Car stinks at idle, too rich?

Posted By: rck850

Car stinks at idle, too rich? - 06/28/11 02:51 AM

I have a mild 440 in my Duster with iron heads and a .528 Mopar cam. The carb is a 800 Holley DP with a Proform main body. At idle it just loads up and stinks. At cruise I have no problems, and the plugs look great. It's just at idle I cannot get the fuel under control.

Posted By: GTXX

Re: Car stinks at idle, too rich? - 06/28/11 03:43 AM

check the vacuum at idle, in gear. Get a power valve that is 1.5 lower than the vacuum reading.

Posted By: sixpackgut

Re: Car stinks at idle, too rich? - 06/28/11 03:54 AM

make sure your throttle blades are set correctly then adjust your intial timing to suite your idle rpm needs

Posted By: radar

Re: Car stinks at idle, too rich? - 06/28/11 04:27 AM

Did you adjust the idle mixture screws for highest vacuum? After setting the timing and verifying your transfer slot exposure (should be right on around 3/4 turn of curb idle screw) that should be your next step. If the curb idle screw needs to be in more than 3/4 maybe look at cracking the secondaries too. There's lots more radical approaches but start with the easy stuff.

Posted By: Cab_Burge

Re: Car stinks at idle, too rich? - 06/28/11 04:31 AM

Quote:

I have a mild 440 in my Duster with iron heads and a .528 Mopar cam. The carb is a 800 Holley DP with a Proform main body. At idle it just loads up and stinks. At cruise I have no problems, and the plugs look great. It's just at idle I cannot get the fuel under control.

As already mentioned check your idle vacume IN GEAR, if the power valves are rated higher than what it idles (IE idles at 5.5 inches in gear and has a 6.5 rated power valve) at change them to a lower opening one first then try it agian. If that doesn't fix it try screwing in teh idle mixture screws to 1/4 to 3/4 turns out from fully seated

I've had several motors with big cams and 850 D.P. that we had to do that to to get them cleaned up at idle

Open the secondary butterflys the same amounts or a tiny bit more than the primarys are also

Posted By: rck850

Re: Car stinks at idle, too rich? - 06/29/11 03:41 PM

Well thanks guys I think I finally fixed it. I opened the secondaries and adjusted the idle and idle mix screws again. It will now idle consistently in stopped in gear. It even seems to be more responsive off idle. Thanks again.

Posted By: LAR_414

Re: Car stinks at idle, too rich? - 06/29/11 03:49 PM

You people kill me......The PV is not operational at idle....Period. Unless you have a Blown out power valve dumping fuel in the vacuum well.

PV enrichens the Main Circuit.

Posted By: sixpackgut

Re: Car stinks at idle, too rich? - 06/29/11 04:22 PM

Quote:

Well thanks guys I think I finally fixed it. I opened the secondaries and adjusted the idle and idle mix screws again. It will now idle consistently in stopped in gear. It even seems to be more responsive off idle. Thanks again.

if the carbs were shipped with properly adjusted rear throttle plates, then half of the carb questions would disappear

Posted By: YO7_A66

Re: Car stinks at idle, too rich? - 06/29/11 04:36 PM

Can a power valve "open" at idle? Yes, if the vacuum is below the PV rating.

Can it provide additional fuel at idle? No, as long as the motor is idling on the idle circuit.
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The power-valve circuit is completely separate from the idle circuit. If you have less vacuum at idle than your power valve is rated, then yes the power valve will open. BUT, the engine will not receive any additional fuel until the main circuit begins to flow fuel out of the boosters.

If your engine is idling high enough that you are no longer on the idle circuit, and you still have less vacuum at this rpm than your power valve rating, then you may be feeding your engine with additional fuel thru the power valve.

Posted By: LAR_414

Re: Car stinks at idle, too rich? - 06/29/11 04:49 PM

Your engine would have to have to be so far out of tune for that to happen. To have an engine actually IDLE with the Main Circuit on would require the blades to be open so far that the idle speed would probably be 3000rpm! Even with a set of air bleeds that brings that circuit on at it's absolute earliest point.

I've messed with carbs for a long time, and tuned them with A/F meters and such. I know what I'm talking about here.

Posted By: YO7_A66

Re: Car stinks at idle, too rich? - 06/29/11 04:53 PM

Larry,
I am agreeing with you.

!!!!!!!!!

My first two written lines just gives the facts for someone who is curious.
My paragraph explains how bad it would have to be in order for it to happen.

