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53wanab and Gary’s04 have both talked recently about higher ratio rocker arms for our SSRs. After doing some preliminary research, I’m encouraged enough to both look further and to comment that valvetrain mods (NOT just rocker arms alone) might be a particularly good idea for owners of 03 and 04 SSRs (NOT 05s).

Let’s first clarify what we are talking about. Most people think only about the rockers arms, but in fact we should be looking at the entire valvetrain, for reasons that are explained below. Starting at the camshaft and working upward towards the valves:


Camshaft:

The purpose of the camshaft is to regulate when, how high, and for how long the valves are opened to admit or expel air. Our ¾ SSR’s LM4 “truck oriented” engine has VERY mild cam timing specs, compared to the “performance” Chevy engines in Corvettes and Camaros. Below, I list our SSr specs and then the performance engine specs in brackets for comparison). In general, more is better for all numbers:
Exhaust valve lift (after rocker arm multiplication): 0.466 inch (0.479 to 0.551)
Intake valve lift: 0.457 inch (0.467 to 0.555)
Duration for exhaust/intake: 190/191 (207 to 218 / 196 to 204)
Lobe separation angle: 114 (116 to 119.5)
Valve timing: 112 / 116 (113 to 117 / 115 to 122)

This means that our cams open the valves to a lower height than most, and keep them open for less time. Both of these attributes work against making maximum power. The reason GM did this is because trucks (not SSRs) are tuned for low and mid range torque versus high end horsepower. We would ideally like MORE lift and MORE duration, but changing cams has 2 downsides:
1. It is not easy given the underhood packaging in an SSR
2. Cams with more duration have lumpier idles that also kill emissions performance
Ideally, we’d like to “get more area under the lift curve” without changing cams, and rocker arms with higher ratios will do that for us (see rocker arms below).


Hydraulic lifters:

These connect the cam to the pushrods, and include a hydraulic reservoir system that provides the required reliable clearance in the valvetrain as the parts change temperature. The lifters in the SSR have one good feature: they ride on the camshaft using roller bearings instead of a friction surface. That is why GM refers to this as a “roller drivetrain”. (However, most people (including me) at first think that means that the rocker arms also have roller bearings where they ride the tops of the valve stems. That is NOT true)


Pushrods:

These are the physical connection between the lifters and the valve rocker arms. They need to be STIFF. If they deflect at high rpm, our valves don’t follow the intended opening and closing profile, and power suffers. Our stock rods are good, but better ones are available, and if you want to spin past 6000 rpm, a good idea.


Rocker arms:

These are the “levers” being pushed UP by the pushrods. They rotate about a fulcrum and push DOWN on the tops of the valve stems. The ratio of the two levers here establishes how HIGH the valves are lifted in comparison to how high the cam profile is at a specific point. Our SSRs are advertised as having a ratio of 1.7 This means that for each 0.001 inch that the cam profile lifts a lifter, the valve will be lifted 1.7 times that much, or 0.0017 inch. In actual fact, the geometry of the rocker arm changes as it rotates, so that we actually only get about 1.54 multiplication for most of the cycle, and PEAK at 1.7 very briefly. The obvious question is why not increase the ratio for more lift? On the higher performance engines, you don’t need to. The 1.7 ratio on those engines (GM likes 1.7 currently) lifts the valves high enough to make good power and not enough to hit the pistons, because the cam profile is higher than ours! But, on our low lift LM4s, this IS a good question. Rocker arms up to 1.8 nominal ratio are available, and some of those have variable geometry that actually delivers up to 1.89 ratio when it is safe to do so (NOT when the valve is at peak lift and near the piston head!).

Remember up above we said that we would ideally like more “area under the lift curve”. Well, it turns out that PROPERLY designed higher ratio rocker arms WILL give us more area under the curve, because they lift the valves higher everywhere in the lift cycle. The other good thing is that they do NOT increase duration, so idle and idle emissions do not suffer.

There is more. Remember above I said that only the lifters on our LM4s have roller bearings? Aftermarket rocker arms are available that have one or BOTH of the following features:
1. Rollers at the tips where they ride on the valve stems
2. Roller bearings at the fulcrum where they rotate in response to pushrod actuation
Getting one, or better, BOTH, of these features is a big plus on reducing friction at high rpm, because friction is lost power AND more generated heat (wonder why the tips of factory rockers look discolored?)


