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Old 05-18-2011, 09:01 PM
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6.2 Diesel to 350 swap "Trans" Questions?

I have an 83 Chevy Diesel with a TH400 that I'm building a "2 piece rear main" 350 for. My question is, what about the flex plate? I was told I need to change out the Torque converter and governor. However, I'm wondering about the flex plate, because the diesel flex plate is a 138 tooth unit, and from what I've read on here, it's heavily weight balanced for the diesel engine, which means it can't be used. Also, does changing the flex plate mean that I need to install the original 350 starter? Basically, I need to know what flex plate I should purchase that will work on my setup? If anybody can help me out with this I'd appreciate it. Thanks

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Old 05-19-2011, 07:11 AM
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You have to change flexplates because the one bolted to the diesel won't bolt on to your 350 crank.

You match the flexplate to the engine/starter. Then the torque converter only has three options for bolt pattern: small 3-bolt, large 3-bolt, and 6-bolt. A 6-bolt converter can be used on a large 3-bolt flexplate, you'll just only use 3 bolts.
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Old 05-19-2011, 09:32 AM
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From what I could find on Summit, all the flex plates that come up for the year of motor I'm using, are 168 tooth. Is this what I'm supposed to use?
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Old 05-19-2011, 10:10 AM
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Either the 153 or 168 tooth flywheel could be used, but I would get the larger one since it will almost definitely have the large pattern. Many aftermarket flexplates are drilled for both patterns.

Make sure your 350 block has the offset hole drilled for the starter. Large flexplates (168 tooth) use starters with an offset mount pattern. Small flexplates (153 tooth) use starters with an inline bolt pattern.

As long as your engine is mostly stock (low rpm torque) the diesel converter will work fine and give you the most MPG and the least heat. If you have upped the engine's power, I would consider a stock gasoline torque converter since it will stall a touch higher. There was a time that those diesel torque converters were highly prized for swaps into gas trucks, RVs, and heavy cars for their low stall and heat. Put it this way... I paid over $450 for a custom built diesel converter just like yours about 10 years ago.

I'm not sure about the 6.2 TH400s... I don't think they have a vacuum regulator. That will need to be addressed. Try the governor as-is first. If it shifts too early for you, its pretty easy to swap that out later with the transmission still in the truck.
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Old 05-19-2011, 12:04 PM
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Awesome thanks! That's what I was looking for.
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Old 05-19-2011, 04:04 PM
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Quote:
Originally Posted by frodin1
From what I could find on Summit, all the flex plates that come up for the year of motor I'm using, are 168 tooth. Is this what I'm supposed to use?
the 168 tooth flexplate will be easier on starting than a 153 tooth.
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Old 05-19-2011, 09:06 PM
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motor swap

i dont think a sbc 350 will bolt up to a diesel trans
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Old 05-19-2011, 10:30 PM
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Your the first person that's said that. Why wouldn't it? TH400 is the same either way isn't it? The only difference I heard was the torque converter and the governor. The 6.2 liter diesel block is the same as a 350 block? I'm just curious , why?
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Old 05-19-2011, 10:38 PM
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I probably shouldn't use the term "the same" when comparing the two, because obviously there are major differences inside and out on the diesel. But as far as bolt patterns go, I pretty sure they are the same.
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Old 05-19-2011, 10:42 PM
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as I recall the 6.2 and 6.5 diesel engine share the chevy bell housing bolt pattern and the location of the side mounts on the block are chevy location too.

it has been a few years since I worked on those old diesel engines... correct me if I am wrong
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Old 05-19-2011, 11:12 PM
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Everything I've read till now says they do. I'm just wondering if knows knows something I don't.
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Old 05-20-2011, 05:34 AM
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In 1981 I pulled a sick diesel from a 1980 Chevy P/U and tried to replace it with a 350. It would NOT bolt to the tranny by bolt pattern. I had to rebuild the diesel. Beyond those details, haven't got a clue as to why 30 years later beyond the fact it cost the owner a lot more bucks. B-O-P bolt pattern vs Chevy, perhaps??

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Old 05-20-2011, 06:25 AM
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the 5.7 Olds engine block based diesel was another animal and had a few problems. Seems like it was required to pull at least 1 cylinder head for repair on each engine with in 20k miles from new. That was a BOP design bell pattern
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Old 05-20-2011, 10:03 AM
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What transmission was in the 81 truck ? From what I understand, the older trucks had a different transmission than what I'm dealing with. I am dealing with a TH400, and trying to bolt up to a small block. Not only that, but I'm pretty darn sure if, I do have any problems, someone probably makes an adapter. I also have a TH350 that was in the back of the truck when I bought it, but I was told this would not bolt up.
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Old 05-20-2011, 10:04 AM
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What is BOP?
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