lifter tap I Give UP! - Team Camaro Tech
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post #1 of 18 (permalink) Old Feb 4th, 01, 05:48 PM Thread Starter
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Has any one had a problem with replace ment lifters in a 68 327/350hp. We have one on #3 piston ex valve. It TAPS TAPS TAPS!!!
WE have changed lifters,cam,pushrods,rockers&nuts Twice!
Have adjusted lifters down to 0 lash + 1/4 turn. Also tried 1/2 turn. It dose not tap at idle But around 2000rpm to 3500rpm it TAPS TAPS TAPS. Runs fine makes good power just can't get rid of the tap
Thanks, TAP TAP TAP??
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post #2 of 18 (permalink) Old Feb 4th, 01, 10:20 PM
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Is the lifters going flat? Is the bottom of the lifter look ground up or beat up? If not, then try this...lay a straightedge across the tops of the rocker studs...this one may be pulling out (assuming you have pressed in studs). If all are straight then you may need to run a brake cylinder hone thru that lifter bore and clean it up...could be something in the bore causing the lifter to stick.

One thing I just thought of that is more of a possability...that valvespring may be broken or very weak. I fought the same problem you describe a few years ago on a 350...the engine idled a little rough but had a noticeable miss above 2k rpms...and the tapping noise. The valve wouldnt adjust right and it turned out that the stock valvespring had broken about 2 coil turns from the bottom...I replaced all the springs with Z-28 replacements and it worked great afterwards. Hope this helps.

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post #3 of 18 (permalink) Old Feb 5th, 01, 02:20 AM Thread Starter
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We checked the springs there good
the lifter moves freely in bore
have not put straight edge on studs yet
but we checked them close with the springs
off they look good, Thanks for the help
TAP TAP TAP!!!!
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post #4 of 18 (permalink) Old Feb 5th, 01, 02:41 AM
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Have you tried replacing the rocker, ball and nut? Maybe something is going on with it and you just can't see it? Does it do it with the valve cover off? Maybe the valve cover is hitting?

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post #5 of 18 (permalink) Old Feb 5th, 01, 03:48 AM
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since you say it runs fine, could it be possible that you have a flattening cam lobe?
hows oil pressure?
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post #6 of 18 (permalink) Old Feb 5th, 01, 05:48 AM
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A thought I had was just to make sure the noise is where and what you think it is would be to kill that cylinder by pulling the plug wire and removing the rocker arm on the suspected valve. It will run a little rought but if you said it shows up at 2 grand you shouldn't hurt anything and still be able to hear the TIC, TIC, TIC if that's it. I just had a problem where all 16 of my new lifters would not stop clicking, even after running the rocker arm nut all the way down. After much hair pulling and the help of a computer cam profiler I discovered I had a bent camshaft. Who'd a thought? I know these things can drive you crazy but you will fix it. Hang in there.

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post #7 of 18 (permalink) Old Feb 5th, 01, 08:17 AM Thread Starter
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hey guys thanks for your help we are still looking. We changed rocker nuts & ball this is the 2nd cam and lifters. Could this be oil related We have 15 lb at idle 35 - 40 at 2500rpm I"ve run small blocks chevys for ever never had this problem before.
TAP TAP TAP !!!
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post #8 of 18 (permalink) Old Feb 5th, 01, 09:46 AM
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Mike,

I know people will argue that you only need 10 lbs. of oil pressure per 1000 rpm and 15 lbs. at idle is fine, and they're right technically right but.............15 lbs of oil pressure at idle usually means you got some bearing problems. Run the engine at about 1800 rpm or so, and give the throttle a quick stab. Does the oil pressure drop a little and then increase? This pretty much indicates a bad bearing, usually a rod but could be both. The pressure should never drop with an increase in throttle.

I'm not trying to scare you but if the bearing were going bad you'd likely have the symptoms you describe. Try that quick test.

Jody
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post #9 of 18 (permalink) Old Feb 5th, 01, 10:54 AM
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I had the same kind of problem. After a lot of searching without finding anything I pulled the motor and disassembled it. The rod bearing nearest the suspected lifter was actually bad - just enough to generate a low level noise that several mechanics identified as lifter noise and one as the piston tapping the head. All wrong - it was "just" a spun bearing. Hopefully, yours is actually the lifter.

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post #10 of 18 (permalink) Old Feb 5th, 01, 05:00 PM Thread Starter
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Tried the oil pressure test have 40psi at 1800rpm did increse with rpm. no drop in pressure I mis read idle pressure it is 