My 305 to Pontiac 400 swap
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Car: 87 TA
Engine: 350
Transmission: 700r4
Axle/Gears: 2.73
My 305 to Pontiac 400 swap
Ok, this is a swap I thought about doing for a long time but never got around to. Then one day I found myself in possesion of a very nice 400. Also, I'm not throwing any big money into this swap. All my big money is going into my 79 formula build. This is just to get a nice functioning pontiac 400 into my 87 TA. So here it goes...
After pulling the 305 I took the time to run new brake lines, clean, and repaint the engine compartment. Also, the mechanical fuel pump on the pontiac 400 is on the driver side, so I recommend moving your fuel line now as well. If you're going with an electronic pump it doesn't really matter.
Motor mounts. If you look hard enough you can find direct bolt in conversion motor mounts. I even posted a link somewhere on the board that I can't find anymore. But they were $90. I paid $17 for OEM replacement 79 firebird frame mounts. For the block mounts I had something lying around.
http://www.yearone.com/serverfiles/f...ain2.asp?cat=4
I had an RW81 conversion kit that I took off an olds 403 from a 79 TA that I used the mounting brackets from and made my own engine support bar to work with the 400.
This is my support bar next to the original and the bracket
Then I bolted the OEM frame mounts to the engine mount, dropped the engine, made sure everything was level and lined up, and welded the motor mounts to the frame. By doing this the engine was actually dropped about 2 inches lower than the stock 305 location. Also, welding the mounts in place allowed me to move the engine forward or backward a bit. I moved it back to leave extra room between the engine and radiator for future modifications. Which with a pontiac motor I recommend a big radiator and electric fan since most pontiac engine (in my experience) are prone to running hot.
Transmission. I started out with a good BOP turbo 400 trans and got a hurst trans crossmember conversion kit from someone on the board. Then a buddy of mine traded me a rebuilt turbo 350 for my 400 so I butchered the hurst kit to make something that would work.
This picture is before adding gussets and cleaning it up. But I welded the extension from the hurst kit directly to the stock crossmember. Worked out great.
Other options for you trans is to buy this adapter plate from JEGS
http://www.jegs.com/i/JEGS/555/60170...oductId=751074
If your 700r4 is good just save yourself the trouble of making or buying a conversion crossmember and torque arm mount and just buy this. I wish I would have. But by the time I discovered it I already had too much invested in my BOP trans and started making stuff...
I havn't finished my torque arm mount yet so I'll get pictures and such of that up as soon as its done. But since the engine and trans is all in place it's time for the driveshaft. Obviously the stock shaft will be drastically too short so I took a stock driveshaft from a 79 TA measured up how long I needed it, about 3" shorter, I can't remember exactly. And took it to a local driveshaft shop to have it shortened and rebalanced. Cost me $60. A far cry from the nearly $400 they wanted to make a new one.
As soon as I get more done I'll add more info and pictures. If anyone has any questions or comment feel free to ask.
Here's a a picture of the engine sitting in the car after I welded the mounts down...
After pulling the 305 I took the time to run new brake lines, clean, and repaint the engine compartment. Also, the mechanical fuel pump on the pontiac 400 is on the driver side, so I recommend moving your fuel line now as well. If you're going with an electronic pump it doesn't really matter.
Motor mounts. If you look hard enough you can find direct bolt in conversion motor mounts. I even posted a link somewhere on the board that I can't find anymore. But they were $90. I paid $17 for OEM replacement 79 firebird frame mounts. For the block mounts I had something lying around.
http://www.yearone.com/serverfiles/f...ain2.asp?cat=4
I had an RW81 conversion kit that I took off an olds 403 from a 79 TA that I used the mounting brackets from and made my own engine support bar to work with the 400.
This is my support bar next to the original and the bracket
Then I bolted the OEM frame mounts to the engine mount, dropped the engine, made sure everything was level and lined up, and welded the motor mounts to the frame. By doing this the engine was actually dropped about 2 inches lower than the stock 305 location. Also, welding the mounts in place allowed me to move the engine forward or backward a bit. I moved it back to leave extra room between the engine and radiator for future modifications. Which with a pontiac motor I recommend a big radiator and electric fan since most pontiac engine (in my experience) are prone to running hot.
Transmission. I started out with a good BOP turbo 400 trans and got a hurst trans crossmember conversion kit from someone on the board. Then a buddy of mine traded me a rebuilt turbo 350 for my 400 so I butchered the hurst kit to make something that would work.
This picture is before adding gussets and cleaning it up. But I welded the extension from the hurst kit directly to the stock crossmember. Worked out great.
