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Getting run on bad
https://slantsix.org/forum/viewtopic.php?t=26006		 Page 2 of 3
Author:  SlantSixDan [ Fri Dec 21, 2007 8:10 pm ]
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The shop screwed stuff up, plain and simple. You're going to need to go through and diagnose this systematically. Hesitation + run-on suggests lean = overheating combustion chambers. Pull all six plugs and read 'em. Are you getting pinging?
Author:  Aggressive Ted [ Fri Dec 21, 2007 9:27 pm ]
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ESP47 and Dan,

That is what I thought too, maybe carbon build up is acting like a glow plug.....especially when the engine is hot.

Another thought is that the vacuum diaphram might be ruptured and leaking air. It could be a air leak plus the carbon build up.

I got my intake off right now and have been running some water injection through the carb sure keeps the head and valves alot cleaner. It has a very crisp start and good snap! :)
Author:  ESP47 [ Sat Dec 22, 2007 2:45 pm ]
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I put the NOS carb on between my first post in this thread and the last one I made yesterday. This new one doesn't need to be rebushed. The thing is that my plugs look really good. I can't figure out what the problem is. I can't even get it to idle in drive at a stop without it choking out and dying after 15 seconds or so. I've never had this many problems with a car in my life.

The engine purred like a kitten after I put the NOS Carter on. For about a week that is. Then it was back to normal where the damn thing just won't idle in drive without a foot on the gas. I'm getting really fed up with this. You guy's are giving me great advice but nothing seems to help. My manifolds are both in good condition. No leaks with either of them and no pinging either.
Author:  Charrlie_S [ Sat Dec 22, 2007 4:10 pm ]
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Do you have a charcole vapor cannister? Is it possible it is bad and allowing charcole to enter the carb, thru the hose between the cannister and the float bowl vent?
Author:  Joshie225 [ Sat Dec 22, 2007 4:24 pm ]
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Quote:
The engine purred like a kitten after I put the NOS Carter on. For about a week that is.
Hmm, I would look inside the carb and see if you're getting trash in there that plugged up the idle circuits.
Author:  tophat [ Sat Dec 22, 2007 5:01 pm ]
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Quote:
3) I take it that you are running points since there was talk of setting dwell. By changing timing you also change dwell.
Dwell is the amount of time the points are closed. Dwell has absolutely nothing to do with timing, you can twist the distributor all around and the dwell will not change. Cheep points will make the dwell bounce around. Dirty points will do the same thing. Do you have a habit of sitting in the car listening to the radio with the key on and engine off? Leaving the key on with the engine off will burn the points up quickly, if the points happen to be closed. I'm sure Dan can recommend who makes good points these days.

I am thinking the problem could be in the timing. Have you plotted the timing curve? If you rev the engine with the timing light hooked up does the timing mark move? If it moves does it move smoothly and repeatably? If so you can rule out a sticking centrifugal advance mechanism. This would be possible even with a reman dist, even more likely. Retarded timing will make things run hot in the chamber, causing the problems others have suggested. Possible even without significant carbon build up.

At 1000 rpm disconnecting the vacuum pod may or may not make the mark move. If you have a hand held vacuum pump you can apply you can test the pod with that, if not you can use your mouth (clean the hose first). Again, with the engine idling, the mark should move repeatably and smoothly. Might be a good time to hit up the loan a tool for the vac pump, it will have a gauge so you will know EXACTLY how many inches of vac advance exactly how many degrees.

Checking the hot compression is a good idea too. Running an exhaust valve tight will burn it in a hurry, even on a brand new engine.
Author:  dakight [ Sat Dec 22, 2007 5:31 pm ]
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Dwell is set by adjusting the point gap. Changing dwell will indeed affect the timing but changing timing has no effect on dwell. For that reason, the points should always be set first then the timing. In fact, the timing should be the last item set in a tune up as both the point gap and the plug gaps will have some effect on timing.
Author:  Zipper [ Sat Dec 22, 2007 9:07 pm ]
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I'm getting the same problem. Recently rebuilt engine (raised compression), had a distributor (Rebuilt) that had to much movement, and some mild to mean run on when hot. It still runs on with the new (new) distributor when its hot. I still cant figure out why. Seems to runs fine with all grades of gas, and I'm just baffled as to why it is
Author:  Joshie225 [ Sat Dec 22, 2007 9:21 pm ]
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The #1 cause of run on is retarded timing which requires a larger throttle opening to maintain idle speed. Combine that with a hot combustion chamber and you get run-on. This is why manufacturers started putting things like throttle positioning solenoids and idle fuel cut-off solenoids on cars in the early '70s.
Author:  ESP47 [ Sun Dec 23, 2007 6:01 pm ]
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Ok so how do you go about fixing hot combustion chambers? Right now the problem seems to be getting worse. I have it idling at 1050rpm in park and it dies immediately in drive if im at a stand still.
Author:  SlantSixDan [ Sun Dec 23, 2007 7:08 pm ]
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I think your first step is to check your ignition and cam timing very carefully and report what you find.
Author:  Aggressive Ted [ Sun Dec 23, 2007 7:30 pm ]
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Advance the timing to at least 12 degrees, 16 would be better if you can adjust it that far. I had to unbolt the limiter on the bottom of the dist. to adjust it to get 16 degrees.
Maybe during the rebuild they retarded the timing.

After the rebuild:
1. What is your compression ratio? How much did they mill off the head and block?
2. Is your cam stock? or modified?
3. Are you sure the valves are adjusted correctly? Did they adjust them hot? Did you check them? .012 and .022 is better.
4. Is your vacuum canister on the distributor holding vacuum?
5. What octane do you run? Have you tried octane boosters?
6. Have you run some Seafoam in the tank yet?
7. Do you think the engine has broken in yet?
8. Is the temp on the hot side from breaking in?

During break-in my engine never did run very consistent because of the heat build up. After about 5000 miles it started to idle more consistently, (steady). It seemed to change a little every time I ran it. I always kept a screw driver handy to tweak the mixture.

Let us know what you find. I just went through all this on my rebuild last year.
Author:  SlantSixDan [ Sun Dec 23, 2007 10:44 pm ]
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Quote:
Advance the timing to at least 12 degrees, 16 would be better
Whoah, hold on, why are we advising him to throw random (and excessive) amounts of initial advance at this engine? That's the kind of wild shot in the dark that often makes it even tougher to figure out tough driveability problems. Instead of guessing and acting at random, let's systematically seek, find and fix the problem. Check the ignition timing and see where it's set. Verify TDC on the indicator is actually TDC in the engine. Then check the cam timing.

Octane boosters or high-octane gasoline aren't necessary. Random chemistry won't help any more than random ignition advance. Seafoam is likewise not needed on an engine as new as this, and the symptoms mentioned aren't being caused by a not-yet-broken-in engine.
Author:  tophat [ Mon Dec 24, 2007 6:40 am ]
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I have to agree with Dan here. Just throwing timing and "mechanic in a can" at it will AT BEST waste time and money. Check everything stated so far and post what you find, it is the only way we can know what is going on to help you.

Good Luck

TopHat
Author:  ESP47 [ Mon Dec 24, 2007 10:28 am ]
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Ignition timing is at 7 BTDC. How do I go about checking cam timing? Sorry but im still learning.
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