340 Pinging using 94

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for high c/r motors , try e85 it's oc rating is much higher and its less costly . you may have to rejet your carb for it
 
pomonamissel said:
for high c/r motors , try e85 it's oc rating is much higher and its less costly . you may have to rejet your carb for it
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May have to reject carb? Yea like buy a whole new carb that flows 33% more fuel. E85 is corn based ethanol, alcohol. You most definitely will need more fuel. And a lot of it.
 
dterry1 said:
I can take a video.

For the "Vehicles don't ping decelerating", why is that? The engine is still firing while decelerating, it's just doing so at a lower RPM. And if the detonation is now occurring at a lower RPM after retarding the timing, I don't see how it's out of the question.

Now I could very well be wrong, and I am not using experience to justify my thoughts, just logic.
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Yes, the engine is firing, but the load on the engine is not there like it is while accelerating. With the throttle blades closed, there is very little fuel being fed into the cylinders.
 
dterry1 said:
Tbh, I have no idea how lower octane will help reduce it

It is what my mechanic recommended
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Your mechanic recommended?? I recommend trading him in for a different model. He should first be looking at the plugs to see if it is one cylinder or all.
As Rusty suggested, a vacuum leak can cause detonation and finding a vacuum.leak is fairly simple with an unlit propane torch. Turn the propane on and direct to the intake gaskets, carb base gasket and vacuum hoses. If the idle changes that is most likely the vacuum leak.
Considering this just started, the possibility of fuel could be possible, but only if high compression was built into the engine. Octane boosters are a bandaid for your real problem. Again pointing the finger at your mechanic, he should have the tools and knowledge to check the advance curve. Rusty could be correct on a broken advance spring.
Another consideration could be a bit of carbon getting hot in a cylinder or two, igniting the mix early.
New to the hobby, eh. I would find a local car club and get to know the people. Every club has people that are good with body work, interior, engines, paint and other components. Many times you can swap time in your talents for time in theirs. And that does not necessarily have to be automotive related. Some have bartered body work or a differential overhaul for getting a deck built. You meet some nice people and save some of that hard earned cash that the left dishonourable prime peckerhead of Canada, daesh dustbin turdo is fervently making harder to come by and to keep.
 
dterry1 said:
I can take a video.

For the "Vehicles don't ping decelerating", why is that? The engine is still firing while decelerating, it's just doing so at a lower RPM. And if the detonation is now occurring at a lower RPM after retarding the timing, I don't see how it's out of the question.

Now I could very well be wrong, and I am not using experience to justify my thoughts, just logic.
Click to expand...
Ping is a description of detonation or preignition. Both can sound like a can of marbles. Detonation and preignition are two separate conditions.
Detonation is a combustion issue caused from a combustion problem. The spark can be occuring too soon, a lean mixture, poor mixture motion allowing a dead spot to get to the auto ignition pressure and temperature.
Preignition is something in the cylinder gets red hot and ignites the air/fuel mix before it is supposed to be ignited. This can be a bit of carbon stuck on the head or piston, too hot spark plugs or a sharp edge.
You stated you do not know about plug temperature ranges. This relates to the heat path for cooling the ceramic of the plug. A hot plug has a long ceramic looking past the ground to where the ceramic is sealed to the metal body. A cold plug has a shorter ceramic. The center electrode and ground will be in the same location for a plug style.
Conventional plugs have the electrode close to the height of the end of the threads of the body. Extended core or tip plugs have a longer ground and the electrode and ceramic stick farther into the combustion chamber. Depending on the cylinder head design, extended core plugs may move the gap closer to the center of the combustion chamber to equalize burn travel distance. On some engines the extended core could interfere with a piston or valve.
Lower compression and low RPM street operation require a hotter spark plug to burn deposits off the ceramic, which can lead to misfiring. Higher compression, higher loads or high RPM generally require a colder plug so they do not overheat and cause preignition. These running conditions cause higher combustion temperatures which will get the colder plugs up to self cleaning temperature.
I hope that explanation helps.
 
dterry1 said:
Actually no, that's why I think it might be the lack of fuel additive, it slowly got worse (I'm assuming as i refilled the tank, the additive got more and more diluted).
It has stopped getting worse, and it's much, much better after I retarded the distributor, although it isn't completely gone.
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Possible you pumped a low octane fuel by mistake, as in wrong fuel at station.
 
If you want to get an idea of how EFFECTIVE cylinder pressure is related to throttle position, just do a compression test with the throttle closed, and record the pressure on each stroke.
You might get a number like 90 psi on the first shot, then
120 , then then 140,150,155 and so on, but eventually, given enough compression cycles, you will get to the same number that you would get with the throttle at WOT. The difference is that on a good engine, at WOT, it might take half as many cycles, and the First shot will be significantly higher..

