Lean Condition?

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MOPARJ

MOPARJ

What can I upgrade now?
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My 73 318, with Comp XE268 cam, stock heads, stockish compression, headers, and Eddie 600 cfm manual choke card is running great on the street and acceleration wise. All plugs look good, a tad whitish, perhaps denoting a slight lean condition, timing set as high as she will take (about 16 degrees intial). It has a MP dizzy with vacuum advanced hooked up. I have noticed that when free revving the motor, say between 1500 and 2500 rpm, i can tell a slight occasional roughness in the motor, perhaps the slightest hint of a miss hear and there. It revs cleanly and effortlessly, though.

Does this sound like it may be attributed to a slightly lean condition? Its not a big issue, but I am just looking for something to work on. lol.
 
stock jetting should be good, maybe your mechanical advance and your vacuum totals are a bit high if you have not closed up your advance slots.
 
I have never once messed with the mechanical advance or adjusted the vacuum advance. I just dropped it in straight from Mopar a few yrs ago. It never pings or detonates, runs fine on 87, however, it does diesel for a sec after being run hard for a while (idle speed in neutral is 900 rpm, which is what it likes with the cam). The dieseling is mostly to due with a slightly aged card, id imagine.

The plugs were replaced when I rebuilt the motor, about 1.5 yrs ago, 16,000 miles.
 
lean on the carter/edelbrock could be jet and rod or the step up springs not matched to your cam.Edelbrocks are typically lean, but having a vacuum gage handy and the strip kit for the carb will make a night and day difference. Sounds lean to me...
 
Considering that it runs well otherwise and does not get hot, is this a major issue to engine longevity or health otherwise, if a tad lean?
 
If you are feeling it studder it's not a good condition. A tad lean is ok. Misfire from and/or pinging from lean is the worst case. What you describe is lean misfire and the tendency to ping is much higher lean which is limiting your timing from what you described. So I'd say in your case, no. Don't live with it. Fix it. Should cost you about $50, or two tanks of fuel.
 
My Barracuda has a '72ish 318 in it, I believe mostly stock but not sure. I have a new Edelbrock 600 on it, just replaced the points system with an electronic setup. My motor also shakes around 2000+ rpms with the vacuum advance hooked up. It is smooth as glass with out the vacuum advance. I am at around 6 initial timing which I think is a bit too low & I am around 35-36 all in but with the vacuum advance hooked up it pulls into the high 50 range. I have been told by various guys with years of Mopar experience not to run the vacuum advance.
You can adjust your mechanical advance relatively easily if you have a newer style Mopar Perf distributor. See this thread: http://www.forabodiesonly.com/mopar/showthread.php?t=67882
I drive the car on weekends & it is 45 years old so I am not worried about getting 2 or so more miles per gallon. Just my 2 cents from my own experience. Hope it helps.
 
phish1270 said:
My Barracuda has a '72ish 318 in it, I believe mostly stock but not sure. I have a new Edelbrock 600 on it, just replaced the points system with an electronic setup. My motor also shakes around 2000+ rpms with the vacuum advance hooked up. It is smooth as glass with out the vacuum advance. I am at around 6 initial timing which I think is a bit too low & I am around 35-36 all in but with the vacuum advance hooked up it pulls into the high 50 range. I have been told by various guys with years of Mopar experience not to run the vacuum advance.
You can adjust your mechanical advance relatively easily if you have a newer style Mopar Perf distributor. See this thread: http://www.forabodiesonly.com/mopar/showthread.php?t=67882
I drive the car on weekends & it is 45 years old so I am not worried about getting 2 or so more miles per gallon. Just my 2 cents from my own experience. Hope it helps.
Click to expand...


The more that I think about it, the more I think it may need to either be unplugged, vacuum advance, or adjust it, as it did this will a 600 cfm holley with 70 primary jets in the from as well. Could be timing related.
 
I may try unplugging the dizzy vacuum advance tonight, just to see. I forgot to mention some instability in the idle quality as well. The idle vanes up and down 50 rpm while in drive at times.
 
Why limit the power and economy by unplugging the vacuum can? I'm just curious. The vacuum can does nothing at idle so initial is not affected. Nor does it at full throttle where the racer crowd runs. Most mopar vacuum cans are adjustable. Get yourself an 11/32" allen wrench and go right into the nipple with it. When it engages the screw inside there, go two turns counter clockwise and re-test. If it still does it, go another two. You're adding preload ti the vacuum advance spring that way and delaying the advance that is causing the timing to bounce.
 
You need a tune up \\\\ plugs--wires--cap--check and clean air cleaner if k&n style or replace.
After the tune up adjust the carb and then drive the car for a while.
After this\\\ check your plugs and change your jetting if needed.
The main reason for your problem is THE SPARK PLUGS.8)

I set my cars up to run the best they can for power with a 3924 auto lite race plug and then when i need to make the motor richer, i just put in a colder plug =3923 auto lite.

