Stg 2 turbo cams..differences. Tsp vs Btr vs Ss2
Thread Starter
Joined: Nov 2010
Posts: 808
Likes: 62
From: Toronto Ontario Canada
Stg 2 turbo cams..differences. Tsp vs Btr vs Ss2 Hello all,
Im about to be pulling my engine apart and refreshing my bottomend from a bad lifter and possibly spun bearings and wiped cam lobe. I was running a Ljms stg 2 turbo cam (226/231 .605/.598 113+4 lsa) and it treated me well.had a nice chop,made good power and very streetable. I believe Summits stg 2 cam is near identical to the Ljms/btr stg 2 being (226/230 .600/.575 113+4 lsa) if I wanted a direct replacement cam.
I see many guys talk about and run the Sloppy stg 2 aswell with good results (228/230 .585/.585 112 lsa). I have always had great experience with Texas speed in the past when my car was N/A with the 228r cam and used that throughout my first turbo setup. I decided to try their stg 2 turbo cam (224/230 .600/.600 113+3 lsa) and upgraded core.
All these cams are very close to eachother,they all work great for boost.But Im curious between them what those small differences mean.the advantages or disadvantages to having more lift,or more intake vs exhaust,the wider lsa or not. If someone were to strictly swap between these cams on a dyno,what should you expect to see power wise if anything..or boost curve wise interms of how the turbo might react? What would be the need to spend $389 vs $269?
Im about to be pulling my engine apart and refreshing my bottomend from a bad lifter and possibly spun bearings and wiped cam lobe. I was running a Ljms stg 2 turbo cam (226/231 .605/.598 113+4 lsa) and it treated me well.had a nice chop,made good power and very streetable. I believe Summits stg 2 cam is near identical to the Ljms/btr stg 2 being (226/230 .600/.575 113+4 lsa) if I wanted a direct replacement cam.
I see many guys talk about and run the Sloppy stg 2 aswell with good results (228/230 .585/.585 112 lsa). I have always had great experience with Texas speed in the past when my car was N/A with the 228r cam and used that throughout my first turbo setup. I decided to try their stg 2 turbo cam (224/230 .600/.600 113+3 lsa) and upgraded core.
All these cams are very close to eachother,they all work great for boost.But Im curious between them what those small differences mean.the advantages or disadvantages to having more lift,or more intake vs exhaust,the wider lsa or not. If someone were to strictly swap between these cams on a dyno,what should you expect to see power wise if anything..or boost curve wise interms of how the turbo might react? What would be the need to spend $389 vs $269?
On The Tree
Joined: Oct 2012
Posts: 171
Likes: 9
Probably not gonna be a whole lot of difference in them. I have experience with the ss2 and the btr/ljms stage 2 and I cant tell any real seat of pants difference. I would feel the ljms may make a little more power up top but dont have any real world data to prove that. Richard Holdener is doing a stage 2 turbo cam test very soon and hes going to be testing a bunch of stage 2 turbo cams from all the big names.
Thread Starter
Joined: Nov 2010
Posts: 808
Likes: 62
From: Toronto Ontario Canada
I agree that most likely power wise might be a difference of very small margin. Im curious to see how the difference in valve events change boost curve,power and torque band with all else being the same aside from just cam swap. Seeing those results can be helpful on planning future builds.
LS1Tech Sponsor
Joined: Jan 2008
Posts: 2,235
Likes: 1,526
From: Ohio, Georgia, Nevada, Texas
This is a good thread OP. We see you're trying to get into the fine details of cams. We like looking at individual valve events. It's one of the first things we look at when it comes time to select a cam.
So we're talking turbo cams here. All five that you've discussed are pretty similar with minor differences. Let’s layout the cam specs and valve events.