Valve springs:

The cam causes the valves to LIFT, but does nothing to bring them BACK down! The valve springs bring them back down. The valve springs in our LM4s are fine at “truck” rpms, and will even work fine up to 6500 rpm or so before they “lose control” of the valves. That loss of control is referred to as “valve float” and it has two really bad results:
1. You lose power (because the valves aren’t where they are supposed to be!)
2. Over time, and sometimes immediately, valve float weakens the valve springs so that they no longer work even to rpm they formerly worked fine at.
Stronger springs would be a really good idea if you want to spin past 6000 rpm, and since that is the easiest and least costly way to make more power, you will some day be shopping for stronger and better springs.


Retainers:

Retainers are the small devices that keep the highly compressed valve spring from flying off the valve stem. They seem low tech but are NOT. The lighter you can make them, the faster you can spin your engine before you get that destructive valve float. At 6000 to 6500 rpm, the inertia loads of even small parts are so high as to create tremendous loads for the valve srpings. Hence, the current fascination with lightweight titanium retainers. They are a good idea!


Keepers:

These are the tiny parts that “keep” the retainers in place on the valve stems. Again, less weight is VERY helpful. Again, titanium is a really good idea.


Valve Seats:

These not only hold the valves in place, but they also provide the bearing surface for the valve springs to ride on. If you spin the engine faster, you need more valve spring pressure to avoid valve float, and that extra spring pressure bears on the valve seat which bears onto soft ALUMINUM in an aluminum head (like on our SSRs). Therefore, if you increase valve spring pressure, you want beefier valve seats that are not distorted by the extra pressure. If they distort, they threaten not only the aluminum bearing surface under them, but also the valve stem.


Valve Seals:

These are what seals the valve stem so that oil does not leak down into the combustion chamber. The only reason I mention them is that on current GM engines, the valve seats and the valve seals are combined into ONE part. So, if you want stronger valve seats, you need to buy the SEPARATE valve SEALS used in previous GM engines.


Pushrod guides:

If you change to stiffer pushrods, you MAY need pushrod guides that help keep the stronger pushrods aligned so that they don’t improperly WEAR other adjacent softer parts on the rocker arm.


One other thing. Valvetrain noise is very bad. Not because it interferes with your stereo system, but because it can falsely set off the knock detectors on your engine, which are unfortunately located VERY close to the valvetrain. If your valvetrain makes enough noise to set off the knock detectors, your protective PCM will assume you are suffering detonation and will aggressively retard your engine’s timing, thus KILLING your power output. Stronger springs and roller bearings tend to make more noise than stock parts. You need to make sure you buy high quality parts that have specifically targeted noise reduction in order to avoid this false triggering of knock detectors.

So, there’s your complete valvetrain.

To review what we might want to do:
1. Increase the area under the valve lift curve by changing to higher ratio rocker arms
2. Spin the engine faster (easiest way to make more power)
3. Increase the spring pressure to avoid valve float at higher rpm
4. Protect the valvetrain against the higher spring pressure
5. Lighten EVERYTHING that reciprocates at high rpm
6. Stiffen the pushrods
7. Add roller bearings wherever we can to replace frictional surfaces

It turns out that you can buy a variety of valvetrain kits from companies like Crane and SLP. You want as many of the following features as your budget can stand:

1. Variable ratio rocker arms that hit high ratios (like up to 1.89 or so) at SAFE points in the lift cycle as these can maximize the area under the lift curve
2. Roller bearings at the tips of the rocker arms
3. Roller bearings at the fulcrums of the rocker arms
4. Titanium keepers
5. Titanium retainers
6. Valve springs that are as LIGHT as possible but HIGH enough in pressure to prevent valve float reliably at even 6500 rpm, but not so high as to unduly stress the entire valvetrain
7. Sturdy valve seats to protect the aluminum heads without distorting
8. Possibly separate valve seals if you do need stronger valve SEATS
9. Stiffer pushrods
10. MAYBE pushrod guides
11. QUIET high quality parts that won’t falsely set off the knock detectors

Easy huh?

Oh, one more thing. A COMPLETE kit (encompassing all or most of the 11 features listed above) will cost about $700 to $800 just for the parts.

Then, you also need two more “tools” that you need to buy or borrow:

1. A valve spring compressor that works by bolting onto the head for each valve position, and allowing you to SAFELY compress each spring using a wrench, until the keeper and retainer can both be removed

2. An air tool that threads into the sparkplug hole, that keeps the cylinder pressurized while you have the valve spring and retainer off, so that the valve does not fall into your engine!

