231 v6 to olds 350 swap

ese79cutty

Not-quite-so-new-guy
Dec 22, 2020
6
1
After a lot of thought I figured I’d change the 231 in my 79 cutlass. I wanted a sbc 350 but I was told I’d need a different style transmisson and a few modifications. LS is out the window lol. So I boiled it down to an Olds 350. I’m not looking for a race car just something that’ll have more power and grunt. From my understanding a olds 350 will bolt right up to the th350 but what other parts and accessories would I need for the actual swap. Also over time I may want to build it but while I have the block out of I would like to change the internal components. Any recommendations on what paths to take, what parts could help me make the olds 350 faster. I’m still using the factory stock rear end ehatever it is I believe it’s a 2:4_ something.
 

81Regal

Royal Smart Person
Apr 5, 2009
1,540
83
Terril Iowa
For the accessories none of the existing brackets will fit plus you will need the frame pads and motor mounts for a 307 Olds. The wiring will also need to be modified.
The 7.5" rear axle isnt as weak as many people would have you believe, its when the tires hook is when parts start to break.
 

ssn696

Living in the Past
Supporting Member
Jul 19, 2009
4,756
113
Mid-life crisis
Make sure you have a TH350 and not a TH200. The 200 has a single bolt on the pan flange at the trans mount. The 350 has a wider pan with 2. If you have a 200, it may hold together long enough for your budget to catch up. Assuming it works well now, it will probably survive a bit if you don’t deliberately let the smoke the out of the tires.
 
Oct 14, 2008
6,847
113
Melville,Saskatchewan
A Buick 350 is a DIRECT swap, everything swaps over. I personally prefer the Olds 350, I have 2 of them. Olds use different mounts and accessory brackets than your current Buick V6.
 
Oct 14, 2008
6,847
113
Melville,Saskatchewan
I think they might but the Buick experts can chime in. I know the 3.8 V6 is a 350 with a two cylinders missing. Unlike Pontiac and Olds, the 455 Buick is a totally different casting correct?
 

81Regal

Royal Smart Person
Apr 5, 2009
1,540
83
Terril Iowa
No the pads are different. There was a company in Alabama that made the mounts to bolt on the frame but no longer around. Most people take the parts from the donor car and attach to the new frame.
 

jiho

G-Body Guru
Jul 26, 2013
789
63

spidereyes455

G-Body Guru
Mar 6, 2013
593
93
Northeastern PA
As said before a Buick 350 is a direct swap. All of your existing parts will transfer over except for the distributor and carb and they use the same mounts. The problem is it can sometimes be difficult to find a good running Buick 350 these days.
Buick 455's are a different animal as they are a true big block vs a 350 which is a small block. The frame and engine mounts are different as are the accessory brackets. When swapping to a 455 Buick most of the swaps I've heard of use 68-72 skylark mounts which have to have the corresponding holes in the frame drilled as there are none there that match up.
Also keep in mind with an Olds 350 swap the fuel line will have to be rerouted to the passenger side as the buick v6 has the fuel lines on the driver side.
 
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