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WARNING LS3 Recall about to happen

immortality

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Stock rockers are cheap cast numbers that barely fit the engineering bill in performance terms. Same as the springs (they are at the operational limit even with the hollow intake). Question marks hang over long term reliability of stock spring / valve / rocker combo, particularly under heavy duty or upgraded operational range / output.
Yes, fully encased bearings and shaft mounts are superior to the weak cageless dangerous stock rockers, and the reduced friction at various loads (power and economy) is measurably better with the more advanced geometry.
Consider the benefit of more volumetric flow upgrading to 1.8rr modifying your effective cam timing without spending a few thousand. Any prospective new cam beyond that can utilise the 1.8rr geometry per LS7 and Gen V and mine to result in less cam face / lifter roller wear.
On the other hand there is zero advantage in sticking with 1.7rr apart from fitting three bolt older cam designs; no advantage sticking with springs at their limit, and lighter stronger pushrods help to deliver more control, particularly over stock peak (5700). I definitely would not be revving an LS3 with stock upper valve train near the factory rev limiter!
You need to remember that GM have peak efficiency and a warranty period in mind when they design engines. Springs only have to be strong enough to control the stock valve train at stock engine speeds and last long enough to get through the warranty period. Any extra weight in the spring just reduces efficiency and fuel mileage. 90% of OEM engines will hardly ever go past 3000rpm in their daily commuter lives which a stock spring will handle just fine for many thousands of miles beyond the warranty period.

BTW, I do like PAC springs and high ratio rockers. Not many mild cams make full use of a stock or mildly ported heads. Even if you get slightly more lift than the peak flow point, as long as the flow doesn't become turbulent you will still make more power because you have more average lift which means more average flow (the all important area under the curve thing).
 

monstar

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You need to remember that GM have peak efficiency and a warranty period in mind when they design engines. Springs only have to be strong enough to control the stock valve train at stock engine speeds and last long enough to get through the warranty period. Any extra weight in the spring just reduces efficiency and fuel mileage. 90% of OEM engines will hardly ever go past 3000rpm in their daily commuter lives which a stock spring will handle just fine for many thousands of miles beyond the warranty period.

BTW, I do like PAC springs and high ratio rockers. Not many mild cams make full use of a stock or mildly ported heads. Even if you get slightly more lift than the peak flow point, as long as the flow doesn't become turbulent you will still make more power because you have more average lift which means more average flow (the all important area under the curve thing).
Yes not many people realise the recommended intake valve lift to prevent choke on LS3 at 5700 is 0.534" FINE with 1.7rr. However recommended exhaust valve lift to prevent choke is 0.535" FAIL with 1.7rr. Of course this lift requirement anomaly compounds with RPM like so:
Code:
RPM    INT        EXH
5800   0.543"   0.544"
5900   0.553"   0.553"
6000   0.562"   0.563"
6100   0.572"   0.572"
6200   0.581"   0.582"
6300   0.590"   0.591"
6400   0.600"   0.600"
6500   0.609"   0.610"
6600   0.618"   0.619"
I know you see what I'm saying but for the benefit of others who see this like a Matrix intro screen, there's a diminishing point where revving your LS3 with stock rockers will choke the engine's potential. Revving it past that point without adding lift is not so productive.
In other words intake starts to choke with 1.7rr around 5850, exhaust starts to choke at 5600.
 

07GTS

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there's a diminishing point where revving your LS3 with stock rockers will choke the engine's potential. Revving it past that point without adding lift is not so productive.
In other words intake starts to choke with 1.7rr around 5850, exhaust starts to choke at 5600.
noticed that on my stock LS2 its limiter is 6600 but soon as u went past 6k u could feel that it wasnt pulling any more just reving so i always changed at 6k
 

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I should add the calculated power output at the RPM given proper lift is met and VE tuned to 98.5% (so yeah theoretical but close):
Code:
RPM    INT      EXH       BHP  RWKW
5700   0.534"   0.535"    414   244
5800   0.543"   0.544"    424   249
5900   0.553"   0.553"    433   254
6000   0.562"   0.563"    442   260
6100   0.572"   0.572"    451   265
6200   0.581"   0.582"    461   270
6300   0.590"   0.591"    470   276
6400   0.600"   0.600"    480   282
6500   0.609"   0.610"    490   287
6600   0.618"   0.619"    500   293
 

