Help - Pinging Problem

[Keith Heberling]

Car is a 1963 Avanti, R1 automatic, fully restored in early nineties, driven occasionally. Pinging problem has developed over last year or so. Plugs are correct and proper burn. Replaced Carter with new Edelbrock which was set up correctly. Valves were set to spec. Replaced Prestolite distributor with new Mallory electronic, the oil pressure vacuum is good. Problem is this, I cannot find the sweet spot in setting the timing. If I advance the timing the pinging is worse, I have retarded the timing as far as possible until engine runs rough and some pinging still there. There is no in between. Use premium gas with and without octane booster. None of these changes have made a difference at all. . One clue that may be helpful here – when engine is cold there is no pinging, when engine temp reaches 180 degrees, it begins to ping when accelerating during cruising speed. It gets increasingly worse as it tops out at 205 degrees. Sound is a pinging/chatter, like valves are floating when accelerating. Frustrated and could use some help in figuring out this problem. Thanks.

Edited August 27, 2010 by Keith Heberling

[Gunslinger]

Does the new distributor have vacuum advance or electronic? I would think vacuum or you would have knock sensors which the Stude engine doesn't have. You could have the vacuum advance hooked up to the wrong port. The Edelbrock carburetor has two places to connect the vacuum line to...ported vacuum and full-time vacuum. Edelbrock will tell you to hook up to the ported vacuum connector.

Since you've changed the distributor, the advance curve may not match the needs of the engine. It may need recurving. You may need to get a timing light that shows timing advance as well and find out what your total advance is, even if your initial advance is correct. If you're getting too much advance as rpm's increase, you definitely need to have the distributor recurved.

If the vacuum advance is coming on too fast and too much it can surely cause detonation. Engine temperature has something to do with it, but it is an aggravation of the problem, not the root cause.

A out of left field possibility...was the engine rebuilt? If so...were the heads shaved resulting in an increase in compression ratio? If the engine wasn't rebuilt, there could be deposits built up on the pistons, which also results in increased compression. I doubt if either would create the problem you describe, though. As I said...just throwing it out.

[adamderosa]

Check to see if your intake heat valve is stuck. It's located in the passenger side exhaust manifold where the down pipe attaches to the manifold. The valve has a thermostatic spring attached to it and you should be able to move it freely. If it's stuck open it can cause the intake temperature to be too high, which can cause pinging.

[Keith Heberling]

Check to see if your intake heat valve is stuck. It's located in the passenger side exhaust manifold where the down pipe attaches to the manifold. The valve has a thermostatic spring attached to it and you should be able to move it freely. If it's stuck open it can cause the intake temperature to be too high, which can cause pinging.

I did not replace the heat valve when engine was rebuilt (early nineties), left it off and did not experience any negatives not having it on. Pinging only started last year or so ago. Thanks

[Keith Heberling]

Does the new distributor have vacuum advance or electronic? I would think vacuum or you would have knock sensors which the Stude engine doesn't have. You could have the vacuum advance hooked up to the wrong port. The Edelbrock carburetor has two places to connect the vacuum line to...ported vacuum and full-time vacuum. Edelbrock will tell you to hook up to the ported vacuum connector.

Since you've changed the distributor, the advance curve may not match the needs of the engine. It may need recurving. You may need to get a timing light that shows timing advance as well and find out what your total advance is, even if your initial advance is correct. If you're getting too much advance as rpm's increase, you definitely need to have the distributor recurved.

If the vacuum advance is coming on too fast and too much it can surely cause detonation. Engine temperature has something to do with it, but it is an aggravation of the problem, not the root cause.

A out of left field possibility...was the engine rebuilt? If so...were the heads shaved resulting in an increase in compression ratio? If the engine wasn't rebuilt, there could be deposits built up on the pistons, which also results in increased compression. I doubt if either would create the problem you describe, though. As I said...just throwing it out.

It is vacuum. Followed another AOAI member's install and used passenger site port. Just for kicks I tried switching it to the driver port, no difference. I will get a decent digital timing light as you suggest. How then do I recurve the electronic distributor (nothing in the instructions).

