6-pak help needed

[Sendero]

My brother has a very fresh engine ( less than 25 miles on it) ..standard 440 6-pak build in a restored car with an mild MP camshaft. The builder really screwed up the restoration of the 6-pak. It never ran well at all.  In fact the builder had the center carb linkage to the outter carb rods "float" ( via washer/cotterpin) rather then be locked down with the screw/nut.  Today we hit some big snags and hope someone can help us out.

Note: Perhaps the biggest alert out of our experience today is my brother put in new Holley plastic sight plugs in last night. Never starting the car, the plugs were "melted" this morning. The tips of the screw portion just melted away on both front and rear carbs. The heads of the site glass just fell into his hands. Interestingly the "original plastic site plug ( years old) in the middle carb is still good. Looks like the new plastic has serious problems.

In any case, here is the basics of the mechanical issue. The best vacuum idle reading we got when we got the car running without aid (without foot on gas) had a best of 17 inches steady at about 1200rpm. The center carb idle screws are backed out 1/4 turn from bottom out. The initial timing is about 15 BTDC without vaccum advance hook up. The center float and the front and rear float are at 1/4 up the site glass window.

The engine can't maintain a steady idle...it will eventually ( minute or two) drop rpm and stall.  If we keep the idle rpm up to 1900-2000 we see about 25 degrees advance and the engine continues to run unassisted though somewhat rough. The curb idle screw was backed out and adjusted back to the point of engagement of the throttle level ..that gave us the minimum idle RPM of 1800 to 1900. Any further backout of the curb idle screw was not possible without losing mechanical contact with the throtle lever. Retarding the timing to drop idle RPM toward 900 works to about 1600 but then the retarded timing stalls out the engine.

If we plug the vaccum line at the center carb thus preventing vacuum signal to the front and rear carbs, the engine maintains the poor condition. Disengaging the carb linkage at the front and rear carbs and ensuring no vaccum signal at the front and rear carbs, added a rich condition from the center carb with a steady rpm still unable to be held.

Not being able to balance the idle rpm to timing with all carbs, we attempted to eliminate the front and rear carbs. We disconnected fuel, vacuum and mechanical linkage; only running from the center carb. Front and rear butterflys were confirmed closed on the outer carbs.. Starting the engine, we could not get down below 1900 rpm without the car stalling.

Putting the car in drive and moving slow, the engne would stall if the accelerator was not pressed. If the gas was given a 1/4 throttle acceleration, the engine would stall. If we kept the car moving with light pedal it ran with no stalling or backfire.

Any help would be appreciated.

[mauve66]

unless its converted to mechanical linkage the outers linkage should float, its only connected so that when the throttle closes, it also closes the outers, the vacuum opens them, the outers should be disconnected from the linkage while setting up the center carb, after the center is set up then the threaded adjusters on the outers should be turned until they "just fall into the holes on the lever" while the motor is turned off.  again the center should be "floating" unless its been converted to mechanical

the only problem i had with my center was after i moved and then had to change the power valve, accelerator pump and accel cam piece so i can't help you with the rest but get the outers disconnected first

[Sendero]

Thanks, we did that and iot is the way it sits now. Vaccum, linkage and even gas is cut off. Only the center carb is functional and we continuw to stall unless we are at approx. 2000 rpm.

[440]

You've checked to make sure everything is correct at #1TDC ?

[cdr]

THAT WONT WORK,you would have to put a block off under the front & rear carbs to completely block all air leaks to isolate the center carb

[b5blue]

Set the idle needles on the outboards, in till just seated and out 1 turn. You'll have to remove the rear carb to get to them, they are in the front of the base.

[mauve66]

fyi, it worked perfect on mine for 1 yr in CO and 1 yr in MO, and i never had to try to adjust any needles in the outers, just changed the springs in the outers
when i moved to NV the engine just had a new cam and head/intake gasket matching and light smoothing/porting/polishing when i changed the PV+

if you block off the outers with a plate then when you put them back on any small amount of air that gets by the throttle plates will re-effect your tune on the center carb

i thought the same thing but on mine when it was running on the center with the outers disconnected on both sides, putting my hand over the top of the outers didn't change the idle at all so mine didn't seem to have any significant amount of air flowing through them

[Chryco Psycho]

with the outboard carbs disconnected you still have air getting in but no idle mix to add fuel . Ethanol gas coul dhave eaten the sight plugs .
Do you have the right gaskets in the center carb , is the power valve new or stiff / stuck open ?

