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Engine swap small to big block

L

Lazybird21

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Hello,
do i need the special swap engine mount (from classic industries or schumacher) to install a b-engine in a 74 small block roadrunner? Or is it possible to use the standard 74 big block mounts anyhow? I already noticed that it wont be plug&play when i tried to fit the engine into the engine bay.
Is it possible to modify the big block mounts to match the small block k-member?
I wasnt aware before that there are different k-members in the 73/74 models.
 
72 and older K members were basically the same between big block and small block but in 73 they redesigned the motor mounts and k frame and unfortunately the k frames were now different between the two. You have a couple of options one is to get the swap motor mounts I know shumacher used to make them and somebody else might make them as well or you can take and cut the mount off the k frame and move them back to line up with your big block spool mounts, I believe if you bolt the transmission to the trans mount it should pretty much tell you where you would need to weld the mounts back on the K frame.
 
Thank you for the reply. Do you know if its a change backwards (or forward) only, or is it possible that a change to the left, right or in height is also necessary?
 
Lazybird21 said:
Hello,
do i need the special swap engine mount (from classic industries or schumacher) to install a b-engine in a 74 small block roadrunner? Or is it possible to use the standard 74 big block mounts anyhow? I already noticed that it wont be plug&play when i tried to fit the engine into the engine bay.
Is it possible to modify the big block mounts to match the small block k-member?
I wasnt aware before that there are different k-members in the 73/74 models.
Click to expand...
This is just some information for you. I had an 83 Dodge Mirada with a 318 in it. I put a 400 in it with standard motor mounts that I think came from a 1976 Cordoba 400. It fit with NO modifications. I also used cheep headers from Summit racing. This was in 2005. The only problem was one tube of the header rubbed on the steering column rubber insulator. Also last year, I put a 400 into a 76 Dodge Aspen using stock motor mounts from Rock Auto 77 Cordoba. Biggest problem with that was the oil pan and a couple K member cuts. We used High flow stock exhaust manifolds on the Aspen.

Aspen a.jpg
 
Robert Shaad how was the clearance between fan clutch and radiator also what oil pan did you use and do you think the recently reproduced oil pan for the big block A-bodies would gain you enough clearance in order to not modify oil pan or k member for clearance? Did you use a C-Body or B-Body drivers side HP manifold?
 
I have read so much in many places all over the internet about people who did not need adapters and others who needed them. I start thinking if it only depends on the oil pan. In my case the biggest problem seems to be the clearence between oil pan and k-frame. If i had another oil pan maybe i wouldnt get the idea to need adapters. I will try to modify my pan at the front and see how the engine sits without the pan-problem.
 
IN Venezuela for years Big Block 73/74 got their 400 engines swaped to 318s ( due the lack of parts for Big Blocks ) and nobody made the change of the K member. HOWEVER they notice how hard is try to fit the transmission mount... SURE... THE DRIVETRAIN IS MISSALIGNED DUE THE DIFF ENGINE MOUNTS LOCATION... but ppl still drive them like that.

BBvsSB73-74k-frame2.jpg
 
This site has many threads about this subject, just search. Buy the adapters or move the frame mounts like kramer suggests in post #2. The Picture Nacho posted is a great reference to save.

Decades ago I bought a 74 Satellite that had been modified 318 to 383 by cutting the K frame and keeping the 318 mount location, not pretty and a lot of modifications. Not to mention it looked funny. If i remember it wasn't the pan but the pan rail that needed clearance. Trans mount mod and a custom length driveshaft too.
 
Last edited:
I can confirm now that oil pan clearence isnt the only problem. After looking at Nachos picture its obvious the the engine will be very bad aligned with big block mounts in small block k-frame. I tried it anyway but the back of the engine is about one inch too far to the driver side. My next try will be to measure how much difference is needed and modify the mounts accordingly.
 
kramer said:
Robert Shaad how was the clearance between fan clutch and radiator also what oil pan did you use and do you think the recently reproduced oil pan for the big block A-bodies would gain you enough clearance in order to not modify oil pan or k member for clearance? Did you use a C-Body or B-Body drivers side HP manifold?
Click to expand...
Oil pan was the biggest problem on the Aspen. If you want, I will ask the owner what he purchased. I did the work. The 400 was a strocker. Nasty Aspen. It is now in New Zealand. Owner loves it.
 
