Ditching LeanBurn on a 1987 Fifth Avenue

I recently purchased a 1987 Fifth Avenue equipped with a 318ci V8. Mopar is
totally new to me and there is a lot I don't know and am very wary of.

This car features Chrysler's Lean Burn system that uses a feedback-style
2bbl carburetor and an electronic ignition system with it's own special
distributor. It seems to be well known how flakey this system can be
causing rough running to randomly leaving you with a dead engine for no good
reason. I refuse to own a car that behanves that way!

My engine runs fairly well, but it does have some issues that I can't get
tuned out and it annoys the heck out of me!

There are conversions that remove the LeanBurn system and give you a plain
2bbl Carter carb from a 1974 Valiant and a vacuum advance distributor with a
Chrysler electronic ignition.

Here is the kink: I want to go a bit further back in time. I have the
right replacment carburetor already that will mount to the intake and match
up with all my vaccum lines, but I want to have a simple points and
condensor ignition as well.

Can anyone give me a part number or a specific vehicle to inquire about so I
can get a vacuum advance POINTS distributor that will be a direct replacment
in my 318?

Wiring it up looks straight forward since I'm going to get an aftermarket
coil with internal resistor for the points. I have no emissions testing
(or visual inspections) where I live and am not concerned with that part of
it.

Thanks,
-Steve

 

Why would you want to go to point instead of the much better and fairly
rock solid electronic ignition?

If it was me... I would stick with the electronic ignition (single
pickup), but switch to the Carter AFB or equivalent.


Mopar basically makes/made 4 distributors: Single point, dual point,
single pickup electronic, dual pickup electronic.. all others are a
variation of these four. All with pretty much interchange with the
other. 318/360 are interchangable. Find a 1972 or earlier 318/360 and
lookup the part tag to find the advance curve.

 

Why? The Chrysler electronic ignition is fairly bulletproof. The only
issue that you're going to have is likely the ballast resistor, and you
still have that with the points style ignition.

That said, if you are looking for ultimate reliability and side of the
road repairability, how about a points style distributor and a CD box,
then you can unhook the CD box if it craps out on the road but you have
a much hotter spark. I don't like just points because they need to be
maintained, if you run a CD it greatly slows point wear.

nate

 

I had thought of going that route, but wasn't really sure about it. In the
past I had a 1968 Scout 800 with a 392ci V8 and it had been converted to
some unknown brand CDI box and it ran fine the entire time I owned (and
abused) it, but I didn't see the reason to have an extra piece of
electronics under the hood.

I've got my dwell meter and I don't mind adjusting points from time to time.
I guess that's one reason I like older cars, so I can always be fiddling
with something. And yeah, I am looking for reliability, but the ease of
(cheap) service is the big thing. I like to get under the hood and replace
or maintain items myself and know what does what and HOW it does what it
does.

Like I said, I'm peculiar! But I'll look into the CDI again and see where I
end up. The ignition doesn't worry me as much as the feedback carburetor
does!

Thanks,
-Steve

 

Well, I'm just odd is all! lol I'm all for technology and improvments, but
I just kinda prefer something that is simple as can be over an electronic
box to take all of the fun out of things. I really don't mind adjusting
points - It gives me reason to use my vintage Sears Dwell Meter! ;-)

Nate Nagel suggested a CDI setup and I will look into that. I know they are
pretty darn reliable and easy to install as well, so we will see.

Thanks for the tips on Mopar dizzys.

-Steve

 

OK, but then before you go making major changes, you need to do some
homework so you don't throw the baby out with the bathwater.

It *can* be, but it isn't necessarily. When everything is working
correctly, the cars run fine. That's not to say you can't make them run
better, you can.

You're probably referring to the steady-throttle surge between about 30
and about 55 mph. It is caused by the EGR system introducing too much
exhaust gas into the intake tract, and it affects all '85-'89 non-cop
M-body cars (this includes yours) with the Holley 2bbl. It *can* be fixed!

And this is just exactly what you'd want to do, *IF* you don't have to
pass emission tests. If you do, you will almost certainly fail if feedback
mixture control is not present, because it is what allows the catalytic
converter to do its job.

