'02 LS6
LPE GT-11 cam, 215/231 .631/.644 118 CL
Stock heads with hollow valves
PAC 1518 springs, 130lbs@1.800" seat, 337lbs@.650"
OE retainers and locks

Thinking about "upgrading" to a roller tip rocker as I've been reading bad things about using the stock rockers much past .600 lift. I have the Comp Trunion upgrade kit but I'm trying to decide if I'm going to install it or upgrade the rockers.

I've read a lot of bad things regarding the heavy nose of roller tip rockers causing valve float. The only affordable roller rockers I've heard of that are light on the tip and don't cause interferance with the heads AND have a good reputation for not breaking are the Yella Terra Ultra-Lites.

Question: Will revving THIS CAM on the OEM HOLLOW VALVES & HARDWARE and THESE SPRINGS using the YT Ultra-Lites to 6800 RPM cause concern for valve float? What RPM would I expect to see the springs start losing control?

I've spoken to LPE a few times and based on the feedback I've gotten from them on other questions I don't think this is something they would answer.

I'm looking for informed input here, not just "YTs work for my .5XX lift cam, you should be fine" kinda stuff. Looking for people who've used the Yella Ultra-Lites with HIGH lift cams. What springs were you using? Hollow/Solid valves?

Thanks!

 

That cam uses very aggressive lobes and needs a dual spring. Can't say if/when you'll have valve float. You may not have it initially, but will have it quicker as the springs will get weaker faster. You do have lightweight valves, but those rockers are heavier than stock. I say get a quality dual spring and do it right the first time. A broken valve spring, especially a single, is not good.

 

Lift is too high for stock heads.

stock 243 heads dont flow much about 580-588 valve lift

the light wt valves should be used for anything above 6600 rpms, and YES the duel springs for that much lift.

 

Yes, a lot of the lift on this cam is not being utilized with the stock heads, but the agressive nature of the lobes gets the valve opened up to and beyond that .580 lift quickly and keeps it there for longer compared to a similar duration cam that has ~.590 lift. That's the thought process at LPE, anyway.

If I decide to upgrade the heads in the future I know the cam will make them shine.

 

Dual spring for the lift requirements? Or the open (closing) force requirements? Is there something inherantly wrong with a beehive spring operating at high lift, or is it just the fear of a broken spring?

The PAC 1518 is "said" to be one of the best springs from a quality/durability standpoint (that's why I bought them) and is rated to .650 lift. I've had my eye on this cam for a few years now and when I broke a stock valve spring two years ago (and got lucky!) I wanted a spring that wouldn't need replacing if I put a high lift cam in.

Taken from Texas Speed's website regarding the PAC 1518:

"PAC Single Beehive Valve Springs Rated to .650" Lift

The PAC single valve springs will use your factory seats, seals, retainers, and locks! We recommend stepping up to a dual valve spring kit if you plan to run more than .650" lift. This is a great option for customers looking for the top of the line beehive valve spring!"

 

If it was my car I would sell the 1518s and go with the 1521's especially if your going with roller rockers. The 1518s are great springs but in my experience lack the pressure to keep the valves from floating with .640 lift and roller rockers. They will work great with the stock rockers however.

 

What's your feeling regarding the stock rockers with a .644" lift cam?

 

I don't think anyone can provide a specific answer to your question, we would all be guessing.

However, having said that you have a very light setup and I would try it. Beehives are used to lighten the valve train and the 1518's are a top spring, along with the PSI 1511ML's. Your valves are extremely light and frankly don't like high force springs (there have been issues over the years that I have seen from guys who went with high force doubles and the LS6 valves).

I think it will work. If you find you are losing control, simply switch to titanium retainers as that will buy you more RPM as right now the stock retainers are steel. If the steel work, keep them as they will last longer than titanium that wear much faster when street driven.

Another key component is the pushrods. 5/16" pushrods will flex. I found that above 6,200 RPM mine were flexing and when I went to 3/8 double taper the top of the curve lifted. You may want to consider the 11/32" Mantons if you do pushrods with the rockers since to correctly set up the rockers you may need to shim them, which will change the pushrod length requirement.

Finally, you must set up the Yella Terra rockers correctly, and that means not following LS1howto.com, which is wrong on installation.

 

I run YT's with a cam with more lift than you have but with PAC 1521's. I'm stable to 6800RPM but my setup is spot on. This is also with heavy 2.200 intake valves. Diligent setup is the secret to any valve train setup.

 

Vettenutts, first off, thanks for the information!

I figured this, but I wanted to be a bit specific to limit the amount of "opinions" I would get cluttering the thread.

This is what I am thinking, but obviously have no experience in this area hence the call for advice. Consider this advice well taken! Off the top of your head, do you know where I can get Ti retainers and how much weight they would save? In all my valve spring searching I don't remember seeing Ti retainers for sale for beehive springs?

If I ever go to aftermarket heads and heavier valves then I guess part of that arrangement would be double valve springs with higher rates.

Yes, I read your excellent write-up on your fancy DT pushrods! If 5/16" pushrods were flexing at 6200 RPM what does that say for the OEM pushrods?!? I've already ordered 5/16" Comp Hi Techs in 7.425" length to work with my stock rockers, I'm sure I will get by with them OK for now...

