Has anyone installed 1.85-1 roller rockers? I understand they have been made for all the Gen III engines now and are an excellent way to increase horsepower. What do you think? :reddevil :reddevil :reddevil
Craig here. I installed the comp cams 1:85 roller rockers about six months ago and I love them.There is a definate difference in the torque and throttle response.
I have to tell you though,I think that I didn't set the propper lifter preload and am getting valve float @ 6000 rpm.Here's the deal.
Ibought these from comp cams and at the time, the tech. told me that the stock springs (since the motor was new)would be fine. Man, I had a bitch of a time adjusting the valves.I had a hard time with the lifters not bleeding down and when I went for my 1/2 turn, the lifter would open the valve.Finally,I wound up at 1/8 turn and found good compression.Now, Iv'e talked to the techs and they sugessted that I should have installed the stronger 26918-16 beehive springs and that they couldn't understand why I was told otherwise before.(common sense told me I should have ). Anyway, I now have the springs and as soon as my chrome valve covers are ready, I'll be doing the new install.
I'll let you know how it goes this time around.
Kens's SSR: The higher ratio rocker arms are an effective mod for 03 / 04 SSRs, (But NOT for 05 / 06 SSRs!!), but you need to be informed about certain qualifiers.
They basically "increase the total area under the curve for valve lift". Because the 03 / 04 cam is so mild and starts starving the engine of intake air as low as 4000 rpm (see the torque curve above 4000 rpm no thse to see what I mean), that increase in "induction area" is particularly effective. You MIGHT see as high as 18 to even 20 more peak hp with this mod on the LM4 engine, and good midrange kick too (I base that number on a recent magazine report that had some defects in the way it did its before and after comparison, but they were basically on the right track).
This DOES require not only much better springs than the ones that come stock on the LM4, but also better pushrods, valve sprin retainers, etc. The entire collection of QUALITY parts will likely cost about $800 and the labor will run 4 to 8 hours depending on how conscientious and meticulous the installer is (you wantt ot pay for a VERY metticulous one!).
While 20 hp does not "sound" very exotic, if this is the ONLY mod you are planning for a while, it is great bang for the buck, as it delivers much, much more than a catback system alone, or exhaust headers alone.
However, it is money "wasted" if you ever change the cam, as a cam with good lift couped with these higher ratio rockers will put the valves into the pistons, which is why you can't do this with 05 / 06 SSRs that HAVE the higher lift cam already. So, you want to decide before doing it whether or not you ever intend to do a cam. The cam is MUCH more costly, as it requires removing a lot of parts and unbolting the engine entrely to successfully install it without removing the engine from the vehicle.
All this and much more detail on the valvetrain is included in my book.
2. The 05 / 06 SSRs with the LS2 engine don't NEED the high ratio rockers, as they already have a high lift camshaf compared to the LM4
3. COMBINING higher ratio rockers with an already high lift cam can lead to either the valves contacting the pistons via either valve float or pure mechanical contact, or other parts of the valvetrain being overstressed and failing. The higher ratio rockers appear to be safe on the LM4 because it has such low peak lift and conservative ramping, and I've seen two successful examples, but I would NOT do this on an LS2 engine unless someone much smarter and more experienced than me tells you he has actually done it, that it was not destructive, and that it actually yielded favorable results being applied to an already good cam.
4. LM4 engines that have been modified with a higher lift and more aggressive ramped cam should also not have this mod done, for the same reasons as in 3. above. (an LM4 with a good cam becomes remarkably similar to an LS2)
1hot12c: Scott, you know that I am not exactly timid about engine mods. My LM4 is pretty strong now (0 to 60 in mid 5s even with a soft start).
Following your understandable reasoning, since I have a cam very similar to that in the LS2 (maybe a tad more agressive on timing, but NOT on lift), I "should" have installed those 1.85 rockers to get that "extra" power, especially since I had the entire valvetrain apart to put the new Z06 cam in anyway.
Notice that I did not, and that MTI Racing did not even suggest it, which tells you where my thinking is at on doing high ratio rockers to engines with already hot cams. And, show me even one project by a reputable shop or magazine that has applied higher ratio rockers to a Z06 cam equipped Gen III vehicle.
In my thinking, high ratio rockers are a very cost effective alternative to a new cam, for engines that have a cam that is on the mild side, IF you would otherwise have to pull the engine to do a cam change, or do everything short of actually pulling it. A higher ratio rocker valvetrain costs less than a cam change under those circumstances, and delivers SOME of the benefits of a cam change (in the case of the LM4, about 20/33 or 60% of the peak power impact).
