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This is in a 2000 silverado. Not the typical LS1tech ride but I know ya'll know your stuff so I wanted to ask here.
I have an Lq9 with 317's, 228/230 cam @ .585 lift 112LSA (sloppy cam), long tubes into 3" Y pipe, no cats, stock exhaust back with a really old flowmaster 40. 5" intake into stock TB and manifold. ls7 lifters, PAC 1912 springs, BTR 7.4 pushrods. MLS headgaskets. Flexfuel injectors on stock fuel pump. Tuned on 93. Ran in 3rd gear through a built 4l60e through 3.73 gears. 20" wheels from a new truck with 285's. E-fans. EGR deleted. AFR was steady in the 12.6-12.9 range through the pull verified on a sniffer.
Thought it would make more on a DynoJet. Any thoughts based on the graph? Everything I've seen has this cam peaking at 6500 or so and should make power all the way to redline, not fall off like this. Let me know if you'd like any more information, I'm thinking somethings choking it somehwere. These seem like 5.3 numbers to me. For reference, buddy has the same motor with a slightly larger cam and better heads putting down 440whp on the same dyno through an 80e that saps more power.
long tubes into 3" Y pipe, no cats, stock exhaust back with a really old flowmaster 40.
Nice looking truck!
1. So are you running dual 3" pipe from headers into a 3" merge, and necking down to 2.75" single exhaust? Got a picture of the Y-pipe merge?
2. What were your MAP sensor readings during the dyno pull?
3. What was the spark timing set at?
I can tell you right now there is no solution without an exhaust solution. And the Flowmaster 40 series is going to have to go bye-bye.
Exhaust optimized yes, bigger throttle body absolutely not at this power level. A bigger than stock throttle body comes into play on a highly optimized build that you're trying to eek out the last 6-10hp.
Exhaust is 1 3/4" headers to 3" collectors, into a 3" Y like this. Then feeds into the stock 2.75" "Cat-back" stock exhaust that has a flowmaster (hearing it called a chokemaster...) muffler, then dual 2.5" or so out the back of the muffler.
Boosting compression by mlling 317 heads 030 or swapping to 243/799s would greatly help.
5 inch intake tube is too much air to go into like 3.5 87mm stock TB choking it.
Your exhaust going into a single 3 is a choker. You need a dual 3 going into a 3.5 or 4 exhaust pipe to a same diameter freeflowing muffler.
The heavy wheels and tire combo will greatly affect hp/torque and acceleration.
Still think it should have made more power, but I would start with above changes and go from there.
I don't always come to this section, but if you have any questions, feel free to message me.
Thanks. I think the next thing up will be to free up the exhaust and go for the TBSS intake with a 90mm+ throttle body. I think it's actually a 78mm TB stock. I wasn't expecting him to take it to almost 150mph on the dyno so I'm sure the heavy wheels had an effect there. Might be able to score some 243's locally too, if so I'm on em. Thank you!
1. So are you running dual 3" pipe from headers into a 3" merge, and necking down to 2.75" single exhaust? Got a picture of the Y-pipe merge?
2. What were your MAP sensor readings during the dyno pull?
3. What was the spark timing set at?
I can tell you right now there is no solution without an exhaust solution. And the Flowmaster 40 series is going to have to go bye-bye.
MAP sensor - no clue.
Timing - I believe I was at 27 degrees WOT
Would the 3" collectors on the headers, merging into a 3" pipe at the Y be restrictive? I was under the impression 3" was plenty for these. I don't think there's a 3" collector to 4" merge Y out there.
Exhaust optimized yes, bigger throttle body absolutely not at this power level. A bigger than stock throttle body comes into play on a highly optimized build that you're trying to eek out the last 6-10hp.
The 78mm TB is on the stock 2000 intake mani I have, if I go to the TBSS they come with a 90mm so I'd at least go to that size. That's plenty though, no need for something bigger without boost IMO.
Exhaust optimized yes, bigger throttle body absolutely not at this power level. A bigger than stock throttle body comes into play on a highly optimized build that you're trying to eek out the last 6-10hp.
This truck has the smallest throttle body ever fitted to an LS. At only a theoretical 78mm, it is most certainly a bottleneck. Porting 78mm throttle bodies to an actual 78mm used to be a good source of income for some people, but now with so many other better options available, it’s recommended to just replace it with something bigger.
