Sorry, but I have some questions about the late B Body Dodge Magnum

[kkritsilas]

Hello:

I would like to get an opinion, and some information regarding the 1979 Magnums. Sorry if this is inappropriate, but this is the model that the Mirada replaced, even though that is pretty much the only thing they have to do with each other.

There are two that I can get to that are for sale, one is an XE, black with what is described with a full load of options except for the sunroof, including leather seats, no rust (but needs to have the vinyl roof replaced and no engine, for $600. The other is a green Magnum GT with T-Tops, no leather or sunroof, otherwise fully loaded, but has some rust and the ECU and power brake booster has been removed (replacement supplied) for $2600. Either car will need to be flat bed trailered out, which I can have a friend go out and do with me. The questions are:

1. I am leaning towards the XE due to lower amount of rust. It isn't the GT model, but I think it is overall a car that would be easier to get into good condition. Is the extra money and bodywork cost worth it on the GT? I am also not a big fan of the green color of the GT.

2. If I do get the XE, it will need an engine. I think that the Magnums in 1979 only had 360s as the biggest engines. I know a Big Block would probably fit with the correct engine mounts (like from Shumacker). What is the clearance around the suspension/steering components like? It can be an issue with the J body cars. How about header clearance on the big blocks in the late B bodies? I know I will need to get a big block A727 transmission, and probably have to move the transmission mount around. I would appreciate knowing if this is worth it, or just stick to a 360. By big Block, I am talking about a 440.

3. What rear end was used in 1979? On the J Bodies that I have, it is an 8.25", both open differentials with 2.94 ratios. Did the 79s come with 8.25" or did they have 8.75" rear ends? Did the GT have a limited slip standard? Consensus here is that the 8.25" is only good for about 300-325 horsepower (using street tires). If I get a big block into the XE, I guess I will probably be needing to find an 8.75"? Does the extra weight of the B bodies change any of this?

4. How bad is it trying to get the Magnum's headlight doors to work? Do they break often, and how hard is it to find parts for repairing them? Motors, linkages (if any) and covers.

I'd appreciate any guidance anybody could provide regarding buying either of these cars. I know some of this has been covered with topics on our cars, but the big block engine swap stuff, for example, is different between our J bodies and the B bodies because our J bodies have the transverse torsion bar front end, and the B bodies have the regular, longitudinal torsion bar setup. I don't know what implications this has for the steering and suspension clearances on the B bodies, and I think that this should be pretty straightforward, as the B bodies did come with big blocks until 1978. The rest is more of a request for information, and opinions. Thanks for your tolerance, and if the mods want to delete the thread, I understand.

Kostas

 

[NoCar340]

1. Go for the XE. Neither car is particularly valuable in the first place, so the GT v. XE isn't going to be a Hemi Road Runner next to a /6 Belvedere where price is concerned, should you decide to sell. If you are looking at either car as an investment, look elsewhere. Neither car is worth the cost of restoring at this point in time if there's any serious bodywork needed. You've really got to want it.

2. As is the case with all '73-up B-bodies, there is a different K-member for a big-block. I have been told that factory spool mounts can be moved to a different position regarding the engine's lugs and it will bolt in, but I have not tried this personally. Header, suspension, oil pan and other clearances are the same as any '73-up Charger/Satellite/Cordoba/etc. since they are the same cars mechanically, as are the R-body St. Regis/New Yorker/Newport. The transmission mount never needs to be "moved around" on any Mopar under which I've worked. It's always in the same place, period. 3/4-speed manual, A904/A727/A99x all bolt to the same mount in the same place. Putting a big block into a B-body is a bolt-in proposition using factory parts. The K-member is easily found, but it's freaking huge. Don't look online for one unless it include free shipping. It's a truck-freight-only item.