[cdr]

fyi, it worked perfect on mine for 1 yr in CO and 1 yr in MO, and i never had to try to adjust any needles in the outers, just changed the springs in the outers
when i moved to NV the engine just had a new cam and head/intake gasket matching and light smoothing/porting/polishing when i changed the PV+

if you block off the outers with a plate then when you put them back on any small amount of air that gets by the throttle plates will re-effect your tune on the center carb

i thought the same thing but on mine when it was running on the center with the outers disconnected on both sides, putting my hand over the top of the outers didn't change the idle at all so mine didn't seem to have any significant amount of air flowing through them

not gonna argue

[Tom Q]

PART 1

This is a guide to tune six packs for street engines. Revised 02-2011
Stroker or non stroker, big block or small block.
Never the final word, but close enough for now, it gets updated from time to time.  

WARNING

Gasoline is flammable and will burn you

Carbon monoxide is produced from running cars
Esp. improperly tuned six pak cars.

USE A CO2 ALARM IN THE WORK AREA!!!!!!!!



This is not for the faint of heart. If you wondered why people shy away from six paks just read on.

When tuned properly Six pak cars turn on! faster & run far better than single 4 barrel cars exc a thermoquad. If you want your six pak car to run like it should do the dance and have the right tools to make it happen. Patience must be used throughout the process. Much of the information here can be used on a 4 barrel as well.  

Some theory of operation:

Things to Remember
Six pak engines run AND idle on all three carbs at all times.  
Only the center carb has an acceleration pump
The outboard are always contributing fuel...always

The car must idle and run/drive like a normal car before attempting any secondary action or wide open throttle passes.  

Whacking the throttle in neutral to see if the outboards open is not a legitimate test!!!

Over jetting will not allow you to get the idle mixture correct as the jet size does contribute to what happens in the idle circuit. Go read the theory of operation in the Mopar book

A good vacuum gage, quality tach in the car and dial back timing light/digital tach [snap on timing light with numeric readout].  

A good ignition system. MSD, Mallory chrome mopar box, NO orange boxes unless you know for sure it is early 80's vintage. Anything made after 1988 is questionable.

Quality distributor cap & rotor
Firecore spark plug wires
Spark plugs of the proper heat range. Clean and gapped
0.040 mopar box
0.050 msd cd type ignition

Vacuum adv distributor with heavy enough springs to hold advance until 1200 rpm.
The distributor phasing has been checked and corrected as necessary
THIS IS IMPORTANT
Distributor vacuum port on carb disconnected and plugged at carb
Mopar viscous fan package

ATTENTION -195 degree thermostat- ATTENTION
                         THIS IS IMPORTANT
60%water-40% coolant with a bottle of water wetter

Pay attention here: If you run a lower temp thermostat, raw fuel will collect in the intake. That fuel burns off in the cruise mode and the air-fuel mixture goes lean.
This is transparent unless the a-f ratio is being monitored with a wideband a-f meter
There will be problems getting it to idle and drivability.

Make sure the timing is 15 - 18 deg btdc [advance] at idle. THIS IS IMPORTANT
Set the timing marks at 15 btdc and align the rotor with the LEADING EDGE of the cap contact-this is one reason the phasing was checked.  
Car in neutral-auto or 4 sp, emergency brake set.
A good quality vacuum gage is required
Connect vacuum gauge to direct manifold vacuum source.

The heat crossover should be blocked on big & small blocks
Note: in temps below 40 degree it will take a good while to get the car warmed up. Block heaters will eliminate the long warm ups.

Automatic cars: be sure there is enough stall in the torque converter or the car may be a real pig idling in gear and have poor get-up & go.

Beware of mopar orange ignition control boxes that retard the timing etc. Orange boxes built after 1988 tend to have issues.

Preparation: on the work bench
Outboards: Remove the lead plugs
Set the outboards idle adj screws out 1/8 turn ccw THIS IS IMPORTANT
Be careful when seating the idle screws to set them before the 1/8 setting. Gently is the word. If you look inside the carb bore you will see the needles poking in ever-so-slightly. They should be equal.

Install the BLACK springs – Just do it, ignore everything else you have read.
Install the BLACK springs – Just do it, ignore everything else you have read.
Yes I repeated that, explained way below

I you have the jetable metering plates, If so read their instructions and follow them.

