Need help tuning Quickfuel carb

-
yellow rose said:
This was wrong 45 years ago, and it's still wrong now.

Passing along bad information for decades won't make people any better at tuning.

The power valve doesn't affect anything at idle, unless the valve is defective. If you set the power valve open at half of idle vacuum you will have to crutch the tune up to cover the hole in the fuel curve on tip in.

Set the power valve opening a couple of numbers below cruise vacuum. Mark Whitner posted a great video on you tube of power valve opening at idle and proves the long told tale of half idle vacuum dead wrong.
Click to expand...
You need vacuum to shut the fuel off. Not enough vacuum to a large power valve and the fuel is just poring in. divide the vacuum in half leans the charge off idle and through the mid range. I found that when using 1/2 the number power valve of vacuum my EGT's on the guages were perfect through the quarter. The motor was like a off and on switch. This is right off idle foot braking. With out doing half it would stumble.

 
Oldmanmopar said:
You need vacuum to shut the fuel off. Not enough vacuum to a large power valve and the fuel is just poring in. divide the vacuum in half leans the charge off idle and through the mid range. I found that when using 1/2 the number power valve of vacuum my EGT's on the guages were perfect through the quarter. The motor was like a off and on switch. This is right off idle foot braking. With out doing half it would stumble.

Click to expand...



No fuel moves through the power valve until you get up on the booster. It's impossible. Like I said, Google Mark Whitner and power valve test or something like that, and he PROVES that the PV doesn't affect idle, unless the valve itself is damaged.
 
My car with a 6.5 went rich right off idle on the Air fuel ratio gauges. I put a 3.5 in and it was good. I am going to a 2.5 . I don't care what others have to say. I see it with my own eyes.
 
Isn't 2500 about where the MSD switches from multi-spark to single strike?
Does that carb have a 4-corner idle system? Yeah I think it does.
Hang on,
You said that was a 380 hp 360cid right? That should have a 288/292 cam and a singleplane on it.
Idle vacuum of 20/15 with 288/292cam, and a single plain?! That don't sound right to me , even with what seems to me, an excessively fast timing curve,unless maybe you are idling it quite fast.
And your problem is mostly or all at part throttle right?
and you said your timing was 18/34 all in at 2500 right?
Are you also running a Vacuum advance, and if yes, then how much is it kicking in?
At 2500 and briskly loaded (as in accelerating briskly) that engine might like 40/42 degrees PT (Part Throttle) timing and not much more. Since your mechanical is 34, this would allow only 6 or 8 from the can. I would disconnect the Vcan and retest.
That engine may want over 50/55* of cruise timing. That would require a Vcan of 20/22* to go with that 34 mechanical.
But if you combine the 22 can with the 34 at 2500, you would be jamming the engine with 54*2500 at PT , and guess how the engine complains about that?
I think, If you have an operational Vcan, that you have more than one problem. So again, I recommend to disconnect the can and retest.

Then, Ima thinking your T-port is off and your secondaries are cracked open too far. And just maybe the butterflies are staggered; that is to say the left and right secondary airvalves do not both park closed at the same time, or, one of the secondary mixture screw circuits has issues..

But I'm guessing,lol

________________________________________________________________
FYI
As to PVs;I run an 8.5 with 11" idle vacuum................. because my street engine told me that's what it wanted. This is real easy to see if you pull it out and sub in a plug; then go for a ride with a vacuum gauge.
But I run a one size smaller than normal MJ, cuz it's a streeter,so the PV has to come in a lil early to cover the hole.This allows me to run a little leaner on cruise/PT. And to cover that, I run a lotta lotta cruise-timing; Up to 60*at one time, and a lotta quench; .034, and a lotta cylinder pressure.
 
Last edited:
Oldmanmopar said:
My car with a 6.5 went rich right off idle on the Air fuel ratio gauges. I put a 3.5 in and it was good. I am going to a 2.5 . I don't care what others have to say. I see it with my own eyes.
Click to expand...


I can't post a link to a thread (because I don't know how with this dam iPad...I may have to go to the mothership and have them show me how to do it) but I said if you google Mark Whitner he has a video on you tube to prove it to you.

Mark Whitner is one of the best carb guys in the country. He proves the power valve has no affect at idle.
 
yellow rose said:
I can't post a link to a thread (because I don't know how with this dam iPad...I may have to go to the mothership and have them show me how to do it) but I said if you google Mark Whitner he has a video on you tube to prove it to you.

Mark Whitner is one of the best carb guys in the country. He proves the power valve has no affect at idle.
Click to expand...
Neither do the MJs at idle, you can take 'em right out and the engine will run just fine. The car will even drive until the throttle valves get out of the transfers.
 
I think it is the Taylor wires.
This weekend I removed all the wires, then I cleaned the dielectric grease out of them As best as I could by spraying carb cleaner on some q-tips and wiping them out.
Some of the wires had too much in them even though all I did was put a small dab on the inside of the boots.
But some of it was smeared up all the way to the metal contact clip area.
So anyways I did that and put them back on and I drove it to work this morning and it felt a lot better specially around 2000-2400 rpm but it still misses pretty hard around 2500-2800 rpm.
And once I got to work I thought I could hear it missing while it was idling.
I think these plug wires are complete junk and in wondering if maybe I’ve damaged a wire or two removing them so many times.
I’m going to order some good firecore wires and fo from there.
It does appear to be the wires though since cleaning out the di-electric grease made a difference.
 
