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Hi,

My 1980 Trans Am is running a 305 (non-turbo) linked to a TH350, where as my 1985 Chevy Van20 has a 350 (TBI) linked to a TH400.

What I intend doing is swapping the engines, along with the tranny, between the two cars however my concern is blowing up the ECU in the process. I don't want to do that.

Would appreciate any advice coming this way.

Best!
 

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Hi,

My 1980 Trans Am is running a 305 (non-turbo) linked to a TH350, where as my 1985 Chevy Van20 has a 350 (TBI) linked to a TH400.

What I intend doing is swapping the engines, along with the tranny, between the two cars however my concern is blowing up the ECU in the process. I don't want to do that.

Would appreciate any advice coming this way.

Best!
I would give this a no vote. There's more involved than the computer that has to come over. All the wiring, fuel system, emissions, etc. The TBI is no gift except for the 350 short block. The heads are the accursed Swirl Ports meant to make torque for a truck not horsepower for a car. The TH400 is a beefsteak transmission in this case for a working truck. For a passenger car with a 350 SBC unless you’re building a competition level 350 this big TH400 isn’t needed. The TH350 is a much better match for a 350 SBC. Not that this swap isn't doable but there's so much involved and in the end so much that's been compromised that I really think that you're money ahead to put a crate 350 into this and either rebuild the TH350 or better yet get your hands on a 700R4, stiffen up the rear axle ratio if its GM's ubiquitous 2.73 with something at least at 3.08 for cruising or steeper if you want a harder launch. Then you reap the benefits of the 700R4’s deeper low than the TH350 or 400 for getting away from stops, and you have the benefits of overdrive 4th and a lock up converter for cruising fast without burning a lot of fuel.

You can get a preview of what the swap you’re thinking of involves at the detail level from Mike Knell’s book "Chevrolet TPI & TBI Engine Swapping". I’d get a copy and read it before going further.

Bogie
 

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I would give this a no vote. There's more involved than the computer that has to come over. All the wiring, fuel system, emissions, etc. The TBI is no gift except for the 350 short block. The heads are the accursed Swirl Ports meant to make torque for a truck not horsepower for a car. The TH400 is a beefsteak transmission in this case for a working truck. For a passenger car with a 350 SBC unless you’re building a competition level 350 this big TH400 isn’t needed. The TH350 is a much better match for a 350 SBC. Not that this swap isn't doable but there's so much involved and in the end so much that's been compromised that I really think that you're money ahead to put a crate 350 into this and either rebuild the TH350 or better yet get your hands on a 700R4, stiffen up the rear axle ratio if its GM's ubiquitous 2.73 with something at least at 3.08 for cruising or steeper if you want a harder launch. Then you reap the benefits of the 700R4’s deeper low than the TH350 or 400 for getting away from stops, and you have the benefits of overdrive 4th and a lock up converter for cruising fast without burning a lot of fuel.

You can get a preview of what the swap you’re thinking of involves at the detail level from Mike Knell’s book "Chevrolet TPI & TBI Engine Swapping". I’d get a copy and read it before going further.

Bogie

Thank you so much. I was thinking of all that and you're right... It's not really worth it. The thing is I;m in karachi, pakistan and we don't have crate motors at our disposal. PLus, What I have running in the Trans Am is a 305 and not a 350.

What do you think about my rebuilding the 305 and adding a mild cam to it?
Please share any other performance mods that might come to your mind.

On a different note, a lot of people are playing with 1UZ's and 1 and 2JZ-GTE's here. What would you say about throwing in one of these?
Just a thought.

Once again, thank you for taking the time out to reply to my post.
Appreciate it.
 

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Thank you so much. I was thinking of all that and you're right... It's not really worth it. The thing is I;m in karachi, pakistan and we don't have crate motors at our disposal. PLus, What I have running in the Trans Am is a 305 and not a 350.

What do you think about my rebuilding the 305 and adding a mild cam to it?
Please share any other performance mods that might come to your mind.

On a different note, a lot of people are playing with 1UZ's and 1 and 2JZ-GTE's here. What would you say about throwing in one of these?
Just a thought.

Once again, thank you for taking the time out to reply to my post.
Appreciate it.
Well that being in Karachi puts a different look on the problem. The TBI from the truck is transportable to the Firebird as is the TH400. But it is big electrical problem to deal with; that really takes being able to get your hands on the electrical system schematics for both vehicles to determine what comes out of the van and then goes into the Firebird.

