305 tbi swap to 350 carb, TBI, TPI questions
Thread Starter
Junior Member
Joined: Jan 2013
Posts: 49
Likes: 0
From: Louisiana
Car: 88 Camaro IROC, 92 Camaro RS.
Engine: 305 tbi, LT1
Transmission: 700r4, 4l60e
Axle/Gears: 3.43
305 tbi swap to 350 carb, TBI, TPI questions
Okay guys soon I will be starting a new job so I'll have some extra money!
I want to get rid of my old POS 305 tbi. My first question what will be better 350 Carbed, TBI, TPI? It will be a daily driver, but I dont care if MPG is kinda bad just not horrible...Second question what parts will I need for this swap? Im a know a little about swaping and engine work but very much willing to learn! (I want to keep the a/c also) Third and final question how much would you estimate the swap cost? I've been looking at the summit crate engines and such. All I really need is around 300HP but the more the better... What can use off of the 305? Thanks in advance for the help!! Please dont kill me on the pollution crap. I've been turning more towards carb... Im a noob so teach me a little something!
I want to get rid of my old POS 305 tbi. My first question what will be better 350 Carbed, TBI, TPI? It will be a daily driver, but I dont care if MPG is kinda bad just not horrible...Second question what parts will I need for this swap? Im a know a little about swaping and engine work but very much willing to learn! (I want to keep the a/c also) Third and final question how much would you estimate the swap cost? I've been looking at the summit crate engines and such. All I really need is around 300HP but the more the better... What can use off of the 305? Thanks in advance for the help!! Please dont kill me on the pollution crap. I've been turning more towards carb... Im a noob so teach me a little something! 
Joined: Mar 2000
Posts: 43,187
Likes: 45
From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
TBI: There is a sticky in the TBI forum about a "budget" 350 TBI swap. Read through that, as it gives all the details about how to get the most out of that.
TPI: Basically you need to find a complete TPI system. It doesn't have to be from a 350, as the only differences between a 305 and 350 TPI are the injectors, knock sensor, and computer tune. People frequently remove their TPI system, so it's not like they can't be found complete.
Carb: Often seen as the easiest and cheapest, it doesn't come without issues. Having a TH700R-4, you'll need to rig up some means of locking up the torque converter clutch, since the ECM will no longer be able to make that decision. Also, the throttle valve cable attachment is critical, so whatever carb you get, you'll need to get a geometry corrector bracket to attach to the carb throttle arm. If you don't do either of these two properly, a burnt out transmission will be your reward.
Fuel delivery is one area that needs attention with any of these choices. The TBI system has the weakest of the in-tank electric pumps the factory used (with the possible exception of the carb pusher pump they used on a few of the factory carb'd cars). If you build a TBI system for more power, you'll need a better pump. If you switch to TPI, you'll need a pump that can put out more pressure. If you go with carb, the fuel pressure needs to be controlled to a carb-friendly 4-7 psi. You can use the TBI pump along with a return-type fuel pressure regulator, but like TBI, at a certain power level the TBI pump won't be able to keep up.
To me, for a daily driver, EFI just makes so much more sense. Easier to start, better driveability, and better fuel economy. Kind of important things, if you ask me.
Cost - too many variables. Above the cost of the engine, and assuming new parts, the carb conversion costs would include: the carb you decide on, $250-$500, cheap to better - it would be best to get one with electric choke; intake manifold, ~$150 for an Edelbrock Performer (probably the best choice for a daily driver); intake manifold gaskets, $30; distributor, $150 or more for a coil-in-cap HEI (you can find cheap Chinese HEI's on eBay for less than that); spark plug wires, ~$50; throttle and TV cable housing bracket, ~$25; TV corrector bracket, $20; TCC lock-up kit, $85-$125; fuel pressure regulator (don't go cheap here - it has to be return-type, which are more expensive), the Mallory 4309 is $100; and if you replace the fuel pump, $125. The TBI air cleaner will fit the carb, most likely, but its single snorkel restricts flow. Plus thermostat housing and thermostat, upper radiator hose, heater hose, and probably something else I'm forgetting.
TPI: Basically you need to find a complete TPI system. It doesn't have to be from a 350, as the only differences between a 305 and 350 TPI are the injectors, knock sensor, and computer tune. People frequently remove their TPI system, so it's not like they can't be found complete.
Carb: Often seen as the easiest and cheapest, it doesn't come without issues. Having a TH700R-4, you'll need to rig up some means of locking up the torque converter clutch, since the ECM will no longer be able to make that decision. Also, the throttle valve cable attachment is critical, so whatever carb you get, you'll need to get a geometry corrector bracket to attach to the carb throttle arm. If you don't do either of these two properly, a burnt out transmission will be your reward.
