Hi, I've recently acquired a GT/CS mustang with a 289 4 barrel auto. The current engine unfortunately has had it after sitting in one place for over 20 years and needs replacement. Would it be a crime to replace the 289 with a 390 also from the same year? As I understand it the 390 was a option at this time. What sort of modifcations would be involved in installing this larger engine? upgrade for brakes, transmission I assume. Is it too much effort ? should I just replace it with another 289? Any advice appreciated.

regards

As I understand it, the biggest issue is the shock towers on a 390 are different than the small block, and these would need to be replaced to make this swap. If you want greater displacement and an easier engine swap, consider a 351W and go with a stroker crank...407ci!!! The 351 fits the engine compartment like a glove and there are many hi-perf parts available for this engine. Just a thought.

Russ

Another thought on this topic is that of the weight of the engine. The 390ci FE engine is quiet heavy, while the 351 is close to the weight of the original 289/302. Front springs could remain and handling characteristics would not be adversely affected. Again, just a thought.

Russ

Thanks for the advice russ but I think I am gonna salvage what I can of the original engine and recondition/rebuilt it, after all only 4000 or so of these cars made would be a shame to modify it. Will use a more common stang for my power car aspirations perhaps ;)

champs,
I commend you on chosing to keep your CS original. An engine can usually be rebuilt as long as the block is not cracked, even pistons rusted in thc chamber can be fixed.
Doug