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305 TBI to TPI swap


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#1 Blackbird Jon

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Posted 15 May 2008 - 11:29 PM

So I am about to swap my '88 350 TPI stuff onto a 305 original TBI short block. Should this thing just fire right up?

Also, how different, if any, are the tune(s) programmed into the same year model, 1988, TPI vs. TBI motors?

Whatever, another black Formula will be back on road sooner rather than later.

#2 SiberianFirestorm

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Posted 16 May 2008 - 03:49 AM

You will need the ECM and wiring harness. i am not 100% sure that a 350 setup will work on a 305, but if it does let me know.

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#3 Mongoose

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Posted 16 May 2008 - 02:47 PM

Be sure to get a 305 TPI knock sensor and you'll either need to change the injectors to 19 pounders or have the programming changed to compensate for the 22#ers in a 305 TPI PROM. TPI and TBI PROMs are totally different animals, it'll need to be changed
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#4 Blackbird Jon

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Posted 16 May 2008 - 07:00 PM

QUOTE(Mongoose @ May 16 2008, 10:47 AM) <{POST_SNAPBACK}>
Be sure to get a 305 TPI knock sensor and you'll either need to change the injectors to 19 pounders or have the programming changed to compensate for the 22#ers in a 305 TPI PROM. TPI and TBI PROMs are totally different animals, it'll need to be changed


You've hit on something Mongoose... I called the dealership and asked about ECMs... they said that either car had the same part# listed for the ECM, but I figured even with the same number, they could have different tunes via the chip.

The plan, just to clarify, is to pull 305TBI from Firebird, mate my 350TPI hardware however it takes to mate it to this 305, then install all back in Formula350 using it's harness and ECM.

So just to help my simpleton mind, parts to be installed to make this work are: TPI intake pieces, TPI injectors, 305TPI knock sensor, and reprogrammed PROM to fit combination... right track?

What about the distributor? Should I run the 305TBI original, or go with the one from my 350TPI?

Keep in mind with suggestions... budget rules and I am sitting on 2 complete cars so hopefully many parts can swap. cool.gif


#5 Mongoose

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Posted 16 May 2008 - 09:39 PM

I don't see how TPI and TBI can use the same ECMs, the PROM for a TPI is physically larger than a TBI PROM. The distributors should be identical small cap HEIs. As long as you're just swapping the engine itself and keeping the receiving car's ecm,harness,TPI and such you're good. You just need a 305 TPI PROM and knock sensor.
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#6 SassySue09

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Posted 17 May 2008 - 06:37 AM

I don't have any info for you about the parts you'd need since I'm more of a carb gal then a TBI/TPI one but I just wanted to wish you luck with the swap and that I hope you don't have too many problems getting it done. cool.gif


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#7 jedimaster

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Posted 17 May 2008 - 06:58 PM

A friend of mine in high school had an 85 305 TPI car with a blown engine- they put a 350 in and bolted everything back up and it ran like a champ (with the engine light on, for whatever reason). I'm not sure if this helps, but there you go.




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