Standard for idle hydrocarbon test is 450. My test results are 818. Any ideas how to lower the results. Idle and loaded carbon monoxide test were great, as was the loaded hydrocarbon test. Motor is a 396.
I do not have to do the loaded tests, but still have the 400 limit of HC at idle. I use a tachometer to check for "lean drop" when setting the idle mix and it has worked well so far. Open up the mixture screws until you are obviously rich and then screw them in a bit until you notice a rapid drop of RPM versus needle position. Back out the screw just enough to get back to the "fast" idle speed. This will take a couple of iterations until both screws are optimised. This will keep it rich enough to avoid the lean misfire at idle but not so rich as to add extra HC. Hope that this works for you, too.
Make sure your timing is set properly, and your dwell (if using points) is on the money.
A new set of plugs doesn't hurt either. What's causing the problem is incomplete combustion. I have a 70 Malibu with a 350, Holley 4 barrel and last time around, hydrocarbons checked in at 73 parts per million!! In NJ we've been going through this for many a moon, so I'm pretty used to "tweaking" to get the "old girl" through. Changing over to HEI made all the difference in the world, though, taking away the "points factor".
Now, after 29 years, it's one less thing to worry about when they stick the probe up your pipe.
Seriously, though, check your ignition system carefully and make sure it's in tip top shape before you try again. Good luck!!
[This message has been edited by MalibuJerry350 (edited 01-08-2000).]
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