I know this is long but it's what I started with. And I didn't know anything. There are 2 posts here. Read and share as you feel.
#1 Post from Moparts
Here is a guide to tune six packs for street engines. Stroker or non stroker, big block or small block
This is not the final word, but close enough
Remember six pak engines run on the center carb and idle on all 3
The car must idle and run like a normal car before attempting any secondary action or wide open throttle passes.
A Good ignition system is required., MSD, Mallory or FBO mopar box, NO orange boxes or chrome boxes unless you know for sure it is early 80’s vintage. Anything made after 1988 is questionable.
Quality distributor cap & rotor
High quality spark plug wires like Firecore 50s
Spark plugs of the proper heat range.
Vacuum adv distributor
The distributor phasing has been checked and corrected as necessary
THIS IS IMPORTANT
Distributor vacuum port on carb disconnected and plugged at carb
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 cap-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 manifold vacuum source.
ATTENTION -195 degree thermostat- ATTENTION
THIS IS IMPORTANT
If you run a lower temp thermostat, raw fuel will collect in the intake
That fuel then burns off in the cruise mode.
Unless you have a wideband air fuel meter you will not see this happening, but you will have problems getting it to idle and see the mixture go leaner in the cruise mode.
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.
Set the outboards idle adj screws out 1/8 turn ccw THIS IS IMPORTANT
Be careful when seating the idle screws to set them, gently is the word
Install the BLACK springs – Just do it, ignore everything else you have read
Set the center carb idle adjustment screws at 1.5 turns out [ccw] THIS IS IMPORTANT
Check the center carb and 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 would 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 The outboards will have the lead plugs covering the idle adj screws.
Starting point for center carb jetting stock 340 use 62’s, highly modified or stroker use 64’s,
Leave the outboards alone for now unless you have the jetable metering plates, if so read their instructions and follow them
You must know what power valve is in the center carb. Typically a 6.5
Fuel level adjustment THIS IS IMPORTANT, this is best done idling at 1000-1200 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.
You must let the car run a 3 or more minutes so the fuel levels off before rechecking level
Center carb the fuel level is at the bottom of the sight plug hole
Secondaries it is just starting to come over the bottom of the sight plug hole
This is critical so get it right.
Set idle to 950 rpm and allow engine to reach operating temp.
Reminder 195 degree thermostat required or fuel will puddle in the intake. .
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.
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.
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. If you do not have control over the idle mixture you have issues that need to be taken care of before proceeding.
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.
Beware of 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 etc.
Recheck idle rpm and set to 900
Drive car like a normal person, no wide open throttle. Is the car rich? Jet down 2 steps until you find the min jet size. You will know when you are lean as you will have no power.
Most times you are over jetted.... Do not over jet!
Over jetted carbs will have poor idle control.
Now reset the initial timing again. 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 15 degrees BTDC.
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
Recheck idle rpm and set to 850
How do you know when you are "there”?
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.
The engine when cold starts easily, runs and drives smoothly from the get go.
The engine when hot restarts immediately without touching the throttle.
When the engine is rev’d and the throttle released it immediately returns to idle.
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.
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.
Notes:
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.
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.
#2 from Moparts
here is a copy of a post made awhile back, but is always useful. i am not the author.
I've been running six pack inductions for about 30 years now, sm blk, big blk, and even the custom 6 pak cast HEMI intake manifolds that I made for the 71 wingcars,.....I don't have anything but, sixpack cars,,,,,,,,I've rebuilt countless numbers of carbs, along with countless installations and tunings,....when there are troubles, it usally due to someone unfamilar with there tuning or functions, or attempts at trying to improve them,......which usally results in "problem" carbs, starting, stalling, flooding issuse!.....seeing your have "new" carbs/ set-uo,....I'd recommend you use a Carter street pump, don't use rubber hose, it's problems down the road!, use a factory style/ repro steel, or stainless steel fuel line kit,a good quality hi flow fuel filter, AFTER the pump!, not before!, you'll restrict the fuel flow, Factory style linkage, no junk progrssive/ mech linkage!, change out the brass side float screw on the fuel bowls (all 3 bowls) with Holleys clear sight plugs, this way you can see your float level, and no gas spills trying to adjust, their like $4 each,.....when setting the fuel level, I've found that it's best to bring it up to half the height of the clear sight plug, (can't do this with the brass sight screw!, unless you have X-ray vision, hence the need to install the clear plastic sights).....plus "if" you ever have a starting problem, just shaking the car side to side will slosh the fuel in the clear site, and you'll know wether or not you have fuel in the bowl,....after you have basically installed the set-up, and started the car, and set an acceptable idle after warm up, with the engine running, set the floats, start with the center carb, the slotted screw on top of the float adjuster, is just a lock screw, you can remove it for now, the 5/8" nut is the adjuster/needle seat nut, rotating it counter clockwise will raise fuel level in the bowl, clockwise will lower it, make small 1/2 turns let the car run a bit, check the fuel in the clear site