ZASX

I NEED SOME HELP ON WHAT I NEED TO CHANGE LIKE RADATOR, DRIVE SHAFT ,HEADERS? ,MUCH THANKS

Oldsguy

What car? There are quite a few threads about 350 to 455 swaps, you may find some pertinant information in those if they were for a similar bodied car.

ZASX

I`M PUTTING THE 425 in the 72 cutlass

Oldsguy

If you car keeping the same transmission you won't have to change the drive shaft. Headers shouldn't be a problem either. Radiator might need to be changed though, not sure.

Oldsproject

I did a 330 - 425 swap in a 65 F85 with little issues. Headers on this car were really tight though. Only real change required was the radiator. Everything else fits fine. Another clearance issue I have (not related to Big Block swap) is the hood clearance between the air cleaner (tight to the hood). This was caused by the performer intake and height of the new carb combined with the edelbrook air cleaner I chose. Not the swap. Use the 350 motor mounts. On mine, tranny (TH350), driveline, etc all fit fine. Goodluck

joe_padavano

I actually did exactly this swap on my first car (68 Vista) when I was young and stupid (shortly after the earth cooled). This was my first exposure to the different crank flange bolt patterns on Olds motors. Here's a tip - DO NOT simply elongate the holes in the 350 flexplate to fit the 425.

Do NOT ask me how I know this...

You probably know to simply bolt the 350 motor mounts to the 425. Yes, you'll need the correct flexplate/flywheel. The 350 starter will bolt up but you may want to invest in a high-torque version at some point. You'll need the correct exhaust manifolds or headers for a big block. You can bolt the 350 accessory brackets to the 425, but you'll need to transfer the water pump and pulleys as well (or at least verify that the water pump on the 425 has the same height as the one on the 350. If your current radiator is a 3-row, you MIGHT squeak by, but I'd go with a four row.

BILL DEMMER

i did a 330 to 425 swap on a '67 cutlass. i had the delta donor car, too.
i used the delta's radiator after swapping the right side saddles.
you're also going to want to use the thicker battery cables that a bbo uses. you're going to want to get a carb. that's set up for the 425, with the '72 throttle linkage connection.


bill

ZASX

will the original drive shaft that came with the 350 fit with the 425 & a 400 tranny in my 72 cutlass

joe_padavano

No. The TH400 is longer (requiring a shorter driveshaft) and the yoke is different.

Oldsguy

Not if the TH400 has a long tail shaft.

ZASX

THANKS AGAIN FOR THE INFO YOU GUYS ARE SAVING ME TONS OF TIME & MONEY

joe_padavano

I assume you meant if the original TH350 was a long tail shaft. That's true, but if it's the original trans in that A-body, it's short.

olds4life

is the 350 a good running one. if so i'm interested if within two hours of me (st. louis).

ZASX

sold it, ran great but wanted more hp .

Rallye469

I did the same swap too...
When it came time for the driveshaft I just measured it all up
and went to my salvage yard.
They kept a pile of shafts there a mile high.
You will need a TH400 yoke.