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View Full Version : 87 Diplomat ex-police car- more power?



1985ShlbyChrger
05-27-2007, 03:36 PM
I just bought an 87 Diplomat ex-police car. I am wondering what I can do to get some more power out of it. It has a 318 with a 4bbl carb. I put on accel plug wires and changed the plugs. The next thing I am going to do is get rid of the Lean-Burn crap, swapping the distributor and computer out and also changing the carb and adding a Edelbrock intake. What else should I do to get some more power? Thanks.

Nate

raccoon
05-27-2007, 03:45 PM
turbos help with power i hear.

ShelbyMotorsports
05-27-2007, 03:51 PM
I just bought an 87 Diplomat ex-police car. I am wondering what I can do to get some more power out of it. It has a 318 with a 4bbl carb. I put on accel plug wires and changed the plugs. The next thing I am going to do is get rid of the Lean-Burn crap, swapping the distributor and computer out and also changing the carb and adding a Edelbrock intake. What else should I do to get some more power? Thanks.

Nate

Thats a great start. After that I would go with headers & exhaust and then a performance camshaft.

Steve

Birddog
05-27-2007, 03:58 PM
Keep the carb it either has a ThermoQuad or Q-jet and there is plenty of tuning for them, lose the lean burn as you said add an MSD box, and open the exhaust, they choked those things down in a major way.


Any pics??

moparman76_69
05-28-2007, 03:16 AM
scratch the MSD box just convert it over to the mopar orange box, new dist. orange box and wiring w/instructions was 199 bucks when I bought mine, of course that was probably 4 years ago now. The heads on the 318 are what really hold it back. I don't remember what casting to look for but I'd get some 360 heads before I put a cam in it.

dds78910
05-28-2007, 08:49 AM
I have a HotRod Mag from a few years ago, and they bought a 318 from a junk yard with 150,000 miles on it and the didnt touch the bottom end and did just head and intake work. With a budget of $1,500.00 the ended up making 406 hp to the crank on a stock bottom end! If you want I can scan the mag later and put it on the site.

Aries_Turbo
05-28-2007, 10:45 AM
www.enginemasters.com they have a budget screamer article and they made 415hp. 360 smogger heads with either the intake or exhaust valves swapped for larger ones and a small amount of cleanup done. cam and intake and it was making that power level :)

Brian

5sp. mini
05-28-2007, 11:44 AM
i.ve got 2 or 3 dist. for stock box ing. lmk if you need one . but your dad might have one. also have a new pionts dist for a big block if you know of anybody needing it. alan

banger68
05-29-2007, 12:10 PM
I heard that some of the later 318's in cop cars got 360 heads. I haven't seen it confirmed though. The 318 heads and lean burn are the 1st to go to make some power. Some of the exhaust systems were really restrictive then too.

boostboy
05-29-2007, 12:25 PM
I dont know what you plan on running, but I had an 86 Dippy cop car I put a 340 intake on it, a demon 650 cfm carb and some exhaust manifolds from a dakota r/t that I had lying around and the difference was amazing! The car wend from a ok daily driver to something that would give a 5.0 a great run for its money. The car also became a great burnout machine!

DB-Rocket
05-29-2007, 06:34 PM
1987 318 should have closed chamber swirlport heads.
Your better off keeping the heads, put bigger valves in them and port them.

If you put 360 heads on that engine you will loose compression, and power.

1985ShlbyChrger
05-29-2007, 08:57 PM
Thanks for all the help guys. There are some great ideas.

Nate

Tony Fields
05-29-2007, 10:56 PM
I believe the 1971-1978 360 "J" heads have the larger exhaust ports and
have 1.88 and 1.68 dia. valves. These heads can pe punched out
to 2.02 Dia. on the intakes. If you want to stay away from headers you
might look at 1972 Dodge Polara 360 exhaust manifolds. I believe
they are the same as the 1972 Cuda and Challenger 340's.