Fuel delivery is one area that needs attention with any of these choices. The TBI system has the weakest of the in-tank electric pumps the factory used (with the possible exception of the carb pusher pump they used on a few of the factory carb'd cars). If you build a TBI system for more power, you'll need a better pump. If you switch to TPI, you'll need a pump that can put out more pressure. If you go with carb, the fuel pressure needs to be controlled to a carb-friendly 4-7 psi. You can use the TBI pump along with a return-type fuel pressure regulator, but like TBI, at a certain power level the TBI pump won't be able to keep up.
To me, for a daily driver, EFI just makes so much more sense. Easier to start, better driveability, and better fuel economy. Kind of important things, if you ask me.
Cost - too many variables. Above the cost of the engine, and assuming new parts, the carb conversion costs would include: the carb you decide on, $250-$500, cheap to better - it would be best to get one with electric choke; intake manifold, ~$150 for an Edelbrock Performer (probably the best choice for a daily driver); intake manifold gaskets, $30; distributor, $150 or more for a coil-in-cap HEI (you can find cheap Chinese HEI's on eBay for less than that); spark plug wires, ~$50; throttle and TV cable housing bracket, ~$25; TV corrector bracket, $20; TCC lock-up kit, $85-$125; fuel pressure regulator (don't go cheap here - it has to be return-type, which are more expensive), the Mallory 4309 is $100; and if you replace the fuel pump, $125. The TBI air cleaner will fit the carb, most likely, but its single snorkel restricts flow. Plus thermostat housing and thermostat, upper radiator hose, heater hose, and probably something else I'm forgetting.
Joined: Sep 2004
Posts: 2,777
Likes: 7
From: Casselberry, FLA
Car: 88 V6 'bird/89TBI bird/85 T/A
Engine: 2.8/TBI/TPI
Transmission: V8 T-5/700R4 x2
Axle/Gears: 3.42 open/2.73 open/ 3.27 9 bolt
Re: 305 tbi swap to 350 carb, TBI, TPI questions
If you're new, and you want to learn, then stick with your "POS" 305 for a while and start doing all the upgrades that you need to do regardless of what engine you decide to run.
As mentioned above, fuel injection is nothing to be afraid of and is also my choice for daily driver with plenty of power. My advice with a 305 TBI is to first replace the fuel pump. I use AC Delco EP381 in all my daily driver stuff. My V6 car, the TPI car, and the TBI that my mom drives to work. They all get that pump and it should deliver enough fuel for nearly 400 HP worth of fun.
Next, your exhaust sucks big time. The TBI cars got the worst of everything to choke them down. Just going under my 88 IROC with the TPI 305 and then looking at my mom's 89 TBI 305 I can't believe the difference. The IROC has a 2 3/4" cat back system from the factory with a better muffler. The cat is bigger and the y-pipe is better. Even the manifolds are better. Every single piece of your TBI exhaust is crap, right from the factory. If you are on a budget, then buy some used TPI manifolds, a MAC y-pipe from hawks third gen, a 3" high flow cat and a 3" cat back system. All of that will still work great on any small block chevy you run in your car.
Once you have that taken care of, next is your cylinder heads. A few people think they're ok but I don't like the swirl port 305 TBI heads. On a budget, you can get some used TPI heads or the 1987 4 barrel carb heads (LG4) and they are a nice upgrade over your stock heads. Those heads also work well with a future upgrade to 350 and your current heads don't. My point is that you can do this without spending a ton of dough and still use all the parts later for really decent performance on the street.
I'd swap in a stock TPI or LT1/LT4 cam and learn how to do PROM tuning too.
Follow all the advice in the ultimate TBI mods articles.
If you do all that, you're gonna learn a ton of great stuff and then basically your car will be ready for you to pick up that 350 Vortec block from the junkyard, rebuild it, and drop it in.
Your car will thank you!
As mentioned above, fuel injection is nothing to be afraid of and is also my choice for daily driver with plenty of power. My advice with a 305 TBI is to first replace the fuel pump. I use AC Delco EP381 in all my daily driver stuff. My V6 car, the TPI car, and the TBI that my mom drives to work. They all get that pump and it should deliver enough fuel for nearly 400 HP worth of fun.
Next, your exhaust sucks big time. The TBI cars got the worst of everything to choke them down. Just going under my 88 IROC with the TPI 305 and then looking at my mom's 89 TBI 305 I can't believe the difference. The IROC has a 2 3/4" cat back system from the factory with a better muffler. The cat is bigger and the y-pipe is better. Even the manifolds are better. Every single piece of your TBI exhaust is crap, right from the factory. If you are on a budget, then buy some used TPI manifolds, a MAC y-pipe from hawks third gen, a 3" high flow cat and a 3" cat back system. All of that will still work great on any small block chevy you run in your car.
