The Dodge Challenger Message Board

This may be of use to somebody. If already posted in the archives Dave, I apologise, http://www.mopar1.us/6barreltips.html

thank you eddie,i can really use this link.cheers.

Another Link. Consider this site SixPack Porn! www.promaxcarbs.com

I placed the LM-1 meter on the R/T. It's a wide band Bosch Sensor that can accurately measure ratios other than just at 14.7(ideal stoichiometric range of 14.7 for gasoline engines) as in a narrow band sensor. After placing the sensor in the bung and calibrating the sensor to ambient oxygen I installed it and went for a cruise. Here is my findings. After the engine was fully warmed up it showed 13.7 to 14.5 at idle. This is very good! At cruise it showed 12.9 to 13.0 which is also pretty good but a tad rich. At WOT it went to 15.0 momentarily then to 13.0 steady all the way to 120 MPH. I think the 'lean spot' is due to the powervalve being 1/2 the idle vacum,(PV=4.5 inches of vacum a 4.5) and it should be no more than 3" below my idle vacum which is 10" in neutral at 900 RPM's. I pulled a sparkplug which only had 30 or so miles on them and they are NGK FR-5's and it showed very little discoloration on the insulator so how much is 'too lean'?? Any input appreciated. I also couldnt figure out how to access my home pc with the 9 pin connector they gave me in the kit, along with a CD for Innovate LogWorks so I could plot the AF ratios on a spreadhsheet, my PC takes standard blade type USB ports,, any ideas? I contacted Innovate but there phone lines are being re-organised,, Thanks www.innovatemotorsports.com

See what the plug colour is like after 100 miles.

The 9-pin connector is what is called a "Serial Connector".

If your PC does not have a Serial Connector port (many new PCs do not) then you can buy a USB-to-Serial adaptor that will plug straight into one of your USB slots (new comuters have lots of these on them).

Try going down two jet sizes on the center carb and see how the mixture reads at cruise and WOT. A 6.5 power valve might be worth a try too.

thanx eddie thatll be very handy when i pull my finger out & get that far
cheers ian

Ill do that,,thanks guys

Ok I bought a USB adaptor, downloaded it to the LM-1 LogWorks and presto! I can view a single input and graph it along a time line which is my only reference point with no RPM input. I saved it to a custom file but would like to figure out how to place it on here! I recorded this file for 45 mins next time I'll record it for 3-5 minutes during a hard takeoff to top end speed. But this thing is pretty amazing and helps tuning a bunch

airfuelEddie wrote:Ok I bought a USB adaptor, downloaded it to the LM-1 LogWorks and presto! I can view a single input and graph it along a time line which is my only reference point with no RPM input. I saved it to a custom file but would like to figure out how to place it on here! I recorded this file for 45 mins next time I'll record it for 3-5 minutes during a hard takeoff to top end speed. But this thing is pretty amazing and helps tuning a bunch

ya know what im digging mine out and maybe this weekend, as it is a long holiday to celebrate freedom from the brits

We should have one to celebrate getting rid of the Yanks.

If you dont have a Serial Port adaptor to USB cable you'll have to get one,,the LM-1 Meter Kit doesnt come with one which is kinda odd since almost all PC's both home and laptop use USB ports anymore, anyways, I got mine at Circuit City for 24 bucks. The LM-1 is a cool Gadget Drew. You can play back a 'run' on the screen and watch the Air Fuel ratios and you can 'see' on a Carbureted Engine when the Carb goes from the idle circuits to the primary and then the power Enrichment,(Holley&Demon PowerValve), then the secondary circuits WOT throttle circuits. This way you can make exact tuning changes and 'see' how it affects the ratio. Unlike a Fuel Injected Intake the carb is full of compromises at anything other than WOT or idle. Or you can switch to a gauge cluster like in a dashboard and monitor the Air Fuel ratio on a gauge. It can also select a RPM Input which could be taken from the ignition or a rotating object. I would like to use an ignition source and 'Map' it with the ratios. Dave has done some thing similar with his and even used 2 other inputs. Manifold vacum and RPM.

I think the LM1 is getting outdated now. They have more up to date products that (hopefully) are more up to date in their conectivity.

Not only do most laptops and PCs not come with serial ports any more, but every socket on the LM1 is mounted upside down which means you have to take care to get some of the connectors in.

dave-r wrote:I think the LM1 is getting outdated now. They have more up to date products that (hopefully) are more up to date in their conectivity.

