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post #1 of 6 (permalink) Old 12-13-2019, 10:43 PM Thread Starter
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1990 Chevy Cummins swap sm465

Looking to Swap my 1990 Chevy 3500 1 ton 2wd with a SM465. It has a 350 small block in it now. Looking to swap a 12 valve cummins into it. What do I need to buy or fabricate. I've never done anything like this before. I have a understanding of what it involves. I would like to know if I can buy an adapter plate online to go to my SM465 or is the bread van adapter the way to go? My grandpa will be helping me with the swap. He was a diesel mechanic years ago. He really doesn't agree with the swap because it's not a Chevy engine. I would like to go with a 6.2 or 6.5 but there isn't many around here and I don't know much about them. The truck is all original 22,000 miles. Don't mind the pulled out tow mirrors LOL .

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post #2 of 6 (permalink) Old 12-13-2019, 11:33 PM
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First off, welcome.
I had mine built by a local shop. Harbour City Diesel. So I don't know all the details.
I can't help with your trans adapter either. I run a NV4500.
The shop slide the trans cross member back 3.5" and shorten the shaft.
Used the gm motor mounts and made adapter plates to the block.
You may need to adjust the seam with a hammer where the firewall and floor pan meet.
Only you and grandpa will know you had too. No one else will see it.
You'll love the Cummins conversion when it's done, and don't even think of doing a 6.5

On a side note, it took around 68 hours iirc.

'92 GMCummins with all the usual crap.
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post #3 of 6 (permalink) Old 12-14-2019, 01:11 PM
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4x4 would be easy but 2wd I'm guess that cross member thats under the motor would be in the way? I'm not sure about the coil front suspension and how much room it leaves you. I'm sure somebody on here has probably figured it out though.
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post #4 of 6 (permalink) Old 12-14-2019, 01:13 PM
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Sorry I'm new to computers. I didn't see the other guys response
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post #5 of 6 (permalink) Old 12-15-2019, 05:43 PM
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Go to the engine swap section of forum it has been done several times and has some well documented write ups on the exact project you are looking to do.

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post #6 of 6 (permalink) Old 12-19-2019, 03:20 AM
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IMO you really have 2 ways to go about it....

1) SM465 or NV4500 (both GM trans) mated to the cummins using the adapter the factory 4BT bread vans used. Without overdrive (SM465), you most likely need to re-gear the axle (14boltFF) to 3.21 for highway speeds.

2) Use a 5/6 speed that comes with the cummins. With overdrive you may be able to tolerate a 4.10 axle. 3.42 or 3.73 would be better.

A body lift can be helpful in positioning the engine. There is also an oil pan difference between 89-93 and 94+. The 94+ style should let you place the engine slightly further forward; although not sure if that's beneficial or not.

93 W250 Club 6BTA |5spd |60/80/3.54/Lockright |4" lift |315/75R16 |HX35 |5x.012s |BD pin & gov spring
90 D250 6BT |5spd |D60/3.54/Lockright
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