6 pack center carb jetting Q

Mikke H · May 10, 2018

Have -70 Super Bee whit 6 pack, manual trans, 3,54 Dana, cast ex.manifolds, 2,5 pipes have the 64 jets in center carb seems to run a little lean, what do you guys run for jets in your setups ? Can i go to for 66 or even ricer ?

OH71RRunner · May 10, 2018

This is one of those things that you'll have to play around with and see what the engine wants.

dadeo · May 10, 2018

My six pack, 4-speed, 4:10, Hughes cam, stock manifolds & exhaust running 65 in center, 82 on outboards.

70sixpkrt · May 10, 2018

I would stay at 64 and play with the outboard mixture set screws first. I'm running 64 in the center. My outboard screws are 1/4 out and center is 1 1/4 out. I'm using the Promax jettable plates on the outboards with 80 jets. My cam is a Straightline Cam 234/[email protected] 540/525 solid with 112 lsa (4* built in) installed straight up. You will have to play around with it to see what it likes. Good luck.

62MAX · May 10, 2018

The cam in my bird is an old Direct Connection Street Hemi grind,280/474.main jets are 65's and ends are 81 passenger side front and rear,83 driver side front and rear with jettable plates,4spd,3.54 dana.runs like a clock.On another note,you don't need to spend $150 for a pair of Promax jettable plates,you can buy a pair of cast jettable plates,same configuration as originals from Quick Fuel for $25 ea,inside the bowl,they both do the same thing and you saved $100 !

PurpleBeeper · May 10, 2018

Mikke H said:
Have -70 Super Bee whit 6 pack, manual trans, 3,54 Dana, cast ex.manifolds, 2,5 pipes have the 64 jets in center carb seems to run a little lean, what do you guys run for jets in your setups ? Can i go to for 66 or even ricer ?

What makes you think it' running lean? Lean at idle or lean while driving? I still have some fine-tuning to do, but I'm running #62 jets in my center carb & bone-stock settings in the outboard carburetors. 440 six pack, 3.91 gears, 4spd, 274H Comp cams with nitrous oxide.

Everyone wants to go "richer", but leaner is faster....just don't go too lean. I'm starting off with the #62 jets at the suggestion of the owner of Six Pack to Go (?) shop in Albequerque, NM.

The real answer to carburetor setting will be determined by an oxygen sensor on a dyno or at the drag strip....seriously. No two motors are the same.

RJRENTON · May 10, 2018

Gentlemen,
I use #66 jets in the center carb and equilivant # 79 on the short branch manifold rinners and #81 on the long branch manifold runners. I also use a 4.5mm opening power valve in the center carb. REMEMBER the number on the Power valve is the OPENING MANIFOLD VACUUM point and NOT THE fuel feed restriction. The feed restrictions are calibrated orifices Located BEHIND (visable when power valve is removed) or underneath the power valve. My engine is an 0.030 bore 440, 11.0:1 TRW forged pistons, Crane equilivant to the Mopar 292 degree .509 lift and 1.6:1 Crane roller tipped rockers. The car has 4.10 Dana gears and A833 trans. I also use a Prestolite dual point distributor @ 35 degrees total advance at 2200 RPM. I also use Champion UJ-11G non projected nose plugs. This is what works for me. Actual jetting (by whatever method) MUST be determined by you by "reading" the plugs and/or time trials. This is just my opinion.
Bob Renton

dla4567 · May 10, 2018

Changing timing and fuel will also make a big difference in jetting. I have a similar setup as you. When I switched to 110 octane tuning was sooooo much easier. With out checking my notes, I think I was running 67s with 92 octane and now use 62s.
Write everything down and only change one thing at a time. You’ll get there.

Mikke H · May 11, 2018

The engine is stock six pack whit the DC stock style tree bolt cam the ignition is Mopar elektronik whit orange box, the problem is a slight twitching at steady speed at all speeds, the funny thing is that if i go uphill the twitching goes away downhill it comes back att axeleration it goes away at steady speed it comes back, tried different timing but increasing timing makes it wors the timing is now set at the facktory 5 degree setting the reason i think it runs lean is that when it gets added fuel from the shooters it runs clean .

69 GTX · May 11, 2018

That is not your main jet. If you buy a quick fuel metering block they have more emulsion jets than the factory metering blocks. This will help with part throttle tuning. Also check your timing before you do anything. You'll probably want 14-18 initial and 30-36 total, all in around 2200-2400. Tune with a vacuum gauge, keep tuning to get max vacuum.

