L99 heads vs LS3/L92

[camaro1]

they are the same

[9c1ny]

just looked at some LS3s today, they have a different casting number in a different location VS the L99

[pharmd]

Originally Posted by 9c1ny

just looked at some LS3s today, they have a different casting number in a different location VS the L99

So now the question begs, are the actual casts different or not? Do they flow the same or not? Surely there is a head shop that is developing a CNC program for these things that has looked at both heads and can provide some clarification...

[Gentry78]

Originally Posted by pharmd

So now the question begs, are the actual casts different or not? Do they flow the same or not? Surely there is a head shop that is developing a CNC program for these things that has looked at both heads and can provide some clarification...

we hope lol

[CamaroSpike23]

Originally Posted by pharmd

So now the question begs, are the actual casts different or not? Do they flow the same or not? Surely there is a head shop that is developing a CNC program for these things that has looked at both heads and can provide some clarification...

the heads themselves are L92 heads. aka L92/LS3/L99/L76 heads.

the L92 castings themselves are the truck version of the LS7 castings.

the major differences are in the valvetrain, lifters, springs, valves, etc.

the L99 has softer springs as well as modified lifters to enable AFM. there are some extra tidbits about the LS3 and L99 cam and valvetrain specs at the bottom of the first post of this thread. http://www.camaro5.com/forums/showthread.php?t=34774


as for cnc porting

http://www.proheads.com/

http://www.sdparts.com/product/88958...ndSprings.aspx

[pharmd]

Originally Posted by CamaroSpike23

the heads themselves are L92 heads. aka L92/LS3/L99/L76 heads.

the L92 castings themselves are the truck version of the LS7 castings.

the major differences are in the valvetrain, lifters, springs, valves, etc.

the L99 has softer springs as well as modified lifters to enable AFM. there are some extra tidbits about the LS3 and L99 cam and valvetrain specs at the bottom of the first post of this thread. http://www.camaro5.com/forums/showthread.php?t=34774


as for cnc porting

http://www.proheads.com/

http://www.sdparts.com/product/88958...ndSprings.aspx

I understand the differences and have read about them a number of times, but you can't believe everything you read

I want a shop who has had both heads off, and has flowed both heads and designed a CNC program with computer modeling to confirm there is no difference. I have spoken with a few different shops using L99's as test cars, and they are questioning this same thing. Mod for Mod the L99 is down on power (from what they have seen first hand) more than what can be accounted for in drivetrain loss, or 0.3 pts compression (aftermarket cam's take and difference if stock cam lift out of the equation).

Richard at WCCH is one of the front runners on LS3 heads, but there are a number of head shops that do this kind of work. Unfortnately, porting an LS3 head on a stock short block, is really not a very good return on investment. These heads usually run $1800 (maybe less on exchange basis), and most are showing 20rwhp or less. Richards heads showed 35rwhp on a LS3 vette with a BIG cam, tested at Redline Motorsports, but that seems to be somewhat of an outlier.

[CamaroSpike23]

Originally Posted by pharmd

I understand the differences and have read about them a number of times, but you can't believe everything you read

I want a shop who has had both heads off, and has flowed both heads and designed a CNC program with computer modeling to confirm there is no difference. I have spoken with a few different shops using L99's as test cars, and they are questioning this same thing. Mod for Mod the L99 is down on power (from what they have seen first hand) more than what can be accounted for in drivetrain loss, or 0.3 pts compression (aftermarket cam's take and difference if stock cam lift out of the equation).

Richard at WCCH is one of the front runners on LS3 heads, but there are a number of head shops that do this kind of work. Unfortnately, porting an LS3 head on a stock short block, is really not a very good return on investment. These heads usually run $1800 (maybe less on exchange basis), and most are showing 20rwhp or less. Richards heads showed 35rwhp on a LS3 vette with a BIG cam, tested at Redline Motorsports, but that seems to be somewhat of an outlier.

mod for mod the L99 should be down on power, it comes stock with 26hp less and add in the drivetrain losses. I can just about guarantee that there will be different casting #'s between the LS3 and L99 and probably even different casting #'s amongst LS3s and L99s respectively. add into the equation the different pistons and tuning required for the L99 over the LS3 and there's extra little bits of power loss here and there that add up.

one thing you mentioned is aftermarket cams. could you point me to where you saw comparisons on cam swaps between LS3 and L99 with the same spec cams? not doubting you, just want to investigate some more.
cus one of the big things that some are not aware of is that you cant just "turn off AFM and VVT and have an LS3". the springs in the L99 are less stiff than the LS3 which could lead to the valves not closing as fast as the LS3 and losing power. The camshaft itself is different as well as the L99 cam phaser which could add to some small rotational power loss. Also the AFM lifters are different as well which could lead to some bleed down at higher rpms.

all speculation at this point, but the thing to keep in mind is that with a cam swap to compare LS3 vs L99 with the same spec cam is that you would have to swap the entire valvetrain to ensure they were equal operating parameters.

