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Mods to put an LS3 in an LS1 Car

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Old Feb 21, 2012 | 12:13 PM
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Default Mods to put an LS3 in an LS1 Car

Ok, guys. I got a 1998 Z-28 I bought as a roller off of a guy who used the motor and trans in a street rod. Long story short, I am putting a iron block 408 with ls3 heads and intake. The question is other than the map sensor needing to be moved to the back of the intake and the injector connector types are different and require an adaptor, what other mods need to happen? I know there was an AIR pump with the factory ls1 which will be removed, so if there a shorter belt to accompany this? What about the factory ls1 vaccum controlled fuel pressue, how is this going to work with the ls3 rail? i don't see a return line or regulartor in the ls3 rail? I guess where i didn't take this thing apart i don't know what my best options are here. Is there anything else im missing?
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Old Feb 21, 2012 | 08:51 PM
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Anyone.
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Old Feb 21, 2012 | 08:55 PM
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The engine sensors and locations are different. Gen III is 24x, gen IV is 52x.

What block & crank do you have?
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Old Feb 21, 2012 | 09:13 PM
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if you have a gen 3 iron block, then most if not all the sensors should be the same as the LS1, and LS3 heads will work just fine with LS1 body car on a 408
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Old Feb 21, 2012 | 09:19 PM
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I would like to know im thinking about doing the same thing.
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Old Feb 21, 2012 | 09:27 PM
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well since you say iron block i assume you mean a gen III block with ls3 heads. in that case pretty much everything will swap over. the only things you would need is the injector adapters to work with the ls3 intake, map sensor relocation, and knock sensor relocation harness. if you wanted to do a complete ls3 swap you would need all of the above and a lingenfelter reluctor wheel converter box because the ls3 uses a 58x tooth reluctor wheel. and the air pump can be removed without issue, it is not belt riven so no shorter belt is needed.
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Old Feb 22, 2012 | 05:53 AM
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What about the fuel system? Where is the return line on the ls3 rail? Also my block has knock sensors in the lifter valley so that made it gen 3 correct? I have a compstar crank with 24 tooth wheel. As far as the year of the block I'm not 100% I picked this thing up from a junk yard and it was already removed, he had like 20 blocks and I picked the cleanest one.


Last edited by onebaddmax; Feb 22, 2012 at 06:03 AM.
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Old Feb 22, 2012 | 07:23 AM
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the fuel system on the ls3 should be all good to go just make sure you get the evap solenoid ith the ls3 intake because I think that is a little different. But since you have a gen 3 block your knock sensors will be fine and so will your cam harness. you will just need a map extension since it will be in the front of the intake.
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Old Feb 22, 2012 | 07:34 AM
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While I'll agree with redbird and it's most likely a genIII, you'll need to confirm the crank reluctor ring is a 24x.

On the later blocks, the knock sensors are on the sides of the blocks. The bosses can be tapped to use the LS1 style knock sensors.
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Old Feb 22, 2012 | 07:36 AM
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So it can be done easyish if you know what your doing?
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Old Feb 22, 2012 | 07:40 AM
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Well it is a bunch of work. Harnesses need to be extended and sensors need to be swapped to LS1/genIII/F-Body style. If it's a genIV/52x motor, the LPE converter box mentioned by redbird is needed OR the crank reluctor needs to be changed to a 24x.
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