440 Lean Burn

77newyorker440

Well-Known Member
Joined
Aug 8, 2020
Messages
511
Reaction score
277
Location
Peanut State, USA
Hello,
Since the last time I posted: Fixed Speedometer Cable, new trans filter, fluid, and pan.

So I have a 77 New Yorker with the 440, and mine still has the stock Lean Burn System. My goal for this car is to have medium 440 performance but keep the luxury look of the car, so it will be a bit of a sleeper. However, I was wondering what I should do with the lean burn system, so I thought I would consult you all. Currently, it is pretty fast, took it for a bit of drive around the neighborhood the other day and it ran very well, but I feel that the 440 could be brought back to its 1960s power a bit more. Therefore what do you all think is the best plan of action? Should I keep the lean burn and do other upgrades like heads and exhaust? The other option would be getting a new 4 barrel (probably from Holley), or even a Holley Six Pack, and putting that on, along with removing the lean burn and adding a new distributor, ignition, and coil. I know a lot of the lean burns went bad, is there any clear way of telling if mine is still good? The carburetor acts up occasionally, if the gas pedal is floored the car will almost stall but it usually jumps forward after about 2 seconds of stall. Also, I have noticed that the lean burn seems to be pretty rare, so would it be worth it to keep it for the car show factor? Please put any opinions, concerns, or suggestions below.
Thanks, 77newyorker440
 

mopar440

Well-Known Member
Joined
Oct 17, 2018
Messages
714
Reaction score
386
Location
St paul
I'd keep it simple, remove lean burn, but save it

Install new Mopar performance distributor, I always install 1 mp advance spring to bring in curve faster

Install Edelbrock performer carb ( easier to tune than holley, I think)

Install true dual exhaust, I think you'll be happy with the performance and reliability
 

1970FuryConv

Senior Member
Joined
Aug 8, 2014
Messages
3,665
Reaction score
3,825
Location
Richmond, VA
I agree with Mopar440. That's a 440 smog motor with compression ratio down in the 8s. To make it super high performance, you'd need to change pistons and up the compression ratio. That's a full engine rebuild.

Ditching the lean burn in favor of electronic ignition and an Edelbrock carb would be a lot less work and expense.
 

CBODY67

Old Man with a Hat
Joined
Mar 27, 2011
Messages
7,268
Reaction score
4,433
As to keeping the Lean Burn system intact, for the originality at car shows and such . . . I suspect that few might really know what the Lean Burn System really was, other than "troublesome". As the system involved spark timing and fuel system modifications, doing the equivalent of the old Mopar Perf Electronic Ignition kit should take care of the ignition part of things, while using OEM-level parts and the normal "Chrysler Look" of things. But it now appears that THAT particular item is not what it was, back then, so other sources and some mix/match of what's still available from Mopar Peft might be in order. Ehrenberg or Mancini as potential sources of such?

The "fuel" component was the specially-calibrated ThermoQuad spreadbore 4bbl. Of course, it will need to be changed, too. The "ThermoQuad-look" Speed Demon carb might be an option, especially with the "composite fuel bowl" variation. Electric choke and should adapt to the factory linkage pretty good. Possibly the "lost motion link" for the cruise control, too? And it should bolt to your existing intake manifold, too.

From there, a dual exhaust kit with 2.5" pipes and the stock 2.5" mufflers can complete things.

Getting the low compression 440s back to their "60s glory" will require a piston swap to gain higher compression in the engine itself. Cyl heads are already at least as good as the earlier ones, with the larger valve sizes and such. Cam specs are at least as good, too, other than for the 440/375 HP cam. BUT forget about horsepower numbers! Focus on off-idle response and normal driveabiltiy issues more than just power at 5000rpm. A vehicle that heavy needs TORQUE to get things moving rather than 5000rpm horsepower.

Also, forget about those "Idle-to-WOT stomps", too. Load the engine against the converter using the foot brake, a bit, then a 1/2-3/4 throttle punch to get going and then WOT past about 30mph in low gear. Especially with a "heavy car" and very possibly 2.71 gears in the rear axle. Not to forget the (suspected) tall P235/75R-15 tires. In other words, get it moving and into the meat of the torque curve, off the line, and then let it breathe so that it needs WOT to do what it can before the 1-2 shift happens. Learning to modulate those things effectively might yield best results. It can be "fun research".

DO check the accel pump output, though, AND the spring tension on the secondary air valve, for good measure.

Some thoughts and observations,
CBODY67
 

Davea Lux

Old Man with a Hat
FCBO Gold Member
Joined
Mar 27, 2017
Messages
8,918
Reaction score
8,073
Location
Cornelius Or
As noted, you are starting with a low compression smog motor with a lot of features that hindered performance in favor of lower emissions. You need to raise the comp ratio to at least 9.5. Use the 440 magnum/HP/TNT cam from 69-70. You also need to figure out is you have a cast iron crank or a forged steel one. Forged steel preferred for any performance build. Toss the stock intake and get rid of the EGR valve. A lot of the '77 cars also have a single exhaust which should be discarded in favor of duals. Stock log style manifolds are also highly restrictive. The A-727 used in '77 is a low stall speed unit that is probably not a good choice for a performance build. To take advantage of the increased horsepower you will also need 3.23 gears. The stock heads will also need some port work and better valve springs to achieve their performance potential. Would also want to toss the stock thermoquad in favor of and after market Holley or AVS carb.

