engine pinging

[ALX69RR440]

Hello all,

Ok I finally started to work on the car and I have a question. The car pings at around 4500 RMP. The initial timing is 13 and 32 total at 2500 RPM. I’m running 91 gas. I tried backing off the timing and it still pings.
I replaced the cap/rotor, wires and plugs (champion something or other) I have an MSD so I set the gap at 50 (is this ok? Old plugs were set at 40. I didn’t notice a change).
Ran the car and still pinging at 4500 RPM.
By mistake I filled the tank with 87. On the way home pinging started at 2800 RPM.
I pumped all of the gas out of the tank and put in 5gal of 110 leaded and 17gal of 91. Pinging stopped! And is running great! Question is, previous owner says car is 9.5:1 compression. 91 should be good right?

Engine info:
68 440 HP Performer RPM intake Holley 750 mechanical secondary
Cam unknown (is there a way to find-out approximate cam specs without tearing down the engine?) Only info I found was a receipt that said "cam 270-280"
Mopar performance distributor
MSD 6AL

Thank you!!

 

[69hemibeep]

Sounds as if you have more compression that that. How was the engine temp? The balancer ring may have moved if its old showing the wrong timing.

 

[A31PKG]

X2

Also, what is your vacuum reading at idle? Is your vacuum advance hooked up?

 

[moparchris]

Sounds as if you have more compression that that. How was the engine temp? The balancer ring may have moved if its old showing the wrong timing.

Yep like he said. The stock heads (906s) are pretty bad at fending off detonation. A true 10 to 1 motor with a small cam will ping in the higher RPMs when cylinder pressure builds. Stick cars make it worse.

 

[ALX69RR440]

Sounds as if you have more compression that that. How was the engine temp? The balancer ring may have moved if its old showing the wrong timing.

I have the stock temp gage and it was reading normal temp. The engine was built in the 90’s but the car sat in a warehouse and was driven no more than 1000 miles since it was built. The engine was built by Bob Lambeck in Northridge CA and in the documentation it shows that the cam was degreed if that means anything. (Sorry new to this)

X2

Also, what is your vacuum reading at idle? Is your vacuum advance hooked up?

Vacuum advance is not hooked up. Do I measure vacuum at the base of the carb? I don’t see anything on the manifold.

Sounds as if you have more compression that that. How was the engine temp? The balancer ring may have moved if its old showing the wrong timing.

Yep like he said. The stock heads (906s) are pretty bad at fending off detonation. A true 10 to 1 motor with a small cam will ping in the higher RPMs when cylinder pressure builds. Stick cars make it worse.

Hi Chis, I’m Alex you met me at Mascar. I’m taking it in to get the rust work done the first week in September.
Well, I have a notebook that details the engine build but it means nothing to me it has a bunch of numbers I don’t understand. I just looked at it again and I’m able to make out 644561 crane cam and 103509 Venolia.
The previous owner said that he changed his mind after all the parts where purchased and he had Bob cut the dome on the pistons to lower compression to 9.5 and at that time the cam was reground but doesn’t know the final specs. Also, in the valve size section there are numbers for each valve:
INT Ex
1 2139 1812
3 2140 1810
5 2141 1808
2 2139 1812
4 2140 1812
6 2140 1812
8 2140 1809

 

[SomeCarGuy]

A few things-

91 is pushing it for 9.5 at low sea level...

You will find a ported vaccum and manifold vaccum on the carb. Look around the base for manifold.

He could have miscut the dome and not got enough. Might have left some sharp edges and they are creating hotspots.

How thick are the head gaskets? If these are 906s, might have used a steel sim. Could go to a thicker one and be good. Longshot.

Plug check? Might be real lean. That would cause this. A 160 stat could be lowering the underhood temps enough to lean out the carb.

TDC check is in order. Like was said, could have slipped.

All that considered, I tend to think that crappy CA gas is the culprit. I bet some 93 from many other states would do just fine. If you do have 906s, a set of aluminum heads may be in your future.

 

[A31PKG]

There are a lot of variables here, based on what you've shared. The following is a very basic base-line tune that may help: Connect a vaccum gauge to a manifold source, that is a source below the throttle plate. There should be a nipple on the throttle plate for this purpose. If not, you can "T" into the PCV port, but only as a second choice. Start the engine and let it idle. Make a note of the vacuum, next rotate the distributor until you achieve the highest steady vacuum reading. Then back it off about 2 inches and lock it down. This should get you in the ballpark where the engine is "happiest". From there you can experiment by advancing or retarding the timing (no more than a few degrees) to fine tune. Make sure you do this with good gas...at least premium. Some engines are happier with the vacuum advance connected, some not. Total advance with it disconnected should be about 38 degress or so at about 2500+/- RPM. Of course, there are many other things that can cause pinging, air/fuel ratio, cylinder pressures, combustion chamber temps, fuel quality, cam timing, etc, etc, but this should get you started.