Center carb
Set the center carb idle adjustment screws at 1.5 turns out [ccw] THIS IS IMPORTANT
Be sure to adjust the idle screw until the throttle blades are closed and the transfer slot is exposed no larger than a square. [Carb will have to be off the car to see this] You only want about .040" of the transfer slots exposed below the throttle plates. If the idle screw is adjusted too high, you will be into the transition circuit, exposing too much of the vertical rectangular slot. Many times the idle screw is adjusted incorrectly to compensate for other issues. This puts the carb into the transition circuit and at that point you have no mixture control on the center carb.

If you have new carbs (untouched) they will have 62 jets in the center carb & a 6.5hg power valve. Starting point jetting stock 340 use 62's, highly modified or stroker use 64's, big blocks start with 64, stroker 65.
You must know what power valve is in the center carb. Typically a 6.5

Reminder 195 degree thermostat required.

Temporarily change out the brass sight plug on the fuel bowls (all 3) with Holley's clear sight plugs, to see the float level without any gas spills

Do not use an idle solenoid; a properly tuned car will have no "run on" issues

Factory style linkage, no progressive/ mechanical linkages!

Fuel pump: Carter street pump.
Factory style fuel lines only.
Use rubber hose only for tuning purposes.
Fuel filter should be in the stock location.
Make sure the linkage is set properly. The rods should fall into the hole on the carb lever.  Do this after you set the throttle blades on the slot?
Check the linkage for any binding, manually open the center carb to wot and see if the secondaries will rotate open. Have an assistant floor the gas pedal and check for wide open throttle

Start car
allow engine to reach operating temp. Set idle to 1000 rpm

Fuel level adjustment THIS IS IMPORTANT, this is best done idling at 1000-1100 rpm
The slotted screw on top of the needle n seat is just a lock screw,
To adj the float level loosen the lock screw to rotate the seat nut,
Turning the adjuster nut counter clockwise will RAISE fuel level in the bowl,
Clockwise will LOWER it
Make only small 1/2 turns and wait 3 or more minutes so the fuel levels off before rechecking level. Patience!!
Center carb the fuel level is at the bottom of the sight plug hole
Secondaries just starting to come over the bottom of the sight plug hole
This is critical so get it right.

Set idle for 900 rpm
If the car won't idle:
Is engine vacuum reading at least 2 hg higher than the power valve rating? If ok proceed, if not correct power valve issue and proceed.
Note some engines only pull 5 hg of vacuum so use a 2.5 power valve.  
Advance the initial timing a bit to see if it helps idle.
Be sure operating temp is 195-210
Be sure some fool did not put light springs in the distributor.

Now set the initial timing to where it wants to be. Somewhere between 10-20 degrees BTDC. The engine will tell you by increasing vacuum and rpm at this point. In some applications the engine does not care, so set it to 12-14 degrees BTDC.
Chart:
Cams with 106-degree ctrlines seem to like initial timing set at 16-22 BTDC
Cams with 108-degree ctrlines seem to like initial timing set at 12-18 BTDC
Cams with 110-114 degree ctrlines seem to like initial timing set at 8-14 BTDC

Re-Set the idle rpm for 900-See if you have "control" over the idle mixture screws on the ctr carb.

Using a good vacuum gage adj center carb mixture to highest reading of vacuum.
This is where the digital [numeric readout] tach is better than the vacuum gage.  
If you do not have control over the idle mixture you have issues that need to be taken care of before proceeding. Over jetting contributes to this

[Tom Q]

Part 2

Typically if you have the center carb idle mixture screws between 1 to 2 turns ccw
you do not have to adjust the outboard idle mixture any further. Starting with the front carb, adj the mixture screws one at a time 1/16th turn ccw, after turning each screw wait and see what the engine vacuum and rpm do. Obviously if you have a wideband a-f gauge you will see what is happening. 

If you are 2 turns out on the ctr carb idle mixture and the idle is still too lean, the outboards need to contribute more fuel to the idle. Open the idle mixture screws another 1/8 turn ccw. Now they will be out a total of ¼ of a turn ccw. Now go back and reset the idle mixture and rpm.

If the idle is too rich no matter what you do...Most times you are over jetted or you have other issues....
Over jetted carbs will have poor idle control. At idle fuel flows from the float chamber thru the main jet then into a the small angular but horizontal passage that leads across to a vertical passage and onto the idle feed restriction where it is mixed with the air coming in from the idle bleed. Remember this. Do not over jet!

Beware of other issues such as poor intake sealing, carb gaskets backwards, the wrong pcv valve, a vacuum leak from the brake booster or other places, wrong pwr valve, wrong thermostat etc.