LJMS stage 2 turbo cam: .605"/.598", 226/231, 113+4 with 2.5* of overlap
IVO: 4* BTDC
IVC: 42* ABDC
EVO: 52.5* BBDC
EVC: -1.5* ATDC
Summit stage 2 turbo SUM-8706: .600"/.575", 226/230, 113+4 with 2* of overlap
IVO: 4* BTDC
IVC: 42* ABDC
EVO: 52* BBDC
EVC: -2* ATDC
BTR stage 2 turbo cam: .605"/.598", 226/231, 113+4 with 2.5* of overlap
IVO: 4* BTDC
IVC: 42* ABDC
EVO: 52.5* BBDC
EVC: -1.5* ATDC
TSP stage 2 (6.0) turbo cam: .600"/.600", 224/230, 113+3 with 1* of overlap
IVO: 2* BTDC
IVC: 42* ABDC
EVO: 51* BBDC
EVC: -1* ATDC
Sloppy Stage 2 cam: .585"/.585", 228/230, 112+4 with 5* of overlap
IVO: 6* BTDC
IVC: 42* ABDC
EVO: 51* BBDC
EVC: -1* ATDC
What are these events and what do they mean?
IVO: Is basically idle quality. The earlier you open the intake, the more air you're taking in on the downstroke (at the expense of idle vacuum).
IVC: Is building compression and torque down low with closing the valve early. Or using inertial charge longer after BDC and closing the valve later to increase power higher in the rpm range.
EVO: Is blowdown. Most of the blowdown occurs even before BDC because of high residual cylinder pressure. Earlier = better evacuation and less pumping loss on the piston upstroke at high speed vs. slight loss of pressure on piston during last degrees of power stroke for low end. Early EVO is good for a turbo application to help the turbo(s) spool up.
EVC: Is in conjunction with overlap. Most useful with open headers, equal length headers, and primary lengths wave tuned to the intake runner and rpm. We don't place much emphasis on extending this event later as it produces reversion with street performance exhaust systems. You will find it common with turbo cams that the EVC is actually BTDC vs. ATDC. This is to help prevent reversion of exhaust gasses getting back into the intake.
Going by the valve events all 5 of these cams would perform about the same.
- With the IVO. They would idle about the same with a nice steady lope. The TSP would be slightly milder and the SS2 slightly choppier.
- The IVC between all of them is 42*. They would all have near identical powerbands giving up some low-end for a strong mid-range and good top-end.
- The EVO is all within 1.5* of each other. These will have good evacuation and be good for turbo spool up.
- The EVC event between them all is -1* to -2.5*. This means they all close the exhaust valve BTDC which is good for alleviating exhaust reversion.
KEY:
IVC= Intake Valve Closing
IVO= Intake Valve Opening
EVO= Exhaust Valve Opening
EVC= Exhaust Valve Closing
BTDC= Before Top Dead Center
ATDC= After Top Dead Center
BBDC= Before Bottom Dead Center
ABDC= After Bottom Dead center
The Summit Cam lobes are proprietary and they carry well at high rpm even with a 918 Beehive spring. This can extend the powerband more than other cams despite similar valve timing. Note Summit Turbo cams use a slightly lower lift exhaust lobe that is softer to break open easier against cylinder pressure on exhaust opening. This takes stress off the rockers and pushrods etc.
Sorry for the long post. We saw you were looking for more fine details on cams and we thought what better way than the valve events.
So we're talking turbo cams here. All five that you've discussed are pretty similar with minor differences. Let’s layout the cam specs and valve events.
LJMS stage 2 turbo cam: .605"/.598", 226/231, 113+4 with 2.5* of overlap
IVO: 4* BTDC
IVC: 42* ABDC
EVO: 52.5* BBDC
EVC: -1.5* ATDC
Summit stage 2 turbo SUM-8706: .600"/.575", 226/230, 113+4 with 2* of overlap
IVO: 4* BTDC
IVC: 42* ABDC
EVO: 52* BBDC
EVC: -2* ATDC
BTR stage 2 turbo cam: .605"/.598", 226/231, 113+4 with 2.5* of overlap
IVO: 4* BTDC
IVC: 42* ABDC
EVO: 52.5* BBDC
EVC: -1.5* ATDC
TSP stage 2 (6.0) turbo cam: .600"/.600", 224/230, 113+3 with 1* of overlap
IVO: 2* BTDC
IVC: 42* ABDC
EVO: 51* BBDC
EVC: -1* ATDC
Sloppy Stage 2 cam: .585"/.585", 228/230, 112+4 with 5* of overlap
IVO: 6* BTDC
IVC: 42* ABDC
EVO: 51* BBDC
EVC: -1* ATDC
What are these events and what do they mean?
