Pinging 505 help

[Geoff 2]

I only read post #1 because the clue was there: blowby.

Rings not seating, lets oil into chamber which reduces the octane rating of the fuel.

Was this engine run on a dyno to 'seat' the rings?
Wrong oil for break in can cause bore glazing...which causes the above. It is very hard to see with the naked eye.

 

[451Mopar]

I googled those pistons and they are flat tops. I think your compression ratio is about 1/2 point higher than you think.
The 505" 440 stroker in my Coronet has the same Comp XR286HR-10 cam. That engine has 440 source stealth heads and Icon 17cc dish pistons, so it has a little bit of quench between the head and the non-dished part of the piston.
Originally ran the same RPM intake too before the EFI. I also had light pinging on 94 octane pump gas. I could have played it safe and used the 24cc dish pistons, or go with the next larger cam.
I would be concerned with the cylinder scratching and blow by. Are the rings gaps too small? Oil in the chamber will really lower the octane level.

 

[1 Wild R/T]

I googled those pistons and they are flat tops. I think your compression ratio is about 1/2 point higher than you think.
The 505" 440 stroker in my Coronet has the same Comp XR286HR-10 cam. That engine has 440 source stealth heads

I googled them too, they have a .010 shorter C/H and a 4cc larger valve relief than the equivalent Icon.. So according to Mahle his numbers are good and 440 source shows the Icon about .3 higher... I'm thinking without taking measurements myself he's pretty close...

Personally I choose the 12cc dished piston and a 84cc closed chamber head.... Seems like a better option but that not what he has to work with...

 

[451Mopar]

I googled them too, they have a .010 shorter C/H and a 4cc larger valve relief than the equivalent Icon.. So according to Mahle his numbers are good and 440 source shows the Icon about .3 higher... I'm thinking without taking measurements myself he's pretty close...

Personally I choose the 12cc dished piston and a 84cc closed chamber head.... Seems like a better option but that not what he has to work with...

I though about getting the next larger size cam, my 505 stroker is about 10.3:1 compression, and the XE286HR-10 has plenty of low end torque. I can shift to the 5th gear overdrive (5-speed manual Legend Gear and Transmission 700 transmission) at 1,500 RPM (about 50 MPH) and still accelerate (with 3.55:1 gears.)

 

[PRHeads]

I realize this post won’t be a of any help to the OP, but when I’m discussing a build with someone, and the requirement is it absolutely positively has to run on pump gas, I always err on the cautious side with regards to CR, and I emphasize the importance of good quench.
Add a couple degrees of cam duration and a slightly wider lsa(to delay intake closing point) for good measure.

 

[beanhead]

You can check the spark plugs to see if there is any evidence of pinging.

This would be my beginning approach as well.
Cut the threaded shell off the plugs and inspect the insulators for silver speckles (piston material)....a magnifying glass and bright light are helpful.

 

[PeteyDaMan]

I realize this post won’t be a of any help to the OP, but when I’m discussing a build with someone, and the requirement is it absolutely positively has to run on pump gas, I always err on the cautious side with regards to CR, and I emphasize the importance of good quench.
Add a couple degrees of cam duration and a slightly wider lsa(to delay intake closing point) for good measure.

I spec'd and built the 505 myself. The only work I farmed out was the machine work. I've built several engines in my lifetime. I've owned "The Beast" for over 40 years and she's gone through 4 different engines and transmissions during that time, all built by me.
Granted, this was the highest HP and I had to do TONS of research but I had spend 3 or 4 years building it in my head reading article after article and honestly, I thought I had it figured out.
Maybe I didn't, maybe I did. The truth will be revealed on the dyno ( I hope).

Anyway, with the help of a couple friends and a couple hours, the engine is out

 

[Mick56]

Sometimes, if some spark plug wires are too close together, they can crossfire and create pinging.

 

[68-500]

Ill throw in my 2 cents. With open chamber heads and pistons without quench pads I believe 9.5-1 is a better CR. I believe you need a tight quench to run 10-1 or higher. While on the dyno and you do find it to actually be pinging. Might try retarding camshaft a few degrees.

 

[PRHeads]

Two engine operating parameters that are often not duplicated on the engine dyno vs actual “in car” conditions are coolant temp and carb inlet air temp.

