How hard would it be to switch a chevy 283 engine to a big block 454 chevy?

i believe the engine mounts should match the big block.also the bell housing. the problem being , to upgrade the drive line to match the added power you would have. you would also have to upgrade the cooling system.

The 409 fit right in, a 454 should fit but there may be interference at the firewall/heater box. The usual fix is the biggest hammer available.

A 350 would be a better choice. That 454 is one heavy SOB and you are going to require some serious upgrade to handle the weight and the power.

New cooling system
front springs
drive-shaft and rear axle
Brakes – min req – front disc conversion

Or simply do what we did. 1965 Chevy p/up. We upgraded to a 283 for bit more power and dropped that in. We also upgraded the entire drive-line, suspension and brakes too. Not really required but it sure rides nice.

you will have to relocate your motor mounts, and depending on the length of the tranny, you may have to have another drive shaft. also, you will need to get some larger springs up front, you know big block springs. but clearance shouldnt be a problem you should have plenty of room under the hood

the motor mounts are the same and it will work with the 400 easy, but you will need a heavy duty radiator

It would match up but you will have many, many other changes first.

Pretty simple swap.
You may need to switch to BB mounts due to the height of the SB mounts. The SB mounts sits about 3/8″ higher up than BB so your 454 might not have the hood clearance depending on what air cleaner you run.

Don’t listen to these nut jobs that says you need a diff rear end o axles. Same rear was used in all the impala’s, so the BB, SB and straight 6 cars all had same one and its plenty strong enough for a 454.

Now on the front springs. You can run the stock springs but the weight of the BB will lower front end by about an inch. Or swap to BB springs to have it sitting at stock ride height

Now if you do the powerglide to th-400 swap you will need to move the transmission crossmember back 6-7 inchs and maybe drill new holes in frame to bolt it up, and you will need to get a diff driveshaft

Theres 2 versions of each trans, so I aint sure what you have but here are the lenghts
Powerglide short tail 24-1/4″ overall
Powerglide long tail 27-1/2″ overall
Th-400 short tail 28-1/4″ overall
Th-400 long tail 34″ overall

Now not sure if you know but the powerglide you have will bolt up to the 454 w/o any probs

You’ll need exhaust manifolds or headers to fit the BB engine, nd may have to tweak your exhaust some to fit up to those BB manifolds.

Cooling system depends on if you have the light duty 2 core rad or the HD 3 or 4 core rad.

All of the wires hooks up about the same

You will need big block pulleys and acc. brackets though.