If I try to set my initial timing at anywhere below 12 degrees, my engine will stall out. I have turned the idle screw in quite a bit, probably too much. I am running a 460, D1VE block, D0VE C heads, Performer RPM intake, Holley Avenger 770, Comp cam 34-336-4. I have backed the adjusting screw out in the dist. vacuum advance out about 15 turns and set the initial at 18 to 20 degrees. This has helped and also has eliminated a lot of the pinging issues I was having. Any suggestions?

 

Yea but the powers to be here. Wont believe me and dont like my spelling and typing

 

Come on guys, I know you have some useful info. Help me out. I do not want to run that much advance.

 

I run all my vehicles around 20* initial and totals around 36*. Some I have run that way for 16+ years. The 460 in My 86 dually sucks at anything less. Havent worked out the total exactly yet or the slope of the curve and exactly were I want it to max out but am a few degrees from were it wants to be at this point.

How does it run. I can idle in 5th gear with my foot off the gas. I will take of in 1,2,or third gear with my foot off the gas. At total weight of truck and trailer of 9840 lbs. I can pull it down to 25 MPH and pull away up a moderate grade in 5th. So far the vacuum advance is disconected. I will deal with that later. Working on idle jetting at the moment and timing. It is a slow process because I dont make runs and check the plugs unless there is a purpose to using the truck. I will also need to disable the steering lock so runs to read plugs for timing and jetting can be done at 500 to 1000 RPM increasing steps and shut down the engine clean.

 

It runs okay, but not as good as it did at 16 degrees initial with the vacuum advance connected. I am having an issue with piston knock though. Disconnecting the vacuum advance helped there, but I lost power so I advanced the timing up to 20 degrees and left the vacuum advance disconnected. I am thinking my valve timing is off. Also, I am running a C6 auto. When I put it in gear it wants to stall even though I am running a 3100 stall speed.

 

Your total advance is to high probably you will most likely need to weld up the timing limit slot. Your total is probably around 44*. Should be around 36. What do your plugss look like. If you can send me a pic of each side and one of the top.

 

Check to make sure your damper has not slipped. TDC the #1 piston anf make sure the pointer is on 0°.

 

Good idea. Get your #1 piston up to top dead center. To check 0 on damper.

 

The damper is good. I have only one degree play before the rotor moves when checking the timing chain play. I am thinking the distributor needs replacing. I backed the initial timing down to ten degrees and my performance is gone, also I now have the engine trying to "run on" when I shut it down along with a spit of smoke back through the carb. When the timing is advanced to the point of piston knock the power is abundant. I am running premium fuel with octane booster (three different types throughout the timeframe) and the knock is still there. This is frustrating to say the least. Thanks for the help.

 

have you checked vacuum readings? You may have a vacuum leak or a valve not sealing. In my experience I would double check for vacuum leaks. Pinch off vacuum lines one at a time and listen for a difference.
I also do not run total advance past 36*.
Lean mixtures, vacuum leaks, and lots of advance could lead to more problems.
I'm not up to speed on your carb but by increasing the idle speed you may have taken the idle circuit out of the situation and you may be running on the mid range or transition circuit.

 

Are you still running EGR? Without it it is very difficult to dial in Vacuum Advance. I have had difficulties sealing a Holley carb to a performer intake I currently use. It was partly due to a plastic 1 " spacer I used. I believe Holley even makes a special plate for this application. It realy threw my tuning off fuel economy and such. Once cured had to go back to base carb settings and begin rejetting.






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Vacuum advance is not effected at all by the EGR or vice-a-versa. A bad or incorrectly disconnected EGR can cause some wierd problems, but it has nothing to do with vacuum advance. I just make a plate and block off the EGR completely but your problem sounds like you had a bad EGR and when you fixed it by replacing the spacer you had to readjust the carb because instead of fixing the problem in the first place you mal-adjusted the carb.

 

Here we go again bear.
One I dont even have provisions for EGR and the vacuum advance wasnt hooked up when I purchased the truck nor have I hooked it up. May never hook it up.

Second EGR cools the temp of the combustion allowing vacuum advance to be used without detonation. With out EGR a vacuum advance of more like 2* is about all you can achieve once the initial timing, distributor timing and the advance curve is optimized.

Went through this years ago with a 390 Mustang. Ran the vacuum hose for the advance unit into the car with a valve and a gage so I could adjust it or turn it off in the car. Made shure I had an adjustable vacuum advance unit on the distributor. Spent months playing with it. Didnt have EGR once I dialed in my initial timing and mechanical the vacuum advance couldnt be adjusted low enough to not detonate unless I ran leaded premium.

 

Another thing
My carb has removable air bleeds, Main jets, removeable Power Valve Feed Restrictions along with other mods. So that I can adjust any circuit in the thing.
My next mod is to remove the steering lock from the truck so I can shut it down clean at any speed to read the plugs. Doing this I can read timing and fuel conditions right off the plugs for any given speed and adjust them accordingly.

 

Rather than screw around with the steering lock, why not just add a switch between the ignition system and the key switch that lets you shut off the ignition when ever you want. On my real race cars I never had an ignition key switch, I always disconnected it, and to deter the bad guys, I had a hidden switch that shut off power to the ignition, fuel pump and fan switches. Oh yeah and it grounded the ignition system at the same time. That way you couldn't hot wire it without disconnecting the wires.