The same thing happens while you are driving, at various throttle settings and various rpms.

Knowing the specifications of the engine, it is possible to back calculate the Effective Compression Ratio from the cylinder pressure. When you do that, you will find out that;
your Effective compression ratio at IDLE might be just 5or6 to 1.
And at 2000 rpm , with the throttle closed and under decel, it might be a tad higher.
And at WOT at rpm of Peak Torque, you could be pushing 11:1 or more Effective, depending on the cam and combo.
And at Part Throttle, you can vary the Effective CR anywhere in between, just by adjusting the throttle position.
In fact, you could even hold the throttle at a steady position in a fixed transmission gear; and the Effective Compression could change everywhere throughout the rpm range as engine efficiency wanders around.
Why is this important?
Well, pressure makes heat, and heat makes power, so the more heat your engine can generate, the more power it can build ....................... right up until the design can no longer deal with the heat. When that happens she can get into preignition and/or detonation, which leads to destruction of parts. So the goal of the Builder and the Tuner, is to not let that happen, by keeping the chamber temperature under control. To do that, we have a number of tools in our toolkit that we can use;
1) anti-detonant,
2) reduced Effective cylinder pressure
3) retarded ignition timing
4) reduced load
5) a reduced cooling system temperature


As others have said, detonation under closed throttle deceleration is as good as impossible...................... because that eliminates all five of the things that can lead to detonation. Yes, it can, still happen, but it's gonna take a hot glowing spot in the chamber to initiate an uncontrolled and inappropriately timed, point of ignition
 
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AJ/FormS said:
If you want to get an idea of how EFFECTIVE cylinder pressure is related to throttle position, just do a compression test with the throttle closed, and record the pressure on each stroke.
You might get a number like 90 psi on the first shot, then
120 , then then 140,150,155 and so on, but eventually, given enough compression cycles, you will get to the same number that you would get with the throttle at WOT. The difference is that on a good engine, at WOT, it might take half as many cycles, and the First shot will be significantly higher..

The same thing happens while you are driving, at various throttle settings and various rpms.

Knowing the specifications of the engine, it is possible to back calculate the Effective Compression Ratio from the cylinder pressure. When you do that, you will find out that;
your Effective compression ratio at IDLE might be just 5or6 to 1.
And at 2000 rpm , with the throttle closed and under decel, it might be a tad higher.
And at WOT at rpm of Peak Torque, you could be pushing 11:1 or more Effective, depending on the cam and combo.
And at Part Throttle, you can vary the Effective CR anywhere in between, just by adjusting the throttle position.
In fact, you could even hold the throttle at a steady position in a fixed transmission gear; and the Effective Compression could change everywhere throughout the rpm range as engine efficiency wanders around.
Why is this important?
Well, pressure makes heat, and heat makes power, so the more heat your engine can generate, the more power it can build ....................... right up until the design can no longer deal with the heat. When that happens she can get into preignition and/or detonation, which leads to destruction of parts. So the goal of the Builder and the Tuner, is to not let that happen, by keeping the chamber temperature under control. To do that, we have a number of tools in our toolkit that we can use;
1) anti-detonant,
2) reduced Effective cylinder pressure
3) retarded ignition timing
4) reduced load
5) a reduced cooling system temperature


As others have said, detonation under closed throttle deceleration is as good as impossible...................... because that eliminates all five of the things that can lead to detonation. Yes, it can, still happen, but it's gonna take a hot glowing spot in the chamber to initiate an uncontrolled and inappropriately timed, point of ignition
Click to expand...
Re:compression cycles: testing compression in diesels an injector is removed, the fuel bypassed and the engine started.
In gas engines all plugs are removed. I used 5 compression strokes to get the compression reading. You will get to a point that the reading no longer climbs, but generally 5 is close enough for a realistic reading.
You will not ever get a compression reading of cylinder pressure during combustion, peak cylinder pressure, without special test equipement. Under load the cylinder pressure could be 1,500PSI.
 
Dale Davies said:
Re:compression cycles: testing compression in diesels an injector is removed, the fuel bypassed and the engine started.
In gas engines all plugs are removed. I used 5 compression strokes to get the compression reading. You will get to a point that the reading no longer climbs, but generally 5 is close enough for a realistic reading.
You will not ever get a compression reading of cylinder pressure during combustion, peak cylinder pressure, without special test equipement. Under load the cylinder pressure could be 1,500PSI.
Click to expand...
Is there a point of contention here to what I said, or are we on the same page?
 
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