It takes a long time and many jet changes to find out what your car likes.
I learned this trick of just changing the plugs from a great race car mechanic.
His name was JAKE KING ,and if your wondering who he was then just look at the bigest name in drag racing history(SOX AND MARTIN)

When i tried this i though it was only going to make the motor a little richer, but i was wrong.It makes the motor alot richer,so make sure you need the extra fuel.(it's worth about a 3 to 4 jet increase)

I have worn out the threads on my 750 double pumper from changing the jet's so much that i had to heli coil all the threads holes.
I have with no exaggeration changed my jets over a 200 times, but in the process learned alot about how the weather effects your performance and how to make the same motor run many diferant ways.

MY POINT IS THE HOT\COLD PLUG WAY TO TUNE FOR THE WEATHER WORKS ,SAVING YOU TIME.
If you use the auto lite race plug, just buy it at ADVANCE AUTO and not summit or jeg's.They charge twice the money plus shipping.HAVE FUN :toothy10:
 
moper said:
Why limit the power and economy by unplugging the vacuum can? I'm just curious. The vacuum can does nothing at idle so initial is not affected. Nor does it at full throttle where the racer crowd runs. Most mopar vacuum cans are adjustable. Get yourself an 11/32" allen wrench and go right into the nipple with it. When it engages the screw inside there, go two turns counter clockwise and re-test. If it still does it, go another two. You're adding preload ti the vacuum advance spring that way and delaying the advance that is causing the timing to bounce.
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Id like to try this first. I think it may be timing related to begin with. The advance may be too quick at the moment. On hard acceleration, it pulls cleanly up through the RPM range, no detonation.
 
T67POWER said:
You need a tune up \\\\ plugs--wires--cap--check and clean air cleaner if k&n style or replace.
After the tune up adjust the carb and then drive the car for a while.
After this\\\ check your plugs and change your jetting if needed.
The main reason for your problem is THE SPARK PLUGS.8)

I set my cars up to run the best they can for power with a 3924 auto lite race plug and then when i need to make the motor richer, i just put in a colder plug =3923 auto lite.

It takes a long time and many jet changes to find out what your car likes.
I learned this trick of just changing the plugs from a great race car mechanic.
His name was JAKE KING ,and if your wondering who he was then just look at the bigest name in drag racing history(SOX AND MARTIN)

When i tried this i though it was only going to make the motor a little richer, but i was wrong.It makes the motor alot richer,so make sure you need the extra fuel.(it's worth about a 3 to 4 jet increase)

I have worn out the threads on my 750 double pumper from changing the jet's so much that i had to heli coil all the threads holes.
I have with no exaggeration changed my jets over a 200 times, but in the process learned alot about how the weather effects your performance and how to make the same motor run many diferant ways.

MY POINT IS THE HOT\COLD PLUG WAY TO TUNE FOR THE WEATHER WORKS ,SAVING YOU TIME.
If you use the auto lite race plug, just buy it at ADVANCE AUTO and not summit or jeg's.They charge twice the money plus shipping.HAVE FUN :toothy10:
Click to expand...

What???? Plugs DO NOT CHANGE THE STOICHIOMETRIC RATIO! I get the feeling that the only Sox you spoke to were the size 6's under your bed.

A colder or hotter plug only varies the path heat takes to get to the head. A colder plug has a shorter heat path, a hot plug a longer one. By no means is changing heat ranges acceptable to compensate for an incorrect air fuel ratio.
 
mr. ramcharger \\ high :wave:-- how ya doing --


MAYBE YOU SOULD THINK ABOUT WHY THEY DID IT FIRST???
THEY WERE ONE OF THE BEST TEAMS THAT EVER RAN MOPARS.

I never said i talked to jake king.
I got the info. from a magazine(mopar muscle)
They did a write up about him after he passed away.
I under stand what your saying ,BUT when your pressed for time at the track or for a night of cruising and you need to make your car richer ,due to a very cold weather change it's fast and it works.
 
Disconnected the vacuum advance for a second and it cured the issue fully. It is smooth as glass. I will adjust the advance.
 
Moparj,
Leave it off.
You can most likely run more timing now and get the car making all the horse power it can.
When you disconected the vacume, it gives the motor less timing in the lower rpm range and let's you give the motor more timing in the higher rpm range were it's less likely to have a detination problem.
Also make sure she has enough fuel (replace and check plugs)
:glasses8: good luck.
 
How much total timing do you have without the vacuum hooked up? I think you need to figure out the total number, I bet it's a bunch, like 38 or so, knowing how the distributors come out of the box.

Do what Moper mentions too, preload the advance can to get it to delay a bit. Put it in gear and watch the timing, does it surge/change? You might have clues to your answer in what you see.

The carb blades may be open a tad too much. That's a cause for diesling.

16* initial is all it will take? Does it kickback on the starter there? I bet it could take more, BUT, 16 isn't a bad area to be in. Dial in 2 more * and see if the idle rpm picks up. If it does pick up reset the idle speed and see if that helps the dieseling issue and also the surging at idle with vac adv hooked up. IMHO, 900 rpm is pretty high neutral idle speed with that cam, more initial will help get it tamed down. What rpm drop do you get when in gear?
 
crackedback said:
How much total timing do you have without the vacuum hooked up? I think you need to figure out the total number, I bet it's a bunch, like 38 or so, knowing how the distributors come out of the box.

