olds swap sb to bb

[buold]

How hard is it to swap a small block olds for a big block olds?
Change motors, trans, torque converter?

I have a 403olds in a 1984 buick regal and would like to put in a 455olds 😀

One local shop said there is nothing to it and I need only the engine for the swap?

Any info would really help

 

[Uncletruck]

With the Olds engines, the big and small blocks are nearly the same. The big blocks have taller decks, and larger main journal sizes. That's about it, so the shop was correct. IMHO the 403 is every bit as good, if not better than the 455, so why switch?

-UT-

 

[Coveted]

you can use your same trans and convertor

 

[buold]

I really like the 403, but i though with the extra 52cids it would be even more of a beast?? If there not that much difference in power?

 

[Blake442]

455's are torque-monsters, and can make some pretty impressive power depending on how you build it.
403's are a good motor too, and are a lot lighter than a big block, but with the money you'd spend on a 403, you could build a 455 with more power, that doesn't have to work as hard.
What transmission do you have? Depending on what you've got, you might want to consider upgrading your trans or swapping to something stronger to handle the added power. Good time to upgrade your rear end too, since the 7.5 probably won't last long if you abuse it...

 

[buold]

The car has a turbo350 and open7.5 rear end. Iam planning to swap the 7.5 in the near future, but the 350 seems to be in really good shape.

 

[Blake442]

Is it the original trans, or has it been rebuilt? I'd recommend beefing it up...

 

[buold]

I think the pre-owner rebuilt it fluid never changes color, every filter change still bright red. I do need to add a cooler and shift kit.

As far as the motor swap I can get a 455 for $300 dollars that is all std. I am going to have to rebuild my 403 because of bearing wear, so would I not be better of take that rebuild money and get the 455 rebuilt? Or put some performance parts on the 403?

My goal for the car is to make a good top end contender, low compression, and a small shot of nos if needed.

 

[buold]

One other reason for swap was the fact I have been told by many people that the 403 is weak and can not take more than 400hp range?

 

[Vern]

The 403 can be built with the right ported heads compression & cam into sweet 400HP 400+TQ pump gas street motor. But the windowed mains make it less than ideal for any high rpm ie frequently seen 5,500+ rpm deal and also less than ideal for spray. The long stroke 455 generally does not like frequently seeing more than 5,500 without some good light weight rotating assembly parts and a good balance but will handle the spray better. Either way find someone with a track record of building powerful Olds motors or you will learn the hard frustrating and expensive way that they are not chevys.