Why go through all this complexity and expense?

On most “performance” engines, doing all the above will get you only a few horsepower – maybe 5 or so. However, on our “truck” engines, with their extremely mild timing, this combination of mods is likely to get you much more than that.

In fact, while I have not yet fully analyzed the Crane 1.8 rocker arm article in the August edition of “Chevy High Performance” that 53Wanab quoted in one of my threads, and I already DO know it has a couple of flaws, I am nevertheless persuaded that it MAY be very close to reality for our SSRs. That particular article shows dyno results that exceed 20 hp gains at many points in the rpm band – especially at the higher rpms, and they stopped their dyno runs at only 6000 rpm, presumably because their spoilsport Silverado PCM shut down the festivities there.

A good mechanic could probably do this job in 4 hours or so, maybe up to 8 hours if he is dedicated to getting the BEST (and QUIETEST) settings for the hydraulic lifters (requires waiting for bleeddown for 30 minutes or so several times in an iterative manner). That still makes this a good “bang for the buck” mod, because regardless of what the aftermarket peddlers try to imply, there are no magical “20 to 30 hp” gains for under $1500. (As I’ve said before, selling high performance work is similar to selling crack cocaine to an unquestioning market. . . )

I am at least convinced enough to do more research myself.

And, I will analyze that Chevy High Performance article in a future posting.

Finally, notice that I said "not 05 SSRs". This is because those engines ALREADY have their valve lift pretty much maxxed out (to SAFE limits). If you put in higher ratio rockers, you might hit the valves! So, you guys with 05s are again shut out of this one I'm afraid. Then again, you already HAVE 90 more hp than the 03s and 04s do.

Jim G
 

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valve train

good shootin Jim,

I can attest to the higher HP results. I used the Comp Cams 1:85 roller rockers.They are very similar to the stock slp design. They are made from a steel alloy that is light yet strong and have a lighter moving mass that the Crane billet aluminium units.
These also come with hardened screw-in studs and push rod guides.The push rods are sold separately and are a must!The push rod guides will eat up the soft stock ones.The tech. at Comp cams said that the springs are good to go since they are of the bee hive design and are new.Pressures are good.Comp Cams also boasts of quieter than stock operation.They also advertise"no valvecover mods neccessary".
I admit,I may have goofed here but I found it neccessary to remove a portion of the windage trays in the front portion of each cover to clear the camlock adjuster bolts, and grind a portion of the casting web as well.Once these mods. were made, no problem sealing the covers.
The reason I say I may have goofed, is that the valves were not properly adjusted before I made the decision to mod the covers.
Thes lifters don't bleed down like we are used to, and the fireing order is completely different than previous small block Chevys.This led to a lengthy adjustment process.I wound up putting in a spark plug in the cylinder I was adjusting,then rotating to low intake cam,1/8 turn on adjuster,rotate to low exhaust cam, 1/8 turn on adjuster, then spin motor to check compression and on to the next cylinder.
These motors are different ducks. You can't just preload 3/4 turn like the old Chevys.Once I figured out what she wanted, it was much easier to handle and what a difference in the throttle speed.
 

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Clarifications

A couple of items to clarify..
First, as to pushrods. One item to be sure of if you chose to run guideplate is that the pushrod MUST be heat treated so they won't wear through and break. Not a fun problem not to mention all of the metal shavings in your egine now.

Number two - the reference to valve seats is not quite accurate. Valve seats are the hardened steel (or sometimes other materials such as beyllium copper) lands in the head installed with an interference fit where the valve head resides when the valve is closed (inside the combution chamber). The valve guide is also a press fit into the head and this is around the stem of the valve. The "top" end of the guide is where the valve seals are installed (if used). The spring seat is where the valve spring makes contact with the head and on an aluminum head the spring requires a steel shim underneath it so it will not eat into the head. The shim needs to be of a size that will not allow the outer of inner spring (usually called a dampener) to contact the head.

Aside from that, a good presentation of what can be done.
Thanks Jim :)
 

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Discussion Starter #4
hdflstf: You are aboslutely correct on both counts.

I should have said "spring seats" rather than "valve seats" to avoid the otherwise inevtiable confusion with the valve seats that the valve head itself seats on when closed.

And I entirely forgot to talk about the need for the pushrods and the pushrod guideplates to be matched to each other if gudieplates are used. I believe you even covered that in an earlier post on the board some time back when 53wanab first discussed this mod.

