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Funny you post this. I have some interesting info for you that I was just thinking about before reading this. I have a low compression 5.3. Right off idle it’s real responsive. I have a 222/233 cam, 3600 yank power adder series (tighter) 9.4:1 compression, 3.46 gears, 25.5” tall tire, 92mm throttle body with a dorman ls2 intake. I had to take some air adder and timing out to kill the over response. So you can dial that in better and it’ll be better. You do not want to lock the Convertor at 2500rpm. I tried that, it only works well with a stock converter with the stock or near stock cam. Other wise, generally you will get some bucking or lack of response. There’s always a trade off when you start modding.
next. I have a 7875 billet turbo and it comes in, in the 2000 rpm range when light accelerating and gives me about 3-4psi so it helps greatly. I’ve driven it with the turbo disconnected and the response is night and day. It feels like a much larger engine with the turbo working. I don’t know what your power goal is but if it fits in the 7875 limit, it makes for a really good combo. I could do a drive around video for you if you like. I’m in the car as I type this, sitting in a parking lot waiting on a buddy to hand him some stuff he needs for his turbo build.
Funny you post this. I have some interesting info for you that I was just thinking about before reading this. I have a low compression 5.3. Right off idle it’s real responsive. I have a 222/233 cam, 3600 yank power adder series (tighter) 9.4:1 compression, 3.46 gears, 25.5” tall tire, 92mm throttle body with a dorman ls2 intake. I had to take some air adder and timing out to kill the over response. So you can dial that in better and it’ll be better. You do not want to lock the Convertor at 2500rpm. I tried that, it only works well with a stock converter with the stock or near stock cam. Other wise, generally you will get some bucking or lack of response. There’s always a trade off when you start modding.
next. I have a 7875 billet turbo and it comes in, in the 2000 rpm range when light accelerating and gives me about 3-4psi so it helps greatly. I’ve driven it with the turbo disconnected and the response is night and day. It feels like a much larger engine with the turbo working. I don’t know what your power goal is but if it fits in the 7875 limit, it makes for a really good combo. I could do a drive around video for you if you like. I’m in the car as I type this, sitting in a parking lot waiting on a buddy to hand him some stuff he needs for his turbo build.
Great input. My tuner really seems to like the 7875 and this info is exactly what I needed to know. I'm sure the 7875 will be plenty for me, with good response down low. A drive around video would be great when you get the chance. I recall from my turbo Buick days if you put a bigger turbo without the converter to match it was a dog at stoplights and I didn't want to end up with that again.
What's air adder? I might suggest we add more timing down low.
This 5.3 runs really smooth everywhere, even with the converter locked at 1500-2000 rpm there's no bucking etc.
Great input. My tuner really seems to like the 7875 and this info is exactly what I needed to know. I'm sure the 7875 will be plenty for me, with good response down low. A drive around video would be great when you get the chance. I recall from my turbo Buick days if you put a bigger turbo without the converter to match it was a dog at stoplights and I didn't want to end up with that again.
What's air adder? I might suggest we add more timing down low.
This 5.3 runs really smooth everywhere, even with the converter locked at 1500-2000 rpm there's no bucking etc.
the air adder. Go to idle. Then airflow. Under the throttle follower heading it says “airflow” and it has a throttle position table. You can add a little to that and it will add more air per throttle percentage.
lol I went ahead and did a video in case you wanted it. I was in the car already. I did punch it a couple times but I had it turned down on the boost controller. It would usually spin and I didn’t want to have to control it while holding the camera. Not fun. Anyways...
That's great, looks to drive just how I want it. What A/R is that unit?
My path is now chosen...
Thanks!
it’s a .96 which I’m about to go to a 1.15 because I’m trying to go up in boost (20+) and it seems to be choking it past 18. My exhaust is a huge factor too
I've started mocking up the turbo and found that those sexy twin turbo headers wont fit around my AC without serious mods. Also, the outlets place v-band mounted twins right into the rad, unless you elbow them. Thirdly, the flanges don't quite fit the bolt holes in the heads ...
Any kits available (CX Racing etc) are the same with regards to the AC, all require mods. I see no sense in spending $1000 on a kit and then have to mod it, so I'm building my own. I'm going with a single billet 7875, using forward and down truck manifolds with a crossover under the crank pulley. All tight but looking good so far.
This is what the final configuration looks like. It's amazing how tight things get in that corner of the car when you add it all up, especially when the old cars have so much room under the hood. I'm hoping heat won't be an issue, I've put heat shields everywhere. I ended up squeezing a 12x3x24 intercooler between the condenser and the rad, it actually came together quite well.
Just waiting to install the charge pipe and fire it up, it's -30C here and I don't wanna open the garage...
Turbo build is done. A success I would say, 550 rwhp @5800, 12 psi boost. Ended up with a Summit Ghost Cam and an Ebay billet 7875. Nice flat torque curve with boost coming on around 2500 with the 3000 stall converter. Plenty of boost for some fun at part throttle, exactly what I wanted. Passing on the freeway is awesome and effortless, should be a hoot in the mountains. Not sure how accurate the Gtech Pro is, but it showed 11.08@137mph on a test flight.
This brings new meaning to the name "Ram Air!" Now about those brakes...
I ended up with an unexplained piston problem on the 5.3. Instead of fixing it I built a square-port aluminum L76 and swapped it in with a VS Racing 7875/0.96 AR. Kept the Ghost Cam and everything else. After a decent break-in period, the numbers are in: the square-port heads, 6.0 displacement, and VS turbo were worth 110hp so now it's at 662 at the tires, at 3000ft elevation. I also noticed the little bit of boost creep is gone, telling me that possibly the cathedral ports are a restriction, with air piling up in front of them? Those big square ports just let it all in...
I ended up with an unexplained piston problem on the 5.3. Instead of fixing it I built a square-port aluminum L76 and swapped it in with a VS Racing 7875/0.96 AR. Kept the Ghost Cam and everything else. After a decent break-in period, the numbers are in: the square-port heads, 6.0 displacement, and VS turbo were worth 110hp so now it's at 662 at the tires, at 3000ft elevation. I also noticed the little bit of boost creep is gone, telling me that possibly the cathedral ports are a restriction, with air piling up in front of them? Those big square ports just let it all in...
big motor, small turbo…..you’ll likely have the opposite of boost creep now. You’ll have a lot of backpressure and boost dropping off. Consider swapping to a 1.25 exhaust housing. It will require the down pipe to be remade.
now if you are happy with it as is (are we ever satisfied tho?) then just leave it alone.
662 wheel hp on the street is PLENTY for me. The tires will never hold as it is. Tuner said she had more if I wanted. I'm not really a dragrace guy anymore and have no interest in caging the car. It's fun to be fast again!
08-29-2020, 01:05 PM
