rickswanson

all stock 89 fifth ave. will i have to change the carb or anything else when i switch to the mp electronic ignition?

rickswanson

its stock 318 2 brl (computer fuel controlled) i believe its called "leanburn system". auto 3 speed tranny, 2.73 rear gear, 26" tall tires. we bought the car for our daughter a couple of weeks ago. her 1st car. anyway the ad said runs good once get warmed up. i noticed under the hood a nice clean engine compartment, alot of new parts. new plugs, wires, dist. cap, fuel filter, air filter, 02 sensor, air intake sensor, egr valve, even new temp sending unit, clean inside the carb. as far as i could see, and some new vacuum hoses. no leaks under car, all the fliuds were nice and clean. a very nice looking 23 yr. old car. we started it up and it was running terrible, like on 6 or 7 cylinders. choke was working fine, kicked down to a low idle. idle silenoid worked when put a/c on. idled, but very rough. took it for a ride and noticed temp gauge was very low. after about 10 miles and temp was just a hair off cold, it was running great. no miss, no stutter, running great. so we took it home and i put a new 195* superstat, and a new 16 lb. rad. cap on it. now we got good temp out of gauge (between 2nd & 3rd mark) and engine warms up quicker. but still every time it starts when cold, it runs terrible til about 10 miles. my daughter works 7.5 miles away and it runs rough there and back. getting less then 10 mpg. got 160+ lbs in all cylinders, pulls 21" of vacuum at 650 rpm (when running right after 10 or so miles). set timing to 7 btdc and noticed it swings to 2 atdc. sorry for long post. thx, rick

TVLynn

The lean burn system was bad when it was new.. Mechanics did not know how to fix them. Their was a conversion kit offered from the dealer years ago. Replacing the distributor would be a good start. Not sure it may have one of the Rochester carbs I would try it with the existing carb first Set the initial timing 5-10 deg BTDC

78doubleR

the lean burn system was replaced with a regular type air cleaner and the distributor was swapped out for one that ran off the orange box computer. you can still buy the kit from mopar performace i believe. my dad had a 78 supercoupe and it had the swap on it with the original thermoquad on it. it worked great! definately a good upgrade to do.
here's the kit on summit: http://www.summitracing.com/search/?...-3690426&dds=1

bremereric

In my M body I run the MSD ready to run Distributor. Very easy to wire in and change out that crappy lean burn computer.

You have Summit and MSD brands to choose from here.

http://www.summitracing.com/search/?...tributor&dds=1

rickswanson

thx for the replys. i'm thinking the computer went out. i unhooked wires and/or plugged the vacuum hoses to, egr switch, air pump switch, egr valve, 02 sensor, air intake sensor, coolant temp sensor (for computer), vacuum advance to computer. start up went perfect, idles great, choke kicks off, a nice smooth 650 rpm idle, (never done that before). engine didn't pull like a v8, kinda, more throttle, the weaker it got. i bumped the timing to 15 BTDC and now it swings to 7 BTDC. this has got to be backwards. at 650 rpm its at 15 btdc and 1000 rpm 7 BTDC all the way up to 5000 rpm at 7 btdc. but, running a whole lot smoother no miss, no hiccups, no stubling i even smoked the tire a few times, w/o power braking. i was looking at this kit from summit http://www.summitracing.com/parts/PRO-66991/ anybody ever used this one? i would just leave it the way it is, but that timing is wrong, so i'm sure her mileage will be bad, and its my daughters car, don't wanna be worrying about break downs. i filled the tank and gonna let her drive it and then check mileage. i'm hoping for 14-15 mpg, we'll see. thanks for your help, rick

Mr.Duster

I have a 86 fifth that computer always went in it. I got one of those [I]Mopar Performance Electronic Conversion Kits with Distributor. It gave it some more power and seems to run alot better.

Mr.Duster

Def get the conversion kit and get rid of that lean burn system will work alot better.

rickswanson

well mpg got a little better. 114 miles on 9.1 gallons = 12.52 mpg. not great, but better then 10 mpg. def gonna order that proform kit from summit. start ups and warms ups are stll alot better. it'll miss sometimes, criuse, part throttle, accelaration, decelaration, at stops, sometimes just at idle. i drove it 32 miles yesterday w/o a single miss. pulled back into driveway, went to put it in park and it started missing, sat ther in drive for about 30 seconds, and it cleared up. i hooked the timing light to each plug wire( when it started missing at idle) and noticed each wire was eratic(not steady) at diff times. it would miss fire on #1, then get better. miss fire on #3, then get better. every plug wire went like that. i also disconnected the electric plug from carb(test drove 12 miles up hills, under loads, hard on throttle, hard on brakes) and didn't see any diff. i hope i can use this carb with the electronic dizzy kit. gonna go ahead and put a new coil on it also. should i go ahead and step up to 8mm wires and performance coil?????? or will stock coil and wires be fine. its already got new 7mm wires on it from previous owner. remember, this is my daughter's daily driver, and daddy has to pay for everything and do all the work, lol. i'll keep updating. thanks, rick