I'm reading that Chevy High Performance article. Very interesting, and very good, despite a few flaws.

Jim G
 

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Gentlemen,

May I compliment all of you on an excellent presentation. This has to be the most in depth perspective on the options available as well as the potential result as I have seen anywhere. What a team:thumbs

If you guys decide to go into the brokerage industry, I will immediately move my accounts into your more than capable hands ;)

Thanks for the information!

My Best,

Rob
 

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JimGnitecki said:
hdflstf: You are aboslutely correct on both counts.

I should have said "spring seats" rather than "valve seats" to avoid the otherwise inevtiable confusion with the valve seats that the valve head itself seats on when closed.

And I entirely forgot to talk about the need for the pushrods and the pushrod guideplates to be matched to each other if gudieplates are used. I believe you even covered that in an earlier post on the board some time back when 53wanab first discussed this mod.

I'm reading that Chevy High Performance article. Very interesting, and very good, despite a few flaws.

Jim G
Jim G. when the " Fanatics " read the article, keep in mind that this is for LM7 truck but the article covers everything you could run into on the LM4 in the SSR, except for space for accessing the engine. ( NOTE: Maybe I should lose some weight!) I have also contacted " BE COOL" Radiators concerning a retrofit including fan/fans for the SSR. They will get back to me.
 

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Jim G. --- There is also an article on OBD-ll Powertrain Control Module and how to program it that you and the other "Fanatics" might be interested in reading.
 

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raveschi said:
Gentlemen,

May I compliment all of you on an excellent presentation. This has to be the most in depth perspective on the options available as well as the potential result as I have seen anywhere. What a team:thumbs

If you guys decide to go into the brokerage industry, I will immediately move my accounts into your more than capable hands ;)

Thanks for the information!

My Best,

Rob
Hmmm
I'm thinking hedge fund - Jim??
 

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hdflstf said:
Hmmm
I'm thinking hedge fund - Jim??
I would buy anything that a HD Fat Boy owner would consider a sound investment :lol

Of course I am a bit prejudice :)

My Best,

Rob
 

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Discussion Starter #12
The LM7 and our LM4 have IDENTICAL valvetrain specificastions, as well as sharing most other parts and ratimgs. The only key difference is that our engines are all aluminum, whereas the LM7 has a cast iron block.

This article is VERY relevant to us, but as stated earlier, there are a few flaws, and I need time to examine what they did thoroughly before I comment on it in wiritng. This article is now backlogged behind another new SSR Board "first" I am planning.

The other article on OBD2 tuning is also first rate in the way it simplifies explaining what you should do. However, it fails to address the biggest issue: how to find and modulate the torque management, absue management, and electornic throttle filtering settings that act like an overly eager Big Brother on our SSRs and symie (temporarily) our efforts to hotrod our rides.

Jim G
 

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JimG: YOu should look into a career in writing for an auto performance mag. I would think they would hire you in a heartbeat! :thumbs
 

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I agree!

cruzned said:
JimG: YOu should look into a career in writing for an auto performance mag. I would think they would hire you in a heartbeat! :thumbs
is this a good next step toward a magnacharger :confused
what about the intake manifold, is it up to snuff :flag
 

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Discussion Starter #16
mikepowell: This is, I think, a fantastic 1st step on the path to a supercharger for the following reason:

With a supercharger, you do NOT want more valve timing overlap, since that encourages inversion (incoming mixture blown back into intake manifold by still present exhaust gases).

Making the valvetrain changes above INSTEAD of buying a "blower cam" makes sense because you get more area under the curve without adding valve timing overlap.

The blower will make good use of that larger area under the curve!

Just remember: once you have gone to higher ratio rockers, do NOT ever install a CAM with more LIFT, or you'll either run the valves into the pistons OR exceed the ability of the valve springs to control the valves and get valve float and then parts breakage.

Jim G
 
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High ratio rockers

Yep,
The 1.85 ratio will definitely make a bit more power. HOWEVER, with that small of a cam, the gains will be marginally effective, I beleive. For comparison sake, we frequently use cams with nearly .600 lift and around 230 degrees duration in bone stock Corvettes(dyno tuned and programmed, of course) with tremendous gains in hp and tq.

I am confident that huge gains can be had for the SSR with only a camshaft and the associated kit (springs, retainers, locks, seals, pushrods, etc.). But that comes at a much greater cost, of course.

With only a ratio change from 1.70 to 1.85 multiplication you are still only talkin' .500 lift and no increase in duration from the stock camshaft.