A combo that spark knocks in the car at 180*+ coolant temp, while ingesting 100*+ inlet air……..may not bother at all on the dyno with 140* water temp while breathing 60-70* air.
On the dyno, the inlet air temp will basically never be as hot as under hood air………but you should be able to get the coolant up to a realistic temp for a street car during testing.

 

[PeteyDaMan]

Two engine operating parameters that are often not duplicated on the engine dyno vs actual “in car” conditions are coolant temp and carb inlet air temp.

A combo that spark knocks in the car at 180*+ coolant temp, while ingesting 100*+ inlet air……..may not bother at all on the dyno with 140* water temp while breathing 60-70* air.
On the dyno, the inlet air temp will basically never be as hot as under hood air………but you should be able to get the coolant up to a realistic temp for a street car during testing.

I have a big ol' hole in my hood that the air cleaner stick out through so as to not use the hot under hood air.
I do have a 6 pack scoop that will eventually cover the air cleaner hole

 

[BSB67]

I don't know if we ever asked exactly what the operating conditions are for the OP's ping to present. I think we're assuming WOT, all rpm. Also plug heat range can make a difference if they are too hot, and the engine is on the edge.

But if he has ping using high octane racing fuel, these details are likely irrevelant.

 

[beanhead]

I don't know if we ever asked exactly what the operating conditions are for the OP's ping to present. I think we're assuming WOT, all rpm. Also plug heat range can make a difference if they are too hot, and the engine is on the edge.

But if he has ping using high octane racing fuel, these details are likely irrevelant.

Agreed, which brings us back to the fact that it may not even be engine ping that the OP is hearing....

I'll share this crazy story-

Some years back, I could have sworn the 440 I was running was getting into detonation.
The plugs looked good. Timing was fine. Compression test was right in line. What the hell's going on....
After awhile I discovered that one of the kids had left a plastic bag (those crinkly ones from the gas station) under the passenger side seat, and since pretty much all my driving is done with all the windows down, when I would "load the engine" the bag would catch wind and rattle. It was hung up on the seat track so it never left it's place.
Combined with the roar from the exhaust, wind and road noise it sounded just like pinging.
Finally found it, removed the bag and never heard it after that.

In other words, it's worthwhile IMO to take the necessary steps to be certain it really is a pinging problem before resorting to doing things like pulling the engine!

 

[PRHeads]

Eh, motors already out now……might as well dyno it and see how it does.

Try it with a normal amount of advance in it, different fuels, etc…….see if you can make it ping on the dyno.

 

[Kern Dog]

Agreed, which brings us back to the fact that it may not even be engine ping that the OP is hearing....


In other words, it's worthwhile IMO to take the necessary steps to be certain it really is a pinging problem before resorting to doing things like pulling the engine!

When I had my troubles some 10 years ago, I was positive that mine was detonating but the engine showed zero evidence of it. The plugs looked fine and the pistons had no marks.

Thicker head gaskets was a crutch but it did seem to work....OR something else changed at the same time and skewed my findings.

 

[gtxrt]

with only 28* total, high octane gas and only 160 lbs of cranking compression something else is going on. couldit be some how the msd is adding extra timing.

 

[lewtot184]

With those open chamber heads and thick gasket quench distance is probably .150". It'll never work at 10:1 compression and pump gas, plus the chambers are probably getting contaminates. I wonder about blowing 160psi with a smallish cam and 500+ cubes?

 

[PRHeads]

He did say he retarded the cam at one point……..might help explain the 160psi.

The last one we did here was:
-505
-10.5cr with good quench
-245/251-110 HR
-EZ heads
Best power on the dyno at 37* timing, pump 93
No ping in the car

 

[BSB67]

To Summerize:
Aluminum heads
10:1 CR
Blows 160 psi on the gauge
Reduced total timing
Reduced Timimg curve
High octane racing fuel

Despite him being near sea level and has no quench, still seems like something else is going on. Oil in the combustion chamber is very possible, but the OP's posts suggest to me he's pretty sharp, and after 1500 miles he'd have plenty of evidance of oil in the combustion chamber. He did mention blow-by >3000 rpm, and did pull the engine, so maybe that's where he's at too.

 

[BSB67]

He did say he retarded the cam at one point……..might help explain the 160psi.

And this is why I think the OP is on his game - 80% of people would call "straight up" as he did as 4 degrees retarded, along with the fact he knew this would help reduce cylinder pressure and the ping problem.