[john]

I have a 70 440 challenger that has picked up a ping I can't seem to shed.I have tried every thing I can think of but no success.

[dave-r]

What temperature is it running at? How many degrees initial timing do you have? How many degrees total timing (without vacuum) do you have? When does it 'ping'?

[john]

About the temp,the engine pings warm or cold.It is much more noticable when the engine is warm.Initial timing is at 5 degrees now but has even been retarded past 0 with no change in the ping. I do not know what the total timing degrees I've never cheked it. I have disconected the vacuum line and tried to see if there was a change but that didn't work. I've even tried a knew distributor. I also took the heads off to check for carbon crystals or anything out of the ordinary inside,nothing there. The ping comes under light to moderate acceleration. It will not ping just being reved or if I power brake it.At cruising speeds I can hear it now and then but if I touch the gas to accelerate a little then I hear it well.

[dave-r]

OK. So your saying that advancing or retarding the timing makes no difference to the noise? If for example you put your initial timing back up to 10 degrees BTDC it gets no worse? Does it not get any louder or come on any easier?

In that case I doubt it is 'ping' you are hearing. More likely a leak in the exhaust somewhere near the engine. Possibly a header gasket.

You could try advancing your timing more and more until you are sure it is pinging to compare that noise with what you are hearing.

Also just make sure your fuel mixture is not too lean.

[john]

It is without a dought a ping. It does actualy get worse when I advance the timeing.It is a louder and more frequent ping.I retarded the timing so far the car barly ran and the pinging was almost non existant but still there.It sounds like a hammer hitting inside the cylinder and makes a interesting ringing noice,not a knock but a ring(we call it a ping). I have richend till I blew black smoke and fouled my plugs and that did nothing for me. After that I put new plugs and wires on and had the carb profesionally tuned and power balanced.

[dave-r]

And you are hearing it in every cylinder on every stroke? Or only some or one cylinder?

[dave-r]

If it was professionally tuned you have already paid to have this problem fixed. Take it back and tell them to put it right. That is what you paid them to do.

Does using high octane fuel make it better? What about adding booster to the tank? What compression pistons have you got in there?

[dave-r]

Another thought. If it was running rich for a long time before you got this problem or it has got a lot of miles on it without a top end re-build it is possible that carbon build-up in the chamber/valves will do this.

[Tore]

maybe the camshaft is worn out, and some of the valves not open fully, and it's going lean.

[dave-r]

The mixture would not change that way. Just the total amount of air/fuel. But even a very worn cam would still open pretty much all the way. If you lost as much as 20-40thou off the base circle of a cam lobe the valve train would get very noisy and clatter a lot due to the lack of lifter pre-load.

[Tore]

I had the same problem on my 440 and when i changed my worn out cam with a new the pinging disepear

[dave-r]

Only the carb can change the air fuel mixture. The noise your engine was making was probably mechanical. There is no way on this earth that valve timing can effect air/fuel ratio.

[Christer]

I think that Tore has a point there. Rip off the valve covers, twist the crankshaft and try to measure how much the valves open. If you measure the valvelift in the same way on all the valves, you will see if any valvelift differs from the rest.

[dave-r]

You have to wait for each lifter to bleed down every time before you measure it if you do that.

But what has that got to do with Johns problem?

Unless you are saying he can't tell a tappet noise from detonation (pinking). Which is possible as they can sound very similar. But a worn cam lobe or lifter tends to be noisy at idle or when revved and John is saying the noise only happens under load.

Please explain to me how less valve lift could make it lean???