Main jets and PV on idle. There can be exceptions. Shrinker explaned hoiw this happens - its about the pressures and flow in the wells. My simplified version - which may not be terchnically as correct: If the relationship between the idle restrictions (IFR, and downstream) is close to the restrictions on the upstream feed side (Main jets) then there's going to be some effect. We can't compare areas directly because the main jet is fuel only, but the air bled into the wells changes the density. One more reason to have the Idle restriction submerged. Then as long as the idle restriction area is at least 4 times smaller than the main jet area, you can be more confident the main jet will have no effect at idle.
 
pjc360 said:
I think it is the Taylor wires.
This weekend I removed all the wires, then I cleaned the dielectric grease out of them As best as I could by spraying carb cleaner on some q-tips and wiping them out.
Some of the wires had too much in them even though all I did was put a small dab on the inside of the boots.
But some of it was smeared up all the way to the metal contact clip area.
So anyways I did that and put them back on and I drove it to work this morning and it felt a lot better specially around 2000-2400 rpm but it still misses pretty hard around 2500-2800 rpm.
And once I got to work I thought I could hear it missing while it was idling.
I think these plug wires are complete junk and in wondering if maybe I’ve damaged a wire or two removing them so many times.
I’m going to order some good firecore wires and fo from there.
It does appear to be the wires though since cleaning out the di-electric grease made a difference.
Click to expand...

I liked Taylor Spiro Pro wires. Used them for a long time. But one day going to check spark plugs I broke the wire at the connection. I was rather surprised because the boot is nicely molded and sealed. So after that I switched to MSDs 8.5 wires for their better heat resistance and durability.
 
I’ve got to go with plug wires at this point, compression is spot on not even 1 psi difference on all 8 cylinders.
Power valve is brand new and same with the gasket, metering block gaskets and fuel bowl gaskets are brand new.
And the fact that I got it to clear up a little bit by removing the wires and cleaning out all the dielectric grease from inside the wires at the connectors.
I’m wondering if this set of wires is just ruined from being taken on and off so many times and with having all the missfires cause of the dielectric grease.
The dielectric grease was causing some of it, I’ll never use that crap again.
Cause it is better the missfire is totally load dependent, the higher the load the more it missfires.
For example in 2nd gear going 50 mph it’s missing but not to bad then when I grab 3rd gear and maintain the same speed of 50 mph the missfiring is a lot worse.
Im going to see if I can isolate which cylinder it is with my timing light today and then swap wires with a different cylinder and see if it follows, then I’ll know for sure it’s the wire.
They all ohmed out ok which is odd, but maybe they are spark scattering too much like oldmanmopar said he saw with a cd ignition and Taylor wi
 
So during my lunch break I took my timing light out and put it on each wire and brought the rpm’s up to around 3k and I couldn’t see missfire in the strobe light on any cylinder.
But when I drive it I can tell it’s stilk missing around 55 mph in 3rd gear which is turning about 2500-2600 rpm.
Before I removed the wires and cleaned the dielectric grease off the plug wire connectors it would start missing at about 45mph.
Now it’s changed and doesn’t start till around 55.
So messing the wires did something and it’s making me think these wires are junk.
Before I order a 125 dollar pair of firecore wires I’m thinking on my way home I’ll stop by napa and grab a 25 dollar pair of their premium Belden wires and put them on.
If it stops missing then I’ll order the firecore wires.
If it continues then I’ll know it’s not the wires, but I’m also going to pull each plug and make sure none of them are fouled prior to putting the new Belden wires on.
This issue certainly feels like ignition when your driving it, like a sharp sudden missfire that comes in and out in and out and shakes the whole truck I can feel it everywhere in the seat, and in the floor boards.
It’s super annoying and I’m thinking since messing with these wires has made a little difference then I’m hopeful that’s what this issue is.
 
I very much doubt this is a wire problem; because it is related to throttle opening.
If the engine takes WOT without issues, then the entire ignition system is fine, including the plugs, and the wires.
A problem like yours that can be made worse with the throttle valve opening, for me,has always been an A/F issue, Except, except, if the timing was too far advanced for the load. But at Part-Throttle and 2500plus rpm, this is hard to achieve, mine like all I can give her,over 45*.
The A/F issue could have it's source outside the carb, and outside the intake. But I'd be willing to bet,it's AFR.
And I've been wrong many times.
And I won't run an MSD on anything I own.
On a street engine,I don't see the point. Heck I've even run a 292/108 cam @11.3Scr......on,get ready for this; on an Orange box, and to 7200, for about 8 months. Then I swapped the cam out...... but still kept the Orange box for about 3 more years. lol.
I lost a decades-old pick-up and an ancient ballast, but never the ECU. I put that O-box on my brothers van a few years ago, and it's still going.
I tried an E-core coil, triggered by a Jacobs CDI-computer, but that didn't last long; the Jacob's died. And the following system didn't like the E-core. So in 2004 I bolted in an Accell sq-top, and that's been sparking reliably for over 100,000 miles.
Hyup, IMHO, this is a mixture issue. And if I had to guess, which I am now going to do,lol,and assuming all other avenues are exhausted(like the T-port sync),then, I'd guess a plugged main air bleed, or a missing anti-siphon weight in the accelerator pump circuit. If the plugs come out white then the former, if black the latter.
HappyHunting
 
take a spray bottle full of water and spray everything down coil ,cap. wires ect. but first set the idle speed at 2500 rpm if there is a problem in will show I chased down a problem like this and it was the coil cracked between the coil tower and neg post.
 
