help with motor swap

Technical Question and Answer - On topic to 71-74 Plymouth B-bodies only.

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moparmike
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help with motor swap

Post by moparmike » Mon Nov 23, 2009 11:21 am

As you may know I own a 72 Sebring Plus, It has a 318 A/C buckets,console etc. I also have a 440 with matching tranny, the 440 has a steal crank and well we are in the process of rebuiding the 440 to swap it for the 318, I also have a lot of road runner parts such as a complete grill I am doing this because I always wanted a GTX . The car is originall from California so it is in great original shape. I guess i feel the need......the need...for speed. I think the motor & tranny will be no problem to swap but my question is about the drive shaft, Will I need a smaller driveshaft a friend tells me he went from a small block to a 383 and used a driveshaft from a 6 cyl dart and it bolted right on.

Any thoughts?
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CtownRunner
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Re: help with motor swap

Post by CtownRunner » Mon Nov 23, 2009 10:41 pm

I don't know if the length is the same for a small block and 727 and BB.
I do also wonder about the rear end itself.
More torque and HP from the 440 I would want to make sure the rear end can handle the load.
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Thack
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Re: help with motor swap

Post by Thack » Mon Nov 23, 2009 11:20 pm

It should fit.

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Smellslike1974
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Re: help with motor swap

Post by Smellslike1974 » Tue Nov 24, 2009 12:01 am

i know in 73-74 small blocks and big blocks have different motor mounts.Not sure if its the same for 71-72.
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landon1
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Re: help with motor swap

Post by landon1 » Tue Nov 24, 2009 1:09 am

my car was changed to 440 power a long time ago, so idk the exact items used, but i do know that i am still using the original 318 saginaw pump and replacement hoses for a '71 318. the 440 was a later model, so it had a pass. side lower hose, so the stock HD radiator could be used, since small blocks are arranged the same way. the rear end is still the stock 8.25 with original highway gears. no problems to report yet, except that i have to replace u-joints (probably never greased, kind of like the rest of the car) :roll:

71440 gtx
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Re: help with motor swap

Post by 71440 gtx » Tue Nov 24, 2009 9:37 am

you need big blocks motor mounts 66-72 b e c body one 383 4oo 440 413 426 w

not 73 up buy a new driveshaft :rant: do not use 39 year old driveshaft :shock:
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1bluegtx
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Re: help with motor swap

Post by 1bluegtx » Tue Nov 24, 2009 6:22 pm

Nothing wrong with a 39 year old driveshaft(driveshafts do not wear out),as long as you put in new universals.
My drive shaft is 51 1/2 inches center of universal to center of universal.(big block with 727)

Looks like the dart driveshaft would be about the right length but it would most likely have the small u-joints.

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moparmike
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Re: help with motor swap

Post by moparmike » Tue Nov 24, 2009 10:35 pm

I picked up a nice posi rear end from a RoadRunner so we are going to install it, Also we beefed up the suspension with Moog. It is an older 440 that came out of a school bus of all things. Steel crankshaft, we are rebuilding it as we speak. Some people say I will not need motor mounts that the 440 will go right in as is. Car also has a/c and I located BB A/C brackets. Please let me know if anyone else has swapped small block to big block and what they encountered. Much appreciated
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71440 gtx
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Re: help with motor swap

Post by 71440 gtx » Wed Nov 25, 2009 11:06 am

39 year old driveshaft(driveshafts do not wear out)

you do not live in ont can :lol: snow ice salt

there are two big block motor mount s 66 -72 biscuit mount and 73 and up spool mount

spool mount will not fit a 66 -72 k frame so what mounts do have?
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Smellslike1974
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Re: help with motor swap

Post by Smellslike1974 » Wed Nov 25, 2009 12:43 pm

i have looked around and they sell smallblock conversion mounts to big block,which would only mean the smallblock and big block motor mounts are not the same.

Or it means people like making stuff for no reason or purpose at all. :lol:
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1bluegtx
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Re: help with motor swap

Post by 1bluegtx » Wed Nov 25, 2009 12:58 pm

Done this swap many times,just use the brackets and mounts for a 1971 or 72 440 and it will set right down on the k member.( 71 v8 k members are the same)No need for high dollar conversion mounts.Radiator will probably need changed to handle the big block.Someone will come on here and tell you the torsion bars will need changed,but they will be fine(actually they will give better weight transfer).Also you will need to rewire the ignition harness because of the 440 distibutor being in the front.

BRIAN
Its not numbers matching
It doesn't run on pump gas
And it doesn't purr like a kitten
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rt-man
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Re: help with motor swap

Post by rt-man » Fri Nov 27, 2009 11:10 am

I'm doing the exact same swap as you, '72 Sat Sebring 318/904/8.25 to 440/727/8.75. We just pulled the 318/904 last weekend. 440 is a '74, either out of a motor home or a police block (extra cooling passages). 452 heads (ported), Comp Xtreme cam, Edelbrock CH4B intake, HP manifolds, Edelbrock 800 Thunder AVS, tti H-pipe exhaust, yada yada
- going with Schumacher mounts
- front factory sway bar
- Addco rear sway bar, but am rethinking that
- hemi torsion bars
- SG rear with 3.23
- Brian is right: need new engine wiring harness
- 613 radiator, recored to 3-row by Glen Ray

Got a replacement PS pulley from Mancini. The one on the 318 is solid. A buddy gave me one from a '67 440 PS pump setup. Looks like the Mancini pulley but smaller diameter, strange.
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