Posted By: LAR_414

Re: Car stinks at idle, too rich? - 06/29/11 04:56 PM

I just don't like the idea of de-educating people by leading them on "theories" that are just that. In the real world, things happen different.

A lot of people keep saying that the PV is messing up your idle. STOP saying that!!!!! Let the Chevy guys tell eachother that! Educate our Mopar guys that this is completely the wrong way to look at an idle problem.

In "theory" it could affect it, but like I said, it would require so many factors and "out of tune" carb issues that you would never even entertain that "talk".

Posted By: Cab_Burge

Re: Car stinks at idle, too rich? - 06/29/11 05:03 PM

Quote:

I just don't like the idea of de-educating people by leading them on "theories" that are just that. In the real world, things happen different.

A lot of people keep saying that the PV is messing up your idle. STOP saying that!!!!! Let the Chevy guys tell eachother that! Educate our Mopar guys that this is completely the wrong way to look at an idle problem.

In "theory" it could affect it, but like I said, it would require so many factors and "out of tune" carb issues that you would never even entertain that "talk".

DUDE, you are so wrong on this

Have you ever tuned a motor that had a big cam in it, 250 + degrees at .050

Or better yet how about one of the Mopar Purple shaft 284 cams in any motor

Power valve opening affects the idle on a motor with a big cam that has less than 8 inches idling in gear at or below 1200 RPM

Not trying to start a fight or disrespect you but when you make comments on here that can be misleading then someone needs to step up and set the record straight

Posted By: LAR_414

Re: Car stinks at idle, too rich? - 06/29/11 05:09 PM

You're just messing with me,....right....I hope.

FYI, my cam is 260 @ .050 with cross ram. I've run a bunch of big cams and single as well as multiple carbs.

I guess I'm too stupid to know how carbs work.

Posted By: sixpackgut

Re: Car stinks at idle, too rich? - 06/29/11 05:17 PM

Quote:

Quote:

I just don't like the idea of de-educating people by leading them on "theories" that are just that. In the real world, things happen different.

A lot of people keep saying that the PV is messing up your idle. STOP saying that!!!!! Let the Chevy guys tell eachother that! Educate our Mopar guys that this is completely the wrong way to look at an idle problem.

In "theory" it could affect it, but like I said, it would require so many factors and "out of tune" carb issues that you would never even entertain that "talk".

DUDE, you are so wrong on this Have you ever tuned a motor that had a big cam in it, 250 + degrees at .050 Or better yet how about one of the Mopar Purple shaft 284 cams in any motor Power valve opening affects the idle on a motor with a big cam that has less than 8 inches idling in gear at or below 1200 RPM Not trying to start a fight or disrespect you but when you make comments on here that can be misleading then someone needs to step up and set the record straight

Cab, we could have argued about this last night when i was in the mood but you ignored it. now the post is deleted.

Posted By: YO7_A66

Re: Car stinks at idle, too rich? - 06/29/11 06:17 PM

""To have an engine actually IDLE with the Main Circuit on would require the blades to be open so far that the idle speed would probably be 3000rpm!""

I agree that on some model of carbs, the main circuit may not be activated until the 3000rpm level. Heck, mine does not activate until around the 3400rpms now that I have delayed it. But since this problem is all over the internet and some people are having this issue, maybe some carb brands or some carb models do have the main circuit starting in the lower rpm range that may be causing the pv to be activated at a higher than normal idle rpm.
I am not trying to de-educate, I am only trying to point out that there might be a problem that some of us do not have to contend with (you and I for example) due to our existing parts.

EDIT:
This is interesting reading for everyone:
http://www.innovatemotorsports.com/forums/showthread.php?t=17859

I am wrong, apparently it is not the main circuit that causes the issue.

""an open power valve at idle will cause the level of fuel in the main well to rise thus causing the IFR to flow more fuel.""

Posted By: RobX4406

Re: Car stinks at idle, too rich? - 06/29/11 06:19 PM

Make sure you have about 16-22* initial timing on that thing to get the throttle plates closed down.

If you can't kill the engine running the idle mix screws in, the throttle plates are open too far.

My 340 has a 528 cam in it and I've got 22* initial and it idles well with a 13.7 AFR and VERY little stink out the pipes.

In my experience 90-95% of "carb" problems at idle are rooted in the ignition system. Usually, not enough initial timing.

Wanna find out if the PV is the culprit... install a PV plug and tune the idle, then, install the PV and see if it remains the same. I used do that all the time on tough to tune deals. Removes a variable so I can get a clean idle.