teringer said:
take a spray bottle full of water and spray everything down coil ,cap. wires ect. but first set the idle speed at 2500 rpm if there is a problem in will show I chased down a problem like this and it was the coil cracked between the coil tower and neg post.
Click to expand...
Hyup, I've seen that too,it made driving in high-humidity no fun.
Good call
 
I’ve had this carburetor apart multiple times and I’ve never seen anything out of the ordinary.
I’m running .028 idle feed restrictors, I’m running .065 idle air bleeds, I’m running .036 high speed air bleeds.
I’m running 65 main jets and 75 secondary jets, float level is hovering around the bottom of the sight glasses.
Power valve is 8.5hg with .045 pvcr’s.
Accelerator pump is a 30cc pump with .028 accelerator pump discharge nozzle with a white pump cam in the number 1 spot.
Idk see how this carburetor could be that far out of tune for a basically stock small block carbed 360 Magnum.
I get 155psi compression on all 8 cylinders, ignition is all brand new.
Timing is 18 initial and 34 total all in at 2500 and I am running vacuum advance which adds an additional 12-14 degrees of timing.
And if it isn’t ignition related why did it feel better after cleaning the dielectric grease off the plug wires and the plugs?
I bought a set of Napa beldin wires and I’m crossing my fingers it’s these Taylor wires arcing.
I’ve read multiple threads of people saying these Taylor’s suck and cause missfires big time.
Apparently the spark just comes right up through the boots and arcs to everything
 
Here is what my cap and rotor look like.
Looks like something is going on inside the cap to have burn marks on the bottom of the cap terminals and the black sooty stuff on the edge of the rotor.

1B529803-0CE3-4667-8BA3-EE9C3D2A7708.jpeg


6E6083AE-99B5-42D9-8970-0D0194F2ABE8.jpeg


F29CF1FC-93F4-4C7A-8208-122BDB91A145.jpeg
 
check for end play in shaft the rotor could be moving up and down
 
I'm still running two sets of tailors I bought in the mid 70s; but NOT with an MSD. Between those two, I wonder if they haven't accumulated close to half a million miles. No I think it would be more. When I bought the first set, they came with a lifetime warranty. The 318 I put them on,is still in service, altho it hasn't always been.Those wires found their way onto my 367 from 99 to around 2002 or 2004. Then I put them back onto the 318 and sold the engine to my son, who then drove it for about 7 years, then sold the whole shebang back to me a few years ago.
The other set I inherited used from my father. He ran those on a Nova for many years. When that car finally gave up the ghost the wires found there way onto his next car and so on until he died. Well,I'm still looking for a Chebby home for them.
IMO, they're great wires, or at least were at one time.
I guess your results might vary,lol.
 
HUH? I don't know why, but all this time Just assumed a red would be more you're shade. But your cuticles look fantastic!
 
Once upon a time (couple years ago) I miss matched brands of cap and rotor. I think my cap was mopar and my rotor was standard. But the rotor was too short and had to arc a long way, and caused a misfire
 
Wrong cap for MSD, actually for almost anything. However, I can't spot any tracking in there yet. The rest looks normal to me. You need the kind of cap with track-busters, the little circles around every tower and two or three around the center tower.
Maybe , just maybe you could be getting some crossfires in the cap, but I've never seen it happen at a particular rpm, and then go away.
Or,maybe your rotor needs to be re-phased.Retard your timing about 8 degrees and disconnect the Vcan, then roadtest.
 
Last edited:
It’s not an msd distributor it’s a firecore distributor and it’s brand new, in phase, and curved.
There is no play at the shaft other then turning the rotor ccw which will Engage the advance springs and allow the rotor to come back a little bit.
 
pjc360 said:
It’s not an msd distributor it’s a firecore distributor and it’s brand new, in phase, and curved.
There is no play at the shaft other then turning the rotor ccw which will Engage the advance springs and allow the rotor to come back a little bit.
Click to expand...
I think you misunderstood, it's the wrong cap for the Multi-Strike MSD system. That's about the cheapest TYPE of cap money can buy, and even if it's working ok today, it's only a matter of time before it makes trouble.
And how did you prove it's correctly phased? That is a very difficult thing to do without sacrificing a second cap.
 
Is there a way to upload videos on here?
I took a video of it so you guys can hear what it’s doing.
The napa wires made it worse, so it’s not the Taylor wires.
 
You must log in or register to reply here.
-

Back
Top