Lazybird21 said:
I can confirm now that oil pan clearence isnt the only problem. After looking at Nachos picture its obvious the the engine will be very bad aligned with big block mounts in small block k-frame. I tried it anyway but the back of the engine is about one inch too far to the driver side. My next try will be to measure how much difference is needed and modify the mounts accordingly.
Click to expand...

I can't say how bad will be the aligment, since as I told, in Vzla the BB to SB change still keeping the BB K member is a tipical swap and everything works... incorrectly made but still works. Dunno if ppl modifies the engine mounts ( not the one on K mmebers, but mounts itself ) thought.
 
hello , i have a 73 Charger se originally with 318 904 automatic , i did an engine/trans swamp from another 73 charger se with big block originally automatic car but was convert it to 4 speeds...anyway , i put the 400 into the SB k-member with no problems or modifications at all , the problem that am having now is highway speed vibration ( 50 mph + ) which i believe is the drivetrain is misalignment , the weird thing is that the transmission fit perfect and also didn't need modification !! don't know if i should order some conversion mount , any link for the part would be much appreciated!
 
Here we go again with the "There is no different K frame/ just use big block motor mounts"
:popcorn2:
Mark
 
Master Gunner said:
Here we go again with the "There is no different K frame/ just use big block motor mounts"
:popcorn2:
Mark
Click to expand...
LOL


Vince kf said:
hello , i have a 73 Charger se originally with 318 904 automatic , i did an engine/trans swamp from another 73 charger se with big block originally automatic car but was convert it to 4 speeds...anyway , i put the 400 into the SB k-member with no problems or modifications at all , the problem that am having now is highway speed vibration ( 50 mph + ) which i believe is the drivetrain is misalignment , the weird thing is that the transmission fit perfect and also didn't need modification !! don't know if i should order some conversion mount , any link for the part would be much appreciated!
Click to expand...

www.engine-swaps.com

They were moving their location quite ago and weren´t able to handle orders, but maybe they are already now.
 
Lazybird21 said:
Hello,
do i need the special swap engine mount (from classic industries or schumacher) to install a b-engine in a 74 small block roadrunner? Or is it possible to use the standard 74 big block mounts anyhow? I already noticed that it wont be plug&play when i tried to fit the engine into the engine bay.
Is it possible to modify the big block mounts to match the small block k-member?
I wasnt aware before that there are different k-members in the 73/74 models.
Click to expand...
There is another
Lazybird21 said:
Hello,
do i need the special swap engine mount (from classic industries or schumacher) to install a b-engine in a 74 small block roadrunner? Or is it possible to use the standard 74 big block mounts anyhow? I already noticed that it wont be plug&play when i tried to fit the engine into the engine bay.
Is it possible to modify the big block mounts to match the small block k-member?
I wasnt aware before that there are different k-members in the 73/74 models.
Click to expand...
There is another company making
Lazybird21 said:
Hello,
do i need the special swap engine mount (from classic industries or schumacher) to install a b-engine in a 74 small block roadrunner? Or is it possible to use the standard 74 big block mounts anyhow? I already noticed that it wont be plug&play when i tried to fit the engine into the engine bay.
Is it possible to modify the big block mounts to match the small block k-member?
I wasnt aware before that there are different k-members in the 73/74 models.
Click to expand...
There is another company making Schumacher conversion mounts now. Can't remember the name but it is in one of the post if you search for it search for Schumacher.
conversion mounts now.
 
I am in the process of rebuilding my 73 RR, The car had a frame off rotisserie restoration in 2004. It was originally a 318 car. When the restoration was done they put in a 400. When they put the 400 in, they had to do so many modifications to make it fit with out getting a bb K frame or conversion mounts. It would have been a lot less work to find either one. Yes you can make a BB fit a SB car, is it worth the extra effort? What they did was beat the holly hell out of the headers. Then they had to cut half the sump from the oil pan. on the trans mount, they slotted the bolt holes on the transmission to make the trans move forward 3 to 4 inches. literally they had the tail shaft on barley going into the shaft seal on the tail housing. They created a lot more work then needed.
Get a BB k member or the conversion mounts. plain and simple. Yes it can be done but is it worth it to make that much work??? Getting the right parts from the start eliminates the hassle.
 
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