[Donny1973]

Greetings. I’ve got this ‘79 400 that I’m planning a 461 stroker build on, along with a ST10, to replace the 305 Chevy and TH350 in my ‘80 TA. It’s a 9790071 with the two motor mount holes per side. Can anyone tell me definitively if the motor mount adapters that most vendors sell are truly a bolt in and go deal or am I still going to have to position the motor and drill new holes in the sub frame? Anyone aware of issues or problems using these adapters? I’m shooting for 500-550hp. Should I just find a later 5 bolt block? Will these hold up? Tips from anyone who’s used the adapters would be appreciated.

[Sirrotica]

Back in the 70s I ran into the same problem confronting you, putting a 1969 428 into a 1973 F body. I made my own adapters that are essentially the same as the fabbed ones you can buy currently (there were no aftermarket units for sale back in the late 70s). Probably a 400 HP engine, that worked fine with the units I made up.

If you decide to use your early engine with adapters, I would also use a turnbuckle or other restraining device off of the left/drivers side cylinder head to take some of the torque off of the adapters and rubber mounts as a preventative measure. With 500 plus ft lbs of torque on tap you can eventually tear steel mounts too.

I swapped a 455 Pontiac in a Jeep pickup truck, and after awhile I tore the left steel portion of the Jeep frame member in half, so it is entirely possible to destroy the steel portion of a mount is it's stressed enough times. The metal eventually fatigues and tears. Using a secondary restraining device, such as a turnbuckle attached to the left cylinder head and attached to the frame, is good insurance.

[Donny1973]

Originally Posted by Donny1973

Greetings. I’ve got this ‘79 400 that I’m planning a 461 stroker build on, along with a ST10, to replace the 305 Chevy and TH350 in my ‘80 TA. It’s a 9790071 with the two motor mount holes per side. Can anyone tell me definitively if the motor mount adapters that most vendors sell are truly a bolt in and go deal or am I still going to have to position the motor and drill new holes in the sub frame? Anyone aware of issues or problems using these adapters? I’m shooting for 500-550hp. Should I just find a later 5 bolt block? Will these hold up? Tips from anyone who’s used the adapters would be appreciated.

I meant ‘69 400. Fat finger strikes again.

[Sirrotica]

From the pictures I knew it was a pre 70 engine.

[Grand73Am]

I can't say how well the engine mount adapters fit and work for the pre-70 engines, since I never tried them. But, since you're not committed to the 69 engine yet, if it were me and I was going to spend the time and money on a stroker build, I believe I'd find a 70-74 400 or a 78-79 w72 to use, which have the holes and avoid the adapters. Of course, you could sell the 69 engine to help recoup some money, if you wanted to.

[78w72]

i had a 1968 350 on a 78 ta that used the adapters, not sure what brand they were since the motor was in the car when i bought it, but it bolted up to the stock frame mounts fine. i replaced it with the original 400 & used the same frame locations.