 

[moparchris]

Hi Alex. I remember who you are. First off thats a great running car and is quite stout. I have built quite a few 440s and raced them in my time. I can tell you for a fact that any piston that has a dome in a 440 with 906 heads will detonate on pump gas. The dome interrupts the flame front across the piston and cause hot spots as a result. These hot spots will cause the detonation (audible ping) under load. The problem I have here with this discussion will result in a melted piston if your not careful. Here is my take on this car. I bet it has more than 9.5 to 1 if it still has a dome on the piston. The reason I say this is because a flat top piston .080 in the hole (stock smogger 440) will create a 8 to 1 engine. A zero deck (piston top even with the deck of the block) flat top piston will be in the 9.9 or 10 to 1 range. These ratios will run fine on pump fuel if the tune up is on the rich side and the timing is a little retarded AND the cooling is below 160 on mild days (less than 80 degrees). Whew. Anyways your car with a dome piston is going to have more than 10 to 1 even if the dome was reduced. Here is an easy way to find out. Do a cranking compression test. Anything under 170 psi? Pump gas ready. Over 170? Better play it safe and run some race gas in it. The problem I have with you hearing an audible ping is WAY beyond when that detonation started. I have one question. How many miles do you plan on driving that awesome Road Runner per year?

 

[ALX69RR440]

Hi Alex. I remember who you are. First off thats a great running car and is quite stout. I have built quite a few 440s and raced them in my time. I can tell you for a fact that any piston that has a dome in a 440 with 906 heads will detonate on pump gas. The dome interrupts the flame front across the piston and cause hot spots as a result. These hot spots will cause the detonation (audible ping) under load. The problem I have here with this discussion will result in a melted piston if your not careful. Here is my take on this car. I bet it has more than 9.5 to 1 if it still has a dome on the piston. The reason I say this is because a flat top piston .080 in the hole (stock smogger 440) will create a 8 to 1 engine. A zero deck (piston top even with the deck of the block) flat top piston will be in the 9.9 or 10 to 1 range. These ratios will run fine on pump fuel if the tune up is on the rich side and the timing is a little retarded AND the cooling is below 160 on mild days (less than 80 degrees). Whew. Anyways your car with a dome piston is going to have more than 10 to 1 even if the dome was reduced. Here is an easy way to find out. Do a cranking compression test. Anything under 170 psi? Pump gas ready. Over 170? Better play it safe and run some race gas in it. The problem I have with you hearing an audible ping is WAY beyond when that detonation started. I have one question. How many miles do you plan on driving that awesome Road Runner per year?

Great info! I estimate less than 1000 a year. I'm now worry that I messed something up. I got on it (5500 RPM for a few seconds) about 4 times and everytime I herd loud pinging. With the 110/91 gas mix is running great. Hopefully I didn't screw anything up.

 

[ALX69RR440]

There are a lot of variables here, based on what you've shared. The following is a very basic base-line tune that may help: Connect a vaccum gauge to a manifold source, that is a source below the throttle plate. There should be a nipple on the throttle plate for this purpose. If not, you can "T" into the PCV port, but only as a second choice. Start the engine and let it idle. Make a note of the vacuum, next rotate the distributor until you achieve the highest steady vacuum reading. Then back it off about 2 inches and lock it down. This should get you in the ballpark where the engine is "happiest". From there you can experiment by advancing or retarding the timing (no more than a few degrees) to fine tune. Make sure you do this with good gas...at least premium. Some engines are happier with the vacuum advance connected, some not. Total advance with it disconnected should be about 38 degress or so at about 2500+/- RPM. Of course, there are many other things that can cause pinging, air/fuel ratio, cylinder pressures, combustion chamber temps, fuel quality, cam timing, etc, etc, but this should get you started.

Thank you. I’ll try doing this. Currently total is set at 32/2500 RPM.

