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engine swap post


Mikstudie

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This is a great post we should save it someplace..

 

 

 

 

Yeah, I just finished up changing out the entire drivetrain. Just working the bugs out of the engine now.

I replaced 350 CI with a 402 BB.

1) Bought new BB Motor Mounts. Mounting is same location as 350 CI.

2) Already had a HD 3 Core Radiator. However, the one that came with my 72 Custom is a little narrower at the filler (passenger side). I put a rubber seal down the length of that side in order to channel the air thru the radiator.

3) I retained the 350 CI front springs and as yet, no problems. Haven't had a opportunity (it's Winter) to really see how well they will hold up, but the drop wasn't servere and I like the rake look. Still have the BB springs if I decide they are needed.

4) BB Fan Shroud required or fan will set deeper into Shroud affecting your cooling. (I know a guy who cut back his 350 Shroud to the first rib and it works perfectly.

5) BB Fan Blade & Fan Clutch needed. (I'm assuming the motor will come with all the pulleys)!

6) BB Water Pump if not with motor your getting!

7) BB brackets (Alternator, Power Steering Pump & AC if ya got).

8) 402 CI or higher throttle cable and possibly throttle cable bracket.

 

Transmission changed over from a TH350 to 400.

1) TH400 Kickdown Switch and wiring harness

2) TH400 linkage bracket (if not with tranny) should you decide to upgrade.

3) Trans. Cooling lines are interchangeable from TH350 to 400. 4) Dip Stick tube may be different from a TH350, I can't remember for sure.

5) You will need to move back your Tranny Crossmember if upgrading to a TH400 and replace driveshaft to a shorter one. Can also have driveshaft modified to fit. (Verify Rear Axle Yoke & U-Joint mount ends are compatible) TH350 U-Joint mounts different from a 400! (If you upgrade, be prepared to likely reconfigure yor exhaust tubes because they will interfer with new placement of crossmember)!

6) Trans Dust Cover is different from a TH350 to 400.

7) Changed out the Tranny Driven Gear to calibrate accurate MPH and odometer reading.

 

Changed out Rear Axle from a factory 10 Bolt non-posi to a 12 bolt Posi with .331 ratio.

1) Drivers side upper Control Arm required for a 12 Bolt. It has a notch made or modified into it due to clearance issues from the two.

 

I think that covers all the mod's I required on mine. Might be forgetting something and if I remember anything else, will advise. If I missed something, I'm sure some of the other guys will refresh my memory (and is required on occasion)!

 

Oh yeah, as for Headers! Do your homework. I've read some horror stories. I'm in the process of adding Headers now that the Breakin on the engine is done. (You won't want to add new Headers until after breakin or the heat will ruin painted/ceramic coating)! Also, your Exhaust Manifold down tubes likely wont align to connect to exhaust manifolds either from a 350 CI to BB!

 

I gotta say as another has so eliquently put it. There is no replacement for displacement. The differnce from a small block to big block was substantial! I'm only upset about it because I finished the project just as Winter was setting in. Now I gotta wait til at least Spring before I can enjoy all that LABOR!! Guess Winter is a good time to take care of all the small stuff.

 

Best of luck on your project. A lot of work but also was for me a whole lot of fun doing it.

 

Have a Good One.......

 

Doug

 

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