If you don't have to pass emissions tests, go for this. The CHrysler
electronic ignition system was the first on the market in '71 and has
proven to be *extremely* reliable and durable. And the Carter BBD
carburetor is the one to pick.

Why? I mean, they work, but the Chrysler electronic system works better
and extends the interval between underhood service needs.

Any '62-'72 318.

Why are you making all these changes? There's nothing wrong with the
external resistor or stock coil.

DS

 

You will want to get the camshaft from that old pre-1973 engine as
well. Lean burn modified ignition, fueling, AND cam timing, and
replacing any 2 of the 3 will NOT work properly.

 

Just make sure you have the procedure for switching from CD to
Kettering ignition down pat - because you WILL need to do it.

 

How sure about that are you? There is an M-Body forum with lots of folks
who tossed LeanBurn without having to swap the cam.

Quote from an M-Body forum:

<<<
I have done this personally on my 87 5th Ave, and the car runs like a dream,
is easy to repair, and solves a lot of the
inexplicable,intermittent,unreliable problems associated with lean burn.
Incidentally, they were called lean-surge because of their problems. Any car
that has a computer attached to the air breather has problems before you
turn the key. Here is the easy cost effective way to do this swap. ( in
canadian dollars, this cost me a total of,$350.00 give or take some tax)
I will provide the parts list, Mother Mopar provides the step by step
instructions,in Mopar performance engine manual, I used stock production
pieces, or rebuilds, and all you need is hand tools, and some common sense.
You will be changing the distributor, the carburetor, the air cleaner,
removing the stock lean-burn computer and replacing it with electronic
ignition, and wiring it up with a Chrysler replacement wiring harness. As
well , if you want I have also solved my transmission problems, by
eliminating the lock up feature by turning it into a regular 3spd. I have
outlined this in another article. Together, this car runs like a mid 1970s
Mopar, starts well. performs well, and delivers very good fuel economy. It
also eliminates everything I have read associated with any lean-burn system
that can best be described as JUNK!

UAP Carb No: C6061 1974 Valiant Carter Carb 2bbl.
UAP Distributor D603 1974 Valiant Vacuum Adv. Dist.
Chrysler ECU Part No: 4111850
Chrysler Wiring Harness Part No: P3690152
Chrysler Ballast Resistor Part No: 4106140

After replacing these pieces, set your initial timing as per Chrysler Specs
at 5 degrees plus or minus 2 degrees.
I guarantee you will never see a coughing, spitting wheezing belching Mopar
in your laneway....Kev

END QUOTE

 

I already purchased the new carburetor needed to convert, but I'veyet to
start to prcoess. Kinda waiting until summertime.

You are dead on about a throttle surge taking place. I hate it. The engine
has super compression, uses no oil, leaks no oil, sounds smooh as can be, so
I've come to the conclusion it was LeanBurn choking it. One moment it feels
GREAT with smooth acceleration and crusing power, then it kinda shudders and
stumbles, then it feels great.... Get the idea?

I'll pull apart the EGR system and clean it out and see what I can do.
Thanks for that tip. If the car performs better, I'll keep LeanBurn for
now. If that sucker leaves me stranded just once, LeanBurn is going out the
window immediately! I use my vehicles for long interstate trips and expect
them to perform. I take care of them, too, and realize parts do fail, but I
won't have something *flakey* under the hood.

Also, I wanted to replace the coil because the current one looks to be
original and at 16 years old, it looks like it's actually swelled and
leaking some oil (?) used for coolant or insulation. Either way, it's old
and I want to get a new one under the hood pronto just for good measure.

Thanks,
-Steve

 

That's wrong. Replacing ELB with a conventional carburetor and ignition
system works great, a cam swap is not necessary.

