Re: 75 roadrunner k frame/ subframe
[Re: xs29l9g]
#2579453
11/17/18 06:18 AM
11/17/18 06:18 AM
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Joined: Aug 2007
Posts: 6,095
Valencia, España
NachoRT74
master
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master
Joined: Aug 2007
Posts: 6,095
Valencia, España
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No, they change. Engine mount locations changes. Have the pics somewhere.
They can fit.. yes, but engine will be out of alignment by a tad, making a tight fit on all drivetrain mounts and could get some linkages issues
With a Charger born in Chrysler assembly plant in Valencia, Venezuela
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Re: 75 roadrunner k frame/ subframe
[Re: xs29l9g]
#2579511
11/17/18 12:35 PM
11/17/18 12:35 PM
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Joined: Sep 2007
Posts: 14,889
up yours
Supercuda
About to go away
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About to go away
Joined: Sep 2007
Posts: 14,889
up yours
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is the f frame/subframe the same on a 75 roadrunner between small block and big block? Not the same. While you can get the other type engine to bolt in, it's cockeyed. Back in my sailor days we swapped a 400/727/driveshaft and the entire front suspension out of an 78 Cordoba into what was a 318 75 Coronet. Tedious but everything bolted right up like factory, because it essentially was.
They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.
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Re: 75 roadrunner k frame/ subframe
[Re: xs29l9g]
#2580176
11/19/18 01:46 PM
11/19/18 01:46 PM
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RWG75
Unregistered
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RWG75
Unregistered
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75 and 76 factory part number books do list different part numbers for small block vs big block b-body k frames. Suspect other years will as well. As for what's actually different between them, couldn't tell ya and if there is in fact something different betting it would take meticulous measurement to figure out.
I've used boneyard donors from 73, 78 and 81 (original engines unknown) in to 75 and 76 small blocks. I've also dropped 440s in to 75s that I yanked the 318 out of. Even with keeping the original C body motor mounts they dropped in after swapping oil pans. If it's tweaked front/back side/side or diagonally I sure can't notice. As in: dropped right in to place like it was made for it and no fighting to get the holes lined up. Hood clears fine with OEM style intake / carb / filter, 440 fan fit in the 318 shroud, etc, etc.
Recall the same experience when putting the 318/904 in the C-body that was headed to the scrap yard after donating the 440/727. Dropped right in. Looked wrong as hell because of how small it was but again, no kinds of fighting to get the mount bolts in.
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Re: 75 roadrunner k frame/ subframe
[Re: ]
#2580203
11/19/18 02:37 PM
11/19/18 02:37 PM
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Joined: Jan 2003
Posts: 16,819
Between Houston & Galveston TX
SattyNoCar
Smarter than no class Flappergass by a mile
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Smarter than no class Flappergass by a mile
Joined: Jan 2003
Posts: 16,819
Between Houston & Galveston TX
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I've never done a small to big block swap, but, one other thing that is different (on '73's anyway) is the sway bar mount. Where the end links attach to the K. The mount for the link is welded in place. No sway bar? No mount. I'm just curious if this is why two part #'s are shown. If not, there should be three (or four?) part #'s then, correct? (the only factory V8 cars I've seen without a sway bar are small block cars). 
John
The dream is dead, long live the dream.......😥
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Re: 75 roadrunner k frame/ subframe
[Re: SattyNoCar]
#2580451
11/20/18 01:28 AM
11/20/18 01:28 AM
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Joined: Dec 2005
Posts: 259
Scatchamatoon
Saskabusa
enthusiast
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enthusiast
Joined: Dec 2005
Posts: 259
Scatchamatoon
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Last edited by Saskabusa; 11/20/18 01:30 AM.
1974 Roadrunner
1967 Charger
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Re: 75 roadrunner k frame/ subframe
[Re: ]
#2580461
11/20/18 01:48 AM
11/20/18 01:48 AM
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Joined: Jan 2003
Posts: 10,559
Freeport IL USA
poorboy
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 10,559
Freeport IL USA
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75 and 76 factory part number books do list different part numbers for small block vs big block b-body k frames. Suspect other years will as well. As for what's actually different between them, couldn't tell ya and if there is in fact something different betting it would take meticulous measurement to figure out.
I've used boneyard donors from 73, 78 and 81 (original engines unknown) in to 75 and 76 small blocks. I've also dropped 440s in to 75s that I yanked the 318 out of. Even with keeping the original C body motor mounts they dropped in after swapping oil pans. If it's tweaked front/back side/side or diagonally I sure can't notice. As in: dropped right in to place like it was made for it and no fighting to get the holes lined up. Hood clears fine with OEM style intake / carb / filter, 440 fan fit in the 318 shroud, etc, etc.
Recall the same experience when putting the 318/904 in the C-body that was headed to the scrap yard after donating the 440/727. Dropped right in. Looked wrong as hell because of how small it was but again, no kinds of fighting to get the mount bolts in. This is Moparts. We can't let real life experiences over ride the book and part number thumpers. Every vehicle built has + and - tolerances. That would mean that anything may fit somewhere else, if the production shift is in your favor, or it may not fit if the production shift was not in your favor. The issue that has always been consistent when dealing with swapping a Mopar big block where a small block used to sit has always been an oil pan or an oil pump/filter clearance issue. My guess is that 9 out of 10 times, the big block clears everything, but if your writing a book, you have to cover your butt for that 1. Gene
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Re: 75 roadrunner k frame/ subframe
[Re: Supercuda]
#2580848
11/20/18 11:23 PM
11/20/18 11:23 PM
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Joined: Feb 2006
Posts: 1,179
Canada
demon
super stock
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super stock
Joined: Feb 2006
Posts: 1,179
Canada
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Hacks gotta be hacking  That photos tells it. Anyone remember the small block to big block swap mods on 73-76 A body K frames? I remember it required cutting the mount off the K frame, and moving it back about an inch on the left. Looks to me like the same principal applies here.
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