Once you have that taken care of, next is your cylinder heads. A few people think they're ok but I don't like the swirl port 305 TBI heads. On a budget, you can get some used TPI heads or the 1987 4 barrel carb heads (LG4) and they are a nice upgrade over your stock heads. Those heads also work well with a future upgrade to 350 and your current heads don't. My point is that you can do this without spending a ton of dough and still use all the parts later for really decent performance on the street.
I'd swap in a stock TPI or LT1/LT4 cam and learn how to do PROM tuning too.
Follow all the advice in the ultimate TBI mods articles.
If you do all that, you're gonna learn a ton of great stuff and then basically your car will be ready for you to pick up that 350 Vortec block from the junkyard, rebuild it, and drop it in.
Your car will thank you!
Thread Starter
Junior Member
Joined: Jan 2013
Posts: 49
Likes: 0
From: Louisiana
Car: 88 Camaro IROC, 92 Camaro RS.
Engine: 305 tbi, LT1
Transmission: 700r4, 4l60e
Axle/Gears: 3.43
Re: 305 tbi swap to 350 carb, TBI, TPI questions
If you're new, and you want to learn, then stick with your "POS" 305 for a while and start doing all the upgrades that you need to do regardless of what engine you decide to run.
As mentioned above, fuel injection is nothing to be afraid of and is also my choice for daily driver with plenty of power. My advice with a 305 TBI is to first replace the fuel pump. I use AC Delco EP381 in all my daily driver stuff. My V6 car, the TPI car, and the TBI that my mom drives to work. They all get that pump and it should deliver enough fuel for nearly 400 HP worth of fun.
Next, your exhaust sucks big time. The TBI cars got the worst of everything to choke them down. Just going under my 88 IROC with the TPI 305 and then looking at my mom's 89 TBI 305 I can't believe the difference. The IROC has a 2 3/4" cat back system from the factory with a better muffler. The cat is bigger and the y-pipe is better. Even the manifolds are better. Every single piece of your TBI exhaust is crap, right from the factory. If you are on a budget, then buy some used TPI manifolds, a MAC y-pipe from hawks third gen, a 3" high flow cat and a 3" cat back system. All of that will still work great on any small block chevy you run in your car.
Once you have that taken care of, next is your cylinder heads. A few people think they're ok but I don't like the swirl port 305 TBI heads. On a budget, you can get some used TPI heads or the 1987 4 barrel carb heads (LG4) and they are a nice upgrade over your stock heads. Those heads also work well with a future upgrade to 350 and your current heads don't. My point is that you can do this without spending a ton of dough and still use all the parts later for really decent performance on the street.
I'd swap in a stock TPI or LT1/LT4 cam and learn how to do PROM tuning too.
Follow all the advice in the ultimate TBI mods articles.
If you do all that, you're gonna learn a ton of great stuff and then basically your car will be ready for you to pick up that 350 Vortec block from the junkyard, rebuild it, and drop it in.
Your car will thank you!
As mentioned above, fuel injection is nothing to be afraid of and is also my choice for daily driver with plenty of power. My advice with a 305 TBI is to first replace the fuel pump. I use AC Delco EP381 in all my daily driver stuff. My V6 car, the TPI car, and the TBI that my mom drives to work. They all get that pump and it should deliver enough fuel for nearly 400 HP worth of fun.
Next, your exhaust sucks big time. The TBI cars got the worst of everything to choke them down. Just going under my 88 IROC with the TPI 305 and then looking at my mom's 89 TBI 305 I can't believe the difference. The IROC has a 2 3/4" cat back system from the factory with a better muffler. The cat is bigger and the y-pipe is better. Even the manifolds are better. Every single piece of your TBI exhaust is crap, right from the factory. If you are on a budget, then buy some used TPI manifolds, a MAC y-pipe from hawks third gen, a 3" high flow cat and a 3" cat back system. All of that will still work great on any small block chevy you run in your car.
Once you have that taken care of, next is your cylinder heads. A few people think they're ok but I don't like the swirl port 305 TBI heads. On a budget, you can get some used TPI heads or the 1987 4 barrel carb heads (LG4) and they are a nice upgrade over your stock heads. Those heads also work well with a future upgrade to 350 and your current heads don't. My point is that you can do this without spending a ton of dough and still use all the parts later for really decent performance on the street.
I'd swap in a stock TPI or LT1/LT4 cam and learn how to do PROM tuning too.
Follow all the advice in the ultimate TBI mods articles.
If you do all that, you're gonna learn a ton of great stuff and then basically your car will be ready for you to pick up that 350 Vortec block from the junkyard, rebuild it, and drop it in.
