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Discussion Starter #1
This has been a long time in the making. Making steady progress every week. Trying to get ready for the Willys rally on Memorial Day down in Moab.
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Nice truck, do you have room for an I'cooler? What axle ratios do you have? Do you have a 5 or 6 speed trans. in mind if the wide(for a diesel) ratio 435 is awkward?

Ed
 

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Thanks for the questions.
I am planning on squeezing an inter cooler in up front down low.
Axles are both Dana 44’s with Eaton Trutrac lockers. 4:10 ratios.
Transmission is a 4-speed NP435 with no overdrive. This is going to be a low speed Moab head-turner. Not a freeway runner. In the future, an NV4500 would certainly switch it up.
 

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Looking nice. Might think on changing your turbo to an HX30W down the road. Would bring on boost much quicker than the H1C. Not sure how much performance you're looking for.
 

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I’ve got 1958 Willys pickup and notice that you also kept the original frame as I did. To me it’s so much simpler as far as mounting the cab and bed compared to using a late model frame. I did box mine extensively and used 81 GM springs and brackets. It looks as though you are using the original springs and shackles ? There’s something about these old Willys that I just love. Keep up the good work. You’re going to love it when you get it on the road. I have 4:11 gears along with a 208 transfer and 4l80e transmission. It’s a lot of fun to drive. I understand your build as off road but the longer you drive it the more you may want to have a highway gear.
 

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real nice build, what tires are those?
Thanks for the question. I was going for the old 'Super Traction' look. Found those tires, but they were more than I wanted to spend. I ended up buying [online] these tires. The brand is Deestone and I believe they are imported from the UK or something. Tire size is 7.50 x 16.00.
 

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I am looking at doing this exact same thing, I just picked up a 52 as well. Keep giving us updates, I'd love to see your progress. I'm building mine as a rock crawler and will 4 link the rear 3 link the front. I haven't decided yet if I'll go coilovers or ORI.
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Discussion Starter #10
Topic: Exhaust manifold.
The exhaust manifold that came with the motor has the turbo-mounting flange at the rear cylinder. To stuff this motor in the truck, that puts the exhaust outlet off the turbo right against the firewall with no room for an elbow to direct it down. As a result, I am looking for another manifold that has the turbo flange mount in the center [between cylinders 2 and 3] with a 45 degree downward angle. Steed Speed sells them and are very proud of them [at $625]. I have read of others that take a 5.9L exhaust manifold and cut them down to get the turbo location where they want it as well. What I am hoping for is some advice on where to pick up a cast iron manifold for this 3.9L. Or what have others done in this situation? Thanks.
 

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I took a first gen manifold and took it took a local welding shop know for doing cast welding. He took my manifold and cut each end cylinder off at slight angle. Then he took small thicker piece of plate and welded it on after heating up manifold in kiln. It turned out great I think he charged me like $65 years ago. Made turbo in perfect center of engine.
 

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There are quite a number of manifolds for the 4bt. The back rear drop was the most common on road engines. The top center mount was found on 4bt's in some of the Ford vans and lots of industrial engines. If you have adequate hood clearance, that one can be had pretty cheap. That's the one you see in Welderwiskey's photos. Cummins part 3901635. Tons of them on ebay. Saw one for $85.88 shipped. Another possible is one that places the turbo up front and tilted away from the head. That one is Cummins part 4934697 or 4984697 and maybe another number. Again a matter of hood clearance. The cut down 6bt manifold is yet another option. Welder, don't think the pulse effect comes into play much if you're using the HX30W which is single scroll. Might be some effect on a twin scroll. Also, there's even a cast iron down pipe similar in design to Welder's. That one is Cummins part 3910992. That one is a little expensive. About $95 was the cheapest I saw.
 

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Char, that downpipe on mine was pretty cheap. I just welded it up from 3” exhaust fittings I got at NAPA. I do wish I’d got a half marmon for the connection to the turbo. So far the flange I used has held up. Good test for my weld also. The flex joint was a available at Summit
 

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Yes, the full Marmon flange is a little tougher to fit. If you had wanted, you could have a machine shop dress the surface of the flange and change it to a half Marmon. I have one of each laying around but forget how much difference there is in thickness. None of the Cummins cast iron exhaust part are very cheap. That one I showed in the photo was actually for and industrial with a vertical muffler. Has a flange with bolt holes on the side to attach it to the exhaust manifold which also had a place for the support brace. Here is another tight 90 outlet pipe but again it's for a half Marmon. You can find these used in the $50-60 range. About $180 new. Ouch. It came on 6bt's in medium duty trucks.
 

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Discussion Starter #18
Greg Morton, I picked up a stock 5.9 manifold from my brother [recently replaced that stock manifold with a stainless one from Steed Speed] and cut each end cylinder off. Puts the turbo in the center and at a 45 degree angle. I just need to cap the ends.
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Discussion Starter #19
My next major decision is exhaust size: 3 inch or 4 inch? What are the upsides and downsides for each? Thanks.
 

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On a 4bt, 3" should plenty. Exit in the turbo is only about 2.5". Now if you were planning some serious big power using twin turbos and one of those was an HX40W then I'd go 4" since that was it's stock outlet. Make sure you use a good free flowing muffler. I had read an article some years ago that said you can actually get the exhaust too big on a turbo diesel and loose some power. The turbo wants a little back pressure, just not too much. Don't know if that was truth or fiction. Now if you wanted to do a slight bit of work to gain a little power, you could do some minor port work. Major porting on a diesel head can be very tricky. This is very minor and proven to work. What you want to do is take your manifold and mark the port location with the gasket. Then clean up the ports removing the mark. Your manifold ports should then be the same size as the gasket. Then use a felt tip with a fairly broad point and mark the head. Gently clean up those ports and leave the mark.You want about a 1/16" border inside the gasket. Going from a smaller port in the head into the larger one in the manifold increase gas flow speed which improves turbo spooling. Don't have to remove the head to do this. Have a shop vac there at the port to suck away any grindings.
 
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