Wideband idle tuning with large cams

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turboking15

turboking15

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Recently got my motor running and have been trying to set idle and get a good base to start street tuning with. Issue i am having is the car runs and smells very rich, but the widebands read 14.5-15.1.

I have done some research and most are saying this is very common on cams with a lot of overlap. So my question to you is what do you do to get large cams to idle well and not smell like raw fuel coming out of the exhaust? Carb is a 650dp baseplate, proform main body, quickfuel billet blocks, and stock holley dp bowls. Cam specs:304/306 242/248 .555/.556 110lsa. Engine is 9.5:1 magnum ported mag heads m1 single plane 1-3/4 primary headers.
 
What's your initial and total timing? Are you running vacuum advance?

This is what I was told once, and it has work amazingly every time I've tuned a motor. With the vacuum advance disconnected, if you have it. Hook up a vacuum gauge below the throttle blades.
1.) Slowly advance the timing while turning down the idle to your normal idle 850 rpm ?
2. ) Once you reach peak vacuum at idle and it will not increase any more, you have found your initial timing point.
3.) Do the math and adjust your distributor so it can only mechanically advance to your "all in" timing. With a Mopar that should be somewhere around 34 to 36 total.
4.) If you have vacuum advance, hook it to a port below the throttle valves and turn down your idle to normal. Either change the pod to get the minimum vacuum advance available, weld the stop and file it back to the right shape, but so that it only adds 5 to 10 degrees of timing, leaving you at 39 to 44 total ting on cruising on the highway (this is conservative timing for highway cruising). Usually, you can end up right around 50 to 53 degrees with full vacuum on the freeway without gas knock. It MUST be hooked up to manifold vacuum, so when you crack the throttle open, the vacuum will almost instantly drop back to your mechanical only setting of 34 to 36 total.

This all assumes you didn't build a motor with too high of compression for pump gas and/or you are not building too much dynamic compression with your cam choice.

BTW, My wideband won't even read my idle mixture on my 493" sixpack motor until it is above about 1800 rpm, so you are lucky.
 
Don't forget that the wideband sensors need to be (broken in) and recalibrated before they smooth out and start giving a reliable reading.

Mine did anyway.
They say to run it for a while and then recalibrate the sensor, so you may have to tune it the old fashioned way at first. (by the sound,feel and plug readings) until the sensor is reliable.
 
a lot of times you cant get the exhaust smell out, this is why they use egr, air pumps, cat converters. you might be to lean try it at about 13.8 to 14.
 
Where is the wideband located? If it's at the end of the exh pipe opening (clamped at the exh tip) then it is going to read lean.
 
it should be in the collector or just after the header between a 10 and 2 o'clock position
 
Timing is locked out at 34, i have a programable 6 if i want a curve but it seems to run the best with it all in all the time. Going to try bumping it up to 36 tonight. I will try a vac gauge tonight as you suggest. Ill have to check on dynamic compression when i have the numbers in front of me. I know static is right around 9.5 so it should be more than happy with the 93 i run.

As far as breaking in the widebands i run AEM uegos which dont require free air calibration and have always been on right out of the box.
 
turboking15 said:
Timing is locked out at 34, i have a programable 6 if i want a curve but it seems to run the best with it all in all the time. Going to try bumping it up to 36 tonight. I will try a vac gauge tonight as you suggest. Ill have to check on dynamic compression when i have the numbers in front of me. I know static is right around 9.5 so it should be more than happy with the 93 i run.

As far as breaking in the widebands i run AEM uegos which dont require free air calibration and have always been on right out of the box.
Click to expand...

None of the stuff I listed will be of any help to you then. Your problem is likely your carb. Probably in the air bleeds, and I'm certainly no expert there. There are a lot of guys on this site that can guide you through tuning your carb through that circuit of it.
 
To jbc426; I read your post #4 saying "it MUST be hooked up to manifold vacuum...". Whats your thinking on that?------And to the OP;are you saying that there is only 16 inches of pipe on the end of the header? In my limited experience with WB sensors, they liked more pipe after them. Seems that atmospheric air gets up into those short pipes giving erroneous readings.I had a car once with a 292/509 in it at 10.7cr, w/alum.heads, and RPMairgap. It did that too.The almost cure was 18* initial, cr bumped to 11.2, and a fair bit of work on the 750dp.Eventually I got rid of that cam. Put in a Hughes fast rate [email protected];more torque and more power and best of all a clean exhaust. I think most of the stink was in the overlap&initial timing.Hope this helps.
 
AJ/FormS said:
And to the OP;are you saying that there is only 16 inches of pipe on the end of the header? In my limited experience with WB sensors, they liked more pipe after them. Seems that atmospheric air gets up into those short pipes giving erroneous readings.
Click to expand...

This is what I was getting at also. Only having 16" of pipe after the wideband may be the problem. At idle, especially with that cam, it's pulling air back up the pipe.
 
Use more than one tool to tune the idle.

I'd use a vacuum gauge to see where it pulls highest vacuum, then look to the A/F meter and see where it falls.
 
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