Even then, you need to swap out most of the valvetrain components in order to reliably handle the higher stresses introduced. This is why I say the TRUE cost of parts for a higher ratio rocker change is about $800.
I have heard manufacturers claim that they can limit the increase in peak lift, and the peak stresses, while increasing area under the curve, but why increase the area under the curve via this less than optimal way when you know what you really need is simply a cam that is more aggressive on DURATION, not lift? Such a cam may challenge idle quality, and low rpm and emissions performance, but can be properly and safely engineered to ensure that the peak acceleration and inertia loads on ALL parts of the valvetrain are reasonable. Trying to do that engineering via rocker arm geometry alone is far from ideal, since you are concentrating the higher stresses in a smaller portion of the entire valvetrain than when you use a more agressive cam.
And, all the installs I have seen with accurately done before and after dyno runs, show that the gains with more aggressively cammed engines are MUCH smaller anyway. Like 5 to 6 hp. Sometimes, no gain or even a loss, when the installed cam was well engineered to begin with.
High ratio rockers arms are a substititute technique best suited for specific situations, that's all, and can subject the valvetrain to stresses much higher than it was designed for. Though some may disagree with me (especially the folks selling the high ratio rocker kits), I stand by my statement.
Jim I see you have changed out your cam setup to the z06. How much more expensive a mod is this to do. What parts are needed? Let me know as I want to complete one of the two mods. I have currently changed out my intake, have Dynatech headers, and the Corsa cat-back system. (Wanted true dual, but MTI isnt selling those kits and I don't know anyone in my area to put one together for me) I also will be receiving my custom tune from Lyndon Wester on Tuesday!! :reddevil :reddevil :reddevil
Ken'sSSR: The cam swap, parts and labor at a reputable shop, is goinng to run about $3000 or even more, so more than double the cost of the rocker arm based approach.
The details are too lengthy for a thread, but I have included all the required data for a knowledgeable installer in my book, Chapter 16 (coming about 2 1/2 weeks from now).
Don't dispair on the exhaust stuff. At some point, you will probably find yourself somewhere where there IS a good exhaust shop, and you can get them to convert you over to a true dual.
I would alsoo point out that fro folks not a million miles from MTI in Atlanta, it can make sense to go there if you are planning work beyond only the true dual exhaust. I pay close attention to who I let work on my vehicles, and will travel to get work done by people I know. That's why I returned to MTI in August for the cam, timing chain, and underdrive pulley work, plus of course, re-dyno tuning.
1hot12c: What I was woried about when I made that statement about not putting the rockers into an LS2 was loss of control of the valves at high rpm, and the effects of long term stress when using the higher ratio rockers to further radicalize an already hot cam. The LS2 spins up to 6500 rpm! I hate it when someone comes to me and says "you said (or implied) I could do this and it would be no problem".
The part that particularly scares me is that valve springs for example will handle an over-stress for a while, (like during an initial dyno pull after the install) but then begin to allow float after visitng those revs a certain number of times. Once you float at 6500 rpm, bad things can happen pretty quickly, and unplanned inertia loads appear. It is inertia loads that cause failure in modern engines.
I am not surprised that several different combinations apaprently led to similar results. Usuall, that means that there is a "cork" somewhere in the system other than the components being swapped, so as long as any specific combination of components exceeds the flow capability of that cork, ANY combination will be fine - until you find the cork and pop it out, at which point the individual combinations get a chance to strut their effectiveness.
This is precisely what happened on my LM4. The initial dyno tune, less the artificial loss due to stiffer gearing (inertia effect - see earlier psotings or my book) gave me 8 to 18 hp depending on which dyno run you believed. The headers were good for mid range, and so was the dual exhaust, but since the cam was stifling the engine above 4000 rpm, we picked up only 20 hp at peak. Once we popped the cork (the cam in my case), we picked up 58 more horsepower instantly. Since that cam is normally only good for 32 to 33 hp at rear wheels when done alone, we proved the cam was the cork.
The Z06 cam grind and Z06 valvetrain in my LM4 is the same one I ran on my factory stock 2002 Z06, and so I knew it was dependable before trying it on the LM4. My SSR is NOT my weekend / good weather toy: it is my ONLY transportation (my wife drives our Mazda Tribute SUV daily). My choice of mods and components therefore reflects a strange combination of 38 years of aggressive hop-ups coupled with the knowledge that going just a bit too far can leave me stranded halfway across the country on the way to a consulting assignment, and having to explain to my wife why the blown up engine is not covered under Chevy warranty.
