Pre 84 Trucks 1st gen pickups

Help! 20R makes tapping sound. Driving my crazy.

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Old Dec 9, 2012 | 09:21 AM
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CottonFog's Avatar
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Help! 20R makes tapping sound. Driving my crazy.

Hey guys, I got every thing dialed in on my little 2wd 20R. I made a video so you can see what I'm talking about. Please take 2 minutes and watch my video so you can hera the noise and see the engine bay and see the timing light and see the tachometer and see that I got everything covered but cant get rid of this, "tap, tap, tap"! Please helop me. Maybe this sound is normal. If so just tell me so I can sleep easy. Thanks in advance for any advice or help. It's much appreciated.
[youtube]https://www.youtube.com/watch?v=qCsVwqVGC7w[/youtube]

https://www.youtube.com/watch?v=qCsVwqVGC7w
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Old Dec 9, 2012 | 10:05 AM
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From: Ofallon Missouri
If you adjusted the valves correctly...you either have a bad rocker or a flat spot on a cam lobe. Lets see that cam.
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Old Dec 9, 2012 | 11:17 AM
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Ok, now we are getting somewhere. How do i look at the cam? Sounds like a weekend project. I'll read up on my Chilton's book. Do i gotta pull out the whole motor to see the cam?
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Old Dec 9, 2012 | 11:32 AM
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From: Ofallon Missouri
You saw it when you adjusted the valves. Take off the valve cover.
Takes less than 10 min.
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Old Dec 9, 2012 | 11:40 AM
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From: Spokane Valley, WA / Rexburg, ID
if you take off the calve cover, (4 nuts on top of the motor) then the cam will be clearly exposed. This is what it looks like (images stolen from google)


That shows the valve cover being removed.

And this is what the cam looks like

Its the round shaft going beween all the springs. Yours will still have rockers on it so it will look more like this.


I hope this helps!
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Old Dec 9, 2012 | 12:14 PM
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yes the house. I'm on my way to meet family for dinner right now. I will pop off the cover and send some pics around /by 8 pm.
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Old Dec 9, 2012 | 01:33 PM
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From: greenville,wi
make sure your not overtightening the valve cover!! 12 inch pounds-ish,or finger tight then half a turn.
if its torqued down too far it will ride on the valvetrain and tick just like your saying.start it up,slowly loosen the four nuts a little at a time and see if it goes away....

Last edited by cman1; Dec 9, 2012 at 01:36 PM.
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Old Dec 9, 2012 | 02:07 PM
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From: Kansas City, Missouri
Overtightening ?

It is so common. It is easy to overighten stuff. I hope that's it.

My 82 diesel had a leak at the rear left of the cover before I took it apart. Found a split gasket from overtightening!
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Old Dec 9, 2012 | 04:06 PM
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You know, I think it may be the over tight valve cover. I loosened it up and I think it went away but now I was able to fixate on some noise coming from the exhaust manifold/header area. It got late on me. I have to leave for Miami early in the morning. I totaly want to explore the lifter and cam issues but I gotta crash. Thanks for the help guys. I will post update wednesday and see if you can help me. Thanks.
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Old Dec 9, 2012 | 04:28 PM
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From: greenville,wi
do yourself a favor,go get a valve cover gasket set and replace it and lightly tighten it down, dont forget to seal the half moon seals with FPG.

Last edited by cman1; Dec 9, 2012 at 04:29 PM.
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Old Dec 11, 2012 | 07:52 PM
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x2 on the valve cover torque. I had the same tick when I adjusted my valves last time and over torqued the valve cover nuts. Definitely try removing the valve cover and re-torquing the nuts first. Make sure you completely loosen the valve cover, not just the nuts or your problem will eventually come back. Also, make sure you're using the right unit of measurement when lashing your valves (metric vs standard). I know it sounds stupid, but people have done it before...including me!

Chances of it being a flat spot in your cam are slim so I wouldn't worry too much about that. After I solved my tick by loosening the valve cover, I still had a little bit of noise coming from the exhaust side as well. I had a slight leak coming from the bottom of the headers where the gasket failed. Installed a new gasket and it sealed back up.

Good luck, let us know how it comes out.
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Old Dec 18, 2012 | 10:27 PM
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From: greenville,wi
didya fix it???
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Old Dec 24, 2012 | 07:49 AM
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From: KY
I have an 81 4wd with 22R that makes the same noise. Can barely hear it run the first 15 or 20 minutes from a cold start, but an hour driving on the highway and it sounds just like that coming to a stop at a red light or stop sign.

I've adjusted my valves and put on a new valve cover gasket. I don't believe I cranked down the valve cover too tightly, but I may have. Truck has 83k on the engine.

Would a failing timing chain tensioner lead to the same noise?
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Old Dec 24, 2012 | 10:09 AM
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From: greenville,wi
yes,also a timing broken chain guide,chain slapping against timing cover.youll hear it more when your slowing down because theres less tension on the chain.
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Old Dec 24, 2012 | 09:26 PM
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Originally Posted by ky-homelite
I have an 81 4wd with 22R that makes the same noise. Can barely hear it run the first 15 or 20 minutes from a cold start, but an hour driving on the highway and it sounds just like that coming to a stop at a red light or stop sign.

I've adjusted my valves and put on a new valve cover gasket. I don't believe I cranked down the valve cover too tightly, but I may have. Truck has 83k on the engine.

Would a failing timing chain tensioner lead to the same noise?
Sounds like mine. i took the cover completely loose as some one previously suggested and got rid of the noise. Now its the exhaust that's making noise so I'm thinking lce header, intake and Webber 32/36 carb, but then they suggest ignition components too stop it comes to like $2k.
Anybody got experience w replacing gaskets/seals at the front main seal? Can this be done w/o pulling radiator? Also, can you add a transmission oil cooling system to a Manuel if you're towing? Does that help?
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Old Jul 9, 2020 | 11:24 AM
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From: Placencia, Belize, Central America
@CottonFog Did you fix it? I know it was a long time ago, but I got the exact same thing on my '79 20R - I'll slack off the acorn nuts this weekend - it is also DRIVING ME CRAZY..!!!
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Old Jun 6, 2021 | 01:15 PM
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Originally Posted by Rusty Bob
@CottonFog Did you fix it? I know it was a long time ago, but I got the exact same thing on my '79 20R - I'll slack off the acorn nuts this weekend - it is also DRIVING ME CRAZY..!!!
Bob, I know this was last year, but I’m having the same problem I believe. Exact same truck except mine isn’t a 4x4 nor is it a deluxe. Just wondering if you found a solution?
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Old Jun 7, 2021 | 02:46 PM
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From: Placencia, Belize, Central America
Nope still got it! I'm inclining towards the timing chain slapping around against the guide due to a faulty tensioner. But no way do I have time or space to look into it. LMK if you make any headway.
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