[pharmd]

Originally Posted by CamaroSpike23

mod for mod the L99 should be down on power, it comes stock with 26hp less and add in the drivetrain losses. I can just about guarantee that there will be different casting #'s between the LS3 and L99 and probably even different casting #'s amongst LS3s and L99s respectively. add into the equation the different pistons and tuning required for the L99 over the LS3 and there's extra little bits of power loss here and there that add up.

one thing you mentioned is aftermarket cams. could you point me to where you saw comparisons on cam swaps between LS3 and L99 with the same spec cams? not doubting you, just want to investigate some more.
cus one of the big things that some are not aware of is that you cant just "turn off AFM and VVT and have an LS3". the springs in the L99 are less stiff than the LS3 which could lead to the valves not closing as fast as the LS3 and losing power. The camshaft itself is different as well as the L99 cam phaser which could add to some small rotational power loss. Also the AFM lifters are different as well which could lead to some bleed down at higher rpms.

all speculation at this point, but the thing to keep in mind is that with a cam swap to compare LS3 vs L99 with the same spec cam is that you would have to swap the entire valvetrain to ensure they were equal operating parameters.

Im referring to information that I have been provided by shops that I have spoken with . Anyone doing a cam swap would use aftermarket valve springs, removing that variable from the equation. The lighter weight valves in the LS3 could create a marginal difference, as could the 0.3 lower compression for the L99. But the power differences that have been seen are WAY more than what 15% vs 20% drivetrain loss can account for.

Hopefully, I will have some more data soon, I'm ordering some parts today that should help to shed a little light on this issue.

[CamaroSpike23]

Originally Posted by pharmd

Im referring to information that I have been provided by shops that I have spoken with . Anyone doing a cam swap would use aftermarket valve springs, removing that variable from the equation. The lighter weight valves in the LS3 could create a marginal difference, as could the 0.3 lower compression for the L99. But the power differences that have been seen are WAY more than what 15% vs 20% drivetrain loss can account for.

Hopefully, I will have some more data soon, I'm ordering some parts today that should help to shed a little light on this issue.

true that they would/should use different springs, but if they upgrade the springs and utilize the stock AFM lifters, the lifters might not be up to snuff to open the valve all the way with the stiffer springs leading to decrease in performance. just brainstorming/speculating now.

[camaro1]

the heads on my L99 engine i pulled out have a factory casting number of 0821, same as many of the LS3 heads

L92, L99, LS3, L76, all the same just different valves and spring combo's

[pharmd]

I spoke to a shop today that says they have flowed both casting #'s and they are equal. I haven't had time and don't plan to go searching deep for all the info, but they said the LS3 castings are a number, and the L99/L92's are the same #...and other that the LS3's having hollow stemmed valves (ie lighter weight) vs the L99/L92, the castings are the same and flow equally on a flowbench.

So now we are left to assume the A6 is just the most inefficient tranny of all time.

As a side note, they said 2 L99's with stock cam and TVS2300 @ 6psi, put down 450rwhp...he didn't say anything about headers/exhaust, CAI though...

Anyone else have modded or supercharged L99 numbers?

[CamaroSpike23]

Originally Posted by pharmd

I spoke to a shop today that says they have flowed both casting #'s and they are equal. I haven't had time and don't plan to go searching deep for all the info, but they said the LS3 castings are a number, and the L99/L92's are the same #...and other that the LS3's having hollow stemmed valves (ie lighter weight) vs the L99/L92, the castings are the same and flow equally on a flowbench.

So now we are left to assume the A6 is just the most inefficient tranny of all time.

As a side note, they said 2 L99's with stock cam and TVS2300 @ 6psi, put down 450rwhp...he didn't say anything about headers/exhaust, CAI though...

Anyone else have modded or supercharged L99 numbers?

good info. thanks

at first glance, compared to an A4's efficiency, yes it is inefficient. but when you realize that there's an extra 2 gears worth of clutch packs, planetaries, etc, IMHO, its expected that it will drag more power from the engine.


as for the heads, flow numbers are great, if the valve is opening all the way. and I dont know off hand the spring compression of the AFM lifters, but id be willing to bet that depending on the stiffer valvesprings used in a cam swap that the valves might not be opening all the way on the L99 and thus not allowing the full flow potential of the head.

and Rpepka is doing a cam/sc install on his 2nd L99 now.

http://www.camaro5.com/forums/showthread.php?t=39189

[Wacker]

Its a guess but if you changed the stock TC to a smaller lighter version you can recoup some of the lost power. You can do this in a vet and achieve a noticeable difference.

[RonC]

Originally Posted by camaro1

the heads on my L99 engine i pulled out have a factory casting number of 0821, same as many of the LS3 heads

L92, L99, LS3, L76, all the same just different valves and spring combo's

My L99 has casting #823 on them, Vin 39xx. My 07 Sierra Denali L92 also has #823 castings. I have a early set from a L92 Escalade casting #5364. Some of the differences may just be the location they were cast at. I think the only difference in the LS3 and the L99 heads is the light weight intake valve and stronger springs according to what I've read about them.

My L99 had the rev limiter set at 6200 RPM.