Other options for you trans is to buy this adapter plate from JEGS
http://www.jegs.com/i/JEGS/555/60170...oductId=751074
If your 700r4 is good just save yourself the trouble of making or buying a conversion crossmember and torque arm mount and just buy this. I wish I would have. But by the time I discovered it I already had too much invested in my BOP trans and started making stuff...
I havn't finished my torque arm mount yet so I'll get pictures and such of that up as soon as its done. But since the engine and trans is all in place it's time for the driveshaft. Obviously the stock shaft will be drastically too short so I took a stock driveshaft from a 79 TA measured up how long I needed it, about 3" shorter, I can't remember exactly. And took it to a local driveshaft shop to have it shortened and rebalanced. Cost me $60. A far cry from the nearly $400 they wanted to make a new one.
As soon as I get more done I'll add more info and pictures. If anyone has any questions or comment feel free to ask.
Here's a a picture of the engine sitting in the car after I welded the mounts down...
Last edited by j dezzy; 11-13-2010 at 01:51 PM.
#4
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Car: 88 Trans Am..
Engine: Hmm... 350? The guy told me
Transmission: 5 speed
Re: My 305 to Pontiac 400 swap
I want this swap!!! My TPI just doesn't feel the same anymore at 200k miles
#6
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Car: 87 TA
Engine: 350
Transmission: 700r4
Axle/Gears: 2.73
Re: My 305 to Pontiac 400 swap
I did actually grind the metal down clean first. I also stated that the picture was before I cleaned it up and added gussets. I used flux core. you can't make weld look pretty with that ****. lol. Plus, I'm not trying to make a gorgeous head turner. I'm just trying to make a fast f-ing car.
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Car: 1989 Camaro IROC-Z
Engine: LB9
Transmission: T-5
Axle/Gears: 3.08 G80
Re: My 305 to Pontiac 400 swap
I did actually grind the metal down clean first. I also stated that the picture was before I cleaned it up and added gussets. I used flux core. you can't make weld look pretty with that ****. lol. Plus, I'm not trying to make a gorgeous head turner. I'm just trying to make a fast f-ing car.
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#8
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Car: 87 TA
Engine: 350
Transmission: 700r4
Axle/Gears: 2.73
Re: My 305 to Pontiac 400 swap
I appreciate the pointers. I used MIG and TIG in auto in high school. Got this MIG/Flux core welder just to do this job actually. It was the first time I used flux core and wasn't aware of the amount of slag it leaves behind. I eventually used this welder to make repairs to my 79 formula during it's restoration. They do look a lot better by this point.
#9
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Car: 1989 Camaro IROC-Z
Engine: LB9
Transmission: T-5
Axle/Gears: 3.08 G80
Re: My 305 to Pontiac 400 swap
I appreciate the pointers. I used MIG and TIG in auto in high school. Got this MIG/Flux core welder just to do this job actually. It was the first time I used flux core and wasn't aware of the amount of slag it leaves behind. I eventually used this welder to make repairs to my 79 formula during it's restoration. They do look a lot better by this point.
#10
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Car: 89' GTA
Engine: L98 with tpi to carb swap
Transmission: 700r4
Axle/Gears: stock
Re: My 305 to Pontiac 400 swap
Thats awesome!!!! im in the middle of a tpi to carb swap, but i trully want a 400 or 455 in my ride! have you ever thought about putting a 200r behind that 400???
#11
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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: My 305 to Pontiac 400 swap
Subscribed!
Can't wait to see where it ends up!
Good luck!!
Can't wait to see where it ends up!
Good luck!!
#12
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Car: 1986 Trans Am WS6/1991 Firebird
Engine: 305 TPI/305 TBI
Transmission: 700R4 in both
Re: My 305 to Pontiac 400 swap
This is a swap I'm strongly considering at the moment, any updates? I'm eager to see more and learn what I'll have to do when I find the right engine and get ready to swap.
#13
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Car: 92 Firebird--02 Grand Prix GTP 2Dr
Engine: Poncho 400--3.8 Supercharged
Transmission: T56 6 Speed--4T65EHD
Axle/Gears: Open 10 bolt 3.42--Internal 2.93
Re: My 305 to Pontiac 400 swap
after seeing how well it fit in the engine compartment, im so going thru with this, time for the machine shop!
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Car: 92 Firebird--02 Grand Prix GTP 2Dr
Engine: Poncho 400--3.8 Supercharged
Transmission: T56 6 Speed--4T65EHD
Axle/Gears: Open 10 bolt 3.42--Internal 2.93
Re: My 305 to Pontiac 400 swap
so are you using the stock electric pump? thats what im planning for mine, just wondering how you routed them. and how does the tranny fit up with the engine with the pointed bell housing? we NEED updates
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