[Christer]

I guess all modern camshafts are overlapping in various degree. That is, both intake and exhaust valves are open at the same time (for a very short time).
Let us take the intake stroke for an example: The intake valve is not only open when the piston is moving downwards. The intake valve starts to open BEFORE the piston has reached it´s TDC and closes AFTER the BDC (Top- and Bottom Dead Center).
If we take a look at the end of the intake stroke, the piston has started moving upwards a little bit but the intake valve is still open! That means that the piston can not start to compress the air/fuel mixture because the camshaft engineers has consciously enabled the combustion chamber to "bleed" a little pressure. Why? Because the gain in having more air/fuel mixture in, is bigger than the loss in pressure (the high flow and the gravity of mass is the reason why the combustion chamber still fills up in spite that the piston is on it´s way up).
If the intake valve is closed when the piston starts to move up, the pressure in the combustion chamber indeed will be higher. If you from the start have a high numerical compression relationship (for example 10:1 or 11:1) this absense of "pressure bleed" might have the effect in a "ping". The engine is pumping pressure in a to large extent!
I hope this makes sence to you. I took the intake stroke for an example. The other strokes act in similar ways. (The problem might as well be a exhaust valve that does not open properly)

[dave-r]

I am not sure that would result in higher cylinder pressures in practice. BOTH valves would have to close early/open late otherwise the pressure would vent through the other valve. There is not much in the way of valve overlap with a stock or near stock cam anyway. It is only high duration cams that have overlap in the range where an increase in compression is necessary.
But I take your point. IF the engine has high compression pistons AND a worn camshaft it may well start to 'pink'.
BUT! A cam that worn would be going 'CLACK, CLACK, CLACK' all the time unless it has adjustable rockers and he adjusted the wear out of the equation. But it would not take long to get noisy again if that was the case because a cam that worn wears ever quicker.

[john]

My engine is a newer rebuild. It has about 7,000 miles since it was rebuilt. It is bored 30 over with stock flat top pistons so I'm not sure on the exact compression ratio. It was professionally rebuilt by a machine shop, even the heads. I do use high octane gas and octane boost but it doesn't seem to help much. I have had the heads off to inspect the valves and to check for carbon buildup but it was exceptionally clean inside. Though I didn't check inside the vales. I was only thinking of the pistons and cylinders. It is hard to say it comes from one or more cylinders but I truly believe from the sound it comes from the right bank and maybe just one cylinder. The reason is that the noice doesn't seem frequent enough to be more the one cylinder. It seems if it was more than one cylinder it would sound like a string of fire crackers. It doesn't sound like that. It is a single ping that is erratic.

[john]

Oh, another thing also which would put the worn cam shaft idea away is the car has not lost much porformance if any at all. It is still very srong and responsive. It just has this pesking ping that I can't shake. I've had a lot of so called profesionals look at it but not a one has been able to give me the right clue to fix it. Every body has thier own ideas and some act like if I keep feeding it high octane gas it will cure its self. I don't want to blow a hole in the top of my piston first. The ping started when I was on my way to a car show. I was 400 miles into the trip when I started to hear it. Here's the reason I thought that it was carbon, I decided to save money and buy cheap gas. SO when I heard the ping I quickly went to gas station got high octane gas and booster for my car. It has been atleast 1500 miles since that day whith no luck yet. I have not put in cheap gas since and never will again.

[dave-r]

What worries me is that this happens even when the engine is cold? It would be interesting for you to hook up an aftermarket temp guage to see exactly what temp this engine is running at. It may simply be too hot around that cylinder.

The people who have looked at this problem are not professionals in my book. A REAL professional with a rolling road and diagnostic tuner would have pinned this problem down to the exact conditions, location and cause in no time at all.

Lets face it. From thousands of miles away I have little chance of finding the problem for you. I can't even hear it!

[Bill]

Dave,
Any possibility that John has leaky plug wires or that they are not routed correctly and are cross-firing? I know that most people like to keep their wires nice and straight for appearance sake but by running wires parallel to one another, they can interfere with one another causing symptoms very much like a bad miss or pre-ignition.

