Dodge M-body Diplomat

Posted By: Tinmans21

Dodge M-body Diplomat - 10/01/12 05:03 PM

I have an 85 dodge diplomat that I plan on turning into a street sleeper. Right now i have the original 318 an a 383 block sitting around. I think it might be safer going with the 318 first an move on up to the 383 soo. . . question is i would like a A833 four speed to go in the car but without sacrificing the bench seat up front an i would like to put a 8 3/4 "489" casting in the rear. An does anyone know how to get a M-body to handle in the corners?

Posted By: racealittle

Re: Dodge M-body Diplomat - 10/01/12 05:48 PM

Quote:

I have an 85 dodge diplomat that I plan on turning into a street sleeper. Right now i have the original 318 an a 383 block sitting around. I think it might be safer going with the 318 first an move on up to the 383 soo. . . question is i would like a A833 four speed to go in the car but without sacrificing the bench seat up front an i would like to put a 8 3/4 "489" casting in the rear. An does anyone know how to get a M-body to handle in the corners?

The Diplomat M body cars were available with a police package that was very effective for handling. I think it was called a S-21 package. The same option was often used in the taxi cab package.

The front swaybar is 1.25 inch, the rear was .75 inch. The rear cop springs had front eye segment bushings that had the 'comfort' holes filled with 3/8" rod and had red paint on the bushing. They had the police 15x7" steel slotted cop rims with dogdish caps. The rims weighed 2 lbs more the other factory steel 15" wheels. The extra steel helped to keep the wheels from flexing on hard corners.

The steering box is more performance oriented than stock.

The 8 1/4 rear axle is plenty strong. An 8 3/4 from b body 1966-67, or 1968-70 can be modified at the perches and used.

I have had a BB in an F body. I had it well sorted. There are many issues to consider. A 360 and a 383 are equal in performance when modified.

My advice is a hot rodded 318 or 360. It will be a better balanced car that should satisfy your needs.

I also did the 4 speed swap, but with bucket seats. An automatic with a shiftkit and 2400-2800 stall would be plenty of fun, (just tight enough for regular driving). I also found the 3.21, 8 1/4, rear axle to be the best compromise.

Posted By: Tinmans21

Re: Dodge M-body Diplomat - 10/01/12 07:37 PM

are you aware of any kits available to really make it handle? I'm not sure but is it possible to lower the car? I know i can with the front torsion bar setup but im not sure about the back. I don't have a 727 laying around but i do have the original 904 or 999 I'm not sure which it had but would either of these hold up to a warmed up 318? maybe with a rebuild or shift kit? Thanks for your advice by the way.

Posted By: cudazappa

Re: Dodge M-body Diplomat - 10/01/12 07:40 PM

An F-body 4 speed had a shifter handle that was designed to be used in conjunction with a bench seat.

An M-body can do reasonably well in the handling dept. The biggest detriment is the lack of torsion bar availability. Firm Feel currently offers 2 sizes above stock (All FJMs use the same T-bars, the cop bars got better bushings) and they aren't cheap (IIRC ~$700)

Good luck with it, they are fun cars.

Posted By: patrick

Re: Dodge M-body Diplomat - 10/01/12 07:52 PM

my old ride was an '86 5th ave, hot rodded. I rebuilt the front suspension with poly bushings, added a 1 1/8" cop spec front sway bar, monroe sensatrac shocks, 11.75" front brake swap, 5 leaf rear springs, 1" rear sway bar, and an 8 3/4" rear with a 3.55 742 limited slip & willwood 12" disc brakes. I also used some 17x8 mustang bullit wheels with 3/4" bolt on adapters and 255/50R17 tires.

I also ran an A500 OD tranny, and considered swapping an A833OD. my '76 duster has a bench seat with the 4 speed, using that shifter would work great with the stock split bench.

engine, I had a 360 with a comp XE262, headers, and RPM air gap and 600 edelbrock carb to start, but replaced it with the stock roller cam 318 short block, regrinding the roller cam by bullet with their HR259/316 lobe for both intake & exhaust, running home ported magnum heads, and using the same carb & intake. ran as strong as the 360, while delivering 16% better fuel economy (17.5mpg vs. 15 in mixed driving).

stick with the small block, and if you're going OEM heads, stick with magnums.

Posted By: racealittle

Re: Dodge M-body Diplomat - 10/01/12 08:26 PM

Quote:

are you aware of any kits available to really make it handle? I'm not sure but is it possible to lower the car? I know i can with the front torsion bar setup but im not sure about the back. I don't have a 727 laying around but i do have the original 904 or 999 I'm not sure which it had but would either of these hold up to a warmed up 318? maybe with a rebuild or shift kit? Thanks for your advice by the way.