Dave
 

Turboomni

Old Man with a Hat
Joined
Dec 14, 2015
Messages
6,219
Reaction score
6,126
Location
MA
I don't know if this is in the cards but, if you want a good deal of torque increase and some rather good hp you could make it a stroker and look stock and run on pump gas for a reasonable price. That is what I am doing on my 69 440 Fury III. It will look all stock and make bucket loads of torque at low rpms into a 3.23 rear with manifolds. My engine will be turquoise with a stock dual snorkel air cleaner and run on pump piss.. Only bling will be old Direct Connection chrome valve covers.
 
Last edited:

Imperialist67

Senior Member
Joined
Jul 16, 2013
Messages
1,303
Reaction score
1,214
Location
Washington, DC
I'd keep it simple, remove lean burn, but save it

Install new Mopar performance distributor, I always install 1 mp advance spring to bring in curve faster

Install Edelbrock performer carb ( easier to tune than holley, I think)

Install true dual exhaust, I think you'll be happy with the performance and reliability

My Diplomat wagon (with 318) had the Lean Burn when I got it, and it ran reasonably well...…. once it got warmed up..... which seemed to take a long time..... but the long throttle delay got REAL old, and frightening in traffic. It was quickly replaced it with an Edelbrock 4 bbl carb, and it really woke things up. Depends on how capable/willing you are with engine work on trying other things, but I'd try the carb swap and see how that goes first. Definitely retain the original components for posterity's sake. Good luck.
 

77newyorker440

Well-Known Member
Joined
Aug 8, 2020
Messages
511
Reaction score
277
Location
Peanut State, USA
Alright, thanks for all the responses guys, I'll probably keep the lean-burn box on the breather for cosmetic purposes, but leave it completely disconnected (no wire plugs or vacuum lines), take out the rest of the wires in that system, put a new 4 barrel carb, perhaps a new intake, and I have been looking into an MSD Distributor, Coil, and Ignition Box, but I will also look into the MoPar performance ignition system that you all recommended. Installing a new starter today, I will update you all on how it goes.
Thanks,
77newyorker440
 

twostick

Senior Member
Joined
Dec 13, 2012
Messages
2,434
Reaction score
2,412
Location
Beautiful Downtown Roebuck Ont.
The compression ratio when cc'd and measured on those smog engines is around 7.8:1 +/- . It's pretty sad.

So if it was mine and I wanted to warm it up a little, I'm doing the performance ignition swap.

I'm keeping the Thermoquad if it can be recalibrated for non leanburn use and if it can't, I'm replacing it with a non lean burn model. Nothing wrong with the stock intake as the stock cam and heads will be wheezing long before the intake does. It will flow enough to support about 5800 rpm. The cam and heads will have their tongue hanging out by 5200 or so.

Next I'm replacing the timing chain and gears which are probably shot anyway and using a multi key set so I can advance the cam timing 4 deg. This will give the bottom end a kick in the pants to help out with the farm tractor compression ratio. The job should be done with a degree wheel to verify the keyways on the new gears are where they say they are (lots aren't) but if you lined up the dots on the old set and the new gears still slip on dot to dot, it's fairly safe to assume the 4 deg slot is where it belongs. If the original set looks like new, I think there are still offset bushing kits available to do the same thing. You drill the drive pin hole in the cam gear out with the prescribed drill and slip in the 4 deg offset bushing.

2.5" minimum dual exhaust with an X pipe and quality low restriction mufflers. That means no turbo drones or Slowmasters.

Assuming a 28" tall tire, a 3.21 axle ratio is readily available for a 9.25 diff and will make the most noticable improvement on the butt dyno.

Kevin
 
Joined
Aug 4, 2019
Messages
81
Reaction score
46
Location
Radium Springs NM
I agree with everyone else about what you can do. I will add one thing more IF you are going to use the old style flat tappet valve lifters, use an oil with high zinc, todays oil is lacking in that department because the newer engines use roller type lifters that don't need zinc to lube the mating surfaces.
 

mopar440

Well-Known Member
Joined
Oct 17, 2018
Messages
714
Reaction score
386
Location
St paul
I agree with everyone else about what you can do. I will add one thing more IF you are going to use the old style flat tappet valve lifters, use an oil with high zinc, todays oil is lacking in that department because the newer engines use roller type lifters that don't need zinc to lube the mating surfaces.
Or rotella, it has zinc. Supposed bad to " double up"
 