[john]

Bill, that is a darn good point and mine were cross firing bad. I had cheap wires that were only 6 months old but didn't stand up the heat I'm guessing. One night I opened my hood while the car was running and I saw a nice lighting show. I quickly bought a new set. I spent 100 dollars on accell 8.8 mm high temp wires that have stainless steel under the outer layer that is supposed to help stop cross fireing. I thought I had the problem licked but no it is still there. O.k., should my intake get hot enough to boil a drop of gas or singe skin if touched? If not mine does,why is this? If that is not normal how can I fix it? My temp gauge always reads in the norm and the radiator has never boiled. I've driven it on long road trips with no problems. Here is something that may or may not be part of tha puzzle. Just before this road trip I discovered that my car did not have a thermostat. The car never came up to temp, atleast according to the gauge. I had assumed it was a faulty gauge or sending unit and replaced both with no change. So I took off the thermostat housing and no thermostat. So I put one in. Maybe temp has something to do with it but then I think of a cold start and it will ping. Maybe there is something to Dave's idea of one cylinder heating to hot. I do have headers on this car. Maybe a header leak is making things to hot. If there is a leak I haven't noticed but I have been so focused on the ping. The headers are old and have been with the car for quite a while. Could they cause the temp under the hood to climb to high? The problem I have with people around here touching it is noone carries 70's service manuels anymore and very few if any do I trust on carborated engines. No manuels and no experience I'm not spending the money for someone to stare at it anymore. I just don't know anyone with the knowledge and equipment.

[Christer]

I still believe that the ping is caused by a worn cam. This can quite easily be checked as I described above. Just measure the distance between the top of the rocker arms and the head when the valves are fully open. It is easier to twist the crankshaft if you unscrew the sparks first.
I am not surprised that you do not experiance any loss in power. Please, don´t laugh now, I will try to do a "homebuilt" calculation. Let´s say that your engine delivers 400 hp when it´s fully OK. Let´s say that 7 cylinders deliver 100% now and that the eighth only deliver 50%. If you muliply 400 with 7.5 and divide it with 8 you get 375 hp. I think it is very hard to recognize a difference of 25 hp! (I know this calculation is not 100% adequate but might give a clue....)
God luck with your engine, and please tell us how it went when you have fixed this problem.

[Tore]

The problem you have John is exactly like the one i had, and then it was the camshaft, just check it out. It's very difficult to recognize difference in power

[dave-r]

I like Bills idea better.

[Christer]

I have a new theory why a worn cam creates a "ping":
Assume that one exhaust cam lobe is worn. This means that the gases won´t flow out through the exhaust port as it is thought. Instead a part of the gases is beeing compressed and left in the cylinder. Then this leftover becomes mixed with the air/fuel mixture that flow in through the intake port. And there you are, you got a problem with a too lean mixture!!!!!!
At least in my head this discussion feels correct.

[dave-r]

Better. But I'm still not convinced because I think a cam lobe that worn would be making a big 'clack,clack,clack' sound. You do get exhaust gasses coming up through the intake runners anyway. In particular on cars with inefficient exhaust systems or large amounts of valve overlap.

This is what makes a carb go black in the venturies after time.

[dave-r]

I still like Bills idea best. But a 'Pro' tuner should have picked up on it still.

John. Read up on the stuff I wrote in the electrical section. If you get a shock from touching the wires or can see then glowing in the dark there is something very wrong.

The intake will get hot. You can't tell what the water temp is from the factory temp gauge. Mine always read low no matter what I did. Turns out it was underestimating the water temp by a good margin. I don't know if it is worth buying a good one at this stage though. An increase in water temp would normally effect all the cylinders.

An electrical problem would only effect one. My moneys still on Bill.

[Christer]

Tore, do you know any good pub where we can have a paint? They are not listening to us anyway

[dave-r]

Pint! Christer. PINT!

Drink paint and you will know about it! Your toilet bowl will look like Andy Warhol has been messing on in your bathroom!

[Christer]

Sorry! That was a colourful mistake. (but it gave me a laugh....)