L99 heads vs LS3/L92

[BigDan]

Originally Posted by pharmd

Do me a favor, some one with an LS3 go out and see what the casting # is on your heads, then some one with an L99 go out and see what the casting # is on your heads. Someone suggested to me that the head casting # was different. We know the LS3 heads contain lighter valves...probably different valve springs also, as the LS3 cam's max lift is over .550 vs the L99 being less than .500, the LS3 CR is more, but only 0.3 more 10.4:1 vs 10.7:1.

But the new question, is...is the head design the same or different. It seems like L99's for the same mods are down more on power than just the what the drive train loss would account for. Saying that even with aftermarket mods (mods being equal...such as cam or whatever), its not right.

I emailed a couple shops that do heads, and asked if they had inspected any bare L99 castings vs LS3 but I got no replies.

Maybe its nothing...or maybe its something...it just "appears" that the L99 is down more power than what drivetrain loss will account for.

This is why im now looking at 2011 GT500.... I was going to get the L99 w/ i/e/cam/stall converter but I just cant live with with the LS3's being faster and making 50whp more then the L99

The 2010 GT500 has improved alot over the years. Pro driver's have already gone 11.95 @120 bone stock with stock tires and 11.59 with drag radials. They even put down 511whp with 540 at the crank. 2011 is going to get the aluminum block so I going to wait another year. Yeah im an auto guy but I cant live with the L99's pathetic whp numbers and if im going to go manual I might as well get Shelby and run 10's with bolt ons. I buy cars based on their powertrain package and its gonna be hard to beat the 2011 Shelby unless I go Vette.

[Wacker]

http://gmhightechperformance.automot...nsmission.html

Found this..don't know if it's directly from GM or someone else's writing. It does mention the block, crank, heads, and intake are shared between the LS3 and L99.

[CamaroSpike23]

Originally Posted by Wacker

http://gmhightechperformance.automot...nsmission.html

Found this..don't know if it's directly from GM or someone else's writing. It does mention the block, crank, heads, and intake are shared between the LS3 and L99.

yup. the heads themselves are, but the valvetrain is not shared.

[Wacker]

Originally Posted by CamaroSpike23

yup. the heads themselves are, but the valve train is not shared.

Yeah the AFM and VVT make the L99 a little more complex. Can't wait to see what type of "Big Cam" they come up with for the VVT. It is interesting to see why they put AFM in the auto only. They make the TC lock and unlock during operation to allow for smooth transition. Even so, you can definitely tell when this is happening, especially with an after market exhaust.

[rayhawk]

Originally Posted by BigDan

This is why im now looking at 2011 GT500.... I was going to get the L99 w/ i/e/cam/stall converter but I just cant live with with the LS3's being faster and making 50whp more then the L99

The 2010 GT500 has improved alot over the years. Pro driver's have already gone 11.95 @120 bone stock with stock tires and 11.59 with drag radials. They even put down 511whp with 540 at the crank. 2011 is going to get the aluminum block so I going to wait another year. Yeah im an auto guy but I cant live with the L99's pathetic whp numbers and if im going to go manual I might as well get Shelby and run 10's with bolt ons. I buy cars based on their powertrain package and its gonna be hard to beat the 2011 Shelby unless I go Vette.

There is nothing wrong with the L99 dyno numbers. You are comparing apples to oranges when you look at dyno results between an automatic equipped car vs. a manual equipped car. If the shelby came in an auto, expect it to put down in the ~450 hp range, but be nearly as fast at the M6. No doubt the Shelby is an awesome car, but you are paying for it.

[Robert91RS]

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.

What makes you say this?
426hp-15%=362.1
400hp-20%=320
Isn't that about average for what we have seen thus far?

[9c1ny]

Originally Posted by Robert91RS

What makes you say this?
426hp-15%=362.1
400hp-20%=320
Isn't that about average for what we have seen thus far?

I think alot of people forget about the advertised 26hp difference

[newcamaroguy7]

what would be the best heads for the l99 when leaving the vvt.. will be porting tb and stock intake soon.. lookin to change heads is there any advantage cuz cam comes next

[rontammy0]

Originally Posted by newcamaroguy7

what would be the best heads for the l99 when leaving the vvt.. will be porting tb and stock intake soon.. lookin to change heads is there any advantage cuz cam comes next

mmmmm..this thread is 5 yrs old..they may not be listening.

[The_Blur]

Originally Posted by newcamaroguy7

what would be the best heads for the l99 when leaving the vvt.. will be porting tb and stock intake soon.. lookin to change heads is there any advantage cuz cam comes next

While I'm not a cam specialist, I can say that it is generally advisable to come up with your goals in terms of power and drivability before picking a cam or any other related parts. I'd recommend buying a cam at the same time as heads. If you're also planning on forced induction, you should consider the benefits of buying that at the same time. Your best bet may be to talk to a couple of reputed vendors who grind cams for input and advice.

Originally Posted by rontammy0

mmmmm..this thread is 5 yrs old..they may not be listening.