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Don't know how to fix this tapping sound need help

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Old Oct 26, 2011 | 04:02 PM
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Car: 86 Firebird LG4
Engine: 350
Transmission: 700r4
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Don't know how to fix this tapping sound need help

It's an old 350 SBC with a flat tappet cam in a 1986 Firebird.

When I start up the car I can see the radiator hoses, heater hoses, etc. vibrating a lot while it's idling. Don't know if that's normal or not? (It's a rough ride sitting in it just while it's idling). I have to keep my foot just barely on the gas pedal to keep it running. I have the front end on jacks and the rear is sitting on tires.

After 2 minutes of it idling I can see some smoke come out of the passenger side by the firewall and it smells pretty bad. Not like an exhaust leak, I think those smell better. The smoke is just regular grey and it's not a lot. I also see a tiny bit of smoke coming out of the carb but it's not tuned yet so that could be why. Also the carb "pop"s at higher rpms.

At first I though it was the (new) donut gaskets on the y pipe so I reinstalled the y pipe to the header and tightened the bolts evenly so I don't see how that could be the problem. Just put in new header gaskets an hour ago.

Also I don't have the timing set or the carburetor tuned in. I'm trying to get rid of this annoying sound first.
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Old Oct 26, 2011 | 04:21 PM
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Car: 91' Firebird SOLD
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Re: Don't know how to fix this tapping sound need help

So, what does the "sound" sound like? I would try 8 ounces of Marvel Mystery oil in the crankcase.
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Old Oct 26, 2011 | 04:46 PM
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Car: 86 Firebird LG4
Engine: 350
Transmission: 700r4
Axle/Gears: 3.23 limited slip
Re: Don't know how to fix this tapping sound need help

Originally Posted by ninetyone
So, what does the "sound" sound like?
http://www.youtube.com/watch?v=0CeWM8wSIEg
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Old Oct 26, 2011 | 05:38 PM
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From: Spring Hill, Fl.
Car: 87 iroc-z
Engine: 454
Transmission: th350
Axle/Gears: 3.73
Re: Don't know how to fix this tapping sound need help

hmmm,...kinda sounds like a rocker way out of adjustment. dont take it to high RPMs til you set the timing.
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Old Oct 26, 2011 | 05:41 PM
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Car: 83 Trans Am / 96 Jeep XJ
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Re: Don't know how to fix this tapping sound need help

Sounds like an exhaust leak to me. A rocker makes a sharper sound and isnt as frequent in repetition as that sound is.
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Old Oct 26, 2011 | 05:45 PM
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Re: Don't know how to fix this tapping sound need help

Originally Posted by bradley23150
Sounds like an exhaust leak to me. A rocker makes a sharper sound and isnt as frequent in repetition as that sound is.
header gasket !!!
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Old Oct 26, 2011 | 05:45 PM
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From: Saint Louis, MO
Car: 86 Firebird LG4
Engine: 350
Transmission: 700r4
Axle/Gears: 3.23 limited slip
Re: Don't know how to fix this tapping sound need help

Originally Posted by bradley23150
Sounds like an exhaust leak to me. A rocker makes a sharper sound and isnt as frequent in repetition as that sound is.
I bet it's those stupid donut gaskets still. I have been trying for weeks to get them to seal up. I swear next time I'm getting a setup that doesn't use them.
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Old Oct 26, 2011 | 05:46 PM
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From: Spring Hill, Fl.
Car: 87 iroc-z
Engine: 454
Transmission: th350
Axle/Gears: 3.73
Re: Don't know how to fix this tapping sound need help

it could be the exhaust. hard to tell in videos. i saw he put new header gaskets on & assumed they werent leaking. i read your post awhile back about the window sweeps. thats a great idea & ill be trying that soon one day. thanx for the tip.
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Old Oct 26, 2011 | 05:47 PM
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From: Saint Louis, MO
Car: 86 Firebird LG4
Engine: 350
Transmission: 700r4
Axle/Gears: 3.23 limited slip
Re: Don't know how to fix this tapping sound need help

Originally Posted by tunedperformanc
header gasket !!!
But I JUST put new ones in today. And the ones before only had a few idling sessions and they didn't look burnt or cracked or anything.

Cleaned both surfaces with paint thinner. I used grade 8 bolts and tightened them to like 30 foot pounds. My torque wrench won't fit so I had to go by feel. I have replaced the header gaskets and donut gaskets twice.


I'm even using the fancy *** aluminum gaskets percy makes. Nothing I do works.

Last edited by 0pyders; Oct 26, 2011 at 06:12 PM.
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Old Oct 26, 2011 | 11:43 PM
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Car: 1986 Camaro Z28 IROC-Z
Engine: 350 Tuned Port Injection, for now.
Transmission: 700R4
Axle/Gears: Posi - 3.23
Re: Don't know how to fix this tapping sound need help

Looks like you have the Edelbrock TES exhaust system. it cant be a rocker because the sound is too fast. A badly adjust rocker is a sharp tap and is hella slower than the tap on the video. So it may be an exhaust leak. One way to variefy ( but investigate first!!!!!!), is by pouring in a bit of "Seafoam" into the carb while its on. The seaform will cause a ton of smoke. So if there is a exhaust leak, a noticable amount will begin to leak at or around the mating surfaces of the header to head, header to y-pipe, or y-pipe to cat. But investigate if seafoam can be dripped into the carb. Seaform helps burn the deposits inside the engine which will cause a ton of white smoke. You can find it at Autozone. Make sure the Camaro is facing up wind.

http://www.youtube.com/watch?v=_w6Qg-Jn13Y
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Old Oct 26, 2011 | 11:56 PM
  #11  
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From: Saint Louis, MO
Car: 86 Firebird LG4
Engine: 350
Transmission: 700r4
Axle/Gears: 3.23 limited slip
Re: Don't know how to fix this tapping sound need help

Ok yeah I looked into it and you can pour seafoam down the carb. Thanks a lot for that response I'll do it tomorrow.
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Old Oct 27, 2011 | 12:17 AM
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Engine: 350 Tuned Port Injection, for now.
Transmission: 700R4
Axle/Gears: Posi - 3.23
Re: Don't know how to fix this tapping sound need help

Another way to find the source of the sound is by putting one end of a hose to your ear while putting the other end on the suspected source. The sound will get louder and louder the closer you get to the source.
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