 

[moparchris]

Hi Alex. I remember who you are. First off thats a great running car and is quite stout. I have built quite a few 440s and raced them in my time. I can tell you for a fact that any piston that has a dome in a 440 with 906 heads will detonate on pump gas. The dome interrupts the flame front across the piston and cause hot spots as a result. These hot spots will cause the detonation (audible ping) under load. The problem I have here with this discussion will result in a melted piston if your not careful. Here is my take on this car. I bet it has more than 9.5 to 1 if it still has a dome on the piston. The reason I say this is because a flat top piston .080 in the hole (stock smogger 440) will create a 8 to 1 engine. A zero deck (piston top even with the deck of the block) flat top piston will be in the 9.9 or 10 to 1 range. These ratios will run fine on pump fuel if the tune up is on the rich side and the timing is a little retarded AND the cooling is below 160 on mild days (less than 80 degrees). Whew. Anyways your car with a dome piston is going to have more than 10 to 1 even if the dome was reduced. Here is an easy way to find out. Do a cranking compression test. Anything under 170 psi? Pump gas ready. Over 170? Better play it safe and run some race gas in it. The problem I have with you hearing an audible ping is WAY beyond when that detonation started. I have one question. How many miles do you plan on driving that awesome Road Runner per year?

Great info! I estimate less than 1000 a year. I'm now worry that I messed something up. I got on it (5500 RPM for a few seconds) about 4 times and everytime I herd loud pinging. With the 110/91 gas mix is running great. Hopefully I didn't screw anything up.

At a thousand a year its not outrageous to buy, and run it on race gas. I buy 2-3 drums of fuel a year and Its about 350-400 a barrel these days. I dont think you screwed anything up but I wouldn't push my luck. I run several cars off those drums too. I run 50/50 mix of 111 and 91 in my heaps. I bet a 55 gallon drum would last a year for you mixing it 50/50.

 

[ALX69RR440]

Hi Alex. I remember who you are. First off thats a great running car and is quite stout. I have built quite a few 440s and raced them in my time. I can tell you for a fact that any piston that has a dome in a 440 with 906 heads will detonate on pump gas. The dome interrupts the flame front across the piston and cause hot spots as a result. These hot spots will cause the detonation (audible ping) under load. The problem I have here with this discussion will result in a melted piston if your not careful. Here is my take on this car. I bet it has more than 9.5 to 1 if it still has a dome on the piston. The reason I say this is because a flat top piston .080 in the hole (stock smogger 440) will create a 8 to 1 engine. A zero deck (piston top even with the deck of the block) flat top piston will be in the 9.9 or 10 to 1 range. These ratios will run fine on pump fuel if the tune up is on the rich side and the timing is a little retarded AND the cooling is below 160 on mild days (less than 80 degrees). Whew. Anyways your car with a dome piston is going to have more than 10 to 1 even if the dome was reduced. Here is an easy way to find out. Do a cranking compression test. Anything under 170 psi? Pump gas ready. Over 170? Better play it safe and run some race gas in it. The problem I have with you hearing an audible ping is WAY beyond when that detonation started. I have one question. How many miles do you plan on driving that awesome Road Runner per year?

Great info! I estimate less than 1000 a year. I'm now worry that I messed something up. I got on it (5500 RPM for a few seconds) about 4 times and everytime I herd loud pinging. With the 110/91 gas mix is running great. Hopefully I didn't screw anything up.

At a thousand a year its not outrageous to buy, and run it on race gas. I buy 2-3 drums of fuel a year and Its about 350-400 a barrel these days. I dont think you screwed anything up but I wouldn't push my luck. I run several cars off those drums too. I run 50/50 mix of 111 and 91 in my heaps. I bet a 55 gallon drum would last a year for you mixing it 50/50.

Ok, Thats what I'll do then. I'll do the compression test first to make sure and then buy a drum of gas. Can you recomed a brand/grade and where to buy it? I paid $50. for 5gl of VP 110 leaded.

 

[ALX69RR440]

is there a way to find-out approximate cam specs without tearing down the engine?

What’s your choice of sparkplug? And gap size with MSD?

You might not have enough information but what’s a good initial and total timing setting? (Street tuning. Just driving to the local MOPAR club meetings and the occasional red light to red light sprint)

 

[SomeCarGuy]

You can measure the cam with a dial indicator.

If you have the octane to support, bumping timing up a few degrees to 34-38 may net some decent gains. The curve may need reworked as it may start hard with more initial. I like mine to start with just a bump of the key and little cranking.

 

[nicanor]

Don't you think bringing the car to a good dyno shop might help the problem? I had similar problems with my 69 Corvette and the dyno shop was able to make adjustments that gave me tons of power with high compression using regular pump gas. I know we think these dyno shops are mostly for fuel injected, but the one who tuned my car in, did an outstanding job.

