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390 exhaust leak or stuck lifter?

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grparen View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote grparen Quote  Post ReplyReply Direct Link To This Post Topic: 390 exhaust leak or stuck lifter?
    Posted: Oct/01/2017 at 1:30am
I just noticed that my 390 engine, which has only about 100 miles on it since a rebuild, has developed a ticking sound at idle.  I thought it might be an exhaust leak but the tick goes away when accelerating whereas I heard that with an exhaust leak the ticking gets louder when accelerating.  So, it may be a stuck lifter.  Any ideas out there?  Also, if it is a stuck lifter, is there a way to free it up without tearing into this new motor?
Gary Parente
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401MATCOUPE View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 401MATCOUPE Quote  Post ReplyReply Direct Link To This Post Posted: Oct/01/2017 at 7:02am
Start with the basics:

1.  Exhaust leak would be the first place to start...AMC's are common to have to the rear bolts on either side come loose, even under low mileage. There was a Service bulletin to replace the bolts with special bolts with drilled shanks, the the bolt would expand fast or faster then the head and would not loosen.

2.  Did you use manifold gaskets?  AMC precision machined the heads and ex manifolds, no gaskets are needed and usually cause leaks but further down the road in mileage then you are.

3. Sticking lifters or "bad" lifter can cause the tapping noise, most commonly I have found it doesn't go away......I have tried Marvel Mystery Oil on some old cars, original engines and had about 50/50 success, however.....never had it work on ticking "new" lifter, I just bit the bullet and pulled the lifters and swapped the lifters....I know you didn't want to hear that.

4.  Did you thoroughly clean the block lifter passage ways with the 3/8"pipe plugs removed, I have seen an incredible amount of debris get caught in this area, have the block "cleaned" only for it to break loose and cause damage....clogging the valve train parts.
Ross K. Peterson
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Post Options Post Options   Thanks (0) Thanks(0)   Quote kenoshakicker Quote  Post ReplyReply Direct Link To This Post Posted: Oct/01/2017 at 7:10am
My first car, a 1968 American with a 199, had a ticking noise all of the time.  Two people told me to put a little ATF in the engine right before it needed an oil change, run it a few days and change the oil.   I did this a few times with no results. The last time I put in a half a quart or better, ran it a few days and the ticking stopped.  I changed the oil, started it up, it ticked for a few seconds and stopped.  The only time it would tick is when it needed an oil change. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rebel Machine Quote  Post ReplyReply Direct Link To This Post Posted: Oct/01/2017 at 8:38am
Did you break the cam in properly? Current oils have insufficient levels of zinc and phosphorus which lead to flat tappet cam failures. Flat tappet cams need the right levels of ZDDP to avoid damage to cam lobes & lifter faces.

-Steve-

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one bad rambler View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote one bad rambler Quote  Post ReplyReply Direct Link To This Post Posted: Oct/01/2017 at 9:18am
Rounded over lobes don’t tick....Look closely around the ports for soot...and if your running stock manifolds check to make sure your heat riser isn`t rattling
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Rebel Machine Quote  Post ReplyReply Direct Link To This Post Posted: Oct/01/2017 at 10:00pm
Originally posted by one bad rambler one bad rambler wrote:

Rounded over lobes don’t tick....Look closely around the ports for soot...and if your running stock manifolds check to make sure your heat riser isn`t rattling


Mine did. Wore a hole in the lifter face.

-Steve-

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Post Options Post Options   Thanks (0) Thanks(0)   Quote ramblinrev Quote  Post ReplyReply Direct Link To This Post Posted: Oct/01/2017 at 10:12pm
Try the exhaust donut. I'll bet that will fix it!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Red20 Quote  Post ReplyReply Direct Link To This Post Posted: Oct/01/2017 at 10:18pm
To add even more to the list of possibilities: I have an Eaton PS pump that sounds a lot like lifter noise at idle...
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ccowx Quote  Post ReplyReply Direct Link To This Post Posted: Oct/01/2017 at 11:34pm
Here is a trick that works some of the time:

Remove the valve cover, after warming up the engine. Put blankets or something over the fenders to catch the mess you are about to make. Start the engine with the cover still off. Take the ticking lifter and loosen it until it starts to rattle and squirt oil all over the place. Let it run for a bit, making a mess, then tighten it down until it stops squirting. Shut it down. Tighten it down to stock specs and restart the engine. This will often blow out whatever crud is sticking in the lifter and causing the problem.

This is not guaranteed, but I have about 50/50 success. It is free to try and does not hurt anything.

Good luck!

Chris

PS: Don't forget to put the valve cover back on!   
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Boris Badanov Quote  Post ReplyReply Direct Link To This Post Posted: Oct/02/2017 at 6:16am
Got headers?
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