Conversions & Swaps LSX Engines in Non-LSX Vehicles
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Old Feb 19, 2018 | 07:45 PM
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Im building a rat rod truck on a 2003 Chevy 2500hd frame and using a 5.3/4L60e out of a 99 half ton. Not knowing hardly anything about Chevy I figured I’d be able to drop the Powertrain in and maybe have to change motor mounts a bit but they are way off. The chassis had a duramax originally, is there a mount kit that i can buy to bolt in my 5.3 or will i have to weld up my own? The motor sitting in the engine bay currently is up higher and possibly back from stock location as well as being crooked. I’m not having any luck searching so any help or a link would be greatly appreciated.
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Old Feb 20, 2018 | 09:44 AM
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The 2500HD is a different frame than the 1500, 1500HD, and 2500.

The duramax isn't even anywhere close to the same engine as a Gen 3/4 small block and nothing is going to be compatible.
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Old Feb 20, 2018 | 09:53 AM
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You would be way ahead of the game if you start with something that already came with a 5.3, It's not cheap to change over wiring/mounts/cooling system and so on.
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Old Feb 20, 2018 | 05:23 PM
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Ill be using the 2500hd chassis regardless. I have a complete 99 that had the 5.3/4L60e in it, i bought it as a parts donor so i have the Powertrain, wiring and computer, cooling system and can cut the frame mounts off to weld on my frame. I wanted the heavier frame and longer for that matter, i had to stretch a crew cab chassis another foot for my cab. So will my best/easiest bet the to cut off the frame side mounts off of the 1500 and weld them in place of the ones on my 2500hd?
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Old Feb 20, 2018 | 05:53 PM
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I was thinking there was a 2500hd with a 6.0 gas engine and sure enough there was, All you need to do is find those mounts and see if they will work on your frame.
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Old Feb 20, 2018 | 06:22 PM
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That’s why i was hoping it could be near bolt in, 6.0 is basically the same block. Where would you recommend looking for the mounts? See if i can track down some used parts or just look for new and return them if they wont work?
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Old Feb 20, 2018 | 10:57 PM
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The problem I see is that you are starting with a diesel-equipped chassis. It could very well have a different engine mount crossmember than the gas-powered trucks. Don't know for sure on GM trucks. The diesel engines are usually heavy enough to require different frame members, if not different frames altogether. This is why it was suggested to use a chassis that was originally gas powered.
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Old Feb 20, 2018 | 11:09 PM
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Do you have emissions testing? Cause gas-diesel can be a bugaboo as well, the VIN on the frame is different gas vs diesel..

Your fighting similar issue to swapping a Jeep straight six into a 4cyl chassis,, its a LOT more rework than you'd think at first.
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Old Feb 21, 2018 | 01:19 AM
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Place your engine and trans where it needs to be,get out the torch,sawzall,scrap metal and weld in those mounts as required,you called it a rat rod after all...
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Old Feb 21, 2018 | 08:48 AM
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There’s no emissions testing that I’m aware of plus when I get the truck titled it will have a new vin and the ones on the body and frame will be void. I have to buy new motor mounts anyways, mine are crunchy, so I can see if they’ll work. If not I plan on cutting the diesel ones out and welding in the gas ones. It’s just gonna take a little longer than originally planned I guess
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Old Feb 22, 2018 | 09:14 AM
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Originally Posted by tfi racing
Place your engine and trans where it needs to be,get out the torch,sawzall,scrap metal and weld in those mounts as required,you called it a rat rod after all...
Kinda what i was thinking?........
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Old Feb 22, 2018 | 12:13 PM
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TFIracing is right.
I'm having a hard time picturing a 99 model rat rod cab.
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Old Feb 22, 2018 | 07:50 PM
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I put together a 1954 international crew cab and am usin the factory front sheet metal and a widened bed on my frame. Waiting on the moderators to approve my picture for the post. I’m wantin an old looking truck on a newish frame and Powertrain.
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