I will be running these manifolds on my '67 Barracuda 360

5sp. mini
05-30-2007, 07:49 PM
yes if it was a police or taxi with a 4 barl. carb. it has 360 heads. i have one that i pulled. if you pull a valve cover it will say on the head. you also have a real cool oil pan baffle in there too. tony will them manifolds fit a A body ? alan

Tony Fields
05-30-2007, 09:39 PM
yes if it was a police or taxi with a 4 barl. carb. it has 360 heads. i have one that i pulled. if you pull a valve cover it will say on the head. you also have a real cool oil pan baffle in there too. tony will them manifolds fit a A body ? alan


Yes they will Alan. My A Body (67) 'Cuda has manual steering and brakes so room was not a problem.

I'm not sure what the Dippy had as far as manifolds, but these are
not a bad choice for the ex cop car.

Nate, a good exhaust choice would be the tti's.....would make the
old cop car sound real good!

Here's the link:

http://www.ttiexhaust.com/
here's what tti made for me:

http://www.turbo-mopar.com/forums/photopost/data/518/medium/49.jpg



Here's a pic of the driver side manifold.

http://www.turbo-mopar.com/forums/photopost/data/518/medium/36005.jpg

Driver's side manifold

http://www.turbo-mopar.com/forums/photopost/data/518/medium/360_manifold.jpg

The passenger side is not a problem as long as the ports are the same size
as the driver's side.

Passenger side manifold:

http://www.turbo-mopar.com/forums/photopost/data/518/medium/36001.jpg


Good luck Nate...I'll help you all I can...just give me a yell.

fleckster
05-31-2007, 10:39 AM
I've also heard/read that the best factory manifolds are the ones that came on the truck Magnum engines. (Yes, the also fit the LA small blocks.) They should be easy to find and they are "supposed to" still fit in the cars. The M-body has a good-sized engine bay so clearance shouldn't be a problem, especially for exhaust since you don't have the torsion bars mounted back under the car to get in the way.

Clay
05-31-2007, 11:15 AM
Ive been told the same thing Fleck. Ive got a set laying around for a rainy day as well.

boostboy
05-31-2007, 11:34 AM
The magnum manifolds are the ones I used and they are Way betther then the ones pictured above. Super free flowing, large dump on them and they bolt right up and fit like a charm. If you can find a set of those, try a 72+ 318A body that has a slight high rise manifold they are decent stock pieces too.

CCTVGod
06-01-2007, 11:12 AM
I just bought an 87 Diplomat ex-police car. I am wondering what I can do to get some more power out of it. It has a 318 with a 4bbl carb. I put on accel plug wires and changed the plugs. The next thing I am going to do is get rid of the Lean-Burn crap, swapping the distributor and computer out and also changing the carb and adding a Edelbrock intake. What else should I do to get some more power? Thanks.

Nate

Hey Nate,

I just joined this list, but I have been a DV-SDAC member since the beginning, and an AHB M-Body knut since 4/03 when I bought my Gran Fury Highway Patrol car (unmarked) from the Philly Police auction for $300.00 :-P

Albeit this forum is a wonderful resource, you may also want to join "Farley's List" . They are a forum dedicated to the F-J-(and especially) M-Body Mopars. There are quite a few M-Body cop car owners on there, as well as other wonderfully disturbed M-Body Mopar phanatics on that list. There are several Fans on that list that have given me lots of insight on how to find some of the harder-to-find Cop-car-only parts (depending on the model of your Cop car), as wel as how to make them go-faster, stop-faster, handle-better, and did I mention go faster?