07GTS

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this is mine with the trinion upgrade, also regular oil changes keep the insides nice and clean ;)

 

dazinau

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This is what I settled on, there are other combos for sure.
Rockers
Yella Terra (Whipple) ~$950
Sold overseas under many brand arrangements, Aussie Yella Terra is at the top of its game.
Stock rocker ratio geometry 1.7:1 is what most cams up to Gen IV (except the LS7) have used. Yella Terra PN YT6667.
LS7, Gen V and later engines use 1.8:1 to eliminate the inevitable cam face / lifter roller wear of LS builds, an alternative to achieve >0.550" lift with control and lower friction vs previously small base circle and aggressive cam lobe ramp. Yella Terra PN YT6668.
I kept AFM with revised lifters from the Gen V, so the base circle of the AFM cam is larger than most Gen IV, meaning lobe lift is just 0.300". So with AFM cams the standard 1.7:1 rockers (0.300" x 1.7) give 0.510" lift at valve, OK from an old school standpoint but not ideal for performance. 1.8 gives 0.540", and 1.85:1 (actually 1.865) gives 0.556" lift (bit more than LS3) with the later AFM cams. Yella Terra PN 6685.
There is a bit to explain the other main benefit - being increased cam size - per the time/area duration of the valve opening. Suffice it to say the start and end points of the opening (time) are of course the same duration but increased acceleration and extent of the valve opening (area) is increased which affects the effective time/area duration like an extra one degree duration per 0.5 increase in ratio.
So with 1.8rr Stock LS3 cam spec effectively becomes 206/213 117.5-2.5 LSA 0.583"/0.556" lift. Which is bloody great.
Springs
Peterson American Corporation (PAC Racing Springs) ~$400 with locks and retainers
The shortlist is PAC 1211x, 1511x, 1219, 1519 and Comp Cams 26915. The PAC 12xx series is a cheaper less treated version of the 15xx series. this is my worksheet:
View media item 436I also have Ferrea hollow stainless valves and so I chose PAC 1511x shot peened nitrided race springs with hardened steel valve locks / collets & Manley chromoly retainers.
View media item 250
Pushrods
Manley LS Chromoly ~$200

It's advisable to check pushrod length and replace with hardened lighter rods with less diameter. My geometry is different in order to get a raised compression and stuff so I went with above after getting sized properly.
View media item 437
Then the labour charge for (less than) five hours, ranges $500 to $900.

Thanks Heaps Monstar! It is very tempting. My dealer waiting on parts with no ETA... Yes. Very tempting....
 

dazinau

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So I'm still driving mine around. Trouble is if ever I get north of 3,500rpm I feel my chest tighten and stop breathing expecting catastrophic engine failure...

Any recommendations on how to drive to take it easy on rocker arms until my dealer gets parts? (or I get sick of waiting and look more into Monstar's suggestion)
 

426Cuda

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So I'm still driving mine around. Trouble is if ever I get north of 3,500rpm I feel my chest tighten and stop breathing expecting catastrophic engine failure...

Any recommendations on how to drive to take it easy on rocker arms until my dealer gets parts? (or I get sick of waiting and look more into Monstar's suggestion)
Less right foot. More changing up gears.
 

Anthony121

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So I'm still driving mine around. Trouble is if ever I get north of 3,500rpm I feel my chest tighten and stop breathing expecting catastrophic engine failure...

Any recommendations on how to drive to take it easy on rocker arms until my dealer gets parts? (or I get sick of waiting and look more into Monstar's suggestion)
Be afraid, mine failed at around 1,000 rpm
 

GMVPSS

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Be afraid, mine failed at around 1,000 rpm
Need a dislike button for that one. :(

I hope there wasn't too much other damage?

I have heard of one in an LS3 breaking as the new owner left the dealership and I have heard of an LSA breaking while moving it around at HSV during assembly. (From one of my Walkinshaw engineering contacts.)
 
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