Pinging B$@&%@rd 440!

[mopower440]

440 .030 over
TRW 2355 pistons, 2.062 compression height, around 9.5:1
MP 284/484 cam installed at 104 (4 degrees advanced)
Bone stock 452 heads..no milling or porting.
Holley street dominator
Demon sizzler built TQ
1 7/8 fenderwell headers
3000 stall convertor
This is in a dart swinger. So I cant get rid of the pinging at the very last 1/8 throttle. Its fine everywhere else. I can stab it and no pinging but when i put that last bit into it, it pings. Even with secondarys open, its fine until i try to shove the pedal through the floor and it pings..Its like the secondarys are open most of the way but that teeny last bit makes it ping, but it also has a good little bit of power in that area. So if i want to richen up that last bit of the secondaries, wouldt i want to tighten the secondary air door more so it takes more to drop it open? The carb was built to the engines specs. So i sent off for a curved distributor to Ron at Halifax and it did help because it was worse but its still there. Its at 16 initial and 34 total. I believe its all in by 3200 rpm. Im thinking it has to be a slight lean spot on that last bit of throttle blade opening since there is no pinging at any other throttle position no matter how quick you stab the throttle. Its so aggrevating, i mean, i can stab the throttle to the carpet and no pinging, but then push down hard and it opens that carb that last little bit and it does this and there seems to be a nice bit of power right there..This is running 93 octane pump gas..i would think 9.5:1 could be fine on that..

 

[RustyRatRod]

What plugs?

 

[mopower440]

What plugs?

I will have to check as i cant remember. I BELIEVE i am using the standard heat range plug for a 1975 new yorker with 440 as thats what the engine came out of originally.

 

[PRH]

MP 284/484 cam installed at 104 (4 degrees advanced)

Was the cam degreed in?

Have you done a cranking pressure test?

Have you tried adding some 100+ octane gas to the tank to see if it cures the problem?

Have you tried reducing the timing a degree at a time to see how far you’d have to go to get it ping free?

 

[RustyRatRod]

Oh and also, what thermostat? When I was having detonation issues with Vixen, the number one biggest thing that helped stop it was putting in a 160 high flow thermostat. Everything else I did helped, but the thermostat stopped it.

 

[PRH]

Its like the secondarys are open most of the way but that teeny last bit makes it ping, but it also has a good little bit of power in that area.

That boost of power your feeling is from increased cylinder pressure……. Which is likely inducing the knock.

 

[dadsbee]

 

[mopower440]

Oh and also, what thermostat? When I was having detonation issues with Vixen, the number one biggest thing that helped stop it was putting in a 160 high flow thermostat. Everything else I did helped, but the thermostat stopped it.

It is a 160 and she runs between 160-170

 

[mopower440]

A better way to explain its is, if i put a stopper on the throttle plate to stop it from going beyond about 98% throttle, it would never ping, no matter how quick you stab the throttle and at whatever rpm, no ping, but you open that throttle plate that last 2% and it pings. So when the pedal hit the carpet, its fine, but put more force on the pedal to force that last tiny bit open, and here is the ping. Its not a lot but its enough and i want it gone so it doesnt hurt anything.

 

[PRH]

You said you can feel the difference…….. cylinder pressure is where that comes from.

Currently you don’t have enough octane for the conditions that exist when you bury the pedal into the carpet.

Either raise the octane, or change the octane requirement……… or put some sort of throttle limiter on the pedal.

 

[mopower440]

You said you can feel the difference…….. cylinder pressure is where that comes from.

Currently you don’t have enough octane for the conditions that exist when you bury the pedal into the carpet.

Either raise the octane, or change the octane requirement……… or put some sort of throttle limiter on the pedal.

oh man that sucks. I have been getting ready to buy some 84cc aluminum heads for this thing and thats going to raise compression even more and probably make this worse! Unless being closed chamber would help for some reason or other?