There are several gents on there with remarkably fast and agile "cop cars" :-) There are some gents that have done big-block conversions, as well as a link to one dude that put a 413 Max Wedge in his Diplomat (YES, it fits!) . He has step by step pix on how he made it fit, and how he kept it from twisting the front of his car off when he steps on the loud pedal :-D

I am working on a 360/360 spec motor for my AHB with a few changes that should make it closer to a 400/360. The tough part about the exhaust and manifold issues with these cars is that they have 3 CATS on them 88-89's do (does yours?? two mini-cats in the y-pipe?) and that ALL of the exhaust shops (at least here in Philly) insist on installing 3 NEW CATS with any new exhaust that they make for you (grrr...everyone is afraid of the DOT). If you have a way around that, you're golden... I "improved" things in MY y-pipe immediately by umm ... 'inspecting' the front 2 CATS with a plasma cutter and removing that "debris" that I found in there *wink* ;-) .Then I replaced the 3rd with a higher performance cat (still have to get rid of that whisper quiet, highly restrictive muffler) I could almost hear the motor scream "THANK YOU!" I expect that I felt about 5-10 hp in my right foot just doing that alone. Its a relatively easy job, and the y-pipe DOES come out without dissassembling the steering linkage. Just turn the wheel all the way to the left after pulling all of the y-pipe bolts and it'll wiggle right out. It only took MY fat-a** about 3 hours to do it :-) Funny thing is that the empty CATS make it sound like it has headers in it...

The next thing you should consider is removing the Lean-Burn computer. It is in the driver's side lick-panel. DO NOT throw it away, as it DOES have collector value as a Police-Only part. It is NOT the same computer as the one that hung on the side of the airboxes on civilian 318's. I would NOT spend lots of money on an ignition unless you are building a motor for yourself. convert it to an Orange Box and you will notice the improvement in throttle response and power immediately. There is not enough "performance" in the motor itself to justify spending any more. The car WILL feel MUCH better just putting the O-Box kit in.

NOTE: Buy an extra O-Box on EBAY, as they are not as reliable as they used to be Lol *sigh*

The miserable exhaust manifolds on the car are next. I unfortunately still have them (too). Although the O-Box and gutting the front CATS will make a noticeable improvement in grunt, the manifolds are choky, and one of them has the butterfly in it that pumps exhaust UP through the intake manifold to fast heat the intake in the cold. Great for Cops...

Last but not least are the major issues with performace exhausts for the M-body cars. If you want to do a dual exhaust, the pipes unfortunately have to come out in front of the rear wheels as the fuel tank is right against the left side leaf-spring and right up against the differential, making it almost impossible to do dual exhausts in any other fashion. Most of the guys rides that I have seen have put exhaust manifolds of choice on their engine, and then just brought them together in one big sewer-pipe that comes out on the passenger side. Not as sexy as duals, but it gets the job done. I have seen one guy on Farley's List that DID do duals by moving his fuel tank, mounting the mufflers in the middle of the belly, and then running the exhaust pipes down the unitbody rails in the rear (ala 5.0 Mustangs of yore). Good luck... if you find a way to do it that looks nice and dosent cost a fortune, I'm all ears!

If your car is an 87, then it has an 850 CFM Rochester QuadraJet. Carter went out of business by then, and Ma Mopar was looking for just the right controlled fuel-leak to stick on these cars. Wanna be sick?!?! If you look closely at the carb (near the electric choke, I believe) you will actually SEE a "GM" emblem embossed on it. YES... this is a GM carb. NO Mopar EVER ran right with a GM carb Lol. I have rebuilt TWO of them, and they are horrific to work on. Take yours OFF of the car, and throw it as far as you can. If you can't throw far, use a baseball bat to get the extra distance ;-) Thermoquads are easy to find and relatively cheap on EBAY. I would NOT stick with the QJ if you convert to an Orange BOx, because the stock QJ has a duty-cycle solenoid on it that will be no longer needed. Electronic carburetors do not belong on non-electronic / non Lean Burn cars. The QJ is too complicated for its own good anyway... The dual plane manifold will work just fine. It'll give you nice torque with whatever carb you stick on there.

NOTE: This is a spread bore manifold!! Do not look for square bore carbs or you will need a mod-plate. Thermoquads are spread bore.