Good luck,
Barry

 

[moparchris]

Don't you think bringing the car to a good dyno shop might help the problem? I had similar problems with my 69 Corvette and the dyno shop was able to make adjustments that gave me tons of power with high compression using regular pump gas. I know we think these dyno shops are mostly for fuel injected, but the one who tuned my car in, did an outstanding job.

Good luck,
Barry

A dyno will show detonation by a immediate jump in the Brake Specific Fuel Consumption. A chassis dyno doesn't have that capability but a good dyno guy could figure it out. I run F&L SP1 fuel. It is 111 octane leaded and it is 6.5 a gallon. The more you buy the deeper the discount. I am trying to piggyback onto a local off road race team since they order 100 55 gallon drums at a time! I would run it at 36-38 total timing with the vacuum advance disconnected. With MSD I run gaps in the .050 range. As far as the cam you would have to degree it to see what the specs are. In a B-body doing a degree with the motor in the car is nearly impossible due to the crank being so close to the K frame. I would just not worry about it since it runs real good and a reputable guy put it all together and speaking from personally seeing the car, the guy who put that car together really knew what he was doing.

 

[mcmopar]

Instead of buying and storing a 55 gallon drum of racing fuel you might want to try a product called Octane Supreme 130. You can find it at many sites on the internet. It is real tetraethyl lead - the same stuff that used to be in gasoline back in the day our cars were new. The websites will tell you how much to add to a tank of gas to get to a certain octane rating when using 89, 91 or 93 octane fuel. It comes in qt. plastic bottles so it is much easier to store than a large drum of fuel and will stay fresh a very long time.
I personally used a product that used to be on the market called Max Lead 2000 which is very similar to the Octane Supreme 130. It too was tetraethyl lead. I am running about 10.5:1 compression and 36 degrees advance of initial timing. It pinged like crazy when I first bought the car but after a tear-down, some head work and a bigger cam it pinged less but was still there. After experimenting with the amount of Max Lead 2000 needed to make the pinging stop I found that all I needed was 6 ounces per tank of 87 octane! It did not take nearly as much as the website said I would need. Shop around and you may find that your price will be anywhere from 25 to 50 cents per ounce. I used to buy 4-6 bottles at a time but if you buy a 12 bottle case you can do even better price-wise. I had great success with the Max Lead 2000 and from what I have read online the Octane Supreme 130 is supposed to have tested better (gave more octane per ounce) than the Max Lead 2000 did.

 

[moparchris]

Instead of buying and storing a 55 gallon drum of racing fuel you might want to try a product called Octane Supreme 130. You can find it at many sites on the internet. It is real tetraethyl lead - the same stuff that used to be in gasoline back in the day our cars were new. The websites will tell you how much to add to a tank of gas to get to a certain octane rating when using 89, 91 or 93 octane fuel. It comes in qt. plastic bottles so it is much easier to store than a large drum of fuel and will stay fresh a very long time.
I personally used a product that used to be on the market called Max Lead 2000 which is very similar to the Octane Supreme 130. It too was tetraethyl lead. I am running about 10.5:1 compression and 36 degrees advance of initial timing. It pinged like crazy when I first bought the car but after a tear-down, some head work and a bigger cam it pinged less but was still there. After experimenting with the amount of Max Lead 2000 needed to make the pinging stop I found that all I needed was 6 ounces per tank of 87 octane! It did not take nearly as much as the website said I would need. Shop around and you may find that your price will be anywhere from 25 to 50 cents per ounce. I used to buy 4-6 bottles at a time but if you buy a 12 bottle case you can do even better price-wise. I had great success with the Max Lead 2000 and from what I have read online the Octane Supreme 130 is supposed to have tested better (gave more octane per ounce) than the Max Lead 2000 did.

Thanks for the info. I am scared of running an octane booster from horror stories passed on through the years. I even had a customer that melted a piston in his Mustang while using 104+. This sounds like its working for you and might be a viable and cheaper option!

 

[ACME A12]

Very interesting stuff, John. I may have to try some of that stuff. I have to add octane booster to Pinkie. It's not quite as bad since I put the Dart Pro 1 heads on it, but back when I was running the cast iron Bowtie Race heads it was an absolute necessity.

 

[mcmopar]

Most octane boosters use something other than tetraethyl lead which can cause serious problems. You may need to check your state's emissions laws to use this stuff. In Florida we don't have any vehicle emissions testing so we can get away with it. I doubt it would be legal for street use in California. It is sold with the proviso that is is for "off-road" use only.