IVO: Is basically idle quality. The earlier you open the intake, the more air you're taking in on the downstroke (at the expense of idle vacuum).
IVC: Is building compression and torque down low with closing the valve early. Or using inertial charge longer after BDC and closing the valve later to increase power higher in the rpm range.
EVO: Is blowdown. Most of the blowdown occurs even before BDC because of high residual cylinder pressure. Earlier = better evacuation and less pumping loss on the piston upstroke at high speed vs. slight loss of pressure on piston during last degrees of power stroke for low end. Early EVO is good for a turbo application to help the turbo(s) spool up.
EVC: Is in conjunction with overlap. Most useful with open headers, equal length headers, and primary lengths wave tuned to the intake runner and rpm. We don't place much emphasis on extending this event later as it produces reversion with street performance exhaust systems. You will find it common with turbo cams that the EVC is actually BTDC vs. ATDC. This is to help prevent reversion of exhaust gasses getting back into the intake.
Going by the valve events all 5 of these cams would perform about the same.
- With the IVO. They would idle about the same with a nice steady lope. The TSP would be slightly milder and the SS2 slightly choppier.
- The IVC between all of them is 42*. They would all have near identical powerbands giving up some low-end for a strong mid-range and good top-end.
- The EVO is all within 1.5* of each other. These will have good evacuation and be good for turbo spool up.
- The EVC event between them all is -1* to -2.5*. This means they all close the exhaust valve BTDC which is good for alleviating exhaust reversion.
KEY:
IVC= Intake Valve Closing
IVO= Intake Valve Opening
EVO= Exhaust Valve Opening
EVC= Exhaust Valve Closing
BTDC= Before Top Dead Center
ATDC= After Top Dead Center
BBDC= Before Bottom Dead Center
ABDC= After Bottom Dead center
The Summit Cam lobes are proprietary and they carry well at high rpm even with a 918 Beehive spring. This can extend the powerband more than other cams despite similar valve timing. Note Summit Turbo cams use a slightly lower lift exhaust lobe that is softer to break open easier against cylinder pressure on exhaust opening. This takes stress off the rockers and pushrods etc.
Sorry for the long post. We saw you were looking for more fine details on cams and we thought what better way than the valve events.
Last edited by Summitracing; Apr 17, 2020 at 07:11 AM.
Thanks for the great reply Summit!
Curious why the summit grind decided to choose less lift on the exhaust side? Theoretically isn't it best max out lift on both sides? All else the same, what would we see dyno graph wise with say .600" lift VS .500" lift? What was the strategy going with .575" on the exh side? The valve is already smaller and flows less than the intake... If anything, to wouldn't you want more lift on the exh. side?
Also what is the theoretical peak RPM range of the Stg 2 summit on a 4.8 with supporting intake and valve train in turbo applications? It happens to be the cam I'm running in my 4.8 and it seems to fall flat about 7k. More like a nose dive really... I was thinking it would carry the rpm out a bit farther. This is with an LS6 intake, S480 T6 combo around 20lbs...
Thanks.
Curious why the summit grind decided to choose less lift on the exhaust side? Theoretically isn't it best max out lift on both sides? All else the same, what would we see dyno graph wise with say .600" lift VS .500" lift? What was the strategy going with .575" on the exh side? The valve is already smaller and flows less than the intake... If anything, to wouldn't you want more lift on the exh. side?
Also what is the theoretical peak RPM range of the Stg 2 summit on a 4.8 with supporting intake and valve train in turbo applications? It happens to be the cam I'm running in my 4.8 and it seems to fall flat about 7k. More like a nose dive really... I was thinking it would carry the rpm out a bit farther. This is with an LS6 intake, S480 T6 combo around 20lbs...
Thanks.
Last edited by Forcefed86; Apr 17, 2020 at 03:19 PM.