Your car will thank you!
So by what your saying I can use parts off of th 305 to slap on the 350 what stock parts can I use? If I go with TPI Iwill have to get a new harness and ECU Is this simple enough for a average joe to install? Should I be looking for a compete pulled 350 with wiring? What websites are best to buy a engine from? I dont have the skills or time to completely rebuild a engine. Thanks for the help guys! Joined: Sep 2004
Posts: 2,777
Likes: 7
From: Casselberry, FLA
Car: 88 V6 'bird/89TBI bird/85 T/A
Engine: 2.8/TBI/TPI
Transmission: V8 T-5/700R4 x2
Axle/Gears: 3.42 open/2.73 open/ 3.27 9 bolt
Re: 305 tbi swap to 350 carb, TBI, TPI questions
There are tons of 305 parts that you can use on a 350. The problem as I see it is that YOUR 305 (any TBI 305) has the least amount of useable parts. On my 305 TBI project car, if it goes to 350 the only thing getting re-used will be the intake manifold and TBI unit. TBI heads suck, exhaust manifolds suck, camshaft sucks. I will just reuse the intake, TBI and front accessory drive stuff.
Before that happens though, I plan on maxing out this 305 and getting the full potential out of the short block. I'm looking for TPI heads, exhaust manifolds, TPI/LT1/LT4 cam and all the mods I stated above. There's no reason to ditch your TBI fuel system until you have maxed it out and then want more. That's just my opinion but I have had good luck with TBI over the years. It will be less work to just maximize your setup than swapping over to TPI or anything else.
Before that happens though, I plan on maxing out this 305 and getting the full potential out of the short block. I'm looking for TPI heads, exhaust manifolds, TPI/LT1/LT4 cam and all the mods I stated above. There's no reason to ditch your TBI fuel system until you have maxed it out and then want more. That's just my opinion but I have had good luck with TBI over the years. It will be less work to just maximize your setup than swapping over to TPI or anything else.
Thread Starter
Junior Member
Joined: Jan 2013
Posts: 49
Likes: 0
From: Louisiana
Car: 88 Camaro IROC, 92 Camaro RS.
Engine: 305 tbi, LT1
Transmission: 700r4, 4l60e
Axle/Gears: 3.43
Re: 305 tbi swap to 350 carb, TBI, TPI questions
There are tons of 305 parts that you can use on a 350. The problem as I see it is that YOUR 305 (any TBI 305) has the least amount of useable parts. On my 305 TBI project car, if it goes to 350 the only thing getting re-used will be the intake manifold and TBI unit. TBI heads suck, exhaust manifolds suck, camshaft sucks. I will just reuse the intake, TBI and front accessory drive stuff.
Before that happens though, I plan on maxing out this 305 and getting the full potential out of the short block. I'm looking for TPI heads, exhaust manifolds, TPI/LT1/LT4 cam and all the mods I stated above. There's no reason to ditch your TBI fuel system until you have maxed it out and then want more. That's just my opinion but I have had good luck with TBI over the years. It will be less work to just maximize your setup than swapping over to TPI or anything else.
Before that happens though, I plan on maxing out this 305 and getting the full potential out of the short block. I'm looking for TPI heads, exhaust manifolds, TPI/LT1/LT4 cam and all the mods I stated above. There's no reason to ditch your TBI fuel system until you have maxed it out and then want more. That's just my opinion but I have had good luck with TBI over the years. It will be less work to just maximize your setup than swapping over to TPI or anything else.
Or maybe jump a little over my budget and get this http://www.crateenginedepot.com/ZZ4-...P9406C944.aspx Joined: Sep 2004
Posts: 2,777
Likes: 7
From: Casselberry, FLA
Car: 88 V6 'bird/89TBI bird/85 T/A
Engine: 2.8/TBI/TPI
Transmission: V8 T-5/700R4 x2
Axle/Gears: 3.42 open/2.73 open/ 3.27 9 bolt
Re: 305 tbi swap to 350 carb, TBI, TPI questions
This is the crate engine:
https://sdparts.com/details/gm-goodw...gines/12530282
This is the camshaft:
https://sdparts.com/details/gm-perfo...parts/12480002
This is the intake:
https://sdparts.com/details/gm-perfo...parts/12496821
The know how to burn new PROM chips you get from our forums here. This is my plan, anyway.
https://sdparts.com/details/gm-goodw...gines/12530282
This is the camshaft:
https://sdparts.com/details/gm-perfo...parts/12480002
This is the intake:
https://sdparts.com/details/gm-perfo...parts/12496821
The know how to burn new PROM chips you get from our forums here. This is my plan, anyway.
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