i have been thinking about doing a big block swap for a while. whenever i finish painting my car i will start on the motor so i figured that if i could find a big block before then i would build it or if not i would make a 383 with a 350 i have now. well i may have stumbled upon a 454 even though i wasnt really looking for one but i just want to make sure that a 700r4,th350, and th400 will all bolt up to a big block. not sure at to what transmission i want to use yet so just asking. I've read most of the posts that are big block swap related but dont remember seeing anything about transmissions.

 

You need a flex plate specific for a 454 because it's externally balanced. The 700R4 and TH350 bolt on identically. The TH400 torque converter has a different bolt pattern on the torque converter but most aftermarket flexplates have a dual bolt pattern to fit the TH350/Th400 torque converters.

A TH350 converter will fit on a TH400

 

I was wondering the same thing. I'm thinking about replacing the smog 305TPI motor with an ATK 489 or 496 BB, and wondered if my TCI 700R4 would bolt up to either one of them? THX for the info...

 

Yup, as Alky said, they ALL bolt up. The glorious wonders of Chevrolet.

Most 454s came from the factory with the 400 if they came with an auto. Regardless, the Powerglide, 350, 400, 700, 4L60E (still basically a 700), and 4L80E will all bolt right up like they were meant to do so.

Gotta get a flex plate with the right balance for however your motor is set up (stock 454 needs about a 28 in-oz unbalance on it); you can drill / slot the converter bolt holes if you have to which is kinda shadetree butt whatever.

 

There is/was such a thing as BOP (buick, olds, pontiac) concerning bolt pattern of transmissions to those makes. The Chev blocks had a different bolt pattern - trans to block. That would require adapter. Remember? If & when that adapter situation changed, I do not know.

 

This is very true, for the PG, 350, & 400. There has never been a BOP version of the 700/4l60E or 4L80E. There are however versions of those for 6-cyl which won't work either. People have been screwed by getting the wrong case for those older transmissions for over 50 years now.

There's never been an "adapter", from the factory. GM just had 2 different case castings for them. Various aftermarket mfrs have made them, usually a sort of plate, with the bolt pattern to bolt to the engine, and some other bolt pattern for a transmission. Best to avoid all that if possible though.

Just gotta make sure the trans you get is in a Chevrolet V8 case if you go with one of the 60s transmissions.

 

In terms of THM350 and THM400 Transmissions...

The Chevrolet Bell-Housing is the less-common casting and the inferior Transmission casting.
The Buick, Oldsmobile, Pontiac, and Cadillac Bell-Housing Version of the THM400 Transmission for example, was available in a stronger Casting.

It is common to find one of these BOP Heavy-Duty Cases, cut off the Bell-Housing and install an SFI Rated Uni-Pattern Bell-Housing.

This would be the same Uni-Pattern found on all THM200-4R Transmissions.

 

Standard (Thin) Casting:



HD (THICK) Casting:



These Cases are Thicker and Stronger in many places...
The Castings are especially stronger in the Rear of the Case and where the Pump attaches.
Often using 8 Bolts over only 6 Bolts.

The Oil-Pain Rail is Thicker and the Tail-Housing Flange is Thicker.


The Area where the Center-Support Splines into the Case (and Bolts to the Case) is Thicker and Stronger...
Notice there is even an additional Case-Lug for the Center-Support to Spline into.

Also the Area where the Oil-Pump Bolts in...
There is more Material for the Pump to Mate to with additional Bolt Holes and Thicker Casting Material over-all.
HD:


Normal:



Pan-Rail Difference:



Gear-Section:


Rear of Case and Flange for Tail-Housing:

 

Also if you have a Buick, Oldsmobile, Pontiac, or Cadillac V8 Engine...
The Material/ Casting in the Bell-Housing Area is also Thicker and Reinforced with additional "Ribbing":