oddscrounger

I should mention that I have a TKO600 that was installed last summer; the shop didn't do a perfect job. I think they did not install the pilot bearing that Mike Forte's provides in their retrofit kit. There's a rattle noise that goes away when I push in the clutch... BUT

This new sound is different. And I don't know if they're related. Imagine pouring your favorite cereal into a ceramic bowl... or iron fillings onto a table surface.. that's the noise I hear echoing out from the passenger side of the vehicle when under a load in gear. No sound like that in neutral if I rev the engine. Usually happens at about 1,500 to 2,500 rpm mostly I hear it in 3rd and 4th gear.

What's your armchair diagnosis?

mlbinseattle

Sounds like timing is too far advanced and you're hearing pre-ignition.

Night rider327

iTrader: (13)

Yep that sounds like detonation (spark knock) to me. I have always described it as rocks in a tin can sound when engine is only under a load.

Detonation will kill your engine!

Check your timing, too advanced timing is the #1 cause, next would be too low of fuel octane

eseibel67

Yes, sounds like detonation. Don't make the engine do it again until you get it corrected.

mlbinseattle

It will eventually burn holes in the top of the pistons.

Apparently, there is a difference between pre-ignition and detonation. I've always called it pre-ignition. This person explains the differences in detail: http://www.nicoclub.com/archives/det...on-tuning.html

mlbinseattle

Another explanation of pre-ignition and detonation. This person explains the two a little better (IMO):

http://www.contactmagazine.com/Issue...ineBasics.html

The author pointed out something to remember between the two:

"As for detonation, it can get hammered on for seconds, minutes, or hours depending on the output of the engine and the load, before any damage occurs. Pre-ignition damage is almost instantaneous."

Either is not good for an engine, especially pre-ignition. I suppose the thing to remember is, if you're hearing knock or pinging, get it checked. Ensure you're using the correct temperature spark plugs, that there are not any over-heating issues, the timing is set correctly, etc.

Actually, I was glad to see this subject come up because it caused me to review the differences between the two. It's been ages since I've dealt with pinging or knock, so it's been a learning experience. (I could have really used the Internet back in the '70's and '80's. lol.)

oddscrounger

The timing is set to base never was messed with. Timing is controlled by the computer. Plus it doesn't sound like it's coming from the engine more like under the vehicle. Engine runs smooth as hell. So I'd have to disagree with all this. An engine just doesn't start detonating or pre-igniting out of nowhere.

86LG4Bird

iTrader: (1)

Did you change the driveshaft?
Way back when I went from a stock steel to a 3.5" AL shaft in my Impala, I immediately noticed a faint ringing sound. It was something my brain adjusted to within a couple of days of driving the car, and I never thought about it since.
The higher the load, the stronger the pulse loads from the U-joint that constantly accelerate and decelerate the shaft. Those pulses are the input that causes the ringing.

mlbinseattle

You wanted an armchair analysis.

Also, if the ICM decides to take a dump, then yes, it will affect your timing. Point is, there are other things that will affect your timing even though the base is set right.

Not saying timing is your problem. Just saying that things can change out of nowhere.

Night rider327

iTrader: (13)

Yes detonation can happen out of the blue all at once if something causes it.

Like bad gas. Did you get gas with in 50 miles of this starting?
If the fuel has water in it, or too low of octane it will cause it.

If the dist. hold down clamp is a little loose and the dist. moved a tad.

If engine starts to run hotter than normal it can cause carbon build up on pistons to act as hot spots/glow plugs and cause pre ign.

If your injectors/carb clogs up and you start to run leaner than normal

If your computer starts to act up it can change timing or air/fuel ratio

If cat converter clogs it can cause higher EGTs.

You asked us what we thought. Based on what you said I feel it's detonation, but it's really hard to figure out sounds over the internet when all we can "hear" is typed words on a screen.

Yes detonation happens in higher gears, when engine is loaded
Yes it sounds like rocks in a can be shook
Yes detonation does not happen out of gear, free reving, no load

oddscrounger

I do appreciate all the comments and I am aware I asked for an armchair analysis, which is exactly what I am getting. I feel like I am always getting gas within 50 miles with my MPG being around 15... lol

I use premium and only go to respectable gas stations... If I had detonation or pre-ignition wouldn't I experience any loss of power? Car still drives great. but...

YES I did replace the drive shaft; well actually I had it shortened to retro fit the TKO600 transmission last summer. But this noise is new. Buddy says it might be a heat shield. It's too cold out in Chicago anyways so I'll be putting it away this weekend.