Recheck idle rpm and set to 900

Drive car like a normal person, no wide open throttle. Is the car rich? Jets down 2 steps until you find the min jet size. You will know when you are lean as you will have no power.   


Now reset the initial timing again. Somewhere between 10-20 degrees BTDC. The engine will tell you by increasing vacuum and rpm some point and then falling off. In some applications the engine does not care, so see chart.

Re-Set the rpm for 900-See if you have "control" over the idle mixture screws. Using a good vacuum gage adj each mixture screw to highest reading of vacuum. If you have a wideband afr meter set to 14.7 See how close you are between the vac gauge and af meter.

Recheck idle rpm and set to 800-950 depending on engine build, hook up vac adv and make sure car still runs/drives properly.

How do you know when you are "there"?
If the car gets up and goes seamlessly you are there
The engine when hot soaked restarts immediately without touching the throttle
The car will idle at 700-900 rpm in neutral and the response is crisp.
There is no smell of raw gas in the exhaust.
The bottom of the intake is not soaked with fuel. Open a carb and look in
The spark plugs are clean and white.   
The engine when cold starts easily runs and drives smoothly from the get go. 
When the engine is rev'd and the throttle released it immediately returns to idle.
The vacuum advance is hooked up and the car drives well.

OK if you made it this far it's time for the Secondaries

The reason you put the black spring is to delay the opening of the secondaries until the engine is ready for it. The engine will run fine on just the center carb till at least 3000 rpm. The air fuel mixture spikes lean when the secondaries open, but at higher rpms this is transparent and has no affect on performance. The opening of the secondaries should be seamless, but very apparent and usually scary to the uninitiated.
Some cars may enjoy a lighter spring.

The secondaries rods should be disconnected and removed and the vac signal blocked.

Please do this safely and with regard for others....
Go out and drive the car on the center carb and determine what rpm the car starts to fall off in power. Take note. 
The car should have a ton of power just with the center carb.
Be sure to several wot runs.
Please do this safely and with regard for others...

Reconnect carb linkage and vac lines; be sure to set the length of the rods properly.
Now go for a drive and see what rpm the six pak hits.
Please do this safely and with regard for others....
Hold first gear or 2nd gear, run up to 2500 rpm, and floor it. What should happen is the secondaries open without any hesitation and the cars gets up and really goes.

The long vacuum hoses for the outboard carbs need to be exactly the same length. 

Pulling a vacuum on the hose should make the vacuum pod open the throttle blade and hold a vacuum

The best way to dial in the secondary air fuel ratio is with a wide band air fuel meter.
A fine tuned seatofthepantsometer and spark plug reading will work for the more experienced.

If you made it this far and the car is bogging when the six pak opens you need to go back and recheck starting at the top. Bogs are usually from the secondaries opening too soon!!

Notes:
Automatic cars with too tight of a converter will cause significant idle rpm drops when in drive, the car will not run at it's full potential so be sure to use the correct converter for the application.

Some cars like staggered jetting.

Reminder 195 degree thermostat required.

If car spits fuel out of the vent it means the o ring on the needle seat is bad.

It's always easier to remove the front carb for rejetting.
Tape over intake and make sure there is never any unaccounted for hardware

If you are using a wideband O2 meter you will see a lean spike when the secondaries open.  It should be small and you should not feel it.

:help:

If the initial timing exceeds 12 degrees BTDC with a MP distributor typically the advance curve will need to be modified so the total timing is not more than 34 degrees BTDC.   

Chart to shorten the slots if you have a non adjustable mopar distributor.
Distributor degrees X 2 + initial= total
18 initial plus 14
32-36 total advance typically
There should be No adv until 1200 rpm
Then the advance should increase slowly until it is "all in" at 24 - 2800 rpm lighter to heavier cars

Dist. degrees / slot size
6.............. .340
7............... .355
8............... .375
9............... .390
10.............. .405
11.5 ........... .420
12.............. .435
13.............. .445
14.............. .460
15.............. .475
16.............. .490
17.............. .505
18.............. .520

[440]

wow, a good read... thanks for posting

[mauve66]

so why no fuel in my outers? you can look down them and the butterflys were fully closed no fuel coming into the carb, idle no change when outers covered, center carb idle would of changed with no air going in from the outers

[Chryco Psycho]

the idle circuit feeds under the throttle plates , as long as you block off the air flow no fule will be pulled in , remove the fuel feed but leave the air flow & it will not run properly

[Sendero]

Please help me understand this.  We pulled off the air cleaner leaving the large vaccum hose connected to his breather. Start the engine. It fires up and goes right to 1900-2000 rpm. And there it runs.

