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Tbi 305 To 350 Swap

1812 Views 4 Replies 4 Participants Last post by  firechicken383
Tbi 305 To 350 Swap idles poorly

I recently swaped my 305 to a 350 in my 93 chevy pickup. I kept all the sensors, tbi, computer. I set the timing at 0 dregrees like it said in the manual. Motor starts fine and runs normal for about 3 to 4 minutes then starts to slightly miss. Computer sets the timing at around 18 to 20 degrees advanced. Goes good when I mash the throttle but almost stalls at ilde in gear at say a light to stop sign.
Could the 305 k.s be at fault? Is there a difference?

keith black flat top pistons
extreme 4x4 comp (cam 4 dgrees advanced ground into it)
crane double rollar chain
ported, polished, balanced
flowtech shorty headers

In time I plan on bigger tbi , performance intake, and chip
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hope i can help

hey there i was wondering if you had any repograming done the the ecm it kinds sounds like its presets are not happy with your cam specs if there is a place there that does reprogramming i would give them a call and quizz them good luck man
Thanks for replying billlt583. No I haven't had any reprogramming done to the prom. I was just going to change the computer to a 350 computer. I just changed the knock sensor and will be changing the esc this weekend. Hopefully that will iron out some bugs.
Checked all the basics? Leaks, wires, plugs etc. What temp is it at when it starts to miss? Any engine codes? I'd be hesitant to start replacing spendy electrical parts if you havent checked these things right. Make sure the timing is correct and the distributor is in right. Check your vaccum with a guage and for leaks.

Normally the sensors will throw a code. See if they cant be tested at a parts store.
I think billlt583 is right about the computer. Also, the 305 injectors and knock sensor are different than the 350. It will obviousely run like this, but maybe not to full potential.

What 4x4 XE cam are you running? I think once you swap for the correct injectors and get your computer program right, it'll be fine.

BTW, In my experience, your engine will really like the initial around 4-8 degrees BTDC instead of the factory "0". I think it will run much better that way. Good luck:thumbup:
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