I was looking at the Mantons - they sound like a great way to go. If I go with the YT rockers maybe I'll step up to the 11/32" Mantons since my overall valvetrain weight will go up, and a stronger pushrod will help with control.

Pushrod mass will affect the weight of the valvetrain as well, though... even though mass added by the pushrod will only affect the valvetrain about 59% as much as mass added post-rocker (using 1.7 ratio rockers). The mass of the larger pushrod is also amplified by the added oil weight it will carry in it's larger diameter body... I guess with this it's only a matter of "try it out and see".

Heavier pushrods might be a good excuse to look into some lightweight retainers! $$$$$

Setting up the Tella Terras looks like a pretty straight-forward operation and definitely something I would do, especially if I'll need new pushrods anyways. Question - how do you check roller wipe with the heads on the car? The lifters wouldn't be pumped up? Can you use an adjustable length pushrod at engine idle to check?

When will the spending end?!?!?!?

 

Care to share the specs of your "little baby cam"?

Do you know what valves you're using (ie how much they weigh)? This could help me based on the known rockers and spring weights you're using.

 

Blue...

What do your valves weigh....thats a very important piece of the puzzle.

Sorry it took me a while to get back to you....have a zillion things on my plate right now!

Assuming they are around 95 grams you should be in good shape....alot depends on how aggressive the ramp of the cam is also....its not so much about the peak number as it is about how fast its launching it off the seat and how quickly its dropping it down.

Comp's new LSL lobes on paper are more aggressive (about .020 more peak lift) but the profile of the cam improves valve control over the older XER lobes.....lots of hours on the spintron to facilitate that happening.

Unfortunately I have no experience with the lobe profile you have but if you have really light valves (under 90 grams), and I suspect you might, that would be helpful in the event the lobes your running aren't very stable. Shooting from the hip....you should be OK assuming the valves you have are reasonably light and you dial in the rest of your valvetrain.

Did I mention a quality lifter is helpful as well as a very rigid pushrod.....LOL




-Tony

 

Pushrod mass is a good trade-off for pushrod stiffness as it has much less effect than components on the valve side. Also, don't forget you have a force muliplier on the pushrod side due to the rocker ratio for valve closure.

As for checking wipe, if you install check springs you can move the piston down the cylinder so the valves can be hand opened and then rotate the rockers through their lift by hand. If you refer to the write-up I did on the work bench, same process except with the head on the car.

Contact PAC and see if the Comp beehive retainers will work with their springs. Not sure if they do and fit is important (don't want it sloppy or a force fit). The steel retainers may still work.

 

Tony, according to these two links below (the second one shows the valves on a scale), the intake valves are 73-74g and the exhausts are 65-66g (I have OEM hollow valves, '02 LS6, stock never modified heads):

http://www.smokemup.com/tech/ls1.php
http://ls1tech.com/forums/generation...id-valves.html

Sorry for not posting this information, I could have easily posted this in my original thread!

Looks like the stock valves are extremely light - a good thing in my case! The intake has a little less lift compared to the exhaust (.631 vs. .644) so that should help with the heavier weight of the intake valve.

I just spoke with Comp Cams and LPE. Comp wouldn't divulge anything since it's a customer cam, and all LPE would tell me is that it's an LSK lobe specific to their design… not much help. According to the fellow I spoke to at LPE, the cam was designed back in the late days of the C5 (2001-4) on the LS1/6 if that tells you anything about what the lobe might be like.

Oh, don't worry about being busy - if you weren't busy building engines your advice wouldn't be as valuable!

Please tell me something I don't know and something that won't cost me more money!!!

On that note, what are your opinions of the OEM lifters? I installed a set of the new OEM LS7 lifters. If I go with the Yella Terra ULs I'll probably get a set of 11/32" pushrods to go with them, unless there's a better option for similar (or not too much more) $$$.

 

True, I just get caught up in thinking about mass problems and probably go overboard.

Right - thanks!

WOW - Comp sure doesn't give those retainers away! They cost almost as much as my springs did, and almost as much as the Patriot dual spring kit that comes with Ti retainers!!! Maybe I'll see if the OEM steel ones work first.

 

The XFI lobes from comp are designed to be run with a single spring as they have smoother open/closing ramp rates to better control the valve. FWIW I ran the 918 springs to 6800rpm on my sleeper cam(218/230 .605/.604 116) with heavy SS 2.02/1.57 valves.

 

This is good info - what rockers were you using? What retainers?

 

stock/steel...ran .581 XER lobes with Manley single springs, titanium retainers and stock ls1 valves spinning to 6800rpm as well for 30k miles

 

Dont like the LSK lobes....they were the worst as far as valve motion intensity goes....extremely fast ramp speeds. BUT....you have everything else in your favor with the lightweight parts.

I would go with a premium lifter though....it would have a better chance of handling the valve acceleration from those lobe designs and I would also consider an upgrade in pushrod stiffness (thicker wall....possible slight increase in diameter, etc.).

Look at the better Morel/Lunati lifters or the limited travel Comp units. PM me if you need more help or assistance.

-Tony