Newbie needs help with /6 tuning

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Dodgex2

Dodgex2

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Hi all, I have a 75 Dart Sport /6

Issue- (1945 Holley) Running rich. Can I ajust this with the idle mixture screw or will it have to be re-jetted? I have no idea what jet is in it now. Mileage is terrible and I have black soot on the drive way, plugs are black too.

Timing is 2* BTDC. From what I have read on here I want to set it at 8*-10* BTDC? I just want to be sure.

Thanks for any help, Matt
 
What plugs are you running ?
New plugs will fire better use ZFR5N 3459 plugs from any auto supply, mine came from NAPA and set the air gap and see what happens :coffee2:
 

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Start the car and let it warm up,once warm adjust the idle mixture screw in(clockwise) untill you notice a slight stumble,then back it out(counter clockwise) till it smooths(about 1/4-1/2 turn) But if its running that rich,you may have wayy too much jet. Try to adjust it first,clean your plugs and go for a drive. Then check your plugs after and report back. I bet you have a 61 jet,and should be at 57-58-59 ish.

As far as timing, somewhere between 8-12* is usually what the slant likes. Keep bumping it up and test driving it till you find what the car seems "happy" with. I bet 12* will be it. I had a 67 Dart and it liked 16*,but then my 70 liked 10*.
 
Thanks guys,

I'm running Bosch plugs not sure what part # I'll pull them and after cleaning check the #

I'll report back tomorrow after adjusting the idle mixture and timing. Thanks!

Matt
 
Good advice on the plugs.

Also make sure choke is fully pulling off once warmed up and its vacuum activated dashpot is not leaking, and float level set properly before messing with jets.
 
All good advice. Start with the air filter, make sure the choke operates correctly and fully opens when warm, and adjust idle mixture. If that doesn't do it, you're looking at taking the carb apart and resetting the float level (and checking for a heavy float), checking the valve for sealing, and/or doing something with the jet sizes. Assuming it's the stock and original carb, that should not be needed. If you need to get inside the carb, get a kit and go through it completely.
 
cudamark said:
All good advice. Start with the air filter, make sure the choke operates correctly and fully opens when warm, and adjust idle mixture. If that doesn't do it, you're looking at taking the carb apart and resetting the float level (and checking for a heavy float), checking the valve for sealing, and/or doing something with the jet sizes. Assuming it's the stock and original carb, that should not be needed. If you need to get inside the carb, get a kit and go through it completely.
Click to expand...


I agree with Mark,if you do go into the carb you can also upgrade the float to one made of brass which is a worthwhile upgrade.I forget who to get it from let me check real quick.
 
Thanks for all the advice everyone,

I checked the air-cleaner-good
The choke operates properly

After warm up I tried to adjust the idle mixture, the screw only turned in about 3/4 turn. The motor never stumbled and it seemed to make no difference. Looks like I'll be re-jetting it. Thanks for the carb rebuild kit suggestion I'll check them out.

I went ahead and adjusted the timing. 10* seemed to be the sweet spot.

Thanks again everyone I'll let you know how the carb rebuild goes, Matt
 
It bottomed out after 3/4 turns? If so then you really need to check your float level/setting,it should be about 1.5-2.5 turns out.While you are in there let us know what jet you have.
 
Thanks again all,

I have not opened up the carb yet because it's a daily driver so I have no idea what jet is in it. What jet should I order from Daytona? I plan on the rebuild kit, new float and jet. FYI I live at 6000ft. Thanks, Matt
 
Dodgex2 said:
Thanks again all,

I have not opened up the carb yet because it's a daily driver so I have no idea what jet is in it. What jet should I order from Daytona? I plan on the rebuild kit, new float and jet. FYI I live at 6000ft. Thanks, Matt
Click to expand...

I would get multiple jets if you have the $$$ get 56-57-58-59 if you can.
 
Although very nearly every Holley carburetor I ever had my hands on (a bunch shall we say) ran rich (slightly to a lot) on the street with the factory jetting (about 2 to 4 jet sizes too large being the norm), I don't think that sounds like your problem. Even with the factory jetting (again rich), you should be able to have some control over the idle by adjusting the screws. Also, the odds are, if the float is bad, or the float adjustment is off enough to cause what your saying, it's going to be puking fuel out the vent.
I'd be looking at a blown power valve. Holleys (especially the 4150-4160 four barrels and their two barrel derivatives) are known for this, to the point of advertising their newer carburetors as having blow proof valves, and having a kit available for modifying older carburetors to prevent the problem. If the power valve goes (if your motor has too low a vaccuum at idle for the # valve you're using, it will act the same way), there's no way in hell you'll keep it from running pig rich at idle, short of dropping the main jet size so far you get lean misfire when the accelerator pump shot runs out every time you accelerate.
Everybody is a "Holley expert" and it sure sounds one of those experts has screwed with yours, but no worries, odds are if you do your homework, work systematically, and buy a few parts, you'll get yours back into shape.
I bought a used one once REAL CHEAP (5 Bucks cheap), because it had the power valves (there are two in a 4150) replaced with plugs, and the jet sizes increased to compensate. It ran so rich, your eyes would tear up standing next to it. Because it idled so rich, the plugs would foul so bad the motor would hardly run. The guy tried all kinds of plugs and couldn't keep any of them in it without fouling. He couldn't figure out the problem, so of course with the car running this way, the carburetor was "defective". I certainly wasn't going to tell him it was an OWNER malfunction.
Turned out to be one the best running Holleys I ever owned once I got it squared away.
.
 
Blue87D100 said:
Start the car and let it warm up,once warm adjust the idle mixture screw in(clockwise) untill you notice a slight stumble,then back it out(counter clockwise) till it smooths(about 1/4-1/2 turn) But if its running that rich,you may have wayy too much jet. Try to adjust it first,clean your plugs and go for a drive. Then check your plugs after and report back. I bet you have a 61 jet,and should be at 57-58-59 ish.

As far as timing, somewhere between 8-12* is usually what the slant likes. Keep bumping it up and test driving it till you find what the car seems "happy" with. I bet 12* will be it. I had a 67 Dart and it liked 16*,but then my 70 liked 10*.
Click to expand...


how do you know the timming? and how do you change it?
 
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