When my 340 goes kapoot which should i get, a 401,425? My car is a 66 Lesabre, would a 401 or a 425 hook up to the same motormounts? I'm realy motor stupid so speek english please. thanx pat
Nope, 401/425 would require not only differnt mounts but a different tranny as well. The easiest install would be a 350 Buick, it will bolt right up to the same motor mounts and transmission. It would require only slight exhaust modification to bolt up as well. Jim Burek
401-425 in a lesabre Pat, From what I understand, the big block 401 or 425 was not available in the 66 lesabre model. It was however, available in the wildcat. The wildcat has a longer wheelbase to accept the larger motor. If you were to install a big block buick into your lesabre it would require pushing the motor back at least 2" & cutting the firewall to accommodate the new location of the motor & trans. I only know this because I am in the process of installing a 455 into a 65 lesabre. Good luck if you decide on this engine swap. Tom :TU:
I have a 1966 Buick sales brochure. It lists the 220 horse 340 w/9:1 compression and a 2-bbl carb as the standard motor in the LeSabre. The only optional motor listed is the 260 horse 340 w/10.25:1 compression and a 4-bbl carb. I have no idea if either a nailhead or a big-block will fit - but I will agree that replacing the 340 with a 350 is an easy swap. But if you aren't looking for maximum power, and are looking for a street cruiser thats a little different, why not just re-build the 340? Change out the cam, get a star-wars air cleaner, and maybe a set of polished aluminum valve covers off a Rover 3.5 (should fit) - man, pop the hood and everyone will be looking at it, and trying to figure out what you're running.
A 350 will bolt right in. Best bang for the buck! If you decide to build the 340, you can bore the block 0.050" and use standard bore 350 pistons and late 350 rods on the 340 crank. No aftermarket intakes are out there for this motor. Cams are still out there and you can port the stock intake a bit.
