71 Duster 360 turbo build

[turbovan]

I’ve had this project going on for about a year now, and figured I’d throw together a thread at some point. This is mostly for those thinking about a turbo build so they may learn from my mistakes. I’m a pretty big function over form guy so prepare yourself for a whole lot of ugly!

My dad gave me the car when I was 17, and we threw a 440/727 in it. Had an 8 3/4 built with 3.91’s, and threw on some SS springs with shocks that were too short. Ran low 14’s at 101-102, wouldn’t hook, and for some reason didn’t want to be shifted at 6500 rpm(I knew nothing). Quickly developed a rod knock then sat for 15 years while I became obsessed with turbos starting off with an ‘89 voyager. 400whp and FWD was fun in a minivan, but spinning tires got old quick so I found Subaru's. 550whp , an easily tuned ecu, and high 10’s was a blast with no traction issues, but the sleeves couldn’t handle it, and I had a child so I parted ways with the car.

About 5 years later things had settled down, and I decided to dig back into the Duster.

 

[turbovan]

I decided a big block wasn’t needed for my power goals, so I found a running 360 locally and threw my trans internals into a small block case. Threw it all back together, and it was back on the road for the first time in many years.

My plan was to sort everything else out, and then begin the hot side build.

 

[turbovan]

The engine was from a circle track car, had a small cam, stock(I was told) pistons, and big valve j heads with a nice valve job. It was already faster than the 440.

sorted the electrical, swapped to a denso alternator, and took it to the track. Low 13’s.

So I moved forward.
Gt45, magnum manifold on the drivers side, and a 2” crossover which I’ve read should support around 1000hp on a turbo build and keep spool up as apposed to 2.25 or 2.5. Passenger side manifold is a center exit type after reading everyone’s difficulties attempting to fab up the forward facing magnum. I believe Subcom said something along the lines of “that bend put more grey hair on my head than...”

Keep in mind, this project is my first time welding so it’s not pretty, but it works.

 

[turbovan]

I found a new, complete 4” power stroke exhaust on Craigslist for $80, and and used it to fab the downpipe which was extremely tight, but it worked.

So the hot side was complete, and the car hit the road with just a downpipe.

Carb is a Holley 650 with solid floats, and then vent tube extensions added with the turbo. Hat is from CSU, and cold side is 3.5” with a xs-power 50mm bov. Waste gate is a xs-power 44mm which is not big enough even with what I believe to be a great flow angle; 8psi is the lowest it’ll go. This wasn’t optimal with so much tuning to go, but I dropped the timing and hoped for the best.

 

[abdywgn]

NICE! looking forward to the new turbo track times.

 

[turbovan]

Here was my first short drive with turbo noises. Carburetor was lean as expected, so I then added vent extensions instead of increasing jet size. This alone brought my AFR’s into the high 11’s, and I jetted up from there.

Wiring and gauge placement was temporary, but a disaster.

 

[turbovan]

I planned to bring the exhaust all the way out the back, but decided to go side exit so I didn’t have to route around the tank.

I still hadn’t done a full pull, and it was time to start tuning which didn’t last long before the smoke show began. The thin Mr. Gasket head gasket had popped immediately which I knew would happen, but had hoped I’d get a little more time out of.
I had planned to pull the engine and check the ring gaps once the gasket blew, but I found plenty of worn out components and decided on a quick refresh.

 

[turbovan]

Unfortunately I opened the motor up to find it had been bored .060 over, and had some cheap cast(not hypereutectic) pistons. I already have history with thin cylinders so I realized this wasn’t going to be my last block. Gapped the rings to 28 top and bottom and threw it back together a little prettier.
Running 1008 head gaskets now.

 

[turbovan]

91 octane and 10psi at 18* of timing under boost. AFR’s were sitting in the low 11’s and the thing moves.




This is a 2nd to 3rd gear pull. I can’t control the hashtag usage of friends



That’s it for today, but I have plenty left to go.

 

[xLURKxDOGx]

Still a scumbag. Hope you made use of those rocker arm shafts you stole. Any problems with my comments feel free to stop by.

 

[dusted]

Very nice, about 12-14psi the stock pistons will crack. Was gonna warn you on the headgasket issue at 8-10 but you beat me to it.. haha. Keep an eye on the AFRs only takes a small piece of trash in the jet to ruin you day!

 

[turbovan]

Very nice, about 12-14psi the stock pistons will crack. Was gonna warn you on the headgasket issue at 8-10 but you beat me to it.. haha. Keep an eye on the AFRs only takes a small piece of trash in the jet to ruin you day!

I had seen several people blow the thin mr. gaskets right off the bat, but they did get me through the hot side build! 1008’s seem to hold up, but wondering when cometics become necessary. Are you saying stock LA pistons crack around 12-14 or Magnums; both?

 

[turbovan]

So it was running strong, and things looked good initially. Then, oil everywhere that didn’t make sense. Coming out from under the valve covers, but little from the breathers. Compression/leak down test was great. Turned out the exhaust crossover had burned through the gaskets(felpro 1213(not s3)), and was blowing exhaust straight up under the valve cover lip. I believe a need for a thicker gasket contributed to the problem.

Unfortunately, I only figured out the above issue because shortly after it was stumbling and I had a dead cylinder; #8.