window, half the window is ideal height, esp. in the front and rear carbs, when they dump in, you don't wanna lean the engine, which on a sixpack car, might "melt" a piston or two!....really!, been, there, done that!....after you set the fuel level in all 3 carbs, reset the idle on the center carb, by disconnecting the linkage on the end carbs, if your using an idle solenoid, make sure it's energized in the up position contacting the center carbs solenoid idle arm screw, set the desired idle, that keeps your car running, factory specs are a guide line, your cam, vacumm, etc, will affect your desired RPM range, after you establish this idle, this is what your car will run with, now de-energize the solenoid, using the idle srew located on the ceter carbs main throttle shaft, set the idle to a bare minimum running idle, this is were your throttle shaft will close down too when you shut off the car, and the idle solenoid de-energizes, if later you have shut down problems of the car desieling, (sputtering run on after shut down) keep lowering the idle screw on the center carb main shaft, untill this is condition is eliminated, the idle solenoid was added to maintain an idle, and allow the throttle blade to choke off the engine on shutdown if needed, when it de-energized, after your center card idle is set, now comes the fun, start the car, in idle, the front and rear carbs are still disconnected at their main throttle linkage, (important note: make sure no vacumm source is hooked up to the front and rear carbs when main linkage is disconnected, cause any reving you may do, might tip in a end carb! with vacumm!, and if you can't shut it down in time, you might lose an engine!....seen it done!)to properly set the fuel/ air mixture idle screws, start with the center carb, hook up a tach.......warmed up, good idle (low)....turn the fuel/ air mixture screws (2) located on each side of the center carb metering block, do one at a time, run it in slowly, until the engine begins to stumble, slowy back it out watching the tach needle, stop when you've obtained the highest rpm reading,....you can also do this with a vacumm gauge attached to MANIFOLD vacumm, I like to use both at the same time, ...repeat the process for the other side, when done, now re-do-it, again, just to confirm settings, now some of the end carbs, have their fuel idle screws "plugged" with lead, they are located in the base, in the front of the carb base plate, under the bowl, if plugged, dig out lead plug, most people think ones for fuel, ones for air , their not!, you'll adjust these screws just like the center carb, except you can't just use a vacumm/ tach gauge,....look into the top of the front end carb, you see 2 small projections in each bore on each side, just below the neck, these are the air bleeds, block off the outer bleed using your finger over the small tiny hole, with the motor running at idle (low), it should stumble or pick up in idle, when you block off, either outboard bleed, set the front carb first, pick a bore, left or right, with it's coresponding baseplate idle screw, block the bleed off with your finger,(make sure the carbs throttle plate is fully closed) do one side at a time, when you block the bleed, if the idle increases, too much fuel, remove your finger, turn the base screw on the side your blocking the bleed on, in, one turn, block the bleed again, listen for the idle, (you could use a tach gauge at this point), if it stumbles/ decreases, no fuel, back the base screw off a half turn, block the air bleed again see where the "idle" is,......keep adjusting in this fashion until there's no change in idle, no increase/ decrease, you now have the ideal fuel/ air ratio for the vacummm requirement on your motor, complete this for both sides of the front carb, shut off the motor, disconnect this carb remove it, re-install it in the rear,....install the rear carb, now in the front, adjust this carb like you did to the last one, after you hook up everything, now here's when most guys will balk at this move,....they'll insist the air/fuel mixture won't be 100% by moving the tuned front carb to the rear, well if your truly familiar with the sixpack set-up, you know getting to the rear carbs base screws is fustrating to say the least, unless your squeezeing every ounze of effeciency out of the motor, this technique is far better than leaving the factory setting/ lead plugs in, with is usally a lean set-up,,,,,,, after setting this relocated carb up, if you wish you can "play" trying to "tweak" the rear carb, this may include a round of removal the "tweak" the screws to obtain that last ounze of "tuning", I've yet to see a "tool", truly capable of fitting into the installed rear carbs "idle screws"......anybody?,
Well, when your "done" setting the air/ fuel "idle" mixtures on the end carbs, connect the end linkages, to the end carbs, do it with the idle solenoid energized, the rods are threaded were they join together on the center carb, they install on the end carbs with rod clips, there is a F/R or left?right handed clip, energize solenoid, do the front carb first, make sure the linkage is pulled far forward on the center carb secondary rail, thread the rod, in or out, until it fits nicely in the hole, then proceed to the rear, repeat this proceedure, now check the linkage for any binding, you should be able to chrack open (engine off!) the center car, WOT, and manually open both carbs by rotating the front carb throttle arm, close the center carb, check all linkage for binding, readjust if needed, now de-energize the idle solenoid, see if any bind is preventing the center carb from closing on the main throttle shaft idle screw, you may have to comprimise on some idle/ and or end carb linkage adjustments to have an ideal, functioning set-up, but once you take the time to do this, you'll appreciate your efforts!,....as far as altering the end carb secondary springs in the vacumm pods,.....I like a sixpack to come in quick,....you'll have to buy 2 sping kits, replace with the "white" springs if you want a quick responding set-up,....if you what a mid range set-up use the "yellow" springs,.....any thing in the brown or black range is worthless.,,,,,Hell I could write a book here, I probally have, if you have any other questions, PM me.......I wrote this for others, to utilize as well,.......
Good luck,
I love mine,
Bill
