Big block in a 75

[captras]

I am considering replacing my weak L48 with a rebuilt 427. I have a TH400 transmission. Is the any problems I can anticipate in replacing the engine, and what about any mods/changes to the front suspension.

 

[Tom73]

You will need stronger springs for the added weight. The factory also used a thicker sway bar. Then don't forget that if you make changes up front then you need to modify the rear to balance the car. Factory added a rear sway bar and a stronger spring there too.

tom...

 

[Stallion]

How would have to have balance the car through the rear? What would that consist of?

 

[JohnZ]

Chassis dynamic response and roll center distribution gets to be a pretty complex subject, but the car is basically designed with some limit understeer ("push") for safety reasons (vs. oversteer, where the rear end comes around). The added weight on the BB front end requires a stiffer front sway bar, and that increased front roll stiffness is balanced on a BB car by adding a rear sway bar (which increases rear roll stiffness) to restore the near-neutral chassis balance.

The SB cars are designed to be neutral with just a smaller-diameter front sway bar; lots of guys make the mistake of adding an aftermarket rear sway bar on a SB car, which drastically increases rear roll stiffness, upsetting the chassis balance, which suddenly makes them "limit oversteer" cars, very likely to swap ends in a hurry under limit-handling conditions. If you add a rear sway bar, you have to compensate for it by also increasing front roll stiffness in order to maintain the limit understeer behavior. Suspensions are very carefully designed and engineered to produce specific vehicle behavior under limit conditions, and countless hours were spent developing the dynamics; it's not a good idea to try and redesign them one piece at a time out of catalogs.