thetaman85

i have a possible good deal on a 350 throttle body injection motor that would make a good replacement due to the timely death of my 305. he wants 300 for it, with 15k on a rebuild. my question is what do i need to change to make this swap work? what besides the motor would be needed?
thanks for all your help

87WS6

iTrader: (1)

You'd need the wiring harness, computer, intake manifold and any other TBI hardware. Though if you ask me going from TPI to TBI is a step backwards. You can mate TPI from a 305 to any 350CID Chevy engine. You may need a cam change depending on whats in the engine, PROM tuning and of course larger injectors but swapping a new block in while retaining your existing TPI setup is by far the easier way to go.

five7kid

iTrader: (14)

It would make a good replacement engine under your TPI, with some minor details to consider.

The 350 TBI has the center two intake mount bolts on each side at a different angle than the others, while your '85 TPI intake base has all of the bolts at the same angle. Options include getting a later style base, modifying those bolt holes on your current base, or putting your 305 heads on the 350 (I'd favor the last option, after freshening up the heads - 305 TPI heads are much better than 350 TBI heads, even on a 350).

The 350 is one-piece rear main seal, while your '85 305 is 2-piece rear main seal, and trucks typically have 168-tooth flexplates vs. 153-tooth used in f-bodies (most 350 TBI engines were in trucks, so I'm assuming that's where this one came from). Simple enough, buy a flexplate for an '86-92 F-body V8 automatic (should be less than $50 new).

You will need a 350 knock sensor and module. Might be able to get those from the vehicle the 350 is coming from. Most people leave the knock sensor itself on the engine when they pull it, so all you may need is the module.

350's used 22 lb injectors from the factory, vs. 19 lb on 305's. You can probably get by with the 19's, except they might not be adequate at max power conditions.

thetaman85

what would be involved in swapping my tpi setup to the 350 tbi?

thanks

five7kid

iTrader: (14)

I addressed that in the 2nd, 4th, and 5th and paragraphs above.

thetaman85

Tyvm

thetaman85

What if I wanted to swap to A carbed 350, what would i need to change? Would I need a computer at all and if I got rid of it would the check engine light be on permanently?
Thanks for your help

five7kid

iTrader: (14)

That would be an EFI to carb conversion, addressed in a tech article linked from the thirdgen.org homepage. Also linked in the "welcome to the carburetor forum" sticky in the Carburetor forum.

If the ECM is completely removed, the check engine light would not come on.