K31 as Single

Bought a K31 for cheap a while back and was just going to flip it but decided to fool around. I know that the ATS A5000 has some t3 housing on it. Wish I had one to look at. I was also reading in older posts that II used to sell machined s400 housings to fit the k31. It got me thinking to try one my self. I purchased a 83/74 S400 .80 housing and started comparing. So after a hours on the lathe and lot of measuring I got it. So with a now k31/s400 hybrid, putting it on the truck is now in process. Gonna run it for a week or two just to play around. I know it isn't the best bet for a 12 valve. Seeing how to its a 71/76/.80 it might be better than I expect. Truck is as described in my signature except an exhaust manifold. Gonna take forever to spool but a rocket ship when it lights. Any one have any thoughts. Might dyno it at scheids in 2 weeks if I get all the parts in time. I will let every one know how it turns out.

Some pictures of how it turned out and comparison to the t6 1.28 housing

Going to choke up right around the RPM where it will actually start to make power is my guess.


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So I finally was able to get around to installing the k31 this weekend. With an s400 compressor elbow, he351 to hx40 exhaust adapter, and the t4 manifold it fit but its tight. Trying to keep it on the low buck otherwise I might have ran a spacer on the manifold and the appropriate down pipe. The Coolant line for the heat exchanger had to be removed in order to make clearance for the massive front cover. No cutting and welding on the intercooler boot needed. I was able to make everything fit without too much interference. I will note that the stock turbo drain does work but needs massaging to fit.

Preliminary runs as of now, with no tuning of the afc as of yet, are yielding a solid 56psi of boost. Temp outside was around 73*. Egts reach 1250 but creep after you hit max boost. With the 5x14 injectors I have no fuel left completely smokeless on the topend. With the limited fuel it takes a bit to stay on top of the charger. If i had the injectors handy Id throw in a set of 5x16s. I can get it to spool around 1900 and am able to lay into it about 2000rpm.

Overall seat of the pants dyno gives me 50hp difference when compared to the 66 that i had on previously.

Isnt a K31 the same thing as an old Aurora 5000?

Yes. They had some different housing options. I just simply just machined a s400 housing to fit for a fraction of the cost.


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Looks good at the very least.


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Next to a 66mm s300 cover

Got to ride in Tyler's truck last night. It is a different animal for sure and will take some getting use to, not so much with the lag but the falling under the charger while cruising thing. Under the hood is inspiring, the kid has it looking super nice. The truck makes your eye balls hurt when it shifts in OD. With the window down it sounds like the truck is going to suck in the passenger fender. Which is impressive because he is running very conservative injectors with this size turbo and still lights pretty well and makes good boost. as a passenger I think it would be difficult to do anything other than go fast in the truck at the moment. Towing the lawn mower would be tough, but for the poor mustang that gets all hormonal at a stop light, watch out.

Were any changes to fueling made for this turbo?

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turbo2387 said:

Got to ride in Tyler's truck last night. It is a different animal for sure and will take some getting use to, not so much with the lag but the falling under the charger while cruising thing. Under the hood is inspiring, the kid has it looking super nice. The truck makes your eye balls hurt when it shifts in OD. With the window down it sounds like the truck is going to suck in the passenger fender. Which is impressive because he is running very conservative injectors with this size turbo and still lights pretty well and makes good boost. as a passenger I think it would be difficult to do anything other than go fast in the truck at the moment. Towing the lawn mower would be tough, but for the poor mustang that gets all hormonal at a stop light, watch out.

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I would think if he put an external gate on this turbo it would be a very nice single.

I have not made any changes to the fuel set up other than minor adjustments on the Star wheel.


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I have a correction to make. The housing on this turbo is a .9 Ar housing not .8. As much Fun as this turbo is I'm going back to my 66. The good news is it is going to Alaska. To run on a different fuel setup and a transmission with a much higher stall. I'm sure that he will chime in after it gets installed.

All the pieces should be here mid next week ! Hopefully winter is late this year ...

Definelty faster than the silver 64. My dp gauge isn't working. I'll get a couple things sorted out and share the results.

Just slapped a stock fuel plate in last week and a stiffer spring turbo2387 mailed me. Took 90% of the surge away. It was spooling surprisingly fast with weak afc spring but would surge eT every gear shift and into lock up. Liking the turbo more and more

Cut the mwe groove to .248" it still will bark but it's easier to avoid now. The factory cut was .140" at 20*. The new one is at 30*

Cutting mwe groove larger - k31 - YouTube