Rybar

iTrader: (11)

Hey guys, problem just appeared recently when driving the car. Now I know this is next to impossible to figure out online but thought I would toss it out there.

I have this strange rattling noise I only hear when the car is accelerating at higher rpms. Around 4-5000 rpms. Seems louder in 1st and 2nd gear.

I thought about detonation, so I tried some octane boost with no luck, I always run 94 octane fuel from the pump. Would octane boost eliminate some of the detonation if it were happening?

I can't figure if it is exhaust, the transmission, or just something under the dash??

Why would it only happen at these rpms under load?

The Motor runs around 11.5:1 compression. And was tuned by a friend of mine on a local dyno.

Here is a mod list:

2002 346 ci Camaro LS1
TSP 233/239 112 595/603 Cam
ETP 215 heads, 60 cc chambers, standard springs
Cometic .040 Head Gaskets
Trend 8.07" .125 wall thickness pushrods
Harland Sharp rebuilt stock rockers
Comp OE 850-16 lifters
Tony Mamo Ported Fast 90 Intake
NW 90mm TB
36# Accel injectors
ARP head Bolts
Stainless Works 1-3/4" polished LT headers
ported LS6 oil pump
LS2 Timing Chain & sprocket
Custom dual 2.5" polished stainless exhaust with x-pipe and Magnaflow mufflers.
ASP underdrive pulley kit (crank & alt)
stock MAF
3.5" custom cold air intake
Autokraft Swap Oil Pan
Taylor 8mm wires
AC Delete

question

iTrader: (2)

Nice ride you got there.
Can you be a little more specific? Where do you think it is coming from, describe this rattle. Does it sound like something in the valvetrain? How loud is it? I'm guessing pretty loud if you can hear it over cam and long tubes.

Rybar

iTrader: (11)

I know what valvetrain noise sounds like. It's some sort of rattling noise coming from under the car or forward the drivers seat, either motor or tranny or something. Only happens around 5000rpm while accelerating, doesn't happen when I rev the motor or the car is in neutral. And you can definately hear it over the exhaust.

Could something wrong in the T56 make this noise?

And would a bottle of octane boost help reduce detonation??

LS6427

iTrader: (2)

Sounds like detonation. I doubt octane boost will do anything, that stuff is a joke and doesn't really up your octane number enough to do anything.

If I were you I'd see if you have leaky valve seal(s).

How long has this engine been in the car? How many miles?

Rybar

iTrader: (11)

I've probably only put a couple thousand miles on the motor since the H/C swap.

Why do you suggest leaky valve seals??

Would there be a power loss with detonation? The motor still feels 100%

And lastly, the car ran well one day, and did this the next. How can something change so drastically from one day to the next to cause detonation?

So would it be best to do a scan of the motor and see what's going on detonation wise?

question

iTrader: (2)

Yes if you have access to a good scan tool do that asap.
Just curious, what kind of fuel system are you running?
Stock tank?

Rybar

iTrader: (11)

Running a Rick's stainless tank with a Walbro intank pump. -6 braided lines throughout and a GM Corvette fuel pressure regulator for the single line to the fuel rail and 36# Accel injectors.

LS6427

iTrader: (2)

Leakdown test.

Well, oil building up on your pistons from leaking valve seals after engine shutdown each time can cause detonation. After the engine gets warmed up that burnt oil will get hot spots, and those hot spots will ignite the fuel/air prematurely...detonation.

It won't happen if the engine is still pretty cool. I'd be curious to see if you get that rattling noise if you go do a WOT run just 5 minutes after start up when the engine is cold. If it doesn't rattle, its a good indication you have burnt oil build-up on your pistons.

Go try that.

Its exactly what the problem was to the engien below. A fully built 434ci. It detonated ONLY after the engine was heat soaked at operating temp. Had the heads rebuilt (all valve seals were leaking) and cleaned the crap off the pistons and it never detonated again.

THE ONLY THING THAT WAS WRONG HERE WAS....bad valve seals. The only symptom was detonation at high rpm....after the engine was running for a long enough period to be heat soaked and at operating temp. It did not detonate till it was hot.
That crud all over the pistons would get hot and act like a spark plug and ignite the fuel/air before the spark plug had a chance to.

Rybar

iTrader: (11)

Interesting, thanks for pointing that out. I will try it out.

