Header Noise or Detination

[Fisher500]

I have a 440 6-pack with a cheap pair of headers and a 4 speed manual on my 70 Charger. I get a metal to metal type noise at about 3000 rpm (kind of a repeating tap tap tap). Its fine with no noise between 0 and 3000 rpm, but once I hit about 3000 rpm, I start to hear this metallic type noise, like a piece of metal hitting another piece of metal. It always kicks in at about the same rpm. Do you think this could be from the headers? It comes in around 3000 rpm, but then if you give it some gas (goose it), it temporarily goes away and then comes back again when the rpm levels out again? I can rev it to 3000+ just sitting in the drive way and don't hear anything. I wasn't sure if this was a header noise, or the engine running lean, or detination.......any ideas are appreciated.

Also, looking under the hood, I have clearance around the headers everywhere, so they don't appear to be touching anything.

 

[khryslerkid]

You dont have the noise unless there is a load on the drive line. (Don't try this at home!)

Place the car in drive with your foot on the brake and the "e" brake engaged. Press slowly on the gas to load the driveline. Have someone help you listen and pinpoint the noise. DO NOT STAND IN FRONT OR BE UNDER VEHICLE! There is a good chance that you could see the marking of a header flange or exhaust pipe on the underside of your car. If your engine would happen to raise real high during this procedure, you have a soft or broken motor mount. Be ready to shut the engine off if this takes place... DO THIS OUTSIDE WITH NOTHING IN FRONT OF VEHICLE.

 

[PurpleBeeper]

exhaust other than headers

My first guess would be the exhaust pipes rattling on the gas tank or the mufflers rattling on the frame.

 

[Stumper]

Try adding some high octane fuel to see if the noise goes away? If it does you'll know it was detonation, if not .....

 

[67 coronet]

sounds like something along the lines of a rod knock or poss a lifter problem.if it was detination it would get worse when you accelerate.check for the headders hitting but you would have the same situation,would get worse with more load.

 

[Mooky]

assuming there are no balanceing issues with your flywheel, what kind of fan/shroud combo are you running...new motor mounts or used? load the drive train makeing it flex and allowing the rotating extremities to connect with something sounds about right...would explain the rhythm....if it where a lifter or piston pin....they would only get louder...not go away. if you can hear it even just slightly at idle then it very well could be an internal tap....but it sure sounds like a high pitch ping ping noise i had on my 4 speed 68 that ended up being a bad clutch or should i say the beginnings of a shattered clutch. hope you can get it figured out before any catastrophic failure....good luck

 

[70rr-brian]

Rod knock....what's your oil pressure and how many miles on it?

 

[RustyRatRod]

Look, internet diagnosis is NOT the way to go on this. Can you post a video with GOOD audio? ANd I don't mean some cell phone garbage. If you can get something good posted, we can help. Otherwise, everybody on this thread is just pissin in a fan.

 

[sublimegtx]

Look, internet diagnosis is NOT the way to go on this. Can you post a video with GOOD audio? ANd I don't mean some cell phone garbage. If you can get something good posted, we can help. Otherwise, everybody on this thread is just pissin in a fan.

LMAO Personally I really try to avoid pissin into a fan never turns out good ... :headbang:

 

[Beekeeper]

LMAO Personally I really try to avoid pissin into a fan never turns out good ... :headbang:

Yea kinda like pissing in the wind:happy7: rustys is right its hard to correctly
Diagnose something like this without hearing it in person

 

[Fisher500]

Great feedback, I really appreciate the ideas. I'll try to see if I can get the noise on a video and post it. The car has about 30,000 miles on the engine rebuild with about 60 psi. It just seems strange that I don't hear it at all until about 3,000 rpm and if I put a little more load on it, it will temporarily go away and then come back when you stop adding more throttle. Also, I forgot to mention I just replaced the clutch with a new Centerforce dual friction. It had the noise both before and after the clutch replacement. The flywheel was machined as well. The sound appears to be coming from in front of the passenger compartment.

Mooky might have a good point with the motor mounts. They are used and the engine seems to sit very low with the oil pan basically touching the tie rod. I've never seen another 440 sit that low in a Charger. Maybe I'm overlooking the obvious.

 

[Deleted member 214]

Makes sense. Loose motor mounts, motor shifts under load, and around 3k it moves enough that it maked intermittent metal to metal contact (header on torsion bar? Oil pan on tie rod?) and if you keep on it, the drivetrain moves enough to maintain contact and the noise stops. Just a theory...

 

[Bigal75]

The headers on my chev truck rattle at a specific RPM, like a wrench tapping the pipes. Cheap black jack headers.

 

[Fisher500]

I'm thinking about trying to change the motor mounts. I think that is why the engine is sitting so low and probably the source of the noise. Has anyone tried doing this before. Is it just the rubber isolator portion that needs replacing? Where is a good place to order new ones....Yearone?

 

[coloradodave]

Local NAPA parts house...........

 

[Sixer]

Harmonics can cause noise like this-and will cause noise at a specific rpm. Try changing timing a few degrees and see if the rpm-noise level moves with it. This is why you'll see weights hung on the exhaust system of some cars/trucks-they dampen harmonics at a certain rpm/load. Exhaust pipe tuning if you will. Ditto the weights hung on some transmission mounts-vibration tuners.

 

[RustyRatRod]

Look....and not trying to be smart here, but why not try some diagnosis rather than simply throwin parts at it? It should be pretty esay to hone in on. You ever heard of a stall test? That's the procedure where you start the car, drop it in gear and slowly run the RPM up in drive. You should be able to duplicate that noise that way, while someone outside the car narrows it down. You'll want to chock the wheels good and keep your hand on the key in case it gets away from you and you can shut it down quickly.

 

[Dennis H]

Agreed with diagnosis. But IF you get motor mounts, I recommend the Schumaker interlockers.