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Old 03-07-2014, 03:51 PM   #1
thefraze_1020
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1984 305 to 1972 350 Swap

I'm getting ready to swap motors in my 1984 Chevy. In it currently is a 305 and a 4-speed with a granny gear (I'm pretty sure it's a Muncie SM465).

How much tinkering do I have to do to put a 350 out of a 1972 in it? The 350 originally was mated to a TH350 automatic. I know I'll have to swap the flexplate for a flywheel.

Will the 305 flywheel bolt onto the 350?
Does an SM465 take a 350 (same bolt pattern)?
Can I swap distributors between the motors, to put an HEI in the 1972 350?
And finally, how interchangeable are the Quadrajet carbs?

Thanks
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Old 03-08-2014, 07:26 AM   #2
Palf70Step
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Re: 1984 305 to 1972 350 Swap

They swap out fairly easy. I put my 70's 350 into my 83.
Distributor swap, no issue at all.
Flexplate & all - the same.
Carbs I am not sure...they should be interchangeable. I had an aftermarket manifold & carb on mine.

Only thing I found as an issue is the dip stick. 83 was on passenger side, 70 on driver's side, thus I could not use the stock exhaust manifold. I used some shorty headers on mine. I am told if your older engine has RAM horn manifolds they will clear, but you'll have to redo the exhaust pipes.

The water temp sender is not that same either between the engines. Smaller diameter hole on the new engine head and the older sending unit will not work the newer gauge.
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Last edited by Palf70Step; 03-08-2014 at 05:57 PM.
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Old 03-08-2014, 09:36 AM   #3
Tx Firefighter
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Re: 1984 305 to 1972 350 Swap

To address what Bill pointed out....

When I've done this swap in the past, I wound up making a dipstick tube out of copper tubing. That way I could get it bent enough to clear the later model exhaust manifold. Its tight but saves doing exhaust work and swapping manifolds.

The sending unit is easier. You need a bushing the screw into the 1/2npt hole in the early engine and then screw the late model sender into it. Its a common part you can get in a hardware store plumbing section.
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Old 03-08-2014, 04:55 PM   #4
thefraze_1020
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Re: 1984 305 to 1972 350 Swap

Well my exhaust on my 84 is shot anyway, so I'm going to put a new exhaust on it. And the manifolds on the 72 350 are usable, so I'm going to stick with stock manifolds and new exhaust.

Thanks guys!
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