70bigblockdodge

Old Man with a Hat
Joined
Jan 19, 2013
Messages
13,062
Reaction score
10,407
Location
Avonmore Pa.
You cannot put much of a cam in those engines because the compression is in the mid 7s at best.
Timing chain and advancing as mentioned above will wake it up.
Dual exhaust because exhaust side needs all the help it can get.
Thermoquad can be fattened up by just filing the mid range and top(thick section of the metering rods) WOT on a lean burn was not lean, only cruise and idle. Just file a little off the side of the rod, you want more fuel to pass between the rod and the jet it goes into. The rod does not have to be round, just have a smaller area filled up in the jet.
Word of caution: file small amount, very small area you are working with.
The stumble you get can be dialed out with spring tension on the secondary air door se you tube for videos on how to adjust this.
It is some fiddley work but not hard. Metering rods can be pulled without disassembly of the carb.
The lean burn distributor is a toss up. It is technically a multi-spark system, that's not a bad thing. The advance curve in the box on the air cleaner is really lazy with no way to change it, I'm sure the vacuum advance is not doing anything for ring wear and fuel mileage because they were trying to lower emissions.
Good luck. Enjoy, and if you learn something it's a good day.
 
Joined
Aug 4, 2019
Messages
81
Reaction score
46
Location
Radium Springs NM
Something I forgot. IF you the engine to stock horse power(350hp) use the Turquoise paint. IF you bump up the horse power using a purple cam. It will bring horse power up to 375hp. Then the engine needs to be painted Hemi Orange to denote difference.
 

MoPar Maniac

Well-Known Member
Joined
Dec 8, 2016
Messages
758
Reaction score
550
Location
St. Charles county, MO
I agree with everyone else about what you can do. I will add one thing more IF you are going to use the old style flat tappet valve lifters, use an oil with high zinc, todays oil is lacking in that department because the newer engines use roller type lifters that don't need zinc to lube the mating surfaces.
Not quite.
Zinc has been found to ruin cat cons over time. That is why it was reduced.
Zinc isn't just for LIFTERS (if they are tapping you have a huge problem). Zinc is the last line of defense wherever there are two pieces of metal coming together, especially bearings.
 
Joined
May 6, 2020
Messages
54
Reaction score
51
Location
San Marcos CA
My parents had a '78 Cordoba 400 with the lean burn and a ThermoQuad.
I changed the main jets from 92 to 95, that made a great improvement.
With that change (with 2.45 gears) we got 19MPG at 90MPH going to Reno once (pre 55MPH national speed limit).
I like the ThermoQuad, and with the correct adjustments they run very well, but the last few rebuild kits we purchased, the accelerator pump shafts failed to hold up, giving the carb a BIG flat spot on my son't '69 Coronet 318.
 

77newyorker440

Well-Known Member
Joined
Aug 8, 2020
Messages
511
Reaction score
277
Location
Peanut State, USA
Something I forgot. IF you the engine to stock horse power(350hp) use the Turquoise paint. IF you bump up the horse power using a purple cam. It will bring horse power up to 375hp. Then the engine needs to be painted Hemi Orange to denote difference.
Right now, the engine makes about 190-210 horsepower, and it is painted MoPar Blue, so my plan was just to repaint it in the same MoPar Blue that it has stock
 

77newyorker440

Well-Known Member
Joined
Aug 8, 2020
Messages
511
Reaction score
277
Location
Peanut State, USA
As noted, you are starting with a low compression smog motor with a lot of features that hindered performance in favor of lower emissions. You need to raise the comp ratio to at least 9.5. Use the 440 magnum/HP/TNT cam from 69-70. You also need to figure out is you have a cast iron crank or a forged steel one. Forged steel preferred for any performance build. Toss the stock intake and get rid of the EGR valve. A lot of the '77 cars also have a single exhaust which should be discarded in favor of duals. Stock log style manifolds are also highly restrictive. The A-727 used in '77 is a low stall speed unit that is probably not a good choice for a performance build. To take advantage of the increased horsepower you will also need 3.23 gears. The stock heads will also need some port work and better valve springs to achieve their performance potential. Would also want to toss the stock thermoquad in favor of and after market Holley or AVS carb.

Dave
I know this is a couple months late, but I have a question about the EGR Valve and Intake. My concern is that an Edelbrock intake would be too tall, leading to bad breather-hood fitment. If I were to put a new intake, this is what I was thinking about choosing: Edelbrock Performer RPM Intake Manifolds 7193 Any opinions and suggestions are appreciated! I am hoping to keep the stock breather if possible
Thanks,77newyorker440
 

Davea Lux

Old Man with a Hat
FCBO Gold Member
Joined
Mar 27, 2017
Messages
8,918
Reaction score
8,073
Location
Cornelius Or
I know this is a couple months late, but I have a question about the EGR Valve and Intake. My concern is that an Edelbrock intake would be too tall, leading to bad breather-hood fitment. If I were to put a new intake, this is what I was thinking about choosing: Edelbrock Performer RPM Intake Manifolds 7193 Any opinions and suggestions are appreciated! I am hoping to keep the stock breather if possible
Thanks,77newyorker440

The spec sheet shows that manifold as being 5.35" tall. Measure the height on your stock manifold and see how much taller the Eddy manifold is. You probably have about 1" or less extra height to work with.

Dave
 
Top