I gave you the info about the factory S-21 option for a number of reasons.

I was in the factory when we were building these cars. We built thousands of these for years. These cars did a pretty good job of carving corners at stock body heights and 225/70/15 tires.

I am suggesting that you can get everything you need from a wrecker, (if you can find one who didn't scrap them all out).

Every so often a well cared for police car from the era does show up for sale pretty cheap.

The 904/999 can do the job. Plenty of upgrade parts are available at reasonable cost.

I suggest to be carefull on how low you make the front end of this car. If you choose to run good headers; you can easily flatten 3 tubes on the crowning of the road in one intersection at high speed. Good, early 340 exhaust manifolds work pretty good, and true dual exhaust pipes exiting on the passenger side rear were available on Imperials in the 1981 or so era. They were also very common in Mexico on a model they called a Dart.

Lowering the back can be done by doing some homework on rear front spring hangers. An example would be to locate a set of superstock F body front hangers. They are about 6 to eight inches long. They can be cut short (to stock length), and drilled for holes where you need them. You can make 3 to 4 sets of holes and get the ride height you are looking for.

If you are stuck for locating the swaybars/springs/wheels from a S-21
package car, I have most of those items, but I am in Canada.

Posted By: TC@HP2

Re: Dodge M-body Diplomat - 10/01/12 08:55 PM

Quote:

The biggest detriment is the lack of torsion bar availability. Firm Feel currently offers 2 sizes above stock (All FJMs use the same T-bars, the cop bars got better bushings) and they aren't cheap (IIRC ~$700)

Gary you running either of these bigger sized t-bars in your Dippy or where they the stock ones?

Posted By: Supercuda

Re: Dodge M-body Diplomat - 10/02/12 12:01 AM

I converted my 87 Diplomat to four speed years ago. Used an A body A833 (non-OD). I used a Hurst Competition shifter and a truck handle to clear the bench seat and the ashtray, I smoke so the ashtray is usually open.

I got the shifter hump and pedal assembly from an 80ish (I think 81) Aspen and I also used the Aspen to make a template to cut the hole in the firewall for the clutch linkage to pass thru. In 81 they eliminated the hole in the M body firewall since a stick wasn't an option anymore.

I had all the info on GeoCities but here's a link to an archive http://www.oocities.org/motorcity/2398/mbody/mbody.html

Posted By: cudazappa

Re: Dodge M-body Diplomat - 10/02/12 12:11 AM

Quote:

Gary you running either of these bigger sized t-bars in your Dippy or where they the stock ones?

I ran a completely stock suspension with the addition of a cop rear sway. (not legal for F-Stock). I could've gone to a larger front sway (rules permit that) and the solid k biscuits (ooo illegal) for not more $$$ but shortly thereafter I was offered a 71 Challenger and had to sell the dippy.

Still one of the nicest cars I've ever owned (44k EASY miles when I got it).

Had a great conversation with Dick at Firm Feel last year about making an F/M handle. Biggest "challenges" to overcome is the front torsion bars and front shocks.

Posted By: cudazappa

Re: Dodge M-body Diplomat - 10/02/12 12:16 AM

Quote:

And does anyone know how to get a M-body to handle in the corners?

Meant to ask, what is the intended use of the car? How far are you willing to go? Budget? In essence, what's your goals and asperations for it?

Posted By: Tinmans21

Re: Dodge M-body Diplomat - 10/03/12 10:43 PM

My main focus will be there rear since it will see some strip time. As for the overall plan its being built as a sleeper so I guess I don't need to worry about turns that often. I'll have to see how the car handles once I get the motor in an back on the street. Thanks for all of your guys help an info!!!

Posted By: cudazappa

Re: Dodge M-body Diplomat - 10/04/12 12:14 AM

Quote:

My main focus will be there rear since it will see some strip time. As for the overall plan its being built as a sleeper so I guess I don't need to worry about turns that often. I'll have to see how the car handles once I get the motor in an back on the street. Thanks for all of your guys help an info!!!

The front does need some help. Solid Bushings for the K-frame. This will help your chassis reaction. Also, stiffen up the front unibody.

In the rear, you will basically "redesign" the suspension. You'll want to use A or B body springs (A springs are the basis for the SS springs) they will require different front hangers(MP, Firm Feel, etc). The FJM springs are really long and not stiff at all. Also with this swap, you'll be eliminating the iso-clamp so you'll have a round front spring eye bushing, and the rear end will be planted right on the spring. Then you'll use traditional A/B body shock plates.

