pinging

[Rooster's82]

If i put anything but the most expensive fuel in my truck it knocks like a cop at a house party and with the good stuff she runs smooth as silk.

I have been told that my timing is off. I have absolutely NO experience or knowledge about timing.

I know there is a GURU out there that can brake it down for me. Why would timing effect the type of gas i can use? What is happening when an engine knocks? How do i fix it so i can put the "cheap" stuff in?

[spudz]

Retard the timming till it doesnt ping.
The textbook definition of knock is this: “The explosive spontaneous ignition of fuel-air mixture ahead of the normal propagating flame and the subsequent cylinder pressure oscillations in homogeneous-charge spark ignition engines.” Otherwords... its firing when its not suposed to. Adjusting the timming retarded or advanced controls when the plugs fire.. Try settin it at around 10 degrees and see what happens. To do this.. loosen the distributer hold down, so the distributer can be turned but still kinda snug. disconect your advance. point your timming light at the marks and set it where you want it.

[Rooster's82]

Originally Posted by spudz

Retard the timming till it doesnt ping.
The textbook definition of knock is this: “The explosive spontaneous ignition of fuel-air mixture ahead of the normal propagating flame and the subsequent cylinder pressure oscillations in homogeneous-charge spark ignition engines.”

DUH! Of course...it make so much sense now! (j/k I'm still sort of foggy)

What is the timing supposed to be at? Is there a reason the timing would have been advanced? Like was it tuned to run premium? Will there be negative effects to retarding the timing?

How do i retard the timing?

[spudz]

well you can have the timing more advanced with premium. So it was prolly tuned to run it.. It would make a little more power like that and be a little more responsive. BUT you can burn a piston leaving it like it is.. pinging is bad for your engine.. SO if you are going to run regular... Retard your timing some.. I added to my first post later. lol sorry for that.

[Rooster's82]

i have only been running premium...I ran one tank with the cheap stuff but the pinging was pretty bad, i ended up adding octane booster to try to stop it.

[454HO]

Originally Posted by Rooster's82

I know there is a GURU out there that can brake it down for me.

Yes, and his screen name is Billla. Here is his FAQ thread to get you started -
http://67-72chevytrucks.com/vboard/s...d.php?t=290498

[BowTieOgre]

I was having the same problem with my '80. If I put the cheap stuff in I got some noises when under heavy load and it would diesel every once in a while. The past two trips to the gas station I put premium in and the problems went away and I picked up 2mpg. Im going to see if I can borrow a timing light this weekend and get it fixed up.

[Rooster's82]

Originally Posted by 454HO

Yes, and his screen name is Billla. Here is his FAQ thread to get you started -
http://67-72chevytrucks.com/vboard/s...d.php?t=290498

WOW...i was under the impression that you just hooked up a timing light and turned the cap.

[jimfulco]

Exactly when does it ping? Full-throttle only? Part-throttle?

[LONGHAIR]

WOW...i was under the impression that you just hooked up a timing light and turned the cap.

It's not the cap, but the entire distributor body that the cap is attcahed to. And for the simple art of just retatrding the "initial" timing, that is all you have to do.
The FAQ that billla wrote is far more comprehensive. It goes into great detail about how to achive "optimum" results. With daily drivers, many/most guys are just not going to go through all of that.
The problem is, simply taking out some of the initial timing (turning the distributor) may not even help. It just depends upon where it is right now. If it is advanced, pulling it back some will probably fix it. If it is set right, there are deeper issues, simply retarding may not help.

As far as negatives, yes there are some.
If you retard the timing (and it solves the ping) you have given up some performance. It is up to you to decide how much and if you can live with it.
You may lose some fuel milage, but probably not enough to justify the cost of premium?

[Rooster's82]

Originally Posted by jimfulco

Exactly when does it ping? Full-throttle only? Part-throttle?

Part throttle just above cruzing....mild acceleration. If i open it up it pings on the way up then it stops at full throttle or pretty close.

Keep in mind that i get absolutely NO ping when running premium.

[Rooster's82]

Originally Posted by LONGHAIR

The problem is, simply taking out some of the initial timing (turning the distributor) may not even help. It just depends upon where it is right now. If it is advanced, pulling it back some will probably fix it. If it is set right, there are deeper issues, simply retarding may not help.

What are the deeper issues i could possibly have if the timing is not the problem?

When retarding the timing do i need a timing light? Or can i just back it up a couple of degrees?

[swb85]

You really need to get a timing light and check to see how much advance you're running. Everything is pure speculation until you verify where it's actually set right now.

[454HO]

Originally Posted by Rooster's82

Part throttle just above cruzing....mild acceleration. If i open it up it pings on the way up then it stops at full throttle or pretty close.

Keep in mind that i get absolutely NO ping when running premium.

Sounds like too much vacuum advance. Retarding the base timing would just be a bandaid at best. I agree, you really need a timing light to see exactly what is going on. Have you made any changes to the engine? Carb or distributor?

[Rooster's82]

Originally Posted by 454HO

Sounds like too much vacuum advance. Retarding the base timing would just be a bandaid at best. I agree, you really need a timing light to see exactly what is going on. Have you made any changes to the engine? Carb or distributor?

I just put on an edelbrock 600cfm manual choke, new plug wires and plugs. But the problem was present with the old carb as well.

