Need help tuning Quickfuel carb

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cookietruck said:
pretty sure in a thread on moparts he said the problem was worse when the temp was colder. my immediate thoughts, lean fuel mixture...
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I didn't realize he had one going on there too. Funny you mention lean fuel mixture, I was thinking the same earlier this morning, top of the idle circuit - put a couple wires in the IABs and see if that solves it. Then decided nah, the description of the miss didn't seem to quite fit. For all we know the plugs so carbon covered thats the immediated cause. Tough to fully get a feel of the issue(s) without being there.
 
I've been thinking for a while, there are probably a few problems going on. Sounds like the mains are lean and they come in around 2500. The "get on it then get off then get back on the throttle and it sometimes clears up" sounds like maybe he gets away from the lean miss using the vacuum secondaries.

The dist cap def looks odd and that is probably a minor problem as well.

The 7 and 8 plugs are dark for some reason. The other plugs are pretty light.

The next step (and first step I would've taken) is put the 68 jets back in it and see how it runs down the highway...
 
Cookietruck I am going to try the 68 main jets today and I will report back as soon as I get it they installed and take it a for a drive.
I have the same thought as you as it being lean and when I open her up it will clear up a little bit because it’s getting extra fuel from the pvcr’s below 8.5hg of vacuum.
I think I know why the distributor cap has the odd burn pattern on the cap terminals.
When I first installed my Taylor wires I used dielectric greas in the boots and I think I used too much.
Because I had dielectric grease clear up in the plug wire where the metal plug terminals clips are, some of it was wedged up in there creating an obstacle for the spark getting to the plug.
When I removed all 8 wires and cleaned the boots out by spraying small blasts of carb cleaner onto a q-tip and re-installed the wires it got quite a bit better and felt smoother.
Prior to cleaning the dielectric grease off the wires the missfire would show up around 45 mph in 3rd gear.
After cleaning the wires the missfire didn’t show up till 55-60 which is about 2500-2600 which right about where the mains start taking over.
I think my mains start to take over around 2300-2400.
So I will install the 68 jets in place of the 65s and cross my fingers that it works.
 
Ok guys, it’s not the carburetor.
I have successfully determined that today.
It’s in the distributor somewhere.
I fired it up this afternoon let it warm up comkmetely and put my timing light on each cylinder and brought the rpm’s up to 2500 rpm.
All 8 cylinders are showing a missfire in the timing lights strobe, there is an obvious huge break in the strobe light when it’s missing.
I reach over and un-plug the vacuum advance and plug it up and bring the rpm’s up to 2500 and it’s smooth as glass on all 8 cylinders and no missfires.
So the vacuum advance is causing whatever is going on, it has to be ether rotor phasing, or when the vacuum advance is applied the reluctor to pick up coil post gap is ether too tight or too far away.
That’s the only things I can come up with at this point.
I’m installing my modified distributor cap now that has a 5/8 hole drilled into directly behind the number one cap terminal and I am going to take some
Pictures of the rotors position with and without the vacuum advance and I will post them up.
 
well that's nice to know.

on factory distributors you can rotate the reluctor 180* and put the pin back in. reset timing and...perhaps the phasing will be better???

did you drive it around without the vacuum advance disconnected??
 
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Ok I think I might finally be getting somewhere.
I took the distributor out and I re-set the magnetic pick up coil post to reluctor tooth gap with and without vacuum applied it’s sitting around .009-.010 I know the stock spec is .008 but I had a hell of a time getting it set at .008 where all teeth were completely equal with and without vacuum applied.
I re-set the mechanical advance to 15 degrees, Installed the distributor and set timing to 17 initial and 32 total.
Vacuum advance is adding an additional 13 degrees right now for a total of 30 degrees at idle.
I am no longer seeing the missfire on any of the cylinders anymore.
But I can still hear a miss right at 2400-2600 rpm.
So now I’m going to pull the front fuel bowl off and install the 68 main jets in place of the 65 main jets and see if the miss goes away.
Because now that I’m not seeing the miss on any of the plug wires but I’m stilk hearing it leads me to believe this missfire is fuel related when before
It was a little of both.
At least that’s my hope, I will report back after swapping to the 68 jets.
Thanks for everyone’s input and patience.
 
