LS2, New Heads, lost power? Ideas anyone?
Thread Starter
Staging Lane
Joined: Oct 2006
Posts: 59
Likes: 0
LS2, Added New Livernois Heads, lost power? Ideas anyone? Posting this up for a friend. He currently has an LS2 GTO with 1-3/4" LT's and a custom N/A cam. He was making fairly good power with it. His dyno sheets were very consistent with repeatable numbers.
He purchased a set of new Livernois STG-3 heads. Also while we were there we had to replace the clutch, and installed an SNL clutch (I think that's the name of it)
Went to the dyno to get tuned and he has a consistent power loss across the powerband of about 14hp and torque. It's as if his dyno chart shifted down.
Trying to figure out why it has dropped. Has anyone had similar issues with upgrading heads? I was thinking, even if for some reason the heads weren't P&P'd like they should be, you wouldn't have a loss you'd at least be at the same power level as before.
Mods:
Custom Cam (232/240-112 612/612 - from memory, may not be exact)
1-3/4" Pacesetter catted
LPE CAI
Yella Terra 1.7
and now the Livernois STG-3 heads
Was making 430/400 solid repeatably
Here's what they pulled on the dyno with the new heads. The old dyno pulls looked the same but were about 14-16hp higher across the band.
He purchased a set of new Livernois STG-3 heads. Also while we were there we had to replace the clutch, and installed an SNL clutch (I think that's the name of it)
Went to the dyno to get tuned and he has a consistent power loss across the powerband of about 14hp and torque. It's as if his dyno chart shifted down.
Trying to figure out why it has dropped. Has anyone had similar issues with upgrading heads? I was thinking, even if for some reason the heads weren't P&P'd like they should be, you wouldn't have a loss you'd at least be at the same power level as before.
Mods:
Custom Cam (232/240-112 612/612 - from memory, may not be exact)
1-3/4" Pacesetter catted
LPE CAI
Yella Terra 1.7
and now the Livernois STG-3 heads
Was making 430/400 solid repeatably
Here's what they pulled on the dyno with the new heads. The old dyno pulls looked the same but were about 14-16hp higher across the band.
Last edited by VesperWillow; Oct 22, 2008 at 12:07 PM.
Thread Starter
Staging Lane
Joined: Oct 2006
Posts: 59
Likes: 0
Same dyno, tuner, and about the same weather.
I don't have details with me on the tune. He's a highly respected and well-known tuner on here though, and in the region. When they did the initial pull to see what the car was doing, it made the same power as it did prior to the heads. Upon beginning the re-tune for the heads, power started dropping.
That's the last I heard, still waiting to hear back from my friend and/or the tuner. They're both baffled.
I don't have details with me on the tune. He's a highly respected and well-known tuner on here though, and in the region. When they did the initial pull to see what the car was doing, it made the same power as it did prior to the heads. Upon beginning the re-tune for the heads, power started dropping.
That's the last I heard, still waiting to hear back from my friend and/or the tuner. They're both baffled.
Trending Topics
The first thing I would want to check is a leakdown/compression test. Generally with a cam that size you would need to notch the piston to clear. Do you know if this was done?
Another thing that might be affecting the power is if the pushrod is the right length. Generally speaking a stage 3 head will change what length pushrod you would use. I have seem some people reuse the same pushrods and one of two things could happen, either it was too short, which would not open the valve far enough, and would be noisy. Or they are too long and could be hanging the valve open.
While neither of these things are guaranteed to be the issue a leakdown will help determine this.
Another thing I would check is to make certain there are no vacuum leaks as well...
Another thing that might be affecting the power is if the pushrod is the right length. Generally speaking a stage 3 head will change what length pushrod you would use. I have seem some people reuse the same pushrods and one of two things could happen, either it was too short, which would not open the valve far enough, and would be noisy. Or they are too long and could be hanging the valve open.
While neither of these things are guaranteed to be the issue a leakdown will help determine this.
Another thing I would check is to make certain there are no vacuum leaks as well...
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo
Five Reasons the Camaro Was the Most Pivotal Player in the Pony Car Wars 2.0
Brett Foote
10 Reasons the LS7 Is GM's Most Extreme Naturally Aspirated V8 Engine Ever
Verdad Gallardo
Teching In
Joined: Dec 2005
Posts: 27
Likes: 0
Thanks for the prompt response Livernois
This is my car..