LS1Tech Sponsor
Joined: Jan 2008
Posts: 2,235
Likes: 1,526
From: Ohio, Georgia, Nevada, Texas
Forcefed86,
No problem. We enjoy interacting with the community.
Thank you for your question. Typically, we set the lift numbers around common spring packs and the scroll limit of a factory rocker. On a turbo engine, the exhaust valve can be opened into elevated residual exhaust pressure. For this reason, we crack the valve open a little slower. This is to relieve the pressure on the pushrod and the rest of the valvetrain. This slower action results in less lift at our target valve velocities.
On your rpm limit, we think there are a couple of things contributing. It’s likely aerating the lifters, and we’d recommend going to some short travels. These aren’t easy to set up. The Comp XD-A adjustable length pushrods make the setup a bit easier. Factory rockers are lighter at the valve than heavy aftermarket roller rockers. This is why we typically recommend a trunnion upgraded factory rocker. The LS6 throttle body size is a little small. You'd likely make gains with a Dorman LS2 intake. You could go with a carb style or short runner fabricated. The problem there is the torque loss and loss of spool. For this reason, we’re leaning toward keeping the factory style intake on it.
Lastly, you could perhaps step into a stage 3 turbo cam. Then you'd need to make sure you have plenty of converter with a 4.8 to come up on the cam.
No problem. We enjoy interacting with the community.
Thank you for your question. Typically, we set the lift numbers around common spring packs and the scroll limit of a factory rocker. On a turbo engine, the exhaust valve can be opened into elevated residual exhaust pressure. For this reason, we crack the valve open a little slower. This is to relieve the pressure on the pushrod and the rest of the valvetrain. This slower action results in less lift at our target valve velocities.
On your rpm limit, we think there are a couple of things contributing. It’s likely aerating the lifters, and we’d recommend going to some short travels. These aren’t easy to set up. The Comp XD-A adjustable length pushrods make the setup a bit easier. Factory rockers are lighter at the valve than heavy aftermarket roller rockers. This is why we typically recommend a trunnion upgraded factory rocker. The LS6 throttle body size is a little small. You'd likely make gains with a Dorman LS2 intake. You could go with a carb style or short runner fabricated. The problem there is the torque loss and loss of spool. For this reason, we’re leaning toward keeping the factory style intake on it.
Lastly, you could perhaps step into a stage 3 turbo cam. Then you'd need to make sure you have plenty of converter with a 4.8 to come up on the cam.
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Thread Starter
Joined: Nov 2010
Posts: 808
Likes: 62
From: Toronto Ontario Canada
This is a good thread OP. We see you're trying to get into the fine details of cams. We like looking at individual valve events. It's one of the first things we look at when it comes time to select a cam.
So we're talking turbo cams here. All five that you've discussed are pretty similar with minor differences. Let’s layout the cam specs and valve events.
LJMS stage 2 turbo cam: .605"/.598", 226/231, 113+4 with 2.5* of overlap
IVO: 4* BTDC
IVC: 42* ABDC
EVO: 52.5* BBDC
EVC: -1.5* ATDC
Summit stage 2 turbo SUM-8706: .600"/.575", 226/230, 113+4 with 2* of overlap
IVO: 4* BTDC
IVC: 42* ABDC
EVO: 52* BBDC
EVC: -2* ATDC
BTR stage 2 turbo cam: .605"/.598", 226/231, 113+4 with 2.5* of overlap
IVO: 4* BTDC
IVC: 42* ABDC
EVO: 52.5* BBDC
EVC: -1.5* ATDC
TSP stage 2 (6.0) turbo cam: .600"/.600", 224/230, 113+3 with 1* of overlap
IVO: 2* BTDC
IVC: 42* ABDC
EVO: 51* BBDC
EVC: -1* ATDC
Sloppy Stage 2 cam: .585"/.585", 228/230, 112+4 with 5* of overlap
IVO: 6* BTDC
IVC: 42* ABDC
EVO: 51* BBDC
EVC: -1* ATDC
What are these events and what do they mean?
IVO: Is basically idle quality. The earlier you open the intake, the more air you're taking in on the downstroke (at the expense of idle vacuum).
