OK, I have the 454 finished up with all new internals and got it fired up while on the engine stand,,,It sounds great with 65# oil pressure at idle and goes to 80# with just a touch of RPMs. Here's where I need some help,,I had read where you can run a turbo 350 behind a 454 BBC. The torque convertor bolt holes on the new 454 flex plate do NOT match up exaCTLY with the bolt holes on the T-350 torque convertor unless you ELONGATE the bolt holes on the 454 flexplate towards the center about 3/8". Both flex plates are 168 tooth and exact same OD. The T-350 flex plate also matches the crankshaft bolt holes pattern on the 454 , altho, the T350 flex plate does not have the balance piece welded on it like the new 454 flex plate does. Is it OK to elongate the 3 convertor holes with my dremal tool?

 

If this response isn’t too late...

Besides noise, there’s significant risk of damage to the torque converter/transmission, engine, and even the driver.

The TC is kept centered by the shafts coming out of the transmission and the bolts through the flex plate. Keep in mind that a TC full of fluid is quite heavy and the centrifugal force of all that weight is being restrained (in part) by the flex plate. With elongated bolt holes, the TC and flex plate could shift relative to each other which will then change the position of the rotational center. Then the TC is wobbling which will quickly destroy its internal components.

It’s difficult to say for sure how bad the damage could be, but there’s enough potential energy to send the flex plate straight through the cabin.

If you really want to use this flex plate, I’d recommend having a machine shop drill new holes in it as they would be able to meet the tolerances necessary to maximize the clamping area of the bolts. They could also balance it.

 

It will damage the transmission and torque converter don’t do it

 

get correct flex plate or a transmission that your flex plate is designed for.