if it still ends up missing at 2500rpm, which is when the main curcuit in your carb comes in, but also when your mech advance and vacuum advance are all working too...you should try driving it with the vacuum advance disconnected.
if that fixes your miss, then you need to look at rotating the reluctor in the dist. i've never looked at a firecore dist. so i'm not sure if it's the same as a factory design...
 
You're killn me Man !
I've been over anxious to hear what in the world was wrong. Glad you're getting somewhere, you've been through it.
I bet by now, you're killing everybody ! LOL
When you finally get your answers, reward yourself with an AFR Kit.
Keep on keepn on !
 
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cookietruck said:
if it still ends up missing at 2500rpm, which is when the main curcuit in your carb comes in, but also when your mech advance and vacuum advance are all working too...you should try driving it with the vacuum advance disconnected.
if that fixes your miss, then you need to look at rotating the reluctor in the dist. i've never looked at a firecore dist. so i'm not sure if it's the same as a factory design...
Click to expand...

I’m not seeing the miss with the timing light anymore at 2500.
But I am still hearing one, before pulling the distributor out I was getting a miss at 2500 with the timing light on every cylinder.
Then I dis-connected the vacuum advance and plugged it off and wasn’t seeing the miss anymore with the light.
So I pulled the distributor and it looked like the pick up coil post to reluctor air gap was too tight, causing the reluctor to hit the pick up coil post on certain teeth.
So I widened the air-gap to .009 to .010 when it was around .007-.008.
Re-installed distributor and set timing and checked all cylinders with the light again and didn’t see the miss anymore on the light.
But since I’m still hearing one that indicates it’s fuel causing the miss I’m hearing now.
Before i think it was a combination of the distributor and fuel, and now I’m hoping it’s jut fuel and increasing the main jet will eliminate it.
I’ll let you guys know when I fire up here in a few after swapping the jets.
I’m in the middle of taking the carb apart now to swap jets.
 
pjc360 said:
Ok I think I might finally be getting somewhere.
I took the distributor out and I re-set the magnetic pick up coil post to reluctor tooth gap with and without vacuum applied it’s sitting around .009-.010 I know the stock spec is .008 but I had a hell of a time getting it set at .008 where all teeth were completely equal with and without vacuum applied.
I re-set the mechanical advance to 15 degrees, Installed the distributor and set timing to 17 initial and 32 total.
Vacuum advance is adding an additional 13 degrees right now for a total of 30 degrees at idle.
I am no longer seeing the missfire on any of the cylinders anymore.
But I can still hear a miss right at 2400-2600 rpm.
So now I’m going to pull the front fuel bowl off and install the 68 main jets in place of the 65 main jets and see if the miss goes away.
Because now that I’m not seeing the miss on any of the plug wires but I’m stilk hearing it leads me to believe this missfire is fuel related when before
It was a little of both.
At least that’s my hope, I will report back after swapping to the 68 jets.
Thanks for everyone’s input and patience.
Click to expand...

You had another thread about this problem and I replied that you were lean on primary jetting. At 2500 rpm the carb has transitioned to the primary jet. Put the stock jetting 68 up front and also put the 28 MABs back in the carb. A 36 MAB is way to big and screws up the the fuel curve of the main circuit. Quick fuel has way to much emulsion in these new fancy multi color metering blocks IMO. If you jacked around with the IFR and leaned that circuit out put it back to factory spec. A .001-.002 change in the idle circuit is huge and needs a corresponding change in IAB to maintain a good fuel curve. Also set fuel level to middle of site glass.
 
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