 

[1WildRT]

I will have to check as i cant remember. I BELIEVE i am using the standard heat range plug for a 1975 new yorker with 440 as thats what the engine came out of originally.

Just started to read this thread.... But Rusty asked a good question & the answer you gave is a problem... A low compression engine needs a hotter plug to keep from fouling... A higher compression engine needs a colder plug to prevent detonation.... There are plenty of other possible causes but that's a cheap easy thing to try so eliminate it as a possibility..

 

[Mopar Sam]

What rpm does it start the pinging? You could slow down the timing curve with heavier springs.

 

[mopower440]

What rpm does it start the pinging? You could slow down the timing curve with heavier springs.

well, its not really any certain rpm, its a certain throttle opening. Just an example, if its at 4000 rpm at 98% throttle opening, there is no ping, but open it that last 2% and it pings a little, even at that same rpm..The timing is all in at 3200 and it never pings unless that last tiny bit of throttle is opened, thats why i was thinking it was a lean condition. Heck, when halifax setup this distributor, he even dialed in the vacuum advance which is runs it up to like 50 degrees or something and it STILL doesnt ping when when the vacuum is working..Obviously the vacuum advance drops out when stabbing the throttle and i didnt even run the vacuum at first and it still does this, so it has nothing to do with the vacuum advance. Its just that last teeny bit of throttle..I know i can richen the secondary mixture some by limiting the secondary air door from opening so far in relation to the secondary butterfly opening but not sure if it will help. I think its propbaby the cylinder pressure like PRH said. sucks because some run more than 9.5:1 without this issue..just my luck

 

[Mopar Sam]

Is it fresh gas?

 

[mopower440]

Just started to read this thread.... But Rusty asked a good question & the answer you gave is a problem... A low compression engine needs a hotter plug to keep from fouling... A higher compression engine needs a colder plug to prevent detonation.... There are plenty of other possible causes but that's a cheap easy thing to try so eliminate it as a possibility..

Hmmm..i need to figure out the coldest plug i can use in this thing and try it then anyways..I use NGK plugs any ideas?

 

[PRH]

There are countless flat top/84cc Ede headed 440’s out there successfully running pump gas.

 

[PRH]

None of what’s being discussed so far eliminates the possibility that you’re feeling that the carb is lean at wot isn’t correct.
If you have tuning parts, add some rear jet(is that a thing on those?) and see if it helps.

 

[Garrett Ellison]

If all else fails and you want to go through it and build it with quench through whatever means, I think could move the cam to straight up. Probably knock down just enough cylinder pressure to prevent the full throttle ping. It's probably got more than enough torque to worry about any loss at low rpm. But I too would try fattening up the secondary side first.

 

[RustyRatRod]

A better way to explain its is, if i put a stopper on the throttle plate to stop it from going beyond about 98% throttle, it would never ping, no matter how quick you stab the throttle and at whatever rpm, no ping, but you open that throttle plate that last 2% and it pings. So when the pedal hit the carpet, its fine, but put more force on the pedal to force that last tiny bit open, and here is the ping. Its not a lot but its enough and i want it gone so it doesnt hurt anything.

Slow the curve down. Put some stronger springs in it.

 

[mopower440]

There are countless flat top/84cc Ede headed 440’s out there successfully running pump gas.

But if the compression turns out to be the issue with the current 88cc heads, how could i run the eddy 84cc without it being worse? Not being smart, truly asking because i dont know, unless the chamber being closed on the eddy makes for a better chamber to stop detonation?

 

[1WildRT]

But if the compression turns out to be the issue with the current 88cc heads, how could i run the eddy 84cc without it being worse? Not being smart, truly asking because i dont know, unless the chamber being closed on the eddy makes for a better chamber to stop detonation?

A closed chamber with a piston near or preferably at zero deck height creates quench which helps prevent detonation....

Info written by a guy who's know a lot more than me...

This article is well written & explains it better than I ever could....