Would the 3" collectors on the headers, merging into a 3" pipe at the Y be restrictive? I was under the impression 3" was plenty for these. I don't think there's a 3" collector to 4" merge Y out there.
Did you know there is a sister site to LS1tech that focuses on trucks? Tons of info over there. Your same login credentials will work at that site. https://www.performancetrucks.net
3.5" and 4" merge is available for Camaro. I don't know what is available as a bolt-on for trucks.
You can do anything you want if you cut and weld. Flowmaster makes a really good merge for exhaust builders.
If you don't want to cut up your exhaust system then you can make the best of it with a straight thru muffler. That will lift torque across the entire band. The Flowmaster 40 series is literally one of the worst mufflers you could have chosen. A straight thru muffler will be loud though, so get one with a large case to help with sound levels.
Did you know there is a sister site to LS1tech that focuses on trucks? Tons of info over there. Your same login credentials will work at that site. https://www.performancetrucks.net
3.5" and 4" merge is available for Camaro. I don't know what is available as a bolt-on for trucks.
You can do anything you want if you cut and weld. Flowmaster makes a really good merge for exhaust builders.
If you don't want to cut up your exhaust system then you can make the best of it with a straight thru muffler. That will lift torque across the entire band. The Flowmaster 40 series is literally one of the worst mufflers you could have chosen. A straight thru muffler will be loud though, so get one with a large case to help with sound levels.
You should be making closer to 400whp vs 300whp!
You're intake system is killing you. Along with your exhaust. Have you tuned your ecu? Switching injectors without tune will eff your performance. I have a 98 WS6, t56. High mileage. 4.10 gears. Now, I did a LS6 top end swap. Pace-sucker LTs and ory, SLP lid, k&n drop in, ported stock LS1 (gen3 size) TB, 160 t-stat, TB bypass mod.. made 392whp/387wtq. The LS6? The LS6 cam is much smaller vs your camshaft. The big, heavy wheels of yours are slowing down your rev's and robbing you some power too. Instead if like the 18% drivetrain loss in a 4l60e trans, you bumped it up to 20% or tad more. Finding an aluminum driveshaft will help drop it back down.
So you have some thinking to do. I'd start looking over the tine 1st !! Send your intake manifold to Peak's to be ported. Or find a gen4 truck intake off a 5.3/4.8 which is equal to a TBSS. Then you'll be able to use a 90mm TB. Being the year of your truck, your TB should be cable driven. So you won't have to worry about the xlink to convert your TB signal like I had to with my 6L build in my 04 Tahoe. Cuz the xlink is pricy new. Luckily I found it used foe $170 shipped. I'm using a small cam. Almost like an LS6 for a truck. Lastly, I'd find different heads. Some 243/799s would really be nice. Especially if you do a quick hand port to clean just the casting bumps and ramps. Or even gen3 5.3/4.8 truck heads. Anything to bump up the compression ratio. And what stall/gears are you running?
Good luck!
Last edited by FU_I_AM_UltraZ; 12-14-2021 at 04:25 AM.
Reason: Type-o's
So, after finding my own thread on Google I decided to come post an update for you. If it's showing up on Google search that means there are other people reading this looking for answers, so here you go.
I took all of the advice here and got rid of the flowmaster for a 3" MBRP exhaust (hate it), put on an FiTech 90mm TB, TBSS mani, c5 filter, new transmission with a 2800 stall, and had it retuned.
I ended up at 338whp. Still disappointed but then again the motor has a ton of miles on it and I've gotten some good years out of it. If I did it again, I would do a "truck" cam to give more low end torque. I think on something weighing 5000lbs the torque helps more than a few more ponies at 5k rpm. Also, a cam with higher lift would have done better. The heavy wheels are absolutely hurting.
So, after finding my own thread on Google I decided to come post an update for you. If it's showing up on Google search that means there are other people reading this looking for answers, so here you go.
I took all of the advice here and got rid of the flowmaster for a 3" MBRP exhaust (hate it), put on an FiTech 90mm TB, TBSS mani, c5 filter, new transmission with a 2800 stall, and had it retuned.
I ended up at 338whp. Still disappointed but then again the motor has a ton of miles on it and I've gotten some good years out of it. If I did it again, I would do a "truck" cam to give more low end torque. I think on something weighing 5000lbs the torque helps more than a few more ponies at 5k rpm. Also, a cam with higher lift would have done better. The heavy wheels are absolutely hurting.