Then I place my thumb over the end of the breather -> air cleaner vaccum hose. The engine stalls in about 2-3 seconds. I did this multiple times.

How is blocking the breather at the air cleaner connector going to stall an engine ?

[cdr]

CK YOUR PCV VALVE it is probably bad & could cause all the problems you are having

[Sendero]

just checked - PCV is good. Good call though- should have thought of that myself.

[Chryco Psycho]

what about an air leak under the intake you close off the air flow into the crankcase & it dies out , pull the intake , you are probably not sealing into the lifter valley

[Sendero]

I would be surprised if that was the case. We read 17 inches of vacuum at 1900-2000rpm. I would assume that if we had a vacuum leak that we would be far lower then 17 at 2000. Or am I off base with this assumption?

I saw an edelbrock video that said if a very high idle was occurring with no ability to decrease it through the idle screw, one should look for a port or carb base leak that was sucking in air. Since we sprayed the carbs to look for leaks...we may as well pull the carbs and rebuild now.

[FLG]

Did the guy that rebuild the sick pack also rebuild the engine? If so, you might want to do a leakdown test to be safe.

[b5blue]

Please help me understand this.  We pulled off the air cleaner leaving the large vaccum hose connected to his breather. Start the engine. It fires up and goes right to 1900-2000 rpm. And there it runs.

Then I place my thumb over the end of the breather -> air cleaner vaccum hose. The engine stalls in about 2-3 seconds. I did this multiple times.

How is blocking the breather at the air cleaner connector going to stall an engine ?

are you talking about the center bowl vent? Time for pics of what you have and are doing....

[Sendero]

Thanks guys, I will be heading down to the brother's place later this week and send some pics.

[Troy]

I guess you didn't see my thread about the clear sight plugs?
http://www.dodgecharger.com/forum/index.php/topic,81365.0.html

Stupid pieces of junk! My car hasn't run right since - but it does have other issues so I can't blame ALL of it on those. I did pull the carbs and cleaned the leftovers of the plugs out of them.

With your idle that high you aren't on the idle circuit any more so trying to tune that is worthless. Look for a vacuum leak.

The outboards are functional and are required for proper idle. On my (relatively) stock engine I can't set the outboard floats to any higher than the bottom of the hole without flooding the engine. That tuning article above is, I believe, for max effort/racing and you need the extra fuel in the bowls to keep from going lean at WOT. Lower your float levels and I bet your idle gets better (once you bring it down). The factory service manual recommends setting them so fuel just dribbles out of the hole.

Troy

[Chryco Psycho]

In the future I split the fuel lines at the Tee under the center carb & leave the lines in place at the bowls , to get to the center carb remove the rear carb first .

[b5blue]

  Try checking the center carb to manifold gasket. It's actually a slightly wider gasket than the outboards. If one checks carefully you'll see that the slot milled into the base for the PCV vacuum extends forward (Towards the front of the engine.) just enough that "if" an outboard carb to intake gasket is used there is a tiny slit or gap that fails to be sealed. The edge of the gasket ends just at the forward edge of the slot. I know this as I have received 6 pack gasket "sets" where all three gaskets are identical and they are not, the center has a wider gasket. 
  Do a search here of anything for six packs, I posted pics and there are links to very helpful posts on other forums on this and other six pack problems. I strongly suggest you make a temporary fuel line rig with rubber hoses fed from Tees so your not constantly undoing and re tightening your solid fuel lines as you run the risk of stripping the threads on your bowls. Also be certain your not running more than 5-6lbs fuel pressure. (Six packs want low pressure but still need volume, The Carter M4845 is the correct pump.)

[1974dodgecharger]

WOWzers...and this all for an increase of 15 to 20HP?

[mauve66]

hemi performance and better manners

[Sendero]

Update: We pulled the fore and aft carbs. The back carb had one of the idle mix scews 1/2 turn from bottom. The other barrel was closer to 3.0 turns.
Fixed that. My brother also adjusted the float level on both outboards to just under the site plug rather than half way upper some write-ups  and we checked the fuel bowls for the remains of the Holley plastic site plugs ( nothing found...must have completely disolved in the gas). Bolted everything back up and the engine fired up and appeared to idle well for a short time. The MP gas lines were leaking like a sieve so we shit down. My brother is buying a new MP set then we will be able to see how it is really running.   

[rt green]

how did you come out when you got everything fixed?