[LONGHAIR]

You really need to get a timing light and check to see how much advance you're running. Everything is pure speculation until you verify where it's actually set right now.

You really need to know where you are starting from.

What are the deeper issues i could possibly have if the timing is not the problem?

When retarding the timing do i need a timing light? Or can i just back it up a couple of degrees?

First of all, I didn't say that "timing" wasn't the problem...just that if the initial timing is set right at this point, just the act of taking away some more may not solve your problem.
There could be other factors:
1)Where is the vacuum advance connected? Ported or Full?
If your distributor was originally made to run with ported vacuum, just the act of connecting it to full vacuum could cause this. (higher octane would mask this) I am assuming by your name that we are talking about an '82 model truck here?
2)Jetting? A lean condition can exaggerate this, where the higher octane was covering it.
3)Engine running temp. Higher cylinder/head temps can make this worse too.
4) Believe it or not, gear ratio. Exceptionally high gears make for a greater load on the engine. It is getting less help (torque multiplication) from gearing, so it "sees" a higher load. This can include taller tires with the same gears.
5)Weight, the actual weight and rolling resistance of the truck is a factor too. Extra weight in the bed can make it worse.

Any combination of these factors could be "covered" by higher octane fuel and it wouldn't take much. If you are "right on the edge" with the higher octane, you would never know, until you drop the octane.

Yes, you really do need a timing light, "a couple of degrees" is very hard to do. Even if you could, you still don't know where you are.

[Rooster's82]

1)How do i know if i have ported or full vacuum advance?

2)Jetting...pings with both carbs q-jet and new edelbrock...i would asume if the q-jet was lean the edelbrock would solve this.

3)My engine has no t-stat so cooling system is running on full at all times. Before i switched to my electric fan the engine rarely broke 170...now it stays between 170-180. the pinging was present before and after the change.

4) Gear ratio...no clue what mine is....i have a 3 speed auto...that is about all i can tell you.

5) I keep my bed pretty much empty...unless i have my bike in there. Every time i have moved the bikes i have been running premium fuel and i have not had any pinging.

[LONGHAIR]

1)How do i know if i have ported or full vacuum advance?

That is as simple as pulling the vacuum line off of the distributor while the engine is running. If you have "full" vac, there will be a change in the idle. The idle speed will drop from loss of advance and from the vacuum leak you just introduced.
With "ported" vacuum..........nothing happens. I would bet that yours is "ported", but simply switching to "full" vacuum with-out any other changes probably will not "fix" it. That will probably bring on new issues, fixable, but different.

2)Jetting...pings with both carbs q-jet and new edelbrock...i would asume if the q-jet was lean the edelbrock would solve this.

Not necessarily.

3)My engine has no t-stat so cooling system is running on full at all times. Before i switched to my electric fan the engine rarely broke 170...now it stays between 170-180. the pinging was present before and after the change.

Even if it has no bearing in this pinging issue, I would put a thermostat back in. That can cause overheating.
But the heat I was really refering to is in the combustion area. If the timing is too late at low speed (idle and just off idle) it creates a lot of heat in the heads and exhaust manifolds. Then when the timing starts advancing as RPM increases, you get pinging.


4) Gear ratio...no clue what mine is....i have a 3 speed auto...that is about all i can tell you.

In the 80s, gearing was usually pretty high, which adds to this problem.


5) I keep my bed pretty much empty...unless i have my bike in there. Every time i have moved the bikes i have been running premium fuel and i have not had any pinging.
05-17-2008 08:24 PM

Added weight can always make the problem worse.

[Rooster's82]

longhair,

Lastnight before i read this i switched the vacuum line from the distributer to the full vacuum side of the carb and the idle went up...not a ton but it did change. This morning I stopped and got some 89 octane gas...I'm waiting to see if it starts pinging or not. If it doesn't, does that mean the problem is solved or is the more i should do?

[454HO]

Originally Posted by Rooster's82

is the more i should do?

It depends on what you want. The ignition timing affects overall drivability - power, economy, emissions, etc. If you are okay with no pinging with 89 octane fuel, then call it a day. If you are more anal and want to optimize your timing curve for the best performance and efficiency, then you need to go back and read the FAQ link I posted. It's really not that complicated to set it up correctly and it would probably save you a bunch of gas $$ .

[Rooster's82]

I see what your saying. Yes, i eventually what to do the full timing and tuning of the engine....but for now i just want to eliminate the ping and protect my engine for related damage. I guess i could just keep running premium until i can set aside an afternoon and get my hands on the right tools.

Also, went home at lunch and the engine started pinging with the 89 gas. So when i was there i switched the vacuum line back to the port side of the carb...drove it for a bit and the pinging was real bad, i stopped as switched it back to the full vacuum side and it ran better but still had a ping to it. So im assuming this confirms that i need full vacuum advance?

[LONGHAIR]

So im assuming this confirms that i need full vacuum advance?

IMHO, everyone should be running on "full vac", but it is not as simple as just swapping the line....as you found out.
But, if it makes the pinging better than on "ported", I would leave it there until you can spend some time on it.

[Rooster's82]

Can someone break down how timing is kept? Like how the distributer works...the timing mechanism inside of it, how the vacuum advance works, and why you look at the balancer to determine the timing. And any other fundamental aspects of how timing is kept.