Not only do most laptops and PCs not come with serial ports any more, but every socket on the LM1 is mounted upside down which means you have to take care to get some of the connectors in.

Yes, they have a LM-1 'turn in' program so you can send your 'old' LM-1 to Innovate and they credit you a certain amount of money for the newer LM-3 which can accept many more inputs. I think I'll stay with what I have, although your setup is all I would ever want

Posted on Cuda-Challenger.com by Tom Quad.


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.
in gear/parking brake locked, keep advancing the timing until the (manifold) vac is as high as it will go then back off the timing until the vac drops 1 in hg and as you are advancing the timing to get to this point keep bringing your idle speed (in gear) back to where it initially was. EDIT forgot the chart, they say it's not dead on but fairly close for a start
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.

Pic for Ade,, this is the parts I replaced with the Pro-Max kit. I think if I had a stroker like Ade or any souped up MoPar powerplant,,this kit with the rear Billet Basepate included in the kit would make tuning much easier. I have a bad habit of bending the damned stock OEM fuel lines so any unnecessary carb removal is a bonus because once bent the lines seem to weep/leak.

Socks,,my PussyCat helping me

Thanks Ed ......and Socks

Just started on stripping this down, diaphragms are ok, all the linkage is present, about to remove the carbs for cleaning.
This is my idea of breskfast

Where is the "like" button on this forum?

This whole site is a 'like' button

I was a little surprised to find the outboard baseplate's don't have any idle screw adjustment at all, the front has the moulded pads but its not machined and the rear has what looks like factory lead plugs where the screws should be. Centre carb looks just like any one half of a Holley, std metering block.
I'm certain to pick up a pr of ProMax metering plates and adj base plates for the outers, if I try and use the setup with my engine as it is now I don't think I'll get its full potential.

The yank versions had lead plugs in the outer throttle plates to hide the idle adjustment screws but the screws were in there. You just had to dig them out. The '72 and later Jensen versions had no provision for idle screws at all. The centre carb provided all the idle mixture fuel.

I've had another look at the rear base and I can see that there could be screws in there, if so I'll dig them out and check em over.
No big issue cos I can always put that base under the front carb and use the ProMax one on the rear one

Because the throttle plates were not easily or cheaply available when I did my Challenger I just modified teh centre carb idle system to cope with the much bigger cam at idle.

Adjusting the rear screws is just about impossible with the center carb in place. But I had SO much practice at removing the centre carb on mine it was no problem at all to do that when setting up the six pack on Andy Robs '70 Charger. I used the "fingers on the air bleeds" method to check for even idle mixture between carbs and a vacuum gauge for correct mixture on that car.

Considering it was stock spec with stock six pack cam it still needed some modification away from the stock six pack settings. I found the mopar performance reccommended settings to be spot on. So I did a little drilling to attain that. The engine needed about 18-20 degrees inital timing as well if I remember right. Loads of vacuum at idle on that engine. I fitted a much higher rated power valve and got shot of the bad bog the car suffered from. It was just taking far too long for the 6.5" power valve to open.

Managed to get the idle mixture screws out of the rear carb and took some pics of the front one too.
Is it possible for me to get the blank one drilled and tapped for screws?
If you look at the air bleeds in the pic of the blank one you can see they are half the size of the std one

Looking closely at the blank base it doesn't actually appear to have a bleed even tho you can see a small dot in the casting. It's not in the same place as the regular base idle bleeds either.
Looking at the carb bodies I'm pretty sure I could drill out the base and install a couple of std Holley idle screws.
I can't have one outboard carb with idle adj and not on the other, easier to modify the centre carb to do it all surely? If I drill the base and it don't work I can always just epoxy them in and seal em up

Give it a go. If it all goes tits up you can get new throttle base plates from Promax anyway.

Hey guys Im going to try a set of Barry Grant six pack carbs but the outboard carbs are to smal
so i have to enlage the veturis on those but if any one is intrested in that projekt i can post it for you.
I have used the Pro Max set up on my old 440 and also on my new stroker and cant complain on those
parts but i realy whant to try a mecanikal setup with acc pump boosters on al carbs in a progressive
linkage !

Sounds good Pat I.m gonna try the std installation on my 440 fist and then drop it onto my stroker at the end of summer using the Promax metering plates.
I think the Davemans car ran a progressive mech linkage