In this specific case of my SSR, I knew I was duplicating my Z06 except with inferior heads and very slightly inferior manifold, but better exhaust (headers AND true dual), plus I had read Will Handzel's book, so I knew I was on safe ground. As it turns out, the 5.3 liter displacement and this particular set of mods is one of those “magical combinations” that performs better than it “should”. At 6000 rpm and above, the gains in horsepower over stock exceeded 100, and at 6500 rpm, the gain was 123 horsepower. If you know how correction factors "work", getting 331 hp at the rear wheels is a miracle when the temperature is 95 degrees, the humidity is so high it is RAINING, and the barometric pressure is the lowest I had ever dynoed at.
I haven't yet looked at that link you posted, but will do so tonight! I am always looking for more knowledge! And, I like it when it is someone ELSE's money and engine finding that knowledge!!
Another nugget from the above magazine article that I'd forgotten: the older LS6 intake manifold with 76 mm throttle body performed better in this test article than the newer LS2 manifold with 90mm throttle body, generating 8 hp more and 16 more ft lb torque. The article advises owners of the newer manifold to try to trade with owners of the older one who might not have yet read the article, and who might incorrectly assume bigger is better.
Bigger is not always better, unless the bigger is really required because it happens to be the current "cork".
It has been said since the release of the LS2 that the intake flows about the same as the LS6 intake. Now keep in mind that the SSR has the raised runner LS2 intake (tests were done with with car intake) which should produce more torque then the LS6 intake. The LS2 intake compared to the stock intake on a 03-04 5.3 SSR should be a considerable difference, like going from a truck 5.3 intake to an LS6. The only way to find out will be to do some side by side testing of these intakes on the SSR. My SSR is stock trim put down the same HP/TQ as the GTO and C6 Vette. The debate is still open on this!
Ken's SSR: Sorry, in all the interesting sidelightd, I did not answer your primary question: how long would a reputable shop take for the mods?
For the dual exhaust: one day if arranged in advance
For the higher ratio rockers: One day, but more if the installer wants to be very meticulous with the adjustments, as the engine will need to be cooled in between.
For the cam install (in which I should have emntioned I inlcuded the cost of both timing chain and underdrive pulley mods, since you have done much of the work to do them in smply getting at the camshaft): Mine took MTI Racing 3 days during which it was a focus of attention, but other work also had to be done on other vehicles. Now mine was their first SSR, and so they had to work out solutions to some new situations they had not encountered on C5s and C6s. Still, the cam is a major deal because of what nees to be done to get it OUT of the engine while still in the SSR! And, of course, plan on dyno time to retune to the new cam. MTI finished my SSR at 9:45 pm on the 3rd day.
MTI has since added another technical wizard to the team.
2005SSR6speed: I had not taken the time to notice this before, until you printed your peak torque as part of your signature above, but your torque peak, though MUCH larger than before, now occurs at a lower rpm (3750) than when your engine was stock. This suggests a cork somewhere in the overall system. If you can accurately locate it and replace the substandard component, you'd probably pick up a lot more power yet!
Are you running stock exhaust manifolds and stock catback system? If so, that's a good place to look, except if you are in California (which I recall now you are), you can't touch those stock headers. But, I think the catback is ok to change to a dual even in California, but you should of course check.
(For those who don't know it, California prohibits replacing ANY components, even if they actually don't increase emissions, unless the replacement parts are CARB certified, and currently no headers are CARB certified for the SSR. Howver, most jurisdictions, even CA I think, allow catback mods, as the theory is that the emissions-affecting devices are the CATS and everything BEFORE them)
JimGnitecki - Very good eye. Mine is going in for a custom exhaust right after Sema is over. I am planning a complete dual system from the exhaust manifolds back with free flowing cats, x-pipe and dual chambered mufflers. I am looking at the stock exhaust manifolds off the new LS7 but might just use the stock LS2 exhaust manifolds due to clearance issues. Either way I will be useing a complete dual 3" system all the way back. I should see some considerable gains from the exhaust side.
On a side note, I will be starting a complete Forged LS2 402 longblock buildup after the begining of the year so stay tuned. I want to put a shot of nitrous on top of the supercharger for a streetable 600 RWHP.