Hoping to get myself into a c6 soon.
Reading this and getting your update.. and reading all the responses really showed the people "helping" had no idea what they were talking about.
A 6.0 DOES NOT NEED a larger throttle body.. that's like when people think a 5.3 needs a 90-102mm.. it's a joke.
That 338 is likely around 420ish at the crank which isn't bad given the build. The heads are holding you back the most, followed by compression. The cam is somewhat of a mismatch for the truck(weight wise) that is something that would do better in a car/very light truck. The extra lift would also help at the expense of reliability but if you threw in a set of better heads(rec port ftw) and a higher lift cam you'd make considerably more.
Reading this and getting your update.. and reading all the responses really showed the people "helping" had no idea what they were talking about.
A 6.0 DOES NOT NEED a larger throttle body.. that's like when people think a 5.3 needs a 90-102mm.. it's a joke.
That 338 is likely around 420ish at the crank which isn't bad given the build. The heads are holding you back the most, followed by compression. The cam is somewhat of a mismatch for the truck(weight wise) that is something that would do better in a car/very light truck. The extra lift would also help at the expense of reliability but if you threw in a set of better heads(rec port ftw) and a higher lift cam you'd make considerably more.
If the WOT MAP pulls below ambient barometric pressure, the engine will make more power with a larger throttle body. 78mm is a noticeable restriction on a 6.0L. Hell an 80mm into a 4" air intake was a noticeable restriction on my L31 350 at only 5,000 rpm.
My buddy had a cam only LQ4 that gained 40 rwhp with a TBSS intake, 92mm DBC throttle body into the existing 4" intake tubing and long tubes.
If the WOT MAP pulls below ambient barometric pressure, the engine will make more power with a larger throttle body. 78mm is a noticeable restriction on a 6.0L. Hell an 80mm into a 4" air intake was a noticeable restriction on my L31 350 at only 5,000 rpm.
My buddy had a cam only LQ4 that gained 40 rwhp with a TBSS intake, 92mm DBC throttle body into the existing 4" intake tubing and long tubes.
Hahahahaha no.. Just no.. Sure if you're still seeing vaccuum you're right but a 6.0 won't see any beneficial gains from 80+.
That 40hp came from the headers and intake not the throttle body 😂😂 god all these people and thinking they need a huge throttle body 😂😂😂😂
65mm Throttle Body 745 CFM
70mm Throttle Body 830 CFM
75mm Throttle Body 915 CFM
80mm Throttle Body 965 CFM
90mm Throttle Body 1170 CFM
95mm Throttle Body 1450 CFM
105mm Throttle Body 1520 CFM
Last edited by 02redchevy; 08-30-2023 at 09:08 PM.
Hahahahaha no.. Just no.. Sure if you're still seeing vaccuum you're right but a 6.0 won't see any beneficial gains from 80+.
That 40hp came from the headers and intake not the throttle body 😂😂 god all these people and thinking they need a huge throttle body 😂😂😂😂
65mm Throttle Body 745 CFM
70mm Throttle Body 830 CFM
75mm Throttle Body 915 CFM
80mm Throttle Body 965 CFM
90mm Throttle Body 1170 CFM
95mm Throttle Body 1450 CFM
105mm Throttle Body 1520 CFM
You are absolutely wrong on the throttle body. I have ported them as well as I have swapped more than enough of them from 78mm to 92mm even using the stock manifold There are gains going from 3.5" intake piping to 4" intake piping even with a smaller throttle body. The MAF frequency does not lie, the more airflow that is moved the more it indicates. Same effect for a carburetor. More WOT power from an 850 cfm vs say a 600 cfm even on an engine that makes ~200 hp. The less pumping losses the more power. An 80mm still pulls a noticeable vacuum on even a stock 6.0L. A 92mm with an adapter shows less losses than an 80mm. A 90mm necked intake reduces those loses entirely. I have tested a Gen III 90mm necked intake as well. I have also run a 102mm on a 90mm intake opening with a 5" air intake. That system provides the same power as a wide open throttle body.
01-24-2021, 06:35 PM
Interpret my dyno sheet? Cammed 6.0 lq9 314hp. 