3. The 8.25" axle is marginal in an FMJ and downright beyond design spec in the 4,200+lb. late B-body with any kind of power; that being said the vast majority of big-block B-bodies did use the small axle. The 9.25" was an option few chose as the smogged 400 wasn't what one would call a world-beater or torque monster. The 9.25" was not standard in any of the HP B-bodies. The last Mopars to use the 8.75" rear axle were the '74 trucks and E-bodies. Some '74 B-cars had them, but the 8.25" was heavily implemented during '73 and moreso in '74. The 9.25" was also available, but was not common other than in wagons, which actually used a C-body axle starting in '71 (it's wider, but it fits). The '71-'72 B-body 8.75" axle (and Dana 60) fits if you get rid of the iso-clamps, which is always a good idea.

4. The Magnum's headlamp doors aren't hard to get working. Usually the problem is in the torsion rod or its mounts. It's the same headlamp motor as used in '70-'72 Chargers, R-body New Yorkers, and Imperials (the only difference is the clocking of the gear housing and occasionally the wire pigtail layout). Due to the '70-'72 application, they're often expensive to buy, but they're pretty easy to service yourself since the #1 problem with the motor is in the contact points. Just steal the wife's emery board to fix 'em. :icon_biggrin: Literally everything around here in junkyards that had that headlamp motor has been picked clean, probably for eBay. If you find a cheap spare, grab it.

The possibility exists that one or both of these cars might have the most-desirable of brakes: the 11.73" rotors with the pin-type calipers. Parts listings and original application information is sketchy at best; my '79 300 had them while my friend's had the big rotors with the sliders. Another friend's '79 Cordoba had the small rotors & sliders (identical setup to the F-body). My 300 was a super early car, the other 300 was built about mid-run and I don't know about the Cordoba, which was a 360-2v car.

The late B-bodies are notorious for rear frame rail rot on par with the E-bodies, but the real trouble spot is the front rails. Bring a pick hammer and a large, screwdriver-style prybar with you. Go over the entire length of the inside of the front rails with the pick hammer, and use the prybar between the steering box and the rail, with the "blade" end on the rail and the curve against the steering box. Push firmly; chances are probably 50-50 that you'll hear the crunch of crumbling frame rail. For whatever reason, the rear rail issues seemed to intensify around '75 (perhaps the low-liftover trunk opening, but that's just a guess) whereas the front rail rust problems go all the way back to '71. Because of the re-engineering, though, it got much worse with the '73 swap to the rubber-isolated K-member. Any rot in the front rails is a deal breaker in my opinion. It's a difficult repair that usually requires changing the entire rail, and the car simply does not warrant the expense. Both my '72 Road Runner 400/4-speed and my '73 Charger Rallye 340/auto went to the crusher because the front rail was absolute toast by the steering box, a condition I saw in several Cordobas I parted over the years and was starting on my '77. My 300 was great in that area, but the springs came through the trunk about two months after I sold it in 1989. :eusa_doh: Conversely, the Chicken and the Charger were both perfect out back.

Other areas to watch include the K-member itself, which is quite susceptible to heavy rust around the rear mount bushings; the body side of the transmission crossmember, through which the torsion bars actually pass rather than being anchored '72-down style; and the torsion bar rear crossmember mounting areas (also rubber isolated and quite prone to rot). The K-member and T-bar rear crossmember are both bolt-in pieces, so if they're bad you'll just have to bolt in new ones--assuming you're lucky and their anchor points are still good. The trans crossmember is a welded part of the unibody and the huge holes through which the T-bars pass allow plenty of crap inside it. It often rusts from the inside out.

All of the above information regarding swapping in big blocks, axles, transmissions, etc. as well as the rust issues apply to the '79-'81 R-bodies as well. Though the Rs were the replacement for the C-bodies, essentially they're B-bodies mechanically.

 

[kkritsilas]

NoCar340:

Thanks for the information, it will come in real handy if/when I go up and see the cars. I am also tending towards the XE, due to the better color, the leather seats, and the reported minimal rust (according to the person who listed it, who knows what the reality will be). I guess I will have some decisions to make should I get the car, but I now have an idea of what I am looking for and at.

Kostas