IVC: Is building compression and torque down low with closing the valve early. Or using inertial charge longer after BDC and closing the valve later to increase power higher in the rpm range.
EVO: Is blowdown. Most of the blowdown occurs even before BDC because of high residual cylinder pressure. Earlier = better evacuation and less pumping loss on the piston upstroke at high speed vs. slight loss of pressure on piston during last degrees of power stroke for low end. Early EVO is good for a turbo application to help the turbo(s) spool up.
EVC: Is in conjunction with overlap. Most useful with open headers, equal length headers, and primary lengths wave tuned to the intake runner and rpm. We don't place much emphasis on extending this event later as it produces reversion with street performance exhaust systems. You will find it common with turbo cams that the EVC is actually BTDC vs. ATDC. This is to help prevent reversion of exhaust gasses getting back into the intake.
Going by the valve events all 5 of these cams would perform about the same.
- With the IVO. They would idle about the same with a nice steady lope. The TSP would be slightly milder and the SS2 slightly choppier.
- The IVC between all of them is 42*. They would all have near identical powerbands giving up some low-end for a strong mid-range and good top-end.
- The EVO is all within 1.5* of each other. These will have good evacuation and be good for turbo spool up.
- The EVC event between them all is -1* to -2.5*. This means they all close the exhaust valve BTDC which is good for alleviating exhaust reversion.
KEY:
IVC= Intake Valve Closing
IVO= Intake Valve Opening
EVO= Exhaust Valve Opening
EVC= Exhaust Valve Closing
BTDC= Before Top Dead Center
ATDC= After Top Dead Center
BBDC= Before Bottom Dead Center
ABDC= After Bottom Dead center
The Summit Cam lobes are proprietary and they carry well at high rpm even with a 918 Beehive spring. This can extend the powerband more than other cams despite similar valve timing. Note Summit Turbo cams use a slightly lower lift exhaust lobe that is softer to break open easier against cylinder pressure on exhaust opening. This takes stress off the rockers and pushrods etc.
Sorry for the long post. We saw you were looking for more fine details on cams and we thought what better way than the valve events.
So we're talking turbo cams here. All five that you've discussed are pretty similar with minor differences. Let’s layout the cam specs and valve events.
LJMS stage 2 turbo cam: .605"/.598", 226/231, 113+4 with 2.5* of overlap
IVO: 4* BTDC
IVC: 42* ABDC
EVO: 52.5* BBDC
EVC: -1.5* ATDC
Summit stage 2 turbo SUM-8706: .600"/.575", 226/230, 113+4 with 2* of overlap
IVO: 4* BTDC
IVC: 42* ABDC
EVO: 52* BBDC
EVC: -2* ATDC
BTR stage 2 turbo cam: .605"/.598", 226/231, 113+4 with 2.5* of overlap
IVO: 4* BTDC
IVC: 42* ABDC
EVO: 52.5* BBDC
EVC: -1.5* ATDC
TSP stage 2 (6.0) turbo cam: .600"/.600", 224/230, 113+3 with 1* of overlap
IVO: 2* BTDC
IVC: 42* ABDC
EVO: 51* BBDC
EVC: -1* ATDC
Sloppy Stage 2 cam: .585"/.585", 228/230, 112+4 with 5* of overlap
IVO: 6* BTDC
IVC: 42* ABDC
EVO: 51* BBDC
EVC: -1* ATDC
What are these events and what do they mean?
IVO: Is basically idle quality. The earlier you open the intake, the more air you're taking in on the downstroke (at the expense of idle vacuum).
IVC: Is building compression and torque down low with closing the valve early. Or using inertial charge longer after BDC and closing the valve later to increase power higher in the rpm range.
EVO: Is blowdown. Most of the blowdown occurs even before BDC because of high residual cylinder pressure. Earlier = better evacuation and less pumping loss on the piston upstroke at high speed vs. slight loss of pressure on piston during last degrees of power stroke for low end. Early EVO is good for a turbo application to help the turbo(s) spool up.
