i got a set of complete vortec heads, how good are the OE rocker arms on these things? im looking to go to maybe 6 grand AT MOST. prolly 450 hp combo, and maybe nitrous in the future...like a 100 shot, 150 at most

mike

 

garbage

 

Alot has been covered regarding Chevy Vortec heads on this board. I would recommend getting crew in studs or pin your current rocker arm stud and depending on the size cam. may want to do some guide work to acommodate larger spring.

 

I run them with poly locks. Absolutely no problems whatsoever in the past 2 years and my motor sees A LOT of abuse and has been over-reved a ton of times.

 

garbage

the same "rubber" crap as any other stock rockers

the "Vortec" buzzword doesn't somehow imbue them with mystical superior properties

 

RB and I strongly disagree on this. He says that they are garbage. I don't. Do a search for garbage and junk rockers and you'll find the discussion.

As far as the stamped rockers, go look at the web sites for LT1 owners (F, Y, and Bcars) and you will find that there are still many owners that still use them even after a cam swap. The rockers on your L31 Vortec heads are the same used on the LT1 engines. Occasional use of them to 6000 rpm is fine as evidenced by the many owners that use them there without complaint or failure BUT there are a few things to remember:

1. They (stamped rockers) have their limits. High rpms isn't so much the limit but the spring loading is. Too stiff a spring + too many rpms will eventually burst the rocker at the slot, or drive the pushrod through the cup in the rocker. Poor maintenance (dirty oil) plus hard use will accelerate either process. IIRC Vizard suggests swapping out the stock rockers for applications over 350 hp, but no where in any of his books does he refer to them as junk or garbage especially at power levels under 350. If they were as rubbery as RB believes then we would have had countless examples of rocker failures to read about, especially on a web forum.

2. All rockers will eventually fail if you load them too much. Vizard shows examples of failure of each type in his valvetrain book. He also noted that the rocker arm stiffness (in 3-point-loading), on a load vs deflection graph, was about the same for stamped as for several roller tip and full roller designs. But for street use with reasonable cams and springs, and therefore power output, the stock rockers are not an impediment nor will they fail.

3. The power gains from friction-reduction roller rockers are usually overstated by rocker manufacturers, so the hp/dollar isn't favorable. GM saw a 5 hp increase when going from flat tappet lifters to roller lifters back in 1987 on the L98 engine with no other changes to the engine, and that was on lifters that were always rolling in contact with the cam. Rockers with roller tips and roller fulcrum do not move at 100% duty cycle so it's not reasonable to expect more than 5 hp gain in the 4500 rpm area just by replacing rollers for stamped rockers. The power gain made from a rocker swap is mostly due to the increased valve lift, because the sbc rockers have a "nominal" 1.5 ratio and the replacement rockers are usually and measureably 1.6. More lift allows more airflow into the engine, and that's where most of the power gains are from.

If you really intend on making 450 hp then you might need some kind of stronger aftermarket rocker, because at 450 hp you will need a bigger cam and stiffer springs to get you there. If you plan to get to 450 using an occasional shot of NO2, then you can probably use the stock hardware.

 

It's not so much a question of "failure", as it is, that the rockers bend and give away lift. Furthermore, they do it in varying amounts from one rocker to another. And even worse than that, stock rockers have totally unpredictable and inconsistent ratios; I've measured anywhere from about 1.38 to 1.46, with an average around 1.42 or 1.43. No 2 are ever the same.

It's not an issue of RPM, or nitrous, or HP. Just simple part weakness.

All you have to do to establish that, is to take a set of rubber ones off, and put on a set of real ones. Even the Comp cast-steel ball-fulcrum ones will provide a DRAMATIC demonstration of the problem. Just do that, and measure the actual valve lift. You'll never use another one again in any build where you're pretending to care how accurate the valve motion is.