71 Duster 360 turbo build

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Right now I am moving the springs inboard to the frame. I hope to get some 305 wide tires in the stock(ish) wheels tubs without having to do an entire mini tub which looks like quite a big job. I’ll see how the new tire wheel setup fits and move forward from there.

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Forgot to post previously. New transmission is in and everything is running great. The converter is very tight. Stalls around 2800, and flashes to 4000 rpm running hy-gard fluid. I will likely thin out the fluid with some ATF +4 to loosen the stall up just a bit.

I’ve done a couple 1/8 mile draggy runs and mph is 100-101 at a very conservative 10psi and 20° timing. I’m just under 9:1 compression and plan to run 15-16psi on pump fuel.

The turbo is DEAD silent which I cannot stand so I’m also upgrading to an anti surge housing. I hope to get at least a little sound out of this 78mm

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What generation is your 78/75?
Mine (twin gen 2.5s) were howling like a banshee on the dyno.
 
I had aluminum bushings pressed in for the rear sliders. I guess it didn’t go well because the spring eye broke from simple hand pressure while getting ready for install. I hope someone has a fresh set up ss springs for sale. These are 20 years old and were made in Mexico(I believe I read these tend to wear out).

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turbovan said:
Forgot to post previously. New transmission is in and everything is running great. The converter is very tight. Stalls around 2800, and flashes to 4000 rpm running hy-gard fluid. I will likely thin out the fluid with some ATF +4 to loosen the stall up just a bit.

I’ve done a couple 1/8 mile draggy runs and mph is 100-101 at a very conservative 10psi and 20° timing. I’m just under 9:1 compression and plan to run 15-16psi on pump fuel.

The turbo is DEAD silent which I cannot stand so I’m also upgrading to an anti surge housing. I hope to get at least a little sound out of this 78mm

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How’s the engine temp in that Phoenix heat? I’ve had mine out over the weekend a few times when it’s 95F and 1000% humidity and coolant temp wants to climb up to and beyond 210 in stop and go traffic. The turbo heat struggle is real. Lol
 
subcom said:
How’s the engine temp in that Phoenix heat? I’ve had mine out over the weekend a few times when it’s 95F and 1000% humidity and coolant temp wants to climb up to and beyond 210 in stop and go traffic. The turbo heat struggle is real. Lol
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I drove around quite a bit on some “mild for Phoenix” 100 degree temp days before I took it off the road to move the springs inboard. Water temp held pretty steady at 190 and oil stayed around 210. I was happily surprised to see it running so cool especially considering my block is half filled.
 
I ordered a replacement leaf spring from summit and will have the bushings pressed in. Hopefully they don’t break the second time around. They are 1” bushings and everything I’ve read says that’s the correct bushing size.

I’m also going to revamp the front suspension while it’s off the road for the next month of hot temps; 118 in our forecast.

I am already running offset bushings in the upper control arms to add caster. I’ll be replacing the lower control arm with poly bushings, and I have built my own adjustable strut rods based on this thread:
diy adjustable strut rods

while it was apart I seam welded and reinforced the k frame. I’m going to be switching to 1.09 torsion bars and fox shocks all in the hopes of greatly improving the cars handling.

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clementine said:
It is a big job. But every time I look at the 325/50s, I feel warm and happy inside. They fit easily.
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I’m sure I’d be happy with the end result, but having never worked with sheet metal before it looks a bit intimidating. I’ll keep researching
 
Received my new leaf springs and letting it settle a bit before I weld in the slider. New wheels and tires arrived. Running 305/35r18 Toyo 888r’s on the rear and 275/35r18’s up front. So far the fit looks great, but the front fenders need a little work before I can drive/turn the wheel.

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turbodart68 said:
I am the one who had the carb we reversed engineered to come up with the “hangar 18 mod” hangar 18 is my buddy. We took my 750 apart and modified his carb exactly the same. I got that carb from Ak Miller and ran a small block blow through set up in the mid 90’s. The PV orifice needs to be opened up and the anti blow back check ball needs to be removed oht of the signal circuit. The carb hat causes lean cylinders even though the O2 sensor says its ok or rich. You need to be at least 10 sizes bigger on the side where the hat points. Also a single plane intake really help with distribution. This is a cool build, i love it when someone has the guts to take on a project like this and is willing to learn. I cant wait to see what it runs at the track. I had a similar set up back in the 90’s. It ran 10.0s at 133 with 2.76 gear off the foot brake with a mostly stock 360.
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@turbodart68 Hello, Are you saying the primary and secondary jets need to be at least 10 sizes bigger on the side the hat points? Thanks
 
Definitely agree, and it works out much better if the hat is pointing to the rear so you’re not running around rich on massive front jets. Then you have to get into lots of PVCR tweaking and the whole thing gets to be more complicated. Switching hat direction is where I really ran out of patience for carb tuning.
 
turbovan said:
Definitely agree, and it works out much better if the hat is pointing to the rear so you’re not running around rich on massive front jets. Then you have to get into lots of PVCR tweaking and the whole thing gets to be more complicated. Switching hat direction is where I really ran out of patience for carb tuning.
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Thats a great idea. The cars we had blow through on were race cars and didn’t really do much on the street.
 


Been messing with the car a bit the last few weeks. Here’s a conservative timing run at 12-13psi
 
I had been worried about low oil pressure for quite some time which I discussed in another thread over in the Small Block Mopar sub forum. The general consensus was that my pressure is fine so I’ve moved forward with tuning, and now I’m running out of fuel and rpm! I hit 101% injector duty cycle at around 15 psi running 55% ethanol so I have bumped my base pressure from 40 to 55psi to gain some headroom. I am also running into what I believe is valve float around 5800rpm. Under boost the engine absolutely will not rev past 6000rpm. I’m running the supplied Speedmaster valvetrain so I have ordered higher rate valve springs in the hopes of alleviating the issue. I don’t know where power will drop off once I’m able to rev it, but I would like the ability to shift at 6500. The next track day is May 10th so I’m really hoping to get everything together and tuned by then.

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What are the symptoms of valve float? Does it happen under any amount of boost or only when you get up into the higher PSIs? Is this with the exhaust wide open? I noticed in my back pressure tests that my RPM was hitting a 5800-5900 ceiling when running through the muffler.
 
What are the spring presssures that Speedmaster published with those heads?
 
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