Don't want to do it but if I can't get a good local mechanic that can rebuild this 401nailhead properly it will be pulled out. I wanna know if a 350 will bolt to the st400 an if not what adapter do I need, an could a 455 also bolt to this trans. I'm trying now to fix what I got just trying to see what my options are,thank you
Unfortunately your nailhead engine and the '66 ST400 trans behind it have a unique bellhousing bolt pattern that's not compatible with the '67 and up Buick/Olds/Pontiac design. You'd have to find an adapter plate to use the '66 trans with a later engine, or better yet find a '67 ST400, which is the last year for the variable pitch torque converter which is also a feature of your '66, but also features the newer BOP bolt pattern. Devon
Devon, couldn't he put the the parts from the earlier transmission into a later transmission that will fit a 350/455? Bob H.
Yes, most of the '66 ST400 internals could be fitted to a later ST400 or TH400 case, except maybe the center support. Devon
That would be my approach, no adapter. But the newer trans will need the oil restrictor added to operate the switch pitch function (still available new). I believe the old center support will fit. But a 70 up center support is an upgrade: the locating teeth were made .040" thinner so that a .040" thick case protection ring could be put in first. Bruce Roe
I'm with you on all of the above. The pressed in case orifice behind the pump is often overlooked. Devon