You think the valve seals would be gone on these heads? They were brand new from ETP fully assembled and only have a couple thousand miles at the most.

LS6427

iTrader: (2)

Yeah, try it. Come off the throttle the instant you hear it though.

New stuff is sometimes messed up a little. Could just be a couple valve seals gumming up one or two pistons.

I just don't know what else can cause detonation like you have. I wouldn't go WOT again till you get that fixed, you can lose an engine from detonation.

LS6427

iTrader: (2)

Also, even it does detonate if you do a WOT run when its not totally hot, doesn't mean thats not the issue.

It could also be misfires at high rpm. Common cause of that is a spark plug wire(s) touching a header/exhaust manifold pipe. Check that too.

Rybar

iTrader: (11)

Thanks for your input, anybody else have any ideas I should look at?

Rybar

iTrader: (11)

Did some "diagnostics" last night.

Put in new TR55 plugs and the old ones all looked the same. Rusty/Golden Brown colour. Also threw in another bottle of octane boost and a bottle of injector cleaner.

Abolutely no change.

But what I did find was the sound is louder in 1st and 2nd, and is also louder when the car is colder. Once it's up to operating temps the noise gets alot quieter. It only does it under load and not when the motor revs in neutral.

I took a buddy for a ride who use to work at a Tranny shop and he said it could be something in the tranny, but he said not to worry to much and maybe change/check the tranny fluid and just keep driving it.

I am thinking this may be a tranny or clutch problem rather than the tune

xBROKEx

iTrader: (7)

could be the exhaust or tranny rattling against the body if one of your motor or tranny mount is worn out

Rybar

iTrader: (11)

Had it at a local tranny shop today who thinks there is something wrong in the tranny. I had the pilot bearing replaced in the tranny last year which was causing a squeeling noise, and recently another shop found my x-member bolts loose and one was missing. So I am not sure if I messed something up in the T56 which has about 50k miles on it.

T56 is stock out of an 02 Z28. Has 50k miles. And I am running a Spec stage III clutch.

JD_AMG

I had the same noises you are getting, it sounded like marbles in a glass jar and only occurred at WOT in gear every now and then. Turned out to be the metal ring/guard thing around the 02 sensor on my exhaust. I clamped it down and the noise has been gone since.

Rybar

iTrader: (11)

So your O2 sensors were loose? What ring/gaurd are you referring to?

JD_AMG

Its weird because looking at pictures I don't see the same thing on other cars. It was a thin, probably 1in long piece of metal around the 02 sensor that was knocking/rattling against the 02 sensor itself. When under the car if I hit the exhaust it would make a very similar noise, thats how I (and a friend) found it. We bent the metal in with a clamp and the noise went away.
I think its worth a try getting under the car and hitting/shaking the exhaust (and maybe other things) to see if you can get the noise.

Rybar

iTrader: (11)

Hey guys, sorry to bring this back up. The noise sort of dissapeared for a while, and now it's come back. I don't know what to do. Is there a way to check the valvetrain or something? The entire top-end is very new.

I know one of my header tubes is very close to the steering box. I wonder if it's touching causing this noise?

I've had another shop take a look and they can't figure it out.

The car seems to run 100% otherwise, power seems fine. I don't want to start tearing the motor and tranny apart only for nothing to get fixed. if the motor or tranny blows up I figure it would be a good time to upgrade.

Rybar

iTrader: (11)

Ok at my wits end here. Please somebody help.

I've installed new solid motor mounts, new poly tranny mount. Had custom motor mount pedestals made for more header clearance and have also just rebuilt my T56 tranny with The Gearbox Stage II kit, new bearings, new 5th, 6th and reverse gears/synchros were also needed. And installed a brand new Spec Stage 3+ clutch. New header gaskets and also checked header to exhaust gaskets and after thousands of $$$$ this noise still eludes me.

I also noticed this noise started happening after my ported Fast 90/90 was installed and told by a local engine builder it could be my TB??

So these are what I think it could be:

- Knock or detonation - would need to check with a scan and adjust tune.

- Maybe a bad lifter or pushrod, but they are very new, maybe a few thousand miles at most. Lifters are from Comp and pushrods are custom from Trend.

- Could this be a blown head gasket??

- Maybe I should replace the O2 sensors, have been told these can sometimes cause a rattle or bad O2's can cause the motor to detonate?

- Bad power steering pump??

PLEASE HELP!!