Pinging

[Pighead]

I am still pinging.

Then I think you need to adjust your timing again. Try retarding just a hair and drive it again. Keep retarding until the pinging is almost all gone.
The older our rigs get, the more we have to learn to tune by ear and SOP...factory settings matter less and less.

 

[mep1811]

I had the timing set to the factory spec. I just had the carb rebuilt by Mark Algazy of Mark's Off road so I realy don't want to mess with it right now.

By retarding the timing would'nt the perforance be affected?

 

[GarageRat]

Not if you're pinging, the thing with tuning a motor is that you have to look for happy mediums. Fuel quality, air quality, humidity, a lot of things affect what timing and jetting your specific motor will need. As the carb was just rebuilt I have a feeling the jetting is good enough and timing is very easy to work with. Retard it 2 degrees at a time until pinging goes away, advance 1 degree and if it still doesn't ping stay there as you want ignition as far advanced as safe. Frankly I'd rather give up a little power if it means the pistons stay nice and solid.

I have a 13:1 compression poncho mill in a '78 T/A that can only take 13 degrees total advance in its current configuration compared to the factory 35 degrees for example, I'd like it a little more advanced but to keep it happy on pump gas that's all it will do. Boosted motors also require less timing advance as boost increases.

 

[FJforty]

Being in the Northwest is nice because there are so many hills to tune my engine. Warm up the engine, drive to the bottom of a hill and flip a U-ee and then drive back up with my foot in it, if it pings I need to back off on the advance. Repeat as necessary.

 

[65swb45]

Mike, this is the first I've 'heard' of this thread, or your problem.

Right off the bat, I am suspicious whether or not your vacuum advance is releasing under load like it is supposed to. Of course, engine temperature is also very, very relevant.

The quick-easy test would be to disconnect the vacuum advance and see if the pinging goes away. I would do this BEFORE retarding the timing below the stock setting. If it makes a difference, then it would behoove you to carefully recheck the routing of the advance vacuum lines to see if all connections are appropriate and intact.

Would also like to know what radiator temp is while this is going on.

Thread is bookmarked now, tho I will be away from the puter again in a few days.

Best

Mark A.

 

[Greenpiece]

Search for my pinging problem thread from a few years ago. I ended up with a new engine. I think my head was shaved too much in a rebuild; causing excessive compression and therefore pre ignition. But Trollhole is asking how your dizzy is hooked up. Meaning, is it vacuum advance, retard, or both? If it has one hose to a brass bell, I think it is just advance. If it has two vacuum hoses to a double sided bell, it is both advance under certain conditions and retard under other. This complicates matters and IIRC was designed to work with the complex smog equipment starting in the mid 70s. Older engines of all makes just had advance I think. There are two components to advance: centrifugal advance, which happens within the dizzy; and vacuum advance, which happens at the bell mounted to the side of the dizzy. If the two components add up to too much advance, you get pre ignition. Vacuum advance should IIRC go to a port at the base of the carb, not to the intake manifold or top of carb. IIRC you should set timing at idle with the vacuum advance hose pulled and plugged (a golf tee works); someone correct me if I'm wrong. If you have de smogged your engine, it might not play well with both vacuum and centrifugal advance. Pull the vacuum line, plug it with a golf tee, cap it off at the bell with a rubber cap from Autozone general parts section, and set the timing to stock. Drive it and see if that cures it, how much power it has, etc. To really measure centrifugal, vacuum, and total advance, you need a timing light with advance measuring capability and you can rev the engine and see how much advance you are getting. I forget what the total should be but your TOTAL ADVANCE may be too much. Also, leaded fuel from the 70s had REALLY HIGH OCTANE. Lead is the ultimate octane booster (high octane = resistance to explosion or detonation). So yes older vehicles were designed to run on high octane. Don't drive an engine with ping too much, you will most likely crack a piston ring then you too will have a new engine or a V8 swap. All this is from memory at least 5 years ago.

 

[Groucho263]

Data point from 2024 for anybody else looking...was looking for info on the pinging for my 2F. My timing was off, so I adjusted back to 7btdc and it's running great.