View Full Version : c1500 350 to vortec 8.1L 496 swap
10-30-2011, 03:58 PM
im looking into a 350 tbi to a 496 8.1L vortec swap need any advise from anyone who has swapped one of these into their obs and what problems i might run into and also little parts i might need, all help would be highly appreciated :scared:
10-30-2011, 04:42 PM
Big job but totally do-able. You'll want a complete donor vehicle to get the engine, transmission, PCM, harnesses, etc. from. You'll run into things like having to modify the driveshaft. You should seriously, seriously consider upgrading your rear axle to something stronger. Assuming you have a C1500? The 10 bolt rear axle won't like that 8.1 at all. At absolute bare minimum a 14 bolt semifloater is suggested.
The area I see you running into real trouble is mating the new engine harness and your old dash harness. I did a similar swap (non-Vortec to Vortec; a '94 6.5TD to a '96 7.4) and I swapped EVERYTHING - including updating to the new style interior so I could run all factory harnesses and new style gauge cluster so no worry of any issues.
Another trouble area will be your fuel pump and lines aren't up to the task; I don't know what the pressure spec on an 8.1 is but if it's the same as a Vortec 7.4 you can get a pump for a '96 3500 with 7.4 and it will swap directly into your existing sending unit, they even look the same. You may want to steal fuel lines from a Vortec 5.7-equipped truck '96-early '97 in the same wheelbase as yours so that the short sections of flex line where it hooks to the sender are rated for the higher pressure. You'll of course need the short flex lines from the 8.1 truck for the fuel rail end near the engine compartment.
10-30-2011, 09:15 PM
ive been looking and think i might just stick with a v-max at the moment i have the fuel pump i will update, the motor mount adapters, the trans is stand alone its a th400 if it will bolt up witch it should but i might need a spacer ive heard people talking about them for a th700r4 i dont know where i would find one thow. also have a wiring harness that is going to be made for the finall install i see that i need to update my lines.
is their any change in how my fuel lines are ran as in do i need return lines etc...
11-03-2011, 09:12 PM
The 8.1 doesn't require anything to bolt to a th400/700r4/4l60/4l80 (old styles). They have two sets of motor mounts on them as well. You will run into trouble with the ac assembly clearing the frame, the cooling fins on the back of the manifold clearing the firewall, and your exhaust.
Other than that the only major difference from any FI motor swap is the electronic throttle body. I imagine they make a LS style throttle body that fits it but I could be wrong.
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