i have a highly built 462 big block and a turbo 350 with a 3200 stall convertor my question is i recently devolped a vibration in the trans tunnel that shook the car extremely bad so had car towed to mechanic and he found the prob to be that the pump on the trans had shifted about an inch so he replaced with a more stought pump and told me to start looking for a turbo 400 is this really the case do i have to have a turbo 400 i thought turbo 350s took a lot of power and torque or is my 462 just to torque for a turbo 350 any help would be helpful thanks.

 

A good baseline is:
th350= 350 lb ft of torque before it breaks. Less if it's old and worn.

th400= 400 lb ft of torque before it breaks

Of course both can be upgraded to handle more by a knowledgeable builder.

 

The th400's can hold a bit more than 400 as history dictates.

For example:
'67 Toro 425 4bbl
compression: 10.5
HP: 385
TQ:480

Th350's I wouldn't gamble on going over 350 lb ft of torque with though.

 

350 needs to be with a 350 get a 400 much tougher tranny. Can get tranny kits but your putting out more torque than the poor 350 was made to handle.

 

Take your car to a different shop. Replacing the pump might fix the immediate problem but you will have to have the transmission rebuilt with aftermarket parts to withstand the high HP and torque of your BBO.

 

Convert to a turbo 400 least cost to build to survive behind your big block