Bill Monk · May 11, 2018

69 GTX said:
That is not your main jet. If you buy a quick fuel metering block they have more emulsion jets than the factory metering blocks. This will help with part throttle tuning. Also check your timing before you do anything. You'll probably want 14-18 initial and 30-36 total, all in around 2200-2400. Tune with a vacuum gauge, keep tuning to get max vacuum.

Couldn't agree more with GTX, he is dead on with a starting place on timing but assuming you have stock style outboard carbs and you think it's running lean, you can still adjust the fuel at the throttle bases. This is a pain if you have stock bases on both carbs (I run a promax base on the rear outboard) so I can adjust without taking it off the car. But it can be done, it's not a perfect way of doing it but if you adjust the front carb first, you can move it to the back then adjust the other. With the engine warmed up and at idle, put your finger over each air bleed on the outboards, if the engine picks up it's too lean, slows down then too much fuel.

69 GTX · May 11, 2018

Also when tuning make sure car is at running temp. Sometimes in a rich condition some raw fuel will accumulate on the floor of the intake, giving you a false rich symptom. Tune for 5-10 minutes, take it out and blow the carbon out and recheck.

69 GTX · May 11, 2018

69 GTX said:
So I pulled the carbs a part today to verify what jets were in there. so here is what was there.
Rear as standing at the front of car.
Pass driver side
92 89
center
62 62
front
89 94
I used pin gages to verify jets. The centers were stamped 642 the reason for checking.
According to holley you need to go up 1 jet size for each 2000 ft of altitude so I will be going up 2 jet sizes on everything.
Also on the metering block I have a 5.5 power valve with 49 jets in the PV passage.
Also a 28 jet on the idle circuit
The emulsion bleeds are 28s
Also I was able to tighten the secondary carb jet plate screws about 1/8th of a turn. So if you install them, recheck them at a later date.
More to come........

This is the jetting on my 440+6, you can see even making 590HP @ 5oooft it only used 62 jets in the center carb.

Mikke H · May 11, 2018

Ok thanks for the advise, tomorrow is my day off so there will be a day of trial and testing i will be back whit results but now its burgers and beer and formula 1 .Thanks again guys !

PurpleBeeper · May 11, 2018

Bill Monk said:
Couldn't agree more with GTX, he is dead on with a starting place on timing but assuming you have stock style outboard carbs and you think it's running lean, you can still adjust the fuel at the throttle bases. This is a pain if you have stock bases on both carbs (I run a promax base on the rear outboard) so I can adjust without taking it off the car. But it can be done, it's not a perfect way of doing it but if you adjust the front carb first, you can move it to the back then adjust the other. With the engine warmed up and at idle, put your finger over each air bleed on the outboards, if the engine picks up it's too lean, slows down then too much fuel.

View attachment 604730

Hey Bill, that is how I set my idle mixture too (love that Promax rear base plate), but I think he's worried about his cruising fuel mixture

Bill Monk · May 11, 2018

Well if that's the case then jetting is much more significant here. What say you Mikke? One thing no one has mentioned including me is you should probably take a look at your plugs to actually confirm you are running lean. That as unless (like beeper said), you have access to a wideband.
This is an outstanding article from 4secondsflat on diagnosing the plugs.
http://4secondsflat.com/Spark_plug_reading.html

dla4567 · May 11, 2018

Installing an O2 sensor was the best thing for tuning my 6 pack. Then you can see where it’s at at all driving conditions.

Mikke H · May 12, 2018

Ok a day off testing got me nowhere the twitch is still there have tried everything but nothing helps vill start testing the elektroniks tomorrow !The only thing i kan tell you is that more than 5 degrees off ignition makes it worse the engine reacts to every change i do air ,ignition even changed thermostat so the engine would run warmer so the systems work but the darn twitch dont go away!

Bill Monk · May 12, 2018

Sorry you are having all this trouble, these things are hard to diagnose when you aren't there to experience what it's doing. Let me ask a few more questions:
How long has it been doing this? Any change just before it started?
Have you pulled a plug to see if you are actually running lean or rich?
Have you checked your float levels in the carbs?
Have you checked your fuel pressure? (in particular around whatever rpm you are getting the stumble) What kind of fuel pump are you running?

Let's eliminate these and if still no good then move on, I have to tell you though that something doesn't sound right with the timing. I have never ever had a big or small block Mopar that ran best at an initial of 5btc. What's the timing light say all in? (3500+ rpm) Should be somewhere around 36btc but every engine is a little different depending on too many things to list here

Mikke H · May 13, 2018

What you say boys bone dry no deposits normal driving no 1 cylinder !

6 pack center carb jetting Q

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