so guys i know many mani of you guys are running aftermarket cams ! i was thinking does anybody know the lift limit on our stock rockers ?

 

I'm not exactly sure what the limit is, but I know that there are guys on this site with well over .600 lift on stock rockers. Harland Sharp and Comp Cams offer trunion upgrades that are a nice alternative to aftermarket roller rockers like the 1.7 Harland Sharp's that I'm running.

 

Agreeeed

I see no reason to run over 600 lift on a stock set of heads, but a well worked set or aftermarket set I can understand..

 

1st off let me say that people run over .600” of lift with stock rockers all the time and I realize this. Many don’t have immediate apparent issues, but not all issues appear in an immediate catastrophic nature, some rear their ugly head as accelerated wear instead.

Most stock LS rockers are only 1.7 ratio and only reach this above .480" valve lift. They actually start the valve off the seat at a 1.54 ratio.

The OE 1.7 ratio LS rocker arm is designed to be used with moderate camshafts of less than .550-inch lift and valve-springs designed for 100,000-mile drive-train warranties.

Running High-Lift Camshafts With OE LS Rocker Arms
OK, so what happens when you use these OE rockers arms with camshafts greater than .550” lift, increase the duration of the camshaft, and add higher rate valve-springs. The higher the mileage, the more pronounced the following will generally become.
> Pitted, galled, and/or destroyed valve tips
> Blued rocker tips
> Worn or destroyed fulcrum bearings
> Valve-spring failures
> Valve stem failures
> Worn-out valve-guides

Lastly, the offset intake rockers of the L92/LS3 and so on, only aggravate most of these items due to side loading. Proper valve-train configuration is the only thing that will slow down the effects.

 

1Bear,

How do you feel about the trunion upgrade and .600 lift?

 

I feel it’s a stop-gap measure at best. Yes, the Harland Sharp and/or Comp pieces are tremendously better than the originals as far as strength and the rockers themselves are adequately strong; it’s the basic design that is the limitation.

 

Good info as always Jarrod, glad you caught this thread Any certain rocker that you recommend for camshafts with aggressive lobes and lift numbers over .550?

(in particular, are my current Harland Sharp's worth hanging on to? )

 

There are good rockers from everyone from Harland Sharp, VHP/Crane, YellaTerra to Jesel and so on. As far as what would be right for any particular set-up would need to be based on how far you need to go with your particular engine, ease of installation and ultimately money. While some of these rockers are basically bolt-on, some are not and require modifications to install them. Not every engine package will require the same type or level of rockers, but that doesn’t mean one needs less attention to detail. While all are important, besides strength and quality, more than anything proper geometry is key to longevity.

 

How often have you seen damaged engines due to this if you don't mind me asking?


I just hardly see people swapping rockers on here. I am guessing it is something being over looked.

 

Just like I started with, people run well over .600” lift all the time without immediate issues. The issues are just accelerated wear and while there are some long term engines running around, a good deal of them are not, so it’s hard to get an accurate read on all of them. So many people run the stock rockers and appear to get away with it that a whole bunch more will never even consider that there may not be anything going on there and might as well do it too. I will say that if your hell bent on sticking with the stock rockers, that the trunnion upgrade may not be a bad idea, as the stock pieces can spit bearings in an otherwise totally stock engine. It happens fairly regular, where someone finds needle bearings in their oil pan. When it comes to overlooked items, valvetrain pieces show up all the time. Very few people here in past polls and what not have ever admitted to ever even measuring spring pressure and installed heights, and instead just drop in the springs. There again, I’m not going to say it won’t run and hold together, it’s just that by doing so you are starting out with a bunch of unknowns. Your valve-train may experience early valve float due to light spring pressure, all the way up to broken springs, and at the very least you don’t have a base record of installed spring pressures to measure against down the road. Spring pressures drop ever time, especially when tortured within a fraction of their life and while you could just replace them on a regular schedule, if you measured everything for a baseline, as long as the measurements add up, you very well could re-shim them back into spec. Also by performing annual spring pressure measurements, you can also somewhat determine a rate of tension loss to help you in your decision of when replacement will become necessary. Not trying to slap anyone in the face, but how many threads have you seen that either involve pushrod length or lifter preload, it almost would seem like a black art, where it is definitely not. I can’t for the life of me figure out why someone wouldn’t mind putting in the time to install a bunch of parts, but then short cut it by not putting in the little bit extra by measuring everything and making some pretty basic calculations.

Of course I guess this where Pro builders come in and what sets them apart.