I'm curious about the temp situation — no pinging, car runs fine for 10 minutes or so, I can punch it, accelerate up a hill whatever and no pinging. When it hits 185 degrees bingo, it's chatter time.

Engine was rebuilt early nineties by a reputable engine shop while I restored the car. Heads were not shaved to my knowledge.

Thanks.

[Gunslinger]

It is vacuum. Followed another AOAI member's install and used passenger site port. Just for kicks I tried switching it to the driver port, no difference. I will get a decent digital timing light as you suggest. How then do I recurve the electronic distributor (nothing in the instructions).

I'm curious about the temp situation — no pinging, car runs fine for 10 minutes or so, I can punch it, accelerate up a hill whatever and no pinging. When it hits 185 degrees bingo, it's chatter time.

Engine was rebuilt early nineties by a reputable engine shop while I restored the car. Heads were not shaved to my knowledge.

Thanks.

I believe the passenger side vacuum connect on the Edelbrock is the ported vacuum, so you're OK there. That temperature thing is baffling...not sure what to make of it and its connection to the problem. How is your PCV valve connected? The Edelbrock carburetor is not drilled and tapped for it like the original AFB was...you have to drill and tap the connection...Edelbrock says to do so in the front, not the back as on the AFB. That shouldn't make a difference for your problem...just bringing that up.

If it turn out your distributor actually does need recurving, it would have to be taken to a shop with a distributor machine just for that purpose.

Detonation is generally caused by too low an octane gasoline, timing advanced too far, the compression being raised, excess temperatures allowing the cylinder head or combustion chamber temps to be too high for the octane rating of the fuel to keep from having pre-ignition (detonation), or some combination of them. 185 degrees is simply not too high to cause that under normal circumstances. It can be a combination of things...maybe the compression ratio was raised, combine that with the timing or timing advance being wrong, add high temps and detonation can happen, but it just doesn't seem too likely for such a complete set of circumstances like that occurring.

I think you really need to get back to basics and eliminate what it's not. Make sure the engine is actually operating at the temperatures the gauge says and not grossly above that. Make sure the engine is tuned properly...timing according to specs (with the vacuum advance disconnected and the line plugged), good spark plugs and gapped correctly. Make sure there's no vacuum leaks anywhere. If everything checks out normal and correct, and the problem still occurs, at least you'll know what it's not.

Do you still have your original distributor? if so...reinstall that and see if the problem occurs. If it doesn't, you know the problem is in the distributor you installed. Does your Mallory have an optical trigger or a magnetic trigger? They both should have an air gap that needs to be set...that should be checked.

You haven't said, but do you have a Mallory, MSD or other brand capacitive ignition box added on? They're not always compatible with some electronic distributors and can cause problems (don't ask how I know that).

There has to be a simple cause for this...I hope you find out soon.

[Keith Heberling]

I believe the passenger side vacuum connect on the Edelbrock is the ported vacuum, so you're OK there. That temperature thing is baffling...not sure what to make of it and its connection to the problem. How is your PCV valve connected? The Edelbrock carburetor is not drilled and tapped for it like the original AFB was...you have to drill and tap the connection...Edelbrock says to do so in the front, not the back as on the AFB. That shouldn't make a difference for your problem...just bringing that up.

If it turn out your distributor actually does need recurving, it would have to be taken to a shop with a distributor machine just for that purpose.

Detonation is generally caused by too low an octane gasoline, timing advanced too far, the compression being raised, excess temperatures allowing the cylinder head or combustion chamber temps to be too high for the octane rating of the fuel to keep from having pre-ignition (detonation), or some combination of them. 185 degrees is simply not too high to cause that under normal circumstances. It can be a combination of things...maybe the compression ratio was raised, combine that with the timing or timing advance being wrong, add high temps and detonation can happen, but it just doesn't seem too likely for such a complete set of circumstances like that occurring.

I think you really need to get back to basics and eliminate what it's not. Make sure the engine is actually operating at the temperatures the gauge says and not grossly above that. Make sure the engine is tuned properly...timing according to specs (with the vacuum advance disconnected and the line plugged), good spark plugs and gapped correctly. Make sure there's no vacuum leaks anywhere. If everything checks out normal and correct, and the problem still occurs, at least you'll know what it's not.