 

[turbovan]

When I pulled the intake manifold it was clear where the exhaust had been blowing up into the valve cover(sorry no pictures), and into the valley. Pulled the piston thinking that I’d just slap a $70 replacement in, but it was worse than I thought. Piston material was everywhere, and my oil was sandpaper. Every bearing ruined.

At this point I was certainly missing the great fuel distribution of EFI, and knock sensor from the Subaru. AFR’s were great, but #7 and #8 were lean and detonating.

Not yet decided on my eventual full build, I sent the block to the machine shop to be cleaned, and grabbed a cheap($100) set of forged factory compression pistons someone had laying around.

 

[turbovan]

While the engine was out I tackled some other projects. I needed my gauges(wideband, boost, fuel pressure) where I could see them better, and I planned to move the battery to the trunk.

I wanted to give fiberglass a try and always liked the positioning of pillar gauges so I went to work making a custom pod.

I also rebuilt the front harness, and hid it inside the drivers side fender. Relays and 10g wire were used to improve headlight performance, and I touched up the engine bay paint.

 

[turbovan]

The engine bay is looking just a little bit cleaner at this point!

Also, traded some junk for a 360 magnum out of a 2000 ram which I plan to build. It’s a 53020006-360 block which has oil holes for shaft rockers.

Help Identifying this Block

 

[turbovan]

So I’m just about caught up at this point. The engine went back in with new pistons, and slightly thicker Felpro 1213s3 stainless core intake gaskets. However, I had made a discovery with my carb during my prior tuning which was that it could move a significant amount of fuel(650cfm strong signal). So I opted for e-85 over our(Arizona) awful 91. Except it turns out my local stations only mix e-50; even better since I get higher octane and slightly less flow required.

I pulled a LOT of plugs and tuned very slowly. only 10* of timing under boost. Fuel distribution was certainly an issue, and I now have the rear jets 12 sizes above square which I attribute mostly to the hat design.

Boost season is coming to an end as the Phoenix summer approaches, and we had one more track night with cool weather on 4/23. The car was sorted and I was excited to turn up the timing at the track. Took it for the famous “one more” tuning run on 4/21 aaaand it threw the fan belt. Spit up most the coolant, but started up and idled nicely once it cooled down. Unfortunately it seemed to want just a bit* too much coolant.

 

[turbovan]

Just a quick oil change before I head to the track!

Compression/leak down was good. Plugs are beautiful, and heads are off now; everything looks good. I can still get a trickle of water out of the oil pan so the leak is likely at the timing cover, but hopefully I haven’t hurt the block. It’s starting to get hot, and I have other priorities so this is probably it for a while. I’ll likely swap from 3.91’s to 3.23’s while it’s down and make sure the pinion angle is acceptable because I believe it’s positive at the moment.

Here’s a draggy run from the fan belt incident(12psi 10*). Idled off the line, rolled into it, let off before the 8th. Best so far was 101mph with a soft street launch letting off before the full 8th(9psi 15*). Recorded on a friends phone though so I’ll post it up if he gets it to me.

 

[dusted]

I had seen several people blow the thin mr. gaskets right off the bat, but they did get me through the hot side build! 1008’s seem to hold up, but wondering when cometics become necessary. Are you saying stock LA pistons crack around 12-14 or Magnums; both?

Magnums but it looks like you have already put a hurting on them!

 

[dusted]

So it was running strong, and things looked good initially. Then, oil everywhere that didn’t make sense. Coming out from under the valve covers, but little from the breathers. Compression/leak down test was great. Turned out the exhaust crossover had burned through the gaskets(felpro 1213(not s3)), and was blowing exhaust straight up under the valve cover lip. I believe a need for a thicker gasket contributed to the problem.

Unfortunately, I only figured out the above issue because shortly after it was stumbling and I had a dead cylinder; #8.

View attachment 1715731522

View attachment 1715731523

Looks like she leaned out on that cylinder. With the carb hat orientation I can see how that can happen.

 

[451 demon]

You said its a gt45 turbo do you know what a/r wheel are? is it just an ebay one. I'm interested in doing a magnum turbo motor just to play with.

 

[turbovan]

You said its a gt45 turbo do you know what a/r wheel are? is it just an ebay one. I'm interested in doing a magnum turbo motor just to play with.

It’s just the standard $160 gt45 off Amazon from “maxpeedingrods.” 1.05 a/r turbine housing.

 

[turbovan]

Well I stayed busy and barely looked at the duster all summer, but cooler weather is on its way! Pulled the pump and timing cover to look for leaks and immediately found a corroded spot behind the water pump had broken through. So I have a new housing on the way, and am researching a change in cam timing while it’s open.

 

[turbovan]

I also struggled with an electrical issue at the end of last season. Everything was good until I installed a battery shutoff switch. The car died on the first test drive and needed a jump. I had successfully re-wired the car and moved the battery a solid month before installing the shutoff. It seemed as if I fried something the first time I killed the engine with the switch. I’ll have to look into that more when it’s back together.

 

[turbovan]

I pulled my under dash harness for a couple other upgrades. I’m going to run microsquirt for timing and data logging alongside my carburetor. I also have it setup for PWM control of my Audi radiator fan which was previously pulling close to 50 amps in “emergency mode.” Besides that I’m throwing a big chunk of aluminum behind the dash to cool my charged air.