78doubleR

if your gunna put a hotter coil on it then 8mm would help you transfer the hotter spark, were i think 7mm would hinder you and not produce the same amount of spark as the 8mm.

rickswanson

i installed the proform kit from summit (very simple to install), new stock coil, new stock 7mm wires, new champion plugs, and small sunpro tach. found true tdc and put timing tape on balancer. the balancer was dead on. i knew at start up it was fixed. idle, take off, part throttle, cruise, and everything in between is so much better. i started off w/ 7* btdc at 650 rpm and it swung to 34* btdc at 2000 rpm, w/ vacuum advanced plugged, but, it was pinging climbing these hills in east tn. so i dropped it down to 5* btdc and swings to 32* btdc at 2000 rpm, no pinging and pulling alot better. i'm not gonna hook up the vacuum advanced, as i think i'm getting plenty of mechanical advanced now. i sure my daughter will be running 87 octane in it, so i'll leave the timing the way it is and hope for decent fuel milage. the electronic dizzy kit is defintly worth every penny. thx for everyones help, rick

TVLynn

The lean burn distributor has two different pickups - crazy timing changes On the street you need the vacuum advance. Not having it will kill your mileage..

rickswanson

the old dist. i took out only had 1 pick up. maybe thats what was wrong w/ it to begin with, i'm not sure. as far as the vacuum advanced, this lean burn carb does not have a ported vacuum port. i tried all the ports and they're full manifold vacuum. i tried to hook up vacuum advance to full mani vacuum and adjusted it down as far as it would go and it was at 22* btdc at 650 rpm and swinging pass 50* btdc. i didn't test drive it that way. i'm pretty sure it would ping and not pull good, and too much advance is def not good for mileage. thoses #s would be good for a race motor, w/ quality heads, but this stocker/daily driver is not gonna like em. i filled the tank up and we'll see about mileage next week or so. i'll keep an update. thx for the info, rick

rickswanson

mpg got a little better, not what i was hoping. from 12.5 before new dist. kit, to 13.8 after. maybe it wasn't filled to full on 1st tank, not sure. still running GREAT!!! i hooked vacuum advance up to full mani vacuum, and of course she's pinging away, every little hill i come to. 1st, 2nd and 3rd gear just pinging away. i started playing w/ ing. timing again. had to drop it all the way down to 2* ATDC at intial, and swing to 24*BTDC at 2500rpm mechanical all in, vacuum advanced hooked up and swinging to 48* BTDC at steady cruise, just to get it to stop pinging. reset carb to highest vacuum in gear. start up's are better, take off's are alot better, throttle response better. will smoke the tire, no power brake, all thur 1st and halfway thur 2nd, never did that before!!!!! maybe i hit the nail on the head w/ this set up. could be excessive carbon build up in combustion chambers causeing the pinging. putting seafoam in tank and will check mpg next week. thx, rick

bremereric

Your vacuum advance should be hooked up to the carb at the timed vacuum port not to full vacuum source. You should never be at 48 dgrees total timing. I run ten with another 25 in at 2,500 rpm. Maybe 36-38 degrees top.

Coronet 500

Here is a good article: http://www.corvette-restoration.com/.../Timing101.pdf

rickswanson

coronet, thx for the article. understanding more about vacuum advance timing. i've set up alot of sb chevys w/ hei and connected vacuum advanced to timed/ported vacuum and adjusted till no pinging. but full mani vacuum makes more sense now. seems like im in the ball park, except for the base timing of 2* ATDC, but thats all she can handle w/o pinging. starting just fine (hot or cold), so i'll leave it be for now. i'm sure the seafoam will help w/ carbon buildup and i'll try again in a few more tanks full and couple bottles of seafoam . bre, this ole lean burn carb does not have a timed/ported vacuum port. all those ports are full vacuum at idle 17"-21". i was sure at least one would be. but they are all under the throttle blades. i didn't realize that until after i got all of new dizzy kit installed. i was very disapointed. she's running better then ever now, so i'll keep checking mpg and we'll see. thx, rick

Arth

I'm looking at the same situation. I have a 1977 Cordoba with Lean Burn System and a Thermoquad carburetor. I was over on Summit's site and looked at several different distributors. I am kind of leaning towards Pertronix Plug & Play due to it's simplicity and I have used their products on my 72 Lincoln with great results. I like the idea of eliminating the ballest resistor which I am told is also a problem area on Mopar products. With regards to the carburetor I am leaning towards an Edelbrock Performer which is actually the Carter AFB (I guess). I've used them on several cars. However, being a square bore carb, I will need to either use and adapter or get a squarebore intake. Again, Summit has a Mopar Performance intake that is a dual plane squarebore intake. Has anyone else done this sort of conversion? TIA

MrOldart2U

There are several ways to ditch the Lean Burn... But I found that on my 77 Newport I had to find another carb for needed vacuum port.... Bought a used Thermo Quad from eggbay for 20 plus 10 shipping, Put a 19.00 kit in it and dropped it on... My car went from 3-4mpg to a hair over 14 in town... 440 car btw..