Remember, with respect to duration, increasing the rocker ratio only increases the area under the lift curve... NOT the actual timing of the event.

I would love to conduct the rocker arm test on your truck (Jim) if you were in town and report the resuts to the forum. But with you in Texas now, that will be difficult.

We at MTI Racing, would be interested in others in the Atlanta area that would like to do this upgrade at a reduced cost for the sake of reporting the results to the Forum.

Don't get me wrong, the rocker ratio increase will defintitely help power... but by how much and is it cost effective... that is the question. RC
 

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MTI Racing said:
Yep,
The 1.85 ratio will definitely make a bit more power. HOWEVER, with that small of a cam, the gains will be marginally effective, I beleive. For comparison sake, we frequently use cams with nearly .600 lift and around 230 degrees duration in bone stock Corvettes(dyno tuned and programmed, of course) with tremendous gains in hp and tq.

I am confident that huge gains can be had for the SSR with only a camshaft and the associated kit (springs, retainers, locks, seals, pushrods, etc.). But that comes at a much greater cost, of course.

With only a ratio change from 1.70 to 1.85 multiplication you are still only talkin' .500 lift and no increase in duration from the stock camshaft.

Remember, with respect to duration, increasing the rocker ratio only increases the area under the lift curve... NOT the actual timing of the event.

I would love to conduct the rocker arm test on your truck (Jim) if you were in town and report the resuts to the forum. But with you in Texas now, that will be difficult.

We at MTI Racing, would be interested in others in the Atlanta area that would like to do this upgrade at a reduced cost for the sake of reporting the results to the Forum.

Don't get me wrong, the rocker ratio increase will defintitely help power... but by how much and is it cost effective... that is the question. RC
What do you estimate the "reduced cost" to run? Not going to hold you to it, just wondering.
 

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Discussion Starter #19
The article in the August issue of "Chevy High Performance" did this very mod to a Silverado with an engine that is IDENTICAL to ours EXCEPT that its block is oiron while ours is aluminum. They reported a 20 hp gain, which is MUCH larger than the more typical 5 to 8 hp I would expect.

There were some flaws in their test. First, they did not test under identical conditions each time. It was cooler when they tested using the new rockers, so some of the gain was surely due to the lower ambient temperature. Plus, they stopped too erly in the rpm range, probably because they left the stock rev limiter unchanged, and it signs off way too early. Then, they also should have tried titanium retainers and keepers, since there is zero added labor to do so, and not that great an additional parts cost.

But, on the other hand, they got these great results without even retuning on the dyno after the swap, as they have other mods planned and did not want to waste the money on a premature dyno tune.

I wrote to Reese suggesting that the reason they got so much gain is that this engine happens to be the "perfect storm" combination. For reasons of corporate standardization and cost reduction, Chevy basically took an "older" performance car engine (the EARLY version of the LS series) and made it suitable for TRUCK use by putting in a "torque" cam (narrower timing) with low lift as well (you don't NEED the higher lift when you sign off at 5600 rpm!). By doing the higher rstio rockers, you are increasing the area under the curve to PARTIALLY compensate for that cam detuning. Of course, as Reese says, an actual cam swap is even more effective, BUT this is simpler and cheaper to do, and maybe a good base for a future supercharger (where more cam overlap is bad because of the reversion problem).

Just a thought. Feedback?

Jim G
 

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great discussion about benefits of rocker ratio and cam profiles- have the crane kit setting
on my work bench and dynatech shipped my headers and cat system friday(will have headers jet coated) will install these two items as soon as headers are coated and will give my "seat of the pants" reaction. have already done many of the same mods many have done- g force
springs,b&m deep sump trans pan,updated rotors and ceramic brake pads, select transmission springs and pistons from 2004 gto(firmer shift quality) but i've really had some
internal debate with myself about what am i really going to do to produce some serious horsepower changes. most everyone has installed the magnason supercharger and been pleased with the results and that was my first reaction and i may take that course but i've also looked at the z06 5.7 engine option( 405 hp/400 ft torque) knock sensors and cam sensors are in the correct locations-better heads/cam and higher compression-factory long block(engine minus intake) for less than supercharger- install it would look stock and carry gm warranty and the additional mods(headers/rockers) should produce number similar to supercharging and i could still supercharge later. plan on doing one or the other very soon.
maybe someone has already done the but would be interested in other opinion-thanks
john
 
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