What would be more beneficial in terms of information?

A leak-down test or a visual snap shot of inside of the cylinder (viewing top side of piston with a borescope)?

Reason I'm asking is because Roush forgot to replace my plugs when they built my engine and I drove it knocking for 28,500 miles. I wonder if there is damage or premature wear.

I currently have knocking between 2,000-3,500 rpm at 3/4 to 100% throttle, but only for the brief moment between you press the throttle to the time the engine responds and starts pulling. Once it pulls, the knock goes away...

Its not the tune (got it dyno tuned) and its not the plugs (correctly gapped and speced).

Any advise is greatly appreciated...

Thanks!!

Leak down should do the trick. Bore scoop is only going to tell you if you have serious damage. With all the carbon in there it won't tell you if you just have slight damage. Is the thing Missing? We've got a leak down test kit here. It's relatively simple to do.
Sounds like you've got either to much timing at part throttle or not enough fuel at part throttle. Sounds like a tune issue.

No missing, no loss in power, nothing...damn thing runs like a...I don't know...its just freakin fast!!!!
I dynoed 436hp and 413tq at the wheels.

VMP tried to get the knock out...2 hours worth...but he couldn't. He did say that he couldn't apply his usual timing on my car. Something unique about my car not wanting to take as much timing...but it did not lose power surprisingly. Same hp/tq figures as the other cars, but not as much timing...about 5 degree less.

So a visual inspection wouldn't yield any significant info? I though maybe I could see if the top ring might be cracked or broken. Though, if it was, would drivability be affected?

I had a leak-down test done on my previous 2008 Mazdaspeed 3 and the dealer charged me over $250 for it.
My tuner said that a leak-down test would require me to remove my valve covers, etc... Couldn't I just rotate each piston to TDC and do the test? Though I don't know what the readings should be...

Thanks Ian!!

Easy Cheap test.... run a few gallons of 104 octane unleaded through it. See if the knock goes away. Mini is Tuned for 104 octan and meth injection. Even with the meth off and 93 in the tank it still doesn't do an audible knock at 3/4 throttle. The knock sensors detect it though.

I thought about that...but the general consensus is to NOT use octane boost in Mustangs...something out it fowling plugs.

I don't know why?? I've used it in other vehicles without any issues...

Not Octane boost. Race gas. Buy it at sebring, 76 station by bithlo , or most race shops. A1 and Murrys come to mind. Hell I've put it in my truck once or twice. As long as it's unleaded you should be fine.

How should I use it? Straight, mix it, etc...? Are there any negative aspects of using it?

As long as its unleaded it won't hurt anything. Drive the car until the tank is mostly empty then add a few gallons of race gas and see if the knock goes away.

You drove a car for 28,500 miles before investigating the reason for the knock? Have you pulled the spark plugs and looked at the tips for unusual signs?

But what you're describing (knocking under specific throttle conditions) sounds like a part throttle tuning issue to me. Like already stated, run 1/2-full tank of 104 unleaded. If the knock is still there, then it's false and you need to isolate the reason for the false reading... sensor, wiring, etc. You can try using something like SeaFoam, GM Top End Cleaner, or Chrysler Combustion Chamber Cleaner, etc to remove buildup. If the knock still exists, fix the tune. I'll check around with some other Ford tuners to see what they think.

I was unaware of the knock until I took my car to a shop and get a limited slip installed...they discovered the knocking when they took it for a road test.

I ran 3 gallons of unleaded 100 octane fuel last night...not too bad at $6.99 a gallon... I waited till my gas light came on...I was running on fumes...

Anyway, the knock is still there...didn't go away.

I spoke with my tuner and he said he removed as much timing as he could and gave me as much fuel as possible to eliminate the knock. He also suggested I modify the PCV system that seems to be horrible on the Mustang. So I'll be installing breathers this weekend and completely cap the intake system. Also, he said he does not like the spark plugs I'm using; Autolite HTO, he says they are junk in removing heat. So I ordered a set of Brisk plugs that are a one piece design unlike the two piece design of the HTO.

