305tbi to 350tbi (or carb) vortec swap

I have a 91 Chevy silverado with a 305 in it that's pretty much worn out. I'm thinking of swapping in a 350 (maybe vortec) if I came across one at the right price. Would I need to do anything special to the tbi or the computer after the swap? Are vortec motors externally balanced?

Also, would the tbi help it breath or would it be restricting it? If the latter, should I switch to a 4 barrel carb?


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I dont care what you run as long as it isnt a weak tb1 motor, but you should go with a vortec they are cheap and will bolt in nice.

Bump. Any other feedback? I'm mainly interested in whether the tbi is better or worse than a 4 barrel for a regularly driven truck and whether i will need the original flexplate for the vortec engine or if i can use the one that is on my truck.

The TBI intake won't bolt up to the Vortec heads, IIRC. You'll need an aftermarket Vortec TBI (GMPP P/N 12496821) or a Vortec 4 bbl. intake w/a TBI adaptor.

I would seriously consider a chip for the ECM.

They have an externally balanced flexplate/flywheel. Try to get one w/the engine.

For ease of tuning and the ability to cam the engine as you choose, a 4 bbl. non-computer engine management system would be my choice. But this leaves the tranny needing a different computer to manage it.

But if you can get by w/a stock cam, with specs that basically mirror the 305 TBI's specs, the TBI will work OK- even though the engine is larger, I've found no drivability issues with this set-up. YMMV, however.

A custom chip would be the ideal solution, but the TBI isn't known for it's upper-end power. It's good for mileage and torque (it is a truck, after all ).

Bottom line- GMPP TBI, computer-compatible cam, keep the stock ECM or use a 350 ECM.

Use a modified chip if you want more cam.