EVC: Is in conjunction with overlap. Most useful with open headers, equal length headers, and primary lengths wave tuned to the intake runner and rpm. We don't place much emphasis on extending this event later as it produces reversion with street performance exhaust systems. You will find it common with turbo cams that the EVC is actually BTDC vs. ATDC. This is to help prevent reversion of exhaust gasses getting back into the intake.
Going by the valve events all 5 of these cams would perform about the same.
- With the IVO. They would idle about the same with a nice steady lope. The TSP would be slightly milder and the SS2 slightly choppier.
- The IVC between all of them is 42*. They would all have near identical powerbands giving up some low-end for a strong mid-range and good top-end.
- The EVO is all within 1.5* of each other. These will have good evacuation and be good for turbo spool up.
- The EVC event between them all is -1* to -2.5*. This means they all close the exhaust valve BTDC which is good for alleviating exhaust reversion.
KEY:
IVC= Intake Valve Closing
IVO= Intake Valve Opening
EVO= Exhaust Valve Opening
EVC= Exhaust Valve Closing
BTDC= Before Top Dead Center
ATDC= After Top Dead Center
BBDC= Before Bottom Dead Center
ABDC= After Bottom Dead center
The Summit Cam lobes are proprietary and they carry well at high rpm even with a 918 Beehive spring. This can extend the powerband more than other cams despite similar valve timing. Note Summit Turbo cams use a slightly lower lift exhaust lobe that is softer to break open easier against cylinder pressure on exhaust opening. This takes stress off the rockers and pushrods etc.
Sorry for the long post. We saw you were looking for more fine details on cams and we thought what better way than the valve events.
This was the most helpful post.Thank you for the detailed answer. I like how you specifically compared each cam I listed and what small effects could take place between them. I didnt think powerwise would be any real pro or con to either of these cams.Nice to know how it affects idle/chop/vacumm..seems like the rest of the engine combination would make all the real difference.These cams are so tight together its just a matter of price and what brand sticker you want to slap on under the hood lol.
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I went with a summit stg 2 and the PAC 919, haven't run it yet so cant give you real world experience with it. Price was my deciding factor as you know up here no such thing as a junkyard priced LS anything. I think i was way over $700$ about 775 if i recall correctly for cam and springs after everyone took their cut. Still cheaper than walking on a sidewalk downtown. Summit treated me very well as usual.
I was going to purchase a turbo and cam elsewhere but couldn't believe the rudeness i encountered from the other place and no it wasn't Jegs. Not what you want to do when someone is holding a credit card in their hand, rant over.
I think Forced86 is the only one I've heard thats having a rev issue, would love to know what the out come to that is. Good luck.
I was going to purchase a turbo and cam elsewhere but couldn't believe the rudeness i encountered from the other place and no it wasn't Jegs. Not what you want to do when someone is holding a credit card in their hand, rant over.
I think Forced86 is the only one I've heard thats having a rev issue, would love to know what the out come to that is. Good luck.
Forcefed86,
No problem. We enjoy interacting with the community.
Thank you for your question. Typically, we set the lift numbers around common spring packs and the scroll limit of a factory rocker. On a turbo engine, the exhaust valve can be opened into elevated residual exhaust pressure. For this reason, we crack the valve open a little slower. This is to relieve the pressure on the pushrod and the rest of the valvetrain. This slower action results in less lift at our target valve velocities.
On your rpm limit, we think there are a couple of things contributing. It’s likely aerating the lifters, and we’d recommend going to some short travels. These aren’t easy to set up. The Comp XD-A adjustable length pushrods make the setup a bit easier. Factory rockers are lighter at the valve than heavy aftermarket roller rockers. This is why we typically recommend a trunnion upgraded factory rocker. The LS6 throttle body size is a little small. You'd likely make gains with a Dorman LS2 intake. You could go with a carb style or short runner fabricated. The problem there is the torque loss and loss of spool. For this reason, we’re leaning toward keeping the factory style intake on it.
Lastly, you could perhaps step into a stage 3 turbo cam. Then you'd need to make sure you have plenty of converter with a 4.8 to come up on the cam.
No problem. We enjoy interacting with the community.
