[jdorour]

66OLDS
Thanks for the positive comments.

I should have looked at the previous posts.
The 425 is a very good engine. There are some issues to watch for...
The 1965 engines have the old 4GC carb and the cam bank angle on the 1965 and some 1966 blocks have a 45 degree cam bank angle that limits the selection of cams and lifters. The crankshaft/flywheel bolt pattern is different than later engines making flywheels hard to find. But the good stuff is a forged crankshaft and good heads.

The 425 was built from 1965 to 1967 (the 455 replaced the 425 in 1968). In 1965 the 425 was rated at 300HP for the Low Compression 2BBL and 310HP for the High Compression 2BBl. The 4BBL engine was rated at 360HP and the Starfire Engine was rated at 370HP. For 1966 and 1967 the 2BBL engines had the same ratings but the 4BBL engine and the Starfire got a 5HP bump to 365 and 375. The top dog was the '66 and '67 Toronado engine rated at 385HP. Interesting side note - The 1966 Pontiac 421CI 4BBL engine was rated at 338HP and the 421 Tri-Power engines where rated at 356 and 376. Buicks 425CI for 1966 was rated at 360HP wit two 4BBL Crabs. Oldsmobile's 425 was rated at 375 with a single 4BBL Carb. Only Chevy could out do Olds for big block power.
Cheers