Ohh.... The Farleys forum:

http://www.dippy.org

Good luck!

They are fun and highly indestructable cars :-)


Gary A. Joseph
Treasurer, and Proud Member
Delaware Valley Chapter
Shelby Dodge Automobile Club\
Treasurer@DV-SDAC.org
1988 Shelby CSX-T (The 'home' of #260, 41K original miles!)
1986 Dodge 600ES LTD Turbo Convertible
1987 Shelby Lancer (used to be Naz's) Yes.. its for SALE! Email for more info
1989 Plymouth Gran Fury AHB "Pursuit Package" (Last of the REAL Police Cars)
1997 Dodge Gr Caravan SE The Legendary 'BIG' Dawg (tow vehicle)
1995 Caravan LE (The Mother Ship)
Gary@cctvgod.com

ShelGame
06-01-2007, 11:29 AM
I've also heard/read that the best factory manifolds are the ones that came on the truck Magnum engines. (Yes, the also fit the LA small blocks.) They should be easy to find and they are "supposed to" still fit in the cars. The M-body has a good-sized engine bay so clearance shouldn't be a problem, especially for exhaust since you don't have the torsion bars mounted back under the car to get in the way.

When I had my Dak R/T, I thought I had read that the Magnum manifolds were OK (2.25" outlet), but the '90/91 non-Magnum manifolds were identical except that they had a 2.5" dump (and therefore flow better). But, that's just from my (very foggy) memory...

5sp. mini
07-19-2007, 09:00 PM
as were on the small block thing i,ve got my 84 318 4v motor out. does anybody have a pic. of a steel crank ves. forged? als

denviola
07-23-2007, 08:43 PM
as were on the small block thing i,ve got my 84 318 4v motor out. does anybody have a pic. of a steel crank ves. forged? als

No pic, however if you have it out, just hold it up or suspend it, then lightly tap one of the counterweights with a wrench or hammer. If you get a "ding" sound, it is forged. If you get a dull thud, it is cast (or cracked).
This used to work every time way back then, hopefully still does.
Denny

5sp. mini
07-28-2007, 12:45 PM
forged it is. off hand how much a 84 318 with 360 heads good crank worth? block has been checked and tanked new cam bearings had new freeze plugs but the shop left a old plug in so i remove new plugs to find old one.:confused: heads have been done but need assmbled. might take to nats to sell. als

WickedShelby88
08-12-2007, 02:34 AM
I'm just mad I didn't pick up a steal in a factory 340 intake from a older mopar from the muscle era so it didn't have any smog garbage whatsoever. I didn't know they fit the 318's although I think the 84 heads on my RC may be a restriction, the em's looks like they flow plenty well and dump right in the middle. I may look to the magnums though. They sound nice. Any news on your dip. I always liked those cars. I wanted to build a mean 318 when I had an 87 5th.

1985ShlbyChrger
08-12-2007, 07:50 PM
I don't think the 340 heads will bolt up to the 318 heads. I think the ports are a different size, depending on the year.

The Dip runs good, put the exhaust on it and it gets a little better gas mileage. The cats were completely plugged on the stock exhaust.

WickedShelby88
08-12-2007, 11:40 PM
lol I found part of my RC's prob today. Somewhat had accidentally put the vacuum line for the diverter valve solenoid on the line for the ESC and the ESC line going to the diverter valve solenoid so it was only getting vacuum at certain times which would explain why sometimes the truck would run really good and others it would just flat fall on its face. I'm getting rid of the air pump altogether and will eventually throw a set of magnum heads and a good intake and demon on, but for now its going to get a good tune-up and the emissions components removed to get some heat AWAY from the intake.

entity
08-30-2007, 04:12 PM
you can find very useful info on allpar.com regarding these cars and what works. I now have another one as my d.d. Fith ave, but none the less a o.e. carbed car. No computer poo to get in the way.