Posted By: Tinmans21

Re: Dodge M-body Diplomat - 10/04/12 01:23 AM

Awesome thanks. I'll prolly have a few more questions about a 318 to 390 build in the near future. That's uncharted territory for me so it's going to be fun. Thanks again for the help

Posted By: Lightning

Re: Dodge M-body Diplomat - 10/04/12 01:53 AM

Quote:

I converted my 87 Diplomat to four speed years ago. Used an A body A833 (non-OD). I used a Hurst Competition shifter and a truck handle to clear the bench seat and the ashtray, I smoke so the ashtray is usually open.

I got the shifter hump and pedal assembly from an 80ish (I think 81) Aspen and I also used the Aspen to make a template to cut the hole in the firewall for the clutch linkage to pass thru. In 81 they eliminated the hole in the M body firewall since a stick wasn't an option anymore.

I had all the info on GeoCities but here's a link to an archive http://www.oocities.org/motorcity/2398/mbody/mbody.html

the pics have gone down from the site

would you happen to have them saved still?

I'm also slowly working on my M- and have the 4-speed already, so I'll be watching this topic closely.

Posted By: Winchester 73

Re: Dodge M-body Diplomat - 10/04/12 01:59 AM

the usual corners are best advice.you guys are missing the obviose advice-WHIEGHT LOSS!

for starters get the following stuff:
aluminum mas cyl
mini starter
headers /sans cats
light rims

for starters dumpster the following stuff:
ac
cruise cont
emmisions junk

and last but most important -teke the bumpers apart and get rid of the "brace"? behind them and get rid of the compression bumper brackets and make some from aluminum to mount the chrome outer visual part of the bumper-300+ pouns whieght loss!i used to drive a wagon that i drove to the scrap yard and gave away the bumpers and drove without them and it instantly became a different car.even braking was noticably improved.the chrome outer shell of the bumper only whieghs about ten lbs,bolt just that on with some aluminum brackets and it would look stock.

Posted By: dart1962_440

Re: Dodge M-body Diplomat - 10/04/12 02:04 AM

Quote:

the usual corners are best advice.you guys are missing the obviose advice-WHIEGHT LOSS!

for starters get the following stuff:
aluminum mas cyl
mini starter
headers /sans cats
light rims

for starters dumpster the following stuff:
ac
cruise cont
emmisions junk

and last but most important -teke the bumpers apart and get rid of the "brace"? behind them and get rid of the compression bumper brackets and make some from aluminum to mount the chrome outer visual part of the bumper-300+ pouns whieght loss!i used to drive a wagon that i drove to the scrap yard and gave away the bumpers and drove without them and it instantly became a different car.even braking was noticably improved.the chrome outer shell of the bumper only whieghs about ten lbs,bolt just that on with some aluminum brackets and it would look stock.

Less weight never hurts. Lower center of gravity helps too.

Posted By: Winchester 73

Re: Dodge M-body Diplomat - 10/04/12 02:31 AM

Quote:

Quote:

I have an 85 dodge diplomat that I plan on turning into a street sleeper. Right now i have the original 318 an a 383 block sitting around. I think it might be safer going with the 318 first an move on up to the 383 soo. . . question is i would like a A833 four speed to go in the car but without sacrificing the bench seat up front an i would like to put a 8 3/4 "489" casting in the rear. An does anyone know how to get a M-body to handle in the corners?

The Diplomat M body cars were available with a police package that was very effective for handling. I think it was called a S-21 package. The same option was often used in the taxi cab package.

The front swaybar is 1.25 inch, the rear was .75 inch. The rear cop springs had front eye segment bushings that had the 'comfort' holes filled with 3/8" rod and had red paint on the bushing. They had the police 15x7" steel slotted cop rims with dogdish caps. The rims weighed 2 lbs more the other factory steel 15" wheels. The extra steel helped to keep the wheels from flexing on hard corners.

The steering box is more performance oriented than stock.

The 8 1/4 rear axle is plenty strong. An 8 3/4 from b body 1966-67, or 1968-70 can be modified at the perches and used.

I have had a BB in an F body. I had it well sorted. There are many issues to consider. A 360 and a 383 are equal in performance when modified.

360 = 383? NEGATIVE!

360
cast crank
1.88 intake valves
small doglegged port heads(probly cracked)
long thin cyl walls
4 head bolts per cyl
wet intake manifold
expensive to get cu inches

383
forged crank
2.08 intake valves
bigger ports
5 bolts per cyl head
dry airgap intake stock
cheap to make into a 426

My advice is a hot rodded 318 or 360. It will be a better balanced car that should satisfy your needs.