Problem I always see with automatics is they age out with their engine and tend not to be happy for very long when a rebuilt or crate motor is bolted up to them. The TH400 is somewhat more resistant to this simply because it is more robust than the TH350 to start with and is overkill behind a 350 so it doesn't tend to wear out as quickly as the TH350 behind a SBC350.

You can always rebuild the 305 and it can take a larger cam with fewer problems than the TBI 350 since the 305 has a carb which is easier to tune for a larger cam than is the injection of the 350. Injection requires burning a new program onto a new PROM chip; this is a bit costly and doesn't always turn out correctly so given the length of your parts supply line that can be a difficult problem. What about the automatic are parts and expertise to rebuild this thing available?

Bogie
 

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Thank you so much. I was thinking of all that and you're right... It's not really worth it. The thing is I;m in karachi, pakistan and we don't have crate motors at our disposal. PLus, What I have running in the Trans Am is a 305 and not a 350.

What do you think about my rebuilding the 305 and adding a mild cam to it?
Please share any other performance mods that might come to your mind.

On a different note, a lot of people are playing with 1UZ's and 1 and 2JZ-GTE's here. What would you say about throwing in one of these?
Just a thought.

Once again, thank you for taking the time out to reply to my post.
Appreciate it.
If you can drop a 2jz-gte in it at a low cost then it is a NO BRAINER. That engine is still one of the best engines ever made.
 

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. Yes, this swap would be way to much work, technical changes for too little benefit...

. Any recycling yards over there that you could pull a carb.'d 350 or 400 engine out of?

. Or, do a rebuild of the 305 with higher compression ratio pistons and a mild cam... what octane gas do you have available?
 

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Discussion Starter #7
Well that being in Karachi puts a different look on the problem. The TBI from the truck is transportable to the Firebird as is the TH400. But it is big electrical problem to deal with; that really takes being able to get your hands on the electrical system schematics for both vehicles to determine what comes out of the van and then goes into the Firebird.

Problem I always see with automatics is they age out with their engine and tend not to be happy for very long when a rebuilt or crate motor is bolted up to them. The TH400 is somewhat more resistant to this simply because it is more robust than the TH350 to start with and is overkill behind a 350 so it doesn't tend to wear out as quickly as the TH350 behind a SBC350.

You can always rebuild the 305 and it can take a larger cam with fewer problems than the TBI 350 since the 305 has a carb which is easier to tune for a larger cam than is the injection of the 350. Injection requires burning a new program onto a new PROM chip; this is a bit costly and doesn't always turn out correctly so given the length of your parts supply line that can be a difficult problem. What about the automatic are parts and expertise to rebuild this thing available?

Bogie
At this stage, rebuilding the 305 seems to be the way to go. I understand you would have gone this way. Procuring parts is always as issue but not the biggest one. I order mine online, from the states usually. Yes, the expertise to rebuild engines/transmission is available. I actually got my TH400 rebuild when i got the van.

The only reason American cars have become scarce is because of the gas prices and the ceiling on the age of the car that can be imported. No car over 3years old is permissible by law to import.

So, what would you recommend to improve the performance of the 305?
 

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Discussion Starter #8
. Yes, this swap would be way to much work, technical changes for too little benefit...

. Any recycling yards over there that you could pull a carb.'d 350 or 400 engine out of?

. Or, do a rebuild of the 305 with higher compression ratio pistons and a mild cam... what octane gas do you have available?

Hi,

I already have a carbed 305 hence won't really wanna go the 350 way unless it;s an absolute must. plus the upside of the 305 is economy. What combo would you suggest to go with on the 305 to retain economy and driving ease while improving the performance. Ok... more inclined towards the performance.

Thank you.
 

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Discussion Starter #10
. Yes, this swap would be way to much work, technical changes for too little benefit...

. Any recycling yards over there that you could pull a carb.'d 350 or 400 engine out of?

. Or, do a rebuild of the 305 with higher compression ratio pistons and a mild cam... what octane gas do you have available?
If you can drop a 2jz-gte in it at a low cost then it is a NO BRAINER. That engine is still one of the best engines ever made.
Thank you for writing in. No, it's going to cost pretty much the same but it's a newer engine hence, better on many levels, yet the simplicity of SBC's is simply overwhelming. Not to forget, the rumble of an american V8.

:)
 
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