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Compatible Parts 305 to 350 Swap

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Old 08-17-2003, 12:34 AM
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Car: '91 Firebird
Engine: 305 TBI
Transmission: 700r4
Compatible Parts 305 to 350 Swap

I have a Lo3(TBI 305) right now. I'm planning to get a junkyard 350 Block sometime soon. What parts can be transferred over to the 350. I don't have a lot of money and I don't have a lot of mechanic skills. Will my TBI setup w/computer, knock sensors, distributor and all transfer to an old 350 block? What parts absolutely won't go? I don't plan on trying to fit the heads on there, I think I know where to get some L31 heads (I think thats what they were). I Know I'll need a new intake if I go with the Vortec heads. I'll also need the bigger injectors too.

Thanks for any help you can give me.
Old 08-17-2003, 12:38 PM
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Well you can basically swap everything on the top end , but since your going with vortec heads you will change the intake . You need a knock sensor out of a vehicle originally equiped with a 350 tbi for it to work with the computer, youll also need a custom tuned chip or a chip from a 350 tbi car as well. Also the injectors like you metioned. You cannot swith the harmonic balancer I know that for sure . You should be able to swap everything else though.Good luck you have a long road ahead of you.
Old 08-17-2003, 08:26 PM
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You can get away with all the 305 parts. THe only thing is it might run a little lean or rich. That's what I'm doing. I have a perf. cam also. It runs real strong but a chip would make it smoother. At certain rpm's it pulls harder. Until you have the extra cash for a custom chip, It will work.
Old 08-17-2003, 11:11 PM
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Car: '91 Firebird
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So I could even use the crank? I'm pretty sure the pistons and rods won't work, will they? I'm not really sure where I could find another tbi car or truck around here for the computer/knock sensor. Or could I get way with using the 305 sensors and computer if I got a custom chip? Hey, how much should a junkyard 350 block cost? The local wrecker said he'd sell me a running 350 out of a van for $400. Should I just try for the shortblock?
Old 08-17-2003, 11:47 PM
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i did the swap and im using my stock harmonic balancer

search for a post called 350 swap about to begin
Old 08-18-2003, 01:37 AM
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Engine: 350, Vortecs, 650DP
Transmission: TH-350
Axle/Gears: 8.5", 3.42
You cannot swith the harmonic balancer I know that for sure .
How sure are you?
Old 08-18-2003, 12:33 PM
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When I was in auto Tech at my high school my buddy and I tried to do it on his 350 block and my teacher said it wont work correctly on the 350.He may have been wrong but I believed him considering he is ASE master certified and has had a couple bad old cars that were heavily suped up. But if TKD89RS did it that proves me wrong right there .
Old 08-18-2003, 12:53 PM
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you may also need a different flexplate, i think i remember the problem being if your motor is a 86' up then it should have the weighted flexplate. the older style motors are internally balanced and so they dun have any sorts of weights
Old 08-18-2003, 01:13 PM
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since my car was a 89 i had the newer style engine. (roller) and my engine i got was a LO5, whcih was also the newer style. so i didn't need a flexplate if i had an automatic. but i did reuse the balancer. and all pulleys. theres pics of my swap here https://www.thirdgen.org/techbb2/sho...hreadid=146434
Old 08-19-2003, 02:23 AM
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Car: yy wife, crazy.
Engine: 350, Vortecs, 650DP
Transmission: TH-350
Axle/Gears: 8.5", 3.42
Originally posted by IROCaholic
When I was in auto Tech at my high school my buddy and I tried to do it on his 350 block and my teacher said it wont work correctly on the 350.He may have been wrong but I believed him considering he is ASE master certified and has had a couple bad old cars that were heavily suped up. But if TKD89RS did it that proves me wrong right there .
He was wrong. The only harmonic damper that's different is for a 400 SBC crank.

The newer 1 pc seal cranks are externally balanced, but only by the flexplate/flywheel. The dampers are the same.

If there's a weight on a harmonic damper, either throw it on a 400 crank, or in the dumpster. It doesn't belong anywhere else.

Last edited by AJ_92RS; 08-19-2003 at 02:27 AM.
Old 08-19-2003, 01:44 PM
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don't know if it was answered or not but yes you can use the 305 crank in the the 350. stroke is the same bore is not, rods yes pistons no(i may be wrong on that, if so someone correct me). and i reused my harmonic balancer as well.


and just asking a question here, but you dont really need a chip from a 350 to do the swap initially do you? im still running the stock 305 chip, the car could run better but it is getting me by for now.
Old 08-19-2003, 03:47 PM
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Engine: 350, Vortecs, 650DP
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Axle/Gears: 8.5", 3.42
Originally posted by Nate's 88
don't know if it was answered or not but yes you can use the 305 crank in the the 350. stroke is the same bore is not, rods yes pistons no(i may be wrong on that, if so someone correct me).
If you really want to know all about using 305 rods and crank in a 350 block..... read this thread.

Pay attention to that Aron213. He plays with a full deck AND has an Ace up his sleeve.
Old 08-19-2003, 09:30 PM
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so i was right.....finally im learning.

too bad i can't say the same for some of the people in that thread.

that thread makes me wonder though. i reused the rods and crank from my 305 to do my 350. i would imagine that the guy balanced everything. he's not a big name guy or anything but i personally think he does good work. this was the 4th or 5th engine the family has had done by him and not a problem one. think i'll just continue my faith in his work and stop questioning it....
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