Do what Moper mentions too, preload the advance can to get it to delay a bit. Put it in gear and watch the timing, does it surge/change? You might have clues to your answer in what you see.

The carb blades may be open a tad too much. That's a cause for diesling.

16* initial is all it will take? Does it kickback on the starter there? I bet it could take more, BUT, 16 isn't a bad area to be in. Dial in 2 more * and see if the idle rpm picks up. If it does pick up reset the idle speed and see if that helps the dieseling issue and also the surging at idle with vac adv hooked up. IMHO, 900 rpm is pretty high neutral idle speed with that cam, more initial will help get it tamed down. What rpm drop do you get when in gear?
Click to expand...


Rob,

I have added more timing, but I never got it to kick back on the starter. It would ping under moderate to heavy load, or under hard acceleration with more timing, but that could have been from the maladjusted vacuum canister being hooked up. For now, until I adjust the advance, I will add a few degree of timing and see how see goes. I am going to drive about 60 miles tonight to Van Nuys Blvd cruise night, so I can do some test and tuning.

Currently, it drops to about 800 rpm in drive. Id like to lower both idle situations by 25-50 rpm, so I will do some experimenting and tuning.

After I disconnected the advance canister yesterday, it pulled hard and cleanly on a few WOT runs, with my GTECH showing a 5.9 sec 0-60, which as decent as it as ran before. No pinging at all.
 
MOPARJ said:
After I disconnected the advance canister yesterday, it pulled hard and cleanly on a few WOT runs, with my GTECH showing a 5.9 sec 0-60, which as decent as it as ran before. No pinging at all.
Click to expand...

This tells me the distributor's advance can is too light. Under full throttle without enough preload, if your engine does develop a little vacuum (many street engines do...) the advance can come in intermittantly and mess with the performance as it fluctuates the timing. It doesnt afffect idle or full throttle. Only adds gas milage and gives better part throttle response.
 
J,

You need to limit the distributor mechanical advance. If you add 2* initial, 2* must be pulled from the mechanical advance mechanism to hit your desired total. It's a two piece puzzle. Initial + mechanical = total. Just adding initial will put you with too much total and detonation will occur.

Get the initial figured out first. I bet it would like more initial than 16*. There are varied viewpoint on this board about how to set initial. I have my way and it works for me. I like as much initial as the engine wants, not some random number, as long as the starter doesn't kickback when hot. Tailor the mechanical to fit your total number. More initial will allow the throttle plates to be shut down more and usually means a cleaner idle and snappier response.

If you twist more initial in and the engine picks up RPM, the engine wants the initial. At some point the increases in advance will be negligible in rpm changes. You found the spot.

Good luck with it. If you want to call, give a holler.
 
Hope your cruise went well and glad to hear that the car is running better.

I always come from a performance or drag racing point of veiw when tuning the engine.
It's so easy to use common words for things and some times people get confused because of this.

I sould have said the mechanical advance timing for your distributer.

When talking total timing crackedback is correct in saying it's the total of the two combined.That is what the word total timing means.
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I only set up the mechanical advance in my distributers and set the timing.
UNHOOK YOUR VACUME ADVANCE AND PLUG THE PORT IT WAS CONNECTED TO \\ YOU DON'T NEED IT.

It's a MECHANICAL DISTRIBUTER ONLY AT THIS POINT.

When setting the timing with a light you have to make sure you rev the motor past the point of your mechanical advance weights ALL IN RPM.

A STOCK DISTRIBUTER CAN BE AS HIGH AS 3500 RPM'S OR MORE WITH THE STOCK SPRINGS INSTALLED ON THE MECHANICAL ADVANCED WEIGHTS.
SO TO SET YOUR TOTAL MECHANICAL ADVANCE TIMING WITH A STOCK DISTRIBUTER YOU WOULD HAVE TO REV IT PAST 3500 RPM'S.
THIS IS WHY YOU WOULD USE A SET OF LIGHTER SPRINGS.

Most of the time it's about 2200 to 2500 rpm's with the lightest springs.
So rev the motor past 2500 rpm's ((( 3000 rpm's)))
I use a set of light weight springs and my timing is always all in by the stall speed rpm of my torque converters.

My timing is the same the hole time my foot is to the floor,all the way to red line.
Your car will make the most power ABOVE 2200 RPMS THIS WAY.

You want to match your distributers springs, that go on the mechanical weights in you distributer ,so you gain no more timing after 2200 rpm's
This will work with any torque converter that has a stall speed ABOVE 2200 rpm's.
This is basically every performance torque converter made.
IT'S THAT SIMPLE.
Firing the piston at the highest point in the compresion cycle gives the most power.
Fuel burns at a giving rate of speed ,and what your looking for is a happy medium between low speed torque and high rpm horse power.
Setting your timing like this gives you the most power where it matters
(((((( 2200 rpm's to well over 6500 rpm,s)))))
let me know how she ran for ya :burnout:
 
There's some mixed info there so I'll simply add my opinion... I tend to have the best results using the vacuum can on street cars, and I dont set timing by rpm or vacuum. It works for others, it never has for me.
 
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