Ignition timing question

[CT9A]

Will to much advance cause a motor to run lean or rich? This is on a small block 350 Chevy with the throttle body injectors.

[HONDA GHANDI]

It should be computer controlled with a knock device. But advanced timing will generally not have much affect on the mixture. Too much advance however will cause high cylinder temps, ignition detonation and higher coolant temps. All of these issues will cause high NOX and Hydrocarbon emissions. High hydrocarbons can be caused by a lean mixture as well.

[CT9A]

Ah, but if I'm having problems with high HC's and high (but still within passing standard) CO's, will this help any?

After putting the timing light on it, the marker on the damper is so far advanced that it's not even within the markers on the timing cover. The stupid sticker says 0 degrees BTDC.

[12seccivy]

Ah, but if I'm having problems with high HC's and high (but still within passing standard) CO's, will this help any?

After putting the timing light on it, the marker on the damper is so far advanced that it's not even within the markers on the timing cover. The stupid sticker says 0 degrees BTDC.
Ghandi gave you a general guideline for what you asked,but I don't think you asked quite the right question.
You should have mentioned what problem you are having ,then ask if timing would affect it.
Are you failing in NOX emissions?Is the only area you have problems in HC reading?
What was the C02 readings on the test?(this helps somewhat)
I'm pretty decent with emissions issues,But Ghandi is more of an expert.

[HONDA GHANDI]

It depends on what is actually causing the failure. The timing may be advanced to fix another running issue. Starting with setting the timing to factory spec is a good start. From there it will take some diagnosis to get down to what is really causing the issue.

[12seccivy]

it will take some diagnosis to get down to what is really causing the issue.
The whole point I was getting at...

[CT9A]

Ok, well I'm off to put the timing at 0 and see what happens.

The readings from the last test are:

HC - 2.0904
CO - 17.9716
CO2 - 502.1224
NOx - 3.0677

All in GPM.

I'm just barely failing the HC part of the test.

I was also told that the plugs that I'm using are crap. I put in Bosch platinums and was recommended by an emissions tech to go back to the basic Autolites since they've been seeing a trend in vehicles failing with platinum plugs, specifically Bosch.

[HONDA GHANDI]

Yeah, Bosch plats suck. Let us know how she does.

[CT9A]

Well, like a dumb shit, I had the wrong wire disconnected for the timing advance. I blame my Chilton's for that one.

Timing is actually right on with stock. Compression in all 8 cylinders is good (145-150) and I replaced the Boschs with Autolites. I'm thinking about picking up a fuel pressure tester to see if I have a leaky injector. I was also thinking about replacing the cat. Does this sound like a reasonable direction to go? I'm tempted to just go test again and see if the plugs made any difference.

[HONDA GHANDI]

Leaky injector will cause High CO and black smoke. A clogged injector (or shitty spray pattern) can cause HC failure however. Cat efficiency may be down as well, the only way to measure it is to take its temp under load. It should be over 700-800F. Cap and wires ok? Any misfires to speak of?

[ryanman]

Get rid of the Bosch & the Autolites, they both suck ass. Get some AC Delcos or some NGK's in there.

[CT9A]

Well, I checked for a leaky injector (tell me if this is a viable way of checking) by disconnecting the injectors and turning the key to the on position. Nothing leaked out of the injectors. I have noticed that at idle I can see some fuel start to pull up on top of the throttle plates.

How would I check for clogged or poor spray patterns in an injector? Maybe I'll just replace the damn things if they aren't too expensive.

Also, how would I check the temp. of the cat while under load? I have a visual of making my brother hang on to the suspension while I'm driving, holding a thermometer to the cat.

[HONDA GHANDI]

You need a raytech infrared temp gun to inspect the cat. Injectors can only really be tested by a fuel injection lab for proper spray pattern and leakdown. If they are visibly leaking while fuel pressure is added to them, they are no good.

[CT9A]

So, the test that I did (unplugging them and turning the ignition on so there's fuel pressure) is good enough? Maybe I'll pull the fuckers out and see what they look like. The manual says there's a few maintenance things I can do to them.

I did find a small vacuum leak between my charcoal canister and the fuel tank sensor.

Hopefully, these corrections are enough to get by the damn emissions testing.

[HONDA GHANDI]

Its possible. Im not sure of the reliability of Chevy TBI injectors so I really cant tell you how they should look/act other than they should NOT be leaking.

[12seccivy]

Its possible. Im not sure of the reliability of Chevy TBI injectors so I really cant tell you how they should look/act other than they should NOT be leaking.
Been having them for 10 years now..
Reliability is pretty decent up to about 100-150k
I believe they have a reseal kit for some of those injectors(they are huge)
But I never resealed them myself though..

[CT9A]

Well, I failed the emissions again. This time it was worse than the last time. The changes that I made were:

Swapping the plugs from Bosch to Autolite
Tightened up a vacuum line in between the charcoal canister and the tank gauge
Replaced the O2 sensor

I checked the cap, and it looked good. I have new wires on there. There are no misfires or hesitations (the truck seems to run perfectly).

I did get a temp gun, not the one that Tobi mentioned, but a cheapy from Harbor Freight and my cat was only at ~570 degrees after the truck was at full temp and had been driven for ~7 miles.

My only two guesses at this point are the injectors and the cat. I'm going to end up rebuilding this damn thing by the time I'm done.