Lt1 engine swap

[03tahoeKC]

I have an 03 Tahoe that has the 5.3 engine. I've recently started the lt1 swap. It's the 5.7 lt1 out of a 95 Roadmaster. I have everything the harnesses and so on. The Tahoe has the mounts with the 4 bolt pattern whereas the 5.7 has the smaller 3 bolt mounts. What out my options and what's the most reasonable thing to do here

 

[The_Family_Tahoe]

I'm not sure why you want to put a gen II motor in a gen III vehicle.
L31 style motors were available in 1999 model trucks sold in Mexico. Those trucks would have the mounts needed to adapt an old style small block into an 03 chassis.
If you want the added displacement of the 5.7 motor in your tahoe, it would be much easier to bore the existing 5.3 LS to accept LS1 pistons thereby getting the 5.7 liters in your existing motor and you won't have to adapt all the different LT1 accessories , mounts, and exhaust to the existing chassis.

 

[L31MaxExpress]

I'm not sure why you want to put a gen II motor in a gen III vehicle.
L31 style motors were available in 1999 model trucks sold in Mexico. Those trucks would have the mounts needed to adapt an old style small block into an 03 chassis.
If you want the added displacement of the 5.7 motor in your tahoe, it would be much easier to bore the existing 5.3 LS to accept LS1 pistons thereby getting the 5.7 liters in your existing motor and you won't have to adapt all the different LT1 accessories , mounts, and exhaust to the existing chassis.

L31 was used through 07 in Mexico but they had LS 4 bolt mount provisions on the blocks.

I swapped a 2004 V6 truck to a 400 SBC a few years back. I used SBC to LS mounting plates with stock LS mounts.

Personally cannot stand the GenIII and GenIV engines myself. Would much rather have a Gen1 or Gen2. 24x swapping the LT1 would fix all of the engines problems in stock form too.

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[L31MaxExpress]

Just looked up the mounts I used. Both plates have countersunk holes. Just a matter a matter of assembling them backwards from the intended use to adapt the SBC engine to the LS mounts. I had to find some countersunk 3/8-16 bolts for the SBC side. Local ACE hardware had them. The 4 bolt brackets that bolt to the LS normally can flip either direction allowing you to align with the set back passenger side mount of the Gen2 if you keep the low mounted compressor.

Adjustable LS Engine Motor Mount Adapter Bracket Kit

www.speedwaymotors.com

 

[03tahoeKC]

Thanks for the help