I have a 1990 GMC G3500 with a 350 and assuming a th400 transmission. The transmission's not the issue. I have an RV weighing about 7500 lbs. My current 5.7 ltr simply won't pull this trailer. It will on flat straight roads but there not enough power. My plan is to replace the current 350 with a 454 VIN "N". Does anyone see any potential problems with the swap? Will the current control unit work? Will the existing wiring harness work? Are engine mounts an issue. Is bolt up to the transmission ok. I know my gas mileage will suck but I need the power big time.
Going from a small block to a big block will require a lot of changes. It may be more cost effective to replace your worn 350 out with a new rebuild with a towing cam or a small block meant for towing (like a 383 stroker). Conversion to carburetor would be your best choice as the tbi is not the best. Going with an overdrive/underdrive kit from GearVendors may also be ideal; factory performance while accelerating or climbing grade is greatly improved by the torque multiplication of 6 forward ratios. It's the same reason the big 18 wheelers have 2 and 3 speed auxiliaries for 10 to 15 or more gears.
Thanks for the info. I'm not a mechanic and will have to pay someone to do the work. I'm looking for the best solution for my Van. I know towing with a van is different then a truck but I have the van and like it. Besides, I can't afford a new truck or the payments for years that come with it. So, it's the van. I would consider the small block. It's like who do I trust to really do the work with the outcome I want and need. In some respects I like the idea of the 454 because of the proven power. If a 350 modified or 383 is answer and somewhat less expensive then that's the way I'll go. I'm just trying to get the right information so I don't screw this up. Thanks
Looking for a Used Vandura in your area?
CarGurus has 14 nationwide Vandura listings and the tools to find you a great deal.
Search GMC Vandura Questions
GMC Vandura Experts