Here are the stock plugs I pulled out:

FNSweet - Roush Forum - AutoXRacer's Detonation Issue

See post #71

See if you can get a scanner and see if it's actually Knocking due to something ignition related or if the knocking is something mechanical like a tensioner or something of that nature.

Thats what I'll be doing this weekend...though with the snow storm headed our way, I'm not sure if I'll be able to get to it...

That thing didn't come with limited slip?

It did, but the stock Ford clutch type limited slip that acts like an open diff while exiting a corner...

I upgraded to a Eaton Detroit TruTrac... Man that thing is awesome!!!

I had a low RPM low end sounding knock, and it was the PCV valve so oil soaked, it vibrated with a knock.
I replaced it and the sound went away.
I read on your other posts that the lines were oil soaked, so maybe check it out!
Good Luck!

Yeah, unfortunately, the Mustang does not have a traditional PCV valve...
But I'll take a look this weekend...

I did get a scan gauge that connects to the OBD2 port and displays sensor info... I am triggering the knock sensor or a second when I smash the throttle...but like I said, its only between the time I floor it, to the time it takes the car to respond and start pulling...

Thanks!!

A couple of comments from some other tuners:

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Does the vehicle have cams? or just a roush stage 3 blower setup? Can you datalog the knock sensors and see what is going on?
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Very likely it is the tune. If it was done on an inertia dyno, there is no way to load the vehicle in that area correctly. It would just blow through it and probably had too much timing added in those areas. Probably just needs a re-tune in those areas. See how much timing it is running there. It should be at almost full boost and at that RPM probably have 10-16 degrees of timing (maybe more if running 93/94 octane).
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What tuning product was used to tune the car? Look in the tune (or ask your tuner) how much timing it is running under those conditions. Can you get a datalog of the timing and knock under those conditions?

Stock cams... Its just a Roush Stage 3 blower setup with supporting mods; injectors, ECU calibration, etc...
I'll have to data log and see whats going on.

Its definitely not tune related. I had the same issue with the stock tune; I thought a custom dyno tune would fix the issue. The tuner did say he lowered the timing in that area as much as he could and added fuel...knock is hitting before any boost kicks in. As soon as the boost kicks in there is no knock.

Like I said, the knock is just limited to when you initially smash the throttle, it knocks, power hits, knock disappears.

The tuner used SCT X3...I'll take a glimpse tomorrow for the timing and knock...its a little hard since it only lasts 2 seconds or so...

Thanks for all the advice... I have decided to let the dealer figure it out know since I'm all out of ideas...

I monitored my knock and timing this morning...unfortunately, I can't data log and provide a graph...

But as a quick and simple glimpse, its occurring at below 14.0 (9.0 to 12.5 to 13.0) degrees of timing between 2,000 and 3,500 rpm. Above 3,500 RPM the timing is above 14.0 degrees anyway and does not knock.

Its weird, I know... Thats why I'm going to leave it to Roush to figure out. I am still hung up that its something mechanical (Roush leaving the wrong plugs in there and driving 30K with them on); though everyone tells me that knock won't progressively kill and engine, it will kill it instantly or not...

Are you using both a upper/blower pulley and a OD crank pulley?

No, just using the supercharger pulley... There are no overdrive pulleys. Just a smaller supercharger snout pulley with a larger idler to take up the belt slack. But it was knocking in these conditions prior to the pulley swap.

Took the car to the pros...seems like my supposedly knocking issue is simply engine resonance... According to the pros, all the Mustangs do it; GT500, Roush, etc... The tech explained that how the exhaust gases hit the cats, it causes different vibes which sound very similar to pinging/knocking...it even sounds metallic. The tech explained that if it were true knock/ping that it would happen throughout the RPM range and not just the first 2 secs of WOT in such a narrow rpm band.

I guess my issue is a non-issue then...

So the answer is more sound deadening material between you and the engine.

Honestly, I don't know if I buy it 100%...

But since its happening in the lower RPM range where no damage can occur, I guess I'll just ignore it...

They did say by changing the exhaust (mid-pipe) that it would probably make the noise (knock/ping) go away...
Might invest in a high-flow cat X-pipe in the near future...would love to go cat-less, but the exhaust would be too stinky.