Big Block Guys, Need Advice: 400ci and 727 into an Imperial

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Bryan M.

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Yep, it's official: I'm big-blocking my '83 Imperial.

It's not my first go-around with shoving a big block into an FJM, but last time was a 440 and the guy I was helping...well...his "come hell or high water" approach made for some interesting stories. This will be a 1975 400ci and 727. Already planning on Schumacher mounts, expecting to have to alter my driveshaft (or go custom) and I'm looking for subframe connectors. I'm planning on using the Hedman headers and I'm looking at torsion bar upgrades in case they feel weak once the car is mobile. Anybody got tips or notes that I should be looking at?
 
a later 400 is the best stock block for the most power out put InAccordanceWith the machine shops

go to Moparts & FABO's bigblock and tech archive for an incredible amount of information

i have a big block 727 if you need one
 
Whatever components you can afford to switch to aluminum vs. cast iron, I would. Brake booster must be changed. I think firm feel makes some stiffer tb's, but they're not cheap. I wouldn't worry to much about the 8.25 if it's basically stock and no slicks. Move the battery to the trunk to shift some weight also.
 
Car is getting power, so I'm looking at rear ends. Was under the impression a big-block Cordoba master cylinder will work, do not want to go the K-car route. I need to figure out what needs to be done to the K-frame now while I've got everything out, or do I just wait until I start the trial fitments?
 
I believe you need a small diameter dual diaphragm booster. A 400 is shorter (height wise) so you may want to check if your stock booster will work. My Aspen is an RB (440 stroked to 500) and non-power brakes so I can't say for sure. All I can suggest on the k-frame is to shave maybe 1/4" off the rear weld flange (where the front of the oil pan sump would be), just to give a little wiggle room. Not a bad idea (on any FMJ k-frame) is weld the halves together better. Mine was what you'd call "casually welded" at the factory..........

I assume Imperial T-bars are same as standard F-body(?) With a BB, A/C, and power steering the stock T-bars seem to be just fine. By my measurements to set the ride height to spec I only had to turn the adjusting bolts another 4-5 turns in (going by memory from the original BB swap in 1989).

Sub frame connectors are highly recommended.

If you have any questions, I'd be happy to help where I can.
 
I'll take a look at the K-frame on mine for the welds for sure. The 440 into a Diplomat I helped with in about 2006 wasn't as bad of a fit as I remember, so I'm hoping that the stock booster will clear. I'm not bothered if I have to get it out of the way to drop the engine in, but if it fits, all the better. Imperial's suspension seems to be AHB stuff...it perfectly matched all of the AHB parts I've been carrying for the last ten or so years. I'm hoping that there isn't a real noticeable amount of weight shifted to the front. I'm already banking on moving the battery to the trunk, and as I understand it the 400ci isn't as heavy as an RB block.
 
Bryan M. said:
I'll take a look at the K-frame on mine for the welds for sure. The 440 into a Diplomat I helped with in about 2006 wasn't as bad of a fit as I remember, so I'm hoping that the stock booster will clear. I'm not bothered if I have to get it out of the way to drop the engine in, but if it fits, all the better. Imperial's suspension seems to be AHB stuff...it perfectly matched all of the AHB parts I've been carrying for the last ten or so years. I'm hoping that there isn't a real noticeable amount of weight shifted to the front. I'm already banking on moving the battery to the trunk, and as I understand it the 400ci isn't as heavy as an RB block.
Click to expand...

What weight you add up front, will balance out the remains of the builder of your 323..it's all good
 
brotherGood said:
What weight you add up front, will balance out the remains of the builder of your 323..it's all good
Click to expand...

I'm not keeping that .....er in the trunk, Brian. Besides, the courts have first dibs on his carcass, I get the scraps afterwards.
 
So far, all signs point to a low-mile engine that was left to sit for a while after it got pulled. Only damage is the windage tray under the intake manifold, it's got pinhole rust from some weird insulation-like crap that was stuffed inside. Internals clean up beautifully after a quick bath in WD-40.
 
The insulation is for both sound absorbing, and to insulate the bottom of the intake from heat. The intake gasket/valley cover is thin and noise and heat go right through it.
 
Mopar Action did a comprehensive article on this swap. I have both the original issue in which it appeared, as well as the Tech Special that contains a reprint of the same article. Unfortunately, I have no way to scan either anymore but if someone would like a photocopy mailed to them I could photocopy and mail it.

440 into F-Body: Hot To Swap
Mopar Action Jun 1992 Vol 4, Num 1 (pg 58)
Mopar Tech Special 1995 Vol 2, Num 1
 
NoCar340 said:
Mopar Action did a comprehensive article on this swap. I have both the original issue in which it appeared, as well as the Tech Special that contains a reprint of the same article. Unfortunately, I have no way to scan either anymore but if someone would like a photocopy mailed to them I could photocopy and mail it.

440 into F-Body: Hot To Swap
Mopar Action Jun 1992 Vol 4, Num 1 (pg 58)
Mopar Tech Special 1995 Vol 2, Num 1
Click to expand...

NoCar340, I would be grateful if you would do that. PM me for information.
 
not sure about stock valve covers, but i used ebay special aluminium valve cover with rattle can wrinkle finish and they wouldn't clear the stock booster, had to use a k-car booster, used a deep center sump oil pan ment for external pick up, and yes i had to shave that fat lip on the back of the k-member, I used hooker 1 7/8th headers they fit, but damn its tight on the passenger side, smacking a few of the tubes helps, also switched to an aluminium manual steering box, look at 440source for their "blemished" water pump housings, picked up a passenger side housing that needed gasket matched, but at $35 for the housing, used a GMB aluminium pump off ebag another $20 check out my build here http://board.moparts.org/ubbthreads/ubbthreads.php/topics/1953459/1.html

37E9CFA0-8710-4B85-93A8-DBE49F142D25_zpsvmt3nyrj.jpg
 
NoCar340 said:
Mopar Action did a comprehensive article on this swap. I have both the original issue in which it appeared, as well as the Tech Special that contains a reprint of the same article. Unfortunately, I have no way to scan either anymore but if someone would like a photocopy mailed to them I could photocopy and mail it.

440 into F-Body: Hot To Swap
Mopar Action Jun 1992 Vol 4, Num 1 (pg 58)
Mopar Tech Special 1995 Vol 2, Num 1
Click to expand...


I've got a sun-baked 82 Imperial from TX--clean&solid but whole interior is toast, so it's going custom w/440...
Is a photocopy and e-mail of it possible??
Thanx!!
 
What do you need to know? I've swapped a 400 block into one and a few other guys here have done so as well.
 
I have that article...according to E-booger in the article the Torsion bars on the FMJ are plenty stout in stock form and don't need replacement when going B/RB.
 
Mr C said:
I have that article...according to E-booger in the article the Torsion bars on the FMJ are plenty stout in stock form and don't need replacement when going B/RB.
Click to expand...
I agree with this.
 
I can attest to that. With the RB in my Aspen, no problems with the t-bars. I'd guess the adjusting bolts are maybe 5 turns in from where they were with the S6 to get the front end at the correct height.
 
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