I also did the 4 speed swap, but with bucket seats. An automatic with a shiftkit and 2400-2800 stall would be plenty of fun, (just tight enough for regular driving). I also found the 3.21, 8 1/4, rear axle to be the best compromise.

Posted By: Tinmans21

Re: Dodge M-body Diplomat - 10/04/12 02:44 AM

I took off the ac smog an my dip didn't have cruise from the factory an was missing all the exhaust from front passenger back. I have a video of it on YouTube back when it was red doing a one tire fryer lol. I want to get rid of all "bump cylinders" as I call em behind the bumpers. There's a site called dippy.org that I found that has some good info about weight loss on m-bodys as well. http://www.youtube.com/watch?v=fKBqiESfMQU&feature=youtube_gdata_player that should b the link of my dippy doing a one tire fire.

Posted By: Diplomat440

Re: Dodge M-body Diplomat - 10/04/12 03:14 AM

my 85 diplomat with totaly stock front suspension and a 440 handles a lot better than i thought it would. i used a 3.23 8 3/4 out of a 66 charger, and an a-833 and pedals out of an aspen. 71 b-body pistolgrip fits the bench seat perfect.
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Posted By: Tinmans21

Re: Dodge M-body Diplomat - 10/04/12 05:34 AM

It's real nice to see an actual picture. Thanks so much

Posted By: Lightning

Re: Dodge M-body Diplomat - 10/05/12 12:48 AM

Agreed.

Tinsman, about 4 of us that have posted so far in this one are from the dippy.org forums, and CudaZappa's the only one so far to take his to an autocross. It's nice to see there's others out there that are looking to corner though definitely.

Posted By: Tinmans21

Re: Dodge M-body Diplomat - 10/05/12 01:54 AM

I don't know what it is about diplomats but i just love it. Its like the family lab that you can't hate no matter what it does. Im stuck between a 318-390 build or 383-496 build. Guess i need to do more info digging.

Posted By: Lightning

Re: Dodge M-body Diplomat - 10/05/12 02:35 AM

keep up with the new Hemi stuff too, they might be more bang for the buck here soon. Blocks were supposed to be about $600 from the dealer from what I remember reading someplace.

Posted By: Fury Fan

Re: Dodge M-body Diplomat - 10/05/12 01:37 PM

Quote:

Agreed.

Tinsman, about 4 of us that have posted so far in this one are from the dippy.org forums,

And this Dippy.org guy is reading along, I'm sure there are a few others, too.

And you're right about the Lab reference, a Dippy has a charisma all its own.

Posted By: TC@HP2

Re: Dodge M-body Diplomat - 10/05/12 04:43 PM

I recall one or both of the mopar rags doing a couple of bent bar build ups at one point or aother. I think one was called Moby Doba, which was a street build, and the other I believe was a Fury or Dippy built for Silver State races.

Might do some google searches to see what turns up. I'll check my old magazine index to see what I can find.

Posted By: Twisted

Re: Dodge M-body Diplomat - 10/09/12 05:13 AM

I think the other one was the Stealth Bomber in Mopar Muscle. Interesting and rather basic build.

Posted By: TC@HP2

Re: Dodge M-body Diplomat - 10/09/12 02:19 PM

Yeah, thats it. Yes, there was not a lot of trick parts in either of them. I do recall one of them added strut rods to eliminate the fore/aft movement during suspension cycles. This was before Firm Feel offered their bigger rate t-bars, so neither of them had those.

Posted By: Tinmans21

Re: Dodge M-body Diplomat - 10/10/12 02:51 AM

Quote:

keep up with the new Hemi stuff too, they might be more bang for the buck here soon. Blocks were supposed to be about $600 from the dealer from what I remember reading someplace.

This caught my attention. Where would i look for this just curious. lol

Posted By: TC@HP2

Re: Dodge M-body Diplomat - 10/10/12 02:24 PM

Start with truck salvage yards. However, this may not be the best bucks down approach as you will have a fair amount of expense in harnesses and controllers to make it work without all the factory computers. But, if you pull it off they make reasonable power with reasonable effeciency.

Posted By: patrick

Re: Dodge M-body Diplomat - 10/10/12 06:44 PM

Quote:

keep up with the new Hemi stuff too, they might be more bang for the buck here soon. Blocks were supposed to be about $600 from the dealer from what I remember reading someplace.

if I were still single and still had one of my 2 5th ave's, I'd be putting a 5.7L hemi in it, stock, save a comp cams roller cam...

Posted By: Winchester 73

Re: Dodge M-body Diplomat - 10/13/12 04:51 AM

a while back i saw a post on an aspen that the owner was swapping in a b body k frame and tbars.iirc it was red.