The Blue is the very first tuning session with the tuner on just a Cam/header car back in january..
The red is the first pull of the day after the stg 3 head install. This was our base pull..
The green was the next pull after that where the tuner added 2* of timing.. Something to note there was 0* of timing on the before tune.. Tuner left timing alone on the old setup.. He only added timing on the last pull to see if it was going to do anything..
The thing he can't figure out is straight from the first pull he didn't have to touch anything.. There was no increase in anything as you plainly see.. He didn't have to adjust a single thing..
The dip at 6k was when the motor had stock heads with cam installed.. We were thinking maybe the comp cam dual springs were the issue to that but we never could figure out what the deal was with that..
I'm completely confused about the whole thing.. Ported heads and I made less power across the entire powerband.. Something just isn't right at all.. Should have seen even just a minimal increase but nothing..
That's what we are trying to figure out..
This is my car..
The Blue is the very first tuning session with the tuner on just a Cam/header car back in january..
The red is the first pull of the day after the stg 3 head install. This was our base pull..
The green was the next pull after that where the tuner added 2* of timing.. Something to note there was 0* of timing on the before tune.. Tuner left timing alone on the old setup.. He only added timing on the last pull to see if it was going to do anything..
The thing he can't figure out is straight from the first pull he didn't have to touch anything.. There was no increase in anything as you plainly see.. He didn't have to adjust a single thing..
The dip at 6k was when the motor had stock heads with cam installed.. We were thinking maybe the comp cam dual springs were the issue to that but we never could figure out what the deal was with that..
I'm completely confused about the whole thing.. Ported heads and I made less power across the entire powerband.. Something just isn't right at all.. Should have seen even just a minimal increase but nothing..
That's what we are trying to figure out..
Last edited by dizz81; Oct 22, 2008 at 02:49 PM.
I have a friend who had issues with Yella Terra rockers (built LS1 in a C5). Car ran erratic, lacked a little power for his mods. A knowledgeable tuner/tech told him to change out his rockers, and his engine smoothed out and had noticeably more top-end power.
Pushrod length is still a good place to start.
Pushrod length is still a good place to start.
I have a friend who had issues with Yella Terra rockers (built LS1 in a C5). Car ran erratic, lacked a little power for his mods. A knowledgeable tuner/tech told him to change out his rockers, and his engine smoothed out and had noticeably more top-end power.
Pushrod length is still a good place to start.
Pushrod length is still a good place to start.
Thread Starter
Staging Lane
Joined: Oct 2006
Posts: 59
Likes: 0
Ok so we pulled some stuff and took a look tonight. Checked the valve lift, it's within .001" of the cam spec. Haven't done a leakdown yet. Took the sparkplugs out and noticed this:
All of bank 2 plugs look normal, like this:
Here's 3 of the 4 plugs from bank 1 (the 4th plug forgot to photo):
Signs of running rich. Connected HPT up and saw the O2 looked like it was reading bank 1 as a smidge leaner than bank 2. Fuel looked the same but can't remember, I'd have to post the scan log.
So.. wondering, with lift being the same all the way around, at this point what'sup. We still want to do a leakdown, but it seems like bank 1 heads are flowing more than bank 2 (which seems like it's flowing like stock). Now that's just a guess, but those plugs were fine before the head swap.
Ideas/comments welcome. This is the first head swap I've ever done and had this issue.
All of bank 2 plugs look normal, like this:
Here's 3 of the 4 plugs from bank 1 (the 4th plug forgot to photo):
Signs of running rich. Connected HPT up and saw the O2 looked like it was reading bank 1 as a smidge leaner than bank 2. Fuel looked the same but can't remember, I'd have to post the scan log.
So.. wondering, with lift being the same all the way around, at this point what'sup. We still want to do a leakdown, but it seems like bank 1 heads are flowing more than bank 2 (which seems like it's flowing like stock). Now that's just a guess, but those plugs were fine before the head swap.
Ideas/comments welcome. This is the first head swap I've ever done and had this issue.