"What is the most, exact precisely defined occurrence in all piston engines? It isn’t ignition timing, combustion, crank indexing, or valve events. It is Top Dead Center. You can’t build an engine with an error at Top Dead Center because TDC is what everything else is measured from. Spark scatter, crank flex and cam timing can move, but TDC is when the piston is closest to the cylinder head in any one cylinder. The combustion process gets serious at Top Dead Center and about 12 degrees after TDC, most engines want to have maximum cylinder pressure. If maximum cylinder pressure occurs 10 degrees earlier or later, power goes away. Normal ignition timing is adjusted to achieve max cylinder pressure at 12 degrees after TDC. If your timing was set at 36 degrees before TDC that is a 48 degree head start on our 12 degree ATDC target. A lot of things can happen in 48 degrees and since different cylinders burn at different rates and don’t even burn at the same rate cycle to cycle, each cylinder would likely benefit from custom timing for each cylinder and each cycle. Special tailored timing is possible but there is an easier way—“Magnificent Quench”. Take a coffee can ½ full of gasoline burning with slow flicking flame. Strike the can with a baseball bat and you have what I would call a “fast burn”, much like what we want in the combustion chamber. The fast burn idea helps our performance engine by shortening the overall burn time and the amount of spark lead (negative torque) dialed in with the distributor. If you go from 36 degrees total to 32 degrees total and power increases, you either shortened the burn time or just had too much timing dialed-in in the first place. If you have really shortened the burn time, you won’t need so much burning going on before Top Dead Center. Now you can retard timing and increase HP. Did you ever have an engine that didn’t seem to care what timing it had? This is not the usual case with a fast burn combustion but an old style engine with big differences in optimum timing cylinder to cylinder will need 40 degrees of timing on some and others only need 26 degrees. If you set the distributor at 34 degrees, it is likely that 4 cylinders will want more timing and 4 cylinders will want less ( V-8). Moving the timing just changes, which cylinders are doing most of the work. Go too far and some cylinders may take a vacation. Now what does quench really do? First, it kicks the burning flame front across and around the cylinder at exactly TDC in all cylinders. Even with spark scatter, the big fire happens as the tight quench blasts the 32 degree old flame around the chamber. Just as with the coffee can, big flame or small flame, hit it with a baseball bat and they are all big instantly. The need for custom cylinder-to-cylinder timing gets minimized with a good quench. The more air activity in a cylinder you have the less ignition timing you are likely to need. When you add extra head gaskets to lower compression you usually lose enough quench that it is like striking the burning coffee can with a pencil. No fire ball here and that .070-.090 quench distance acts like a shock absorber for flame travel by slowing down any naturally occurring chamber activity. A slow burn means you need more timing and you will have more burn variation cycle-to-cycle and cylinder-to-cylinder, result more ping. Our step and step dish pistons are designed not only to maximize quench but to allow the flame to travel to the opposite side of the cylinder at TDC. The further the flame is driven, the faster the burn rate and the less timing is required. The step design also reduces the piston surface area and helps the piston top stay below 600 degree f (necessary to keep out of detonation). All of our forged pistons that are lower compression than a flat-top are step or step dish design. A nice thing about the step design is that it allows us to make a lighter piston. Our hypereutectic AMC, Buick, Chrysler, Ford, Oldsmobile and Pontiac all offer step designs. We cannot design a 302 Chevy step dish piston at 12:1 compression ratio but a lot of engines can use it to generate good pump gas compression ratio. Supercharging with a quench has always been difficult. A step dish is generally friendly to supercharging because you can have increased dish volume while maintaining a quench and cool top land temperatures. You may want to read our new design article for more information. ".

By John Erb
Chief Engineer
KB Performance Pistons

 

[PRH]

I’ll ask again…….. did you degree the cam?

 

[mopower440]

I’ll ask again…….. did you degree the cam?

yessir, Its at 104 instead of 108

 

[RustyRatRod]

Do you have a Holley you can try on it? Sometimes, Thermoquads can lean out on the top and that could certainly cause it. Just a simple swap for diagnosis.