Looking to see what serpentine belt I need to use on a 3800 sc swap. I already have the supercharger belt. But I'm looking for the drive belt to power the air conditioning and alternator. I am using a factory 3800 air conditioning. The donor engine is out of a 1998 Pontiac Grand Prix GTP.

The belt you will need depends on your layout. You most likely removed the Power steering pump, Where you mounted the Alternator and tensioner all changes what belt you will need. If you have the original belt, cut it and wrap it around your belt drive system and take a measurement. You will want to compensate for the tensioner movement, i like to load it fully so I get the minimum length and then go a size or 2 up from what ever that ends up being. Get what you think and the next length up. Can always return the one you don't use. It is a bit of trial and error.

If you used someone's prefabricated alternator relocation kit, they should know what the belt needed is.

[This message has been edited by jelly2m8 (edited 04-24-2025).]

The right size serpentine belts to use on any swap is a difficult question to answer. It depends on what AC compressor is used, what alternator is used, what type tensioner is used, what supercharger pulley is used, what intercooler you have and more importantly how everything is mounted. Best to measure up with a tape measure and go from there. Jelly2M8 has it right.


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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 05-06-2025).]