I have a 1966 425 that I am rebuilding to drop in my 72 cutlass. The tranny that was attached to the motor when I traded for itis a TH350. Is that what the 425's had? It seem to me that the motor might produce to much torque for that tranny is that true? If I switch to a TH400 in my 72 Cutlass what issue are going to arise?
Thanks
Dave

 

The 425 were only installed in the big Oldsmobile from 1965 to 1967. The TH350 did not come out until 1968. The transmission that belongs to that engine should be a TH400 with a switch pitch converter.
I recommend that you install a TH400 with your 425. You will need a cross member and drive shaft to install a TH400 in your Cutlass. You may also need a longer speedometer cable.

If you are going to do any modifications to the engine keep in mind that there are two different engine blocks for the 1966 425. The M, ME, ML (2BBL) and N, NE (4BBL)code engies have a 45 degree lifter bank angle and the NS (Starfire) and NT (Toronado) have a 39 degree lifter bank angle like all later Olds engines.

1966 Ninety Eight Convertible, Air, NS Code 425 with Tri-Power and factory Dual Exhaust.