Thank you for your question. Typically, we set the lift numbers around common spring packs and the scroll limit of a factory rocker. On a turbo engine, the exhaust valve can be opened into elevated residual exhaust pressure. For this reason, we crack the valve open a little slower. This is to relieve the pressure on the pushrod and the rest of the valvetrain. This slower action results in less lift at our target valve velocities.
On your rpm limit, we think there are a couple of things contributing. It’s likely aerating the lifters, and we’d recommend going to some short travels. These aren’t easy to set up. The Comp XD-A adjustable length pushrods make the setup a bit easier. Factory rockers are lighter at the valve than heavy aftermarket roller rockers. This is why we typically recommend a trunnion upgraded factory rocker. The LS6 throttle body size is a little small. You'd likely make gains with a Dorman LS2 intake. You could go with a carb style or short runner fabricated. The problem there is the torque loss and loss of spool. For this reason, we’re leaning toward keeping the factory style intake on it.
Lastly, you could perhaps step into a stage 3 turbo cam. Then you'd need to make sure you have plenty of converter with a 4.8 to come up on the cam.
I'd really like to rev this thing out to 7500 or more on the 1-2 shift. (glide). Would help me a ton. The previous 214/217 @ 111 .565 lift cam did well. but fell flat around 6700. It had Summit 1.8 roller rockers on it. I have since gone back to the standard rocker. I was fearing PTV clearance with the summit STG2 and 1.8 Roller rockers. 799 Heads are milled .030 as well, LS9 gaskets. Hardened push rods measured to length. Factory 4.8 lifters. I had heard stories of adding a bit more than OEM spec preload wise to the factory lifters to help with valve control as well? (basically squeeze half the oil out) Any take on that? The car is honestly quick enough as it is trap wise for my cage. I just feel revving it a bit higher would be easier on it and help the 1/8th times a ton.
I also have a 2" divided hot side that I think could be to blame. Back pressure is steady around 1.4:1 at 20lbs and 7k on a T6 S480. I'm a little worried about the short runner intakes. I'd love to retain the factory hood. But that sticks me with the ultra short 7" tall Sheet metal intakes. Feel like I may not be able to get up on the converter if I do that. (17 stator PTC 9.5)
TECH Fanatic
Joined: Feb 2015
Posts: 1,080
Likes: 178
Thanks for posting graphs. Crossover occurs at 5250rpm (expected) so run006 (red) peaks hp around 5750 (assuming scale is 500/block). Shifting at 6200 makes sense. What happened on run008 (green)? Looks like boost got ramped in really fast and then timing pulled. Everything peaked early (peak hp dropped to 5000).
LS6 with factory 78mm TB. I was under the impression that a mild 4.8 wouldn't benefit much from a TB size increase NA and if boost is just changing the density, that shouldn't be a big factor either. But I've never tested a larger TB, or an intake other than OEM.
TECH Fanatic
Joined: Feb 2015
Posts: 1,080
Likes: 178
Thanks 86. I would expect your 4.8 should easily go to 7200, and likely 7800 based on lots of dyno graphs of 5.3 and 5.7s (even 6.0s) with LS6 and 78mm TB. Data log not showing anything in the tune that's shutting motor down? If cam is degreed to spec'd ICL (wouldn't hurt to check cyl 8 too), you could retard it 4* to see if motor picked up rpm.
Thats what I always thought. Seems like plenty rev the factory intakes past 7. They may not be gaining power... but they should at least hold it. Feel like I peak at 6500ish and it carries to 7ish then falls flat on its face. Even if I'm in 1st and try to carry it out to 7500 its slower the nose literally drops. As you mention I have a hard time believing it's the hotside since it carried the 370" out to 6800or so, don't know what else to try. Everyone said it was springs. So tested and ordered BTR .660 springs. THen they all said it was the cam, ordered a cam, Then it was the intake, then the hotside.... I don't get it. No IGN Miss or misfire feel, No rise in AFR's to indicate a spark issue. Tried gaping plugs to .015 with no change. .024 now. d585 coils at 4ms. Tested springs as well they are over 400 closed. Been hunting it for years honestly. May have to bite the bullet and redo the hotside in 2.25" and see what happens. Would be cheaper than dropping $500 on a SR intake anyway.
