to the technology we are using today. The roller fulcrum and hardened design make for a rocker that will last just as long as the motor does while keeping heat and noise levels down.

If you cannot find a cheap set of 1.7's, PM me I have a whole set of 16 with under 100k miles on them I'd let go for pretty cheap off a 4.8L.

Modern_Muscle

iTrader: (11)

ITs going to be a stock LS2 cam, specs: 200/203 duration .500/.500 lift
My friend is getting some stuff together for me, and I would guess factory LS2 springs too.

This is all geared at mostly midrange torque. Well, Low-midrange.

But Like I said, I know 1.7s are factory, but if I went to 1.8s, would it help/hurt the cam down low/mid?

knuckles

iTrader: (9)

.500 lift on stock heads is plenty. on the ls2 cam i think that you have to change a lot of stuff to make it work. the cam position sen. is on the wrong end.

Modern_Muscle

iTrader: (11)

They are built from the same cores as the LS1/LS6/Truck cams. There is a place for it in the correct spot for my application. Already checked that out

But, I may be putting on a S/C later on down the road, and PP these heads, so I want to go ahead and check out rockers, while I found a couple sets at almost unbeatable prices now.

And given what you said InchUp, going from 1.7 rockers to 1.8 would take lift from .552 to .585, and then a .601 with a 1.85, based on that .325 lift.

Modern_Muscle

iTrader: (11)

so I took .500, and divided it by 1.7, giving me .294 lift.
mult by 1.8 and its .529.
mult by 1.85 and its .544


any thought to that?

I was thinking the 1.8s look the best, so I dont put too much lift on the heads, but a tad more than stock.

InchUp

iTrader: (2)

If that is the case with the LS2 cam, then 1.8's are a good match. Make sure your springs are up to par to handle the lift. LS6 yellow springs are a good investment, $53-54 bucks for a whole set of 16 from Lingenfelter's website under LS1 valvetrain.

I'm curious, why the LS2 cam? The 02+ LS6 camshaft is much better suited for boost and would not require you to change rockers at all. Even with the stock 1.7 ratio it still has more lift than an LS2 cam with 1.85's. The '02+ LS6 cam can be ordered from GMPP for under $200 brand new, and if memory serves it's a 204/218 .551/.547 on a 117.5 LSA. On a 5.3L it's a cam worth 30-35hp and +/- 5lb-ft of torque, meaning it's a very efficient camshaft if you look at the gain of hp vs. torque.

budhayes3

iTrader: (19)

Since you're set on rockers, the Crane 1.8's are very nice from what I've read. They're pricey and a pain to adjust, but they're supposed to be top notch. Harland Sharp rockers are also nice, I have 1.7's (I swapped them in when I was chasing some valvetrain noise that I thought might have been the rocker arms). They basically bolt right in with little or no modifications to the heads or valve covers (I ground relief notches in my heads on the side where the pushrod goes into the rocker, as the clearance looked tight), and shouldn't need any adjustment. I just torqued mine to spec. The HS's are "relatively" cheap compared to some (got mine for under $400 from TSP at the time).

You might want to double check that the LS2 cam has a provision for the cam sensor...thought I read where someone tried swapping one in a GENIII and got cam sensor codes since the cam wasn't machined for the sensor. The GENIV engines get the cam signal off of the cam gear, and the sensor is in the front of the engine as opposed to the rear.

fastrt

iTrader: (48)

I think they are right about the ls2 shaft not working, but the ls2 heads have ls6 yellow springs in them, I think.