Do you still have your original distributor? if so...reinstall that and see if the problem occurs. If it doesn't, you know the problem is in the distributor you installed. Does your Mallory have an optical trigger or a magnetic trigger? They both should have an air gap that needs to be set...that should be checked.

You haven't said, but do you have a Mallory, MSD or other brand capacitive ignition box added on? They're not always compatible with some electronic distributors and can cause problems (don't ask how I know that).

There has to be a simple cause for this...I hope you find out soon.

First off, thank you for taking the time to put some thought into this. The sparks plugs are correct for the engine, gapped to spec and burning the way they should. I had the same problem with the old distributor, hence buying the new distributor. It's a Mallory Unilite unit which I purchased from Dave Thibealt. It connects to the resistor and coil and according to Dave is the properly matched voltage. Not sure if optic or magnetic. Vacuum last checked seemed fine. I had timing set to spec at 4 degrees, but wasn't cutting it so that's when I started retarding or advancing to see if that changed things, which it didn't. One item to note, last time I checked timing the mark was bouncing all over, I couldn't get a good read…

[Gunslinger]

If your timing mark is bouncing all over, your valve timing could be off...the timing gears aren't installed properly, a tooth on one of the gears has broken off...neither of which sounds likely as that would be causing problems all the time...not just after the engine passed 180 degrees. A vacuum leak can cause the timing marks to jump around, but that would be all the time as well.

It sounds like the distributor is not the problem...unless it's installed wrong...a cog off of the gear. That can do all kinds of funny things, but again...probably all the time.

This is really baffling...it's probably a simple problem, just one that's going to take some real testing and eliminating of possibilities to determine.

[ernier]

Your pinging increases with temprature because it is pre-ignition. The mixture is exploding with heat and compression before the piston has reached tdc and possibly before the spark occurs.

Your timing mark bouncing around could be spark scatter. You may have ignition wires that are leaking electricity and causing other cylinders to fire when they shouldn't or not fire when they should. It can also mean you have a bad cap, rotor or loose breaker plate in fact anything that would cause a misfire can show up as a bouncing timing mark. Remember all that's happening when the mark bounces is that the light is coming on, being energized, when it shouldn't. Spark scatter between the wires is the most common cause.

You could have a carbon build up that stays hot enough to begin combustion before TDC.

That being said...here's where I would start. Check mechanical advance up past 3500 rpm. Safe would be no more than 32-34 degrees even 30 would be OK. With Vacuum advance attached total timing should be no more than 44 degrees. These are estimates as all engines like different settings.

There's a curve kit available for the Mallory from Summit Racing. You may have to curve the distributor to limit mechanical advance while allowing you to run more initial advance. That's what I have to do with my R2. I run 14-15 degrees initial but limit total advance to 28-30. This way off idle performance is crisp but no ping at full throttle.

Too lean a mixture can cause pinging but timing is more common. If you feel a surge at cruising speeds you may be a little lean.

Pinging at full throttle would not be caused by your vacuum advance as vacuum disappears at the advance can at full throttle.

Try a colder plug. A J10Y or equivalent. I run R43S AC's. The colder plug means that it cools quicker between firings and may help pre-ignition by eliminating a hot spot that could light off the mixture early.

Last but not least if you fill up at the same station all the time try another place. I had a high compression Pontiac that was very touchy especially in the warm weather. If I filled up at the local Sunioco station it pinged more readily than when I filled up a few miles away. My guess is that the station was not actually selling preminum but charging for it. You never know.

ErnieR

[PackardV8]

At what ambient temp does your gauge reach 205? Mine stays around 180-185 most of the time.

Have you confirmed the centrifugal and vacuum advance totals?

jack vines

[adamderosa]

Has the pinging problem been happening since this carb was installed? If so, I wonder if it could be jetted a little too lean. This would explain why the engine runs better when it's first started, and the choke is on, enrichening the mixture. When the engine warms up and the choke comes off, the mixture leans out. The jets and metering rods are pretty easy to change on the Eldebrock cabrs if you have the tuning kit.

