What to use????????? 401 or 425

[g-g-g0]

Looling to "build" a 401 or 425 for a '57 restrod project. I have been told that I should looking to start with a 401 as opposed to a 425. I would think that the 66 425 is the ultimate motor, yet I am being told that I should start with a 401 especially if it should need to be bored. So would the experts please give me their opion/advise as to which engine is the best, Is one year motor better than others? Appreciate any and all input!

Thanks,

Gary

PS: Want to keep the car a nailhead!

[Mr Riviera]

If you can find a 425 that is std now and may need to bore 30 over thats the way I would go . Otherwise do a 401 . I would not bore a 425 more then 30 to be safe . A 425 will cost more but well worth it in my book . Remember a 63 401 or 425 will not bolt up to a turbo 400 - I am guessing thats what you will use - without modifications . Look for a 64-66 . Hope this helps .

[Pete Phillips]

Like Dick Sweeney says, the 425 is more expensive to rebuild than a 401. The rebuild parts are very expensive--I guess because the engine is more scarce and was not used for many years.

Pete Phillips, BCA #7338

[NTX5467]

With the Buick 401 being much more plentiful, I think that would be the better choice of the two. There's no "magic" in those extra 24 cubic inches, even in the original horsepower and torque ratings of the 4bbl motors. Only real difference in the size specs is the piston bore being larger on the 425, with the stroke being the same. With the different piston weights of the 425, that would mean the connecting rods most probably would have different GM part numbers on them, but with "the balance" being different to coincide with the heavier pistons in the 425s.

Usually, a .030" overbore is what's needed to "clean up" a used cylinder bore surface. Just as .010"/.010" will clean up a used crankshaft's journals--unless a nice polish job will do it.

In "hot rodding" one of these motors, remember that "torque is king" rather than horsepower. "Horsepower" is what happens just before the trans shifts to a higher gear at WOT, but it's low and mid-range torque that helps make tire smoke and get you past slower traffic with just mild throttle input (rather than always needing WOT). Torque is what makes the car a joy to drive as it just takes a little throttle and . . . you're GONE.

Update the ignition to electronic. Possibly update the carb and intake (the intake to possibly use one of the new stand-alone throttle body fuel injection kits). Free-up the exhaust flow in the pipes and muffler department. And that might be all you need to have a really enjoyable car. The later versions have more flexibility in the intake and carb area.

With the engine's basic "torque" production design characteristics (bore/stroke ratio, rod length/stroke ratio, valve sizes and related port sizings), it's not going to be a serious "screamer" as a Chevy small block V-8, but that torque pushing you back in the seat is something the Chevy small block V-8 just can't do, even with more rpms.

Depending upon which rear axle ratio is already in the car can determine which transmission you might upgrade to . . . IF an upgrade is possible with the enclosed driveshaft set-up which Buick used back then. But that can come later, if at all.

I was looking in the current issue of Rod & Custom magazine last night and found a repro Cadillac and Olds air cleaner, from that general time. Big, round, with air intakes on each side. Very reasonably priced, too!

Just some thoughts,

NTX5467