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Not comparing like motors IMO. How large is your turbine wheel and AR housing? How much power would you say your motor is making NA? In boost? Head flow? You’re running a more cubes and I’d guess pretty high rpm as well? Do you have actual backpressure readings? I wouldn't think the amount of pressure applied to the WG port is a good indication of actual back pressure. The larger the gate valve face, the more pressure will be needed to keep it closed. A 60mm WG will require more pressure to stay shut than a 40mm WG etc.. WG pressure chamber size would also come into play I'd think. Again I’m not taking any sides, it depends on the setup as a whole IMO.
It's a1.32 with a.96 exhaust wheel. Something is holding my car back about 3-5 mph. I have checked the motor, trans, converter, new turbo, etc. we noticed at the bottom of my manifolds the heat coating is starting to change colors. No where else on the manifolds is it changing. That leads us to believe that is the hottest part. We think it's because it's necked downtown 2.25 instead of staying 2.50. I'm going to change it just for testing purposes to see what results I get and I will share them.
It's a1.32 with a.96 exhaust wheel. Something is holding my car back about 3-5 mph. I have checked the motor, trans, converter, new turbo, etc. we noticed at the bottom of my manifolds the heat coating is starting to change colors. No where else on the manifolds is it changing. That leads us to believe that is the hottest part. We think it's because it's necked downtown 2.25 instead of staying 2.50. I'm going to change it just for testing purposes to see what results I get and I will share them.
On paper the smallest point in the system dictates the pressure. (Bernoulli's Principle) From what I’ve read the exit on the T6 1.32 scroll was around 1.6”. So in theory changing your hot side piping to 2.5 shouldn’t change turbo drive pressure. That’s assuming that your exh. Gas velocity isn’t moving so fast that it’s causing disruptive airflow on the current setup.
As we all know what’s on paper doesn’t always play out in the real world. Would be great data if you logged actual back pressure before and after. Looking forward to your results! Thanks for sharing it with all of us.
This was my first attempt at a hot side build, sure was a lot of fun to make and I hope it works well. I still need to spend some time inspecting and cleaning up the welds, as well as cleaning everything to make sure no metal filings are left behind.
That's a PT7675 and Precision 66mm wastegate. I realize the 90* angle isn't optimal, but I've seen that done a lot (even here on this forum) and it seems to work out well enough for folks. Next week I'll build the downpipe and cold side, support bracket, then everything comes out of the truck. I gotta fix that rust soon, its embarrassing in these pics...
Which manifolds did you end up using?
Looks good, nice and simple
Well...I'm not exactly sure. We have a pile of LS manifolds at the shop, so I just grabbed the non-EGR ones and started eyeballing. I'm pretty sure they're just truck manifolds. I still have not fully welded the v-bands to the manifold, from what I've been reading I need to pre-heat, weld, and cool slowly (likely in an oven).
don't be afraid to cut and weld those manifolds to fit your application . I have cut and welded them and have not had an issue yet. I just clean up the manifolds with a grinder and weld them. I like to weld in short beads and jump around to get heat in the whole area. here is what I do to one so it fits a 70 nova. that is a 2.25 pipe and I will cut it short and weld on a vband.
I did pre-heat the manifolds in front of a big ol' shop heater, then just had at it with the MIG. No cracks, no problems! (Whew)
I finished up the fabrication work, fairly satisfied given it's my first ever time doing this. Thanks to teh interwebz the amount of info here and elsewhere is incredibly helpful. Even though the inner fender isn't in there I made sure it clears everything nicely. 3.5" downpipe all the way to the crossmember. Unfortunately the heater box had to go, I've got a "hot rod heater" that'll fit under the dash and get the job done. I had a leftover 2004 GTO "cold air intake" pipe that also miraculously fits the turbo and will place an air filter down behind the headlights. Should work well in the daily-driver application. I love having 2 big boxes of LS stuff...it always comes in handy.
Now who's got a Turbo 5.3/4L80E Holley EFI base tune I can use? lol
Nice build. How much boost do you plan on running?
I don't know. This whole project is kinda different for me, no real "goal" except have some fun on the street and the occasional visit to the track. Right now it's got the weak-sauce 3lb spring in the wastegate. Hey, gotta start slow and fix the usual issues with any new build before going straight to max power, right?
Anyway, I worked yesterday from 8:45am til 10pm and managed to get it fired up. Still a lot of work to do but it sure felt good to hear it come to life. I worked for a while this morning solo and got the idle tuned real nice. After using HpTuners for a while this Holley system is a piece of cake.
Ended up making a pass today on my crappy street tires, I just went to spectate and didn't plan at all on running.
Loafed to a 12.46@114 on 9lbs of boost and 4,000lb race weight. I had both of my tanks full of E85 (40 gallons) but at least took the time to remove tools and other crap I had in the bed. Spun so bad my first try the truck gained 40mph on the back half of the track!
Ended up with a 12.46 by not opening it up until I was about thru second gear. I have no doubt cranked up and with my DR's it'll scream.
Also, the 2" hotside works amazing. I can build 4lbs of boost on the footbrake on the street. I torched 2nd gear in my junkyard 4L80E, but as a transmission hoarder, I had another junkyard special ready to go. I'm gonna take it easy until after the Power Tour then hammer down all summer.
Ended up making a pass today on my crappy street tires, I just went to spectate and didn't plan at all on running.
Loafed to a 12.46@114 on 9lbs of boost and 4,000lb race weight. I had both of my tanks full of E85 (40 gallons) but at least took the time to remove tools and other crap I had in the bed. Spun so bad my first try the truck gained 40mph on the back half of the track!
Ended up with a 12.46 by not opening it up until I was about thru second gear. I have no doubt cranked up and with my DR's it'll scream.
Also, the 2" hotside works amazing. I can build 4lbs of boost on the footbrake on the street. I torched 2nd gear in my junkyard 4L80E, but as a transmission hoarder, I had another junkyard special ready to go. I'm gonna take it easy until after the Power Tour then hammer down all summer.
Your truck looks sweet! I love c10's! I'm sure with drag radials you'll be tearing up the track with that heavy beast.
Drove the truck on Power Tour, and much to my surprise theblock picked it for a feature article. They nailed all the facts except 2...its not my first build and I'll definitely be making passes before drag week!
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RUST 