[Keith Heberling]

Has the pinging problem been happening since this carb was installed? If so, I wonder if it could be jetted a little too lean. This would explain why the engine runs better when it's first started, and the choke is on, enrichening the mixture. When the engine warms up and the choke comes off, the mixture leans out. The jets and metering rods are pretty easy to change on the Eldebrock cabrs if you have the tuning kit.

Good thought, I could change the metering. However, I checked the plugs immediately after a run and they were burning exactly the color they should be. If it were running rich would it not show up on the plug?

[ernier]

Good thought, I could change the metering. However, I checked the plugs immediately after a run and they were burning exactly the color they should be. If it were running rich would it not show up on the plug?

Too lean a mixture is way down the bottom of the list as a cause of pinging. You would have other symptoms as well like a surge at cruise, poor "tip in" throttle reponse meaning the car would not respond quickly to light throttle input or have a flat spot on light acceleration.

ErnieR

[PackardV8]

FWIW, with today's fuel, plug readings are not as reliable as back in the leaded fuel days.

Maybe I missed it if you posted, but what are your cranking compression, centrifugal and vacuum advance totals? These are my starting points for any ignition tuning.

jack vines

[adamderosa]

Hey Keith - just wondering, have you solved the pinging problem?

[Keith Heberling]

Hey Keith - just wondering, have you solved the pinging problem?

Sorry for the absence, I've been out of town on business. Not yet, but did get a chance to check vacuum over the weekend, no leaks, and it's pulling fine. Since my schedule is going to be hectic between work and family the next few weeks I'm going to leave the car with Randy Wolfe, an old Studey enthusiast who works at a local garage so he can check advance levels and ponder for a while. Hopefully I'll get to the bottom of this at some point. Thanks for all of your suggestions.

[Bob Bryant]

I don't have nay advice on the technical or mechanical side, but I agreed with ernier's suggestion that you try a different brand of gas. I was using a high octane product in my R-1 and having a detonation problem. I changed to a different brand of high test gas and the performance improved considerably. It happens that I am now using Sunoco.

[Keith Heberling]

I don't have nay advice on the technical or mechanical side, but I agreed with ernier's suggestion that you try a different brand of gas. I was using a high octane product in my R-1 and having a detonation problem. I changed to a different brand of high test gas and the performance improved considerably. It happens that I am now using Sunoco.

Yes, I thought that also. I've tried Sunoco 94 with and without octane booster. It contained 10% ethanol which can be an issue also, so I tried another brand's high test that contained no ethanol, with and without octane booster, and the pinging is always there after you run the car for about 1/2 an hour after it reaches temp. No change no matter what gas.

[Keith Heberling]

Sorry for the absence, I've been out of town on business. Not yet, but did get a chance to check vacuum over the weekend, no leaks, and it's pulling fine. Since my schedule is going to be hectic between work and family the next few weeks I'm going to leave the car with Randy Wolfe, an old Studey enthusiast who works at a local garage so he can check advance levels and ponder for a while. Hopefully I'll get to the bottom of this at some point. Thanks for all of your suggestions.

Update – I spoke with Randy at the Strausstown show on Sunday. After explaining the litany of fixes I've gone through with no results, his immediate thought was one or several cracked valve seats. He has seen in before in Studey engines. Exhaust leaks back into the cylinder and once engine is at temp it affects combustion and in turn causes pinging. He's going to take the car this fall, pull the heads and see what is what.

[ernier]

I gues that's possible but the general consensus has been that Stude heads aren't particularly prone to valve seat issues. I would also think that a cracked seat would bring along with it a burned exhaust valve and a subsequent miss.

Again, my Stude experience is limited only to my own R2 but I would certainly make sure of the advance curve and condition of advance mechanism in the distributor before I pull the heads.

IMHO.

ErnieR

[Twnchgr]

Update – I spoke with Randy at the Strausstown show on Sunday. After explaining the litany of fixes I've gone through with no results, his immediate thought was one or several cracked valve seats. He has seen in before in Studey engines. Exhaust leaks back into the cylinder and once engine is at temp it affects combustion and in turn causes pinging. He's going to take the car this fall, pull the heads and see what is what.

Sunken but never cracked. But these things would show up in a compression or leak down test...???