DS

 

It's not a question of it needing cleaning. It's poorly calibrated. The
real fix is to open up the EGR vacuum amplifier and replace its mainspring
with a stiffer one (the spring from the lockup control body in an A998 or
A999 auto trans works well) but you can also recalibrate the system by
buying a new aftermarket EGR valve (my preference is for a Standard-brand
unit). The new valve will come with several orifice plates. The idea is to
use an orifice plate that has a smaller calibration hole than your
original valve. There's a bit of guesswork involved here, since the
orifice in your original valve is built into the valve body, rather than a
separate plate. However, the new valve will come with a chart that tells
which plate to use according to the original equipment valve part number.
So you can start from there and select a plate with a smaller hole.
Alternatively, you can easily make your own orifice plate by drilling a
hole in the center of a correctly-sized round metal disk. This is all
fairly obvious once you buy the new valve.

Coils don't deteriorate from age alone. But if yours has swelled and is
leaking oil, then yes, replace it. However, don't mess with a coil that
has an internal resistor. Get the correct replacement coil; it's the same
for lean burn and non-lean-burn.

DS

 

Thanks for clearing up the EGR valve bit for me. I made the assumption the
valve was just carboned up or worn out. I'll swing by a few parts stores
and see what I can find regarding a new EGR valve.

 

One good reason to listen to DS' advice is that an internal coil
resistor will make your car harder to start in cold weather. The
stock ignition circuit has a bypass circuit built into it that puts
full voltage to the coil when the starter is running (bypassing the
ballast resistor) putting the resistor in the coil eliminates the
possibility of doing that.

nate

 

I've been a Mopar guy for 25+ years, and you do NOT want to do this.
Trust me. The Mopar electronic ignition system that has been recommended
to you is one of the most reliable ignition systems ever put on a
spark-ignition engine of any type. Points don't even come close to the
reliabilty you'll get with the electronic setup.

 

clare wrote:

Uh... no.

The 2-bbl 318 cam grind didn't change more than a gnats eyelash from the
late 60s until the roller cam replaced it in the mid/late 80s, and even
the roller cam has virtually the same profile. Lean Burn modified SPARK
timing by having the computer replace the mechanical weights and springs
in the distributor, but worked with the same valve (cam) timing as the
318 always had.

 

Okay, I'll take the advice of everyone and stick with the electronic
ignition when I do remove the LeanBurn setup and go with a conventional
carburetor and distributor. Don't crucify me for saying this, but I really
didn't have much faith in late 70's through the late 80's Chrysler products
and so I wasn't about to stick Chrysler branded electronics back under the
hood! But I'll give it a shot and maybe I'll eventually become a die-hard
Mopar fan myself! lol

Thanks,
-Steve

 

I had a 1977 Dodge Aspen with the slant 6. That car never stranded me,
the body rotted off it instead. Finally got rid of it in the early 90's.

 

If you search around and really want to 'splice' something in, you can use
the Mopar EI distributor and use a GM HEI module instead of the mopar black
box...some guy over at www.moparts.com has a site to help you wire up a 4 or
7 pin module, not much advantage over the mopar EI, other than 'everybody'
has chevy available over the counter....

-rob

 

Mopars from 75-85 have a deservedly bad rap, to be sure. But here's my
take on it- the actual engineering DESIGN of those cars was just as good
as Chrysler was always known for but assembly quality control was a
nightmare. But its 2004 now. Time has performed quality control on the
surviving ones- the ones that are still running are the ones that were
put together WELL. And they're better designed than a Ford or GM from
that era, even if the Ford and GM was a safer buy when new because of
the Chrysler QC/QA problems.

I'll never forget an '83 Gran Fury that my father had years ago. It was
an ex highway-patrol unmarked car. No pursuit package, just a 318-2bbl
administrative/undercover sedan that had 90,000 miles on it when he
bought it at auction. Butt ugly too- obviously had been stationed in far
west Texas and was sandblasted nearly down to primer. Even the
windshield was hazed with sand pits. But the darn thing consistently got
over 20 mpg and logged another virtually trouble-free 130k miles on top
of the 90k before he traded it for a 92 Dakota. I don't think he ever
added a pint of transmission fluid or had the A/C charged! On the few
occasions I drove the thing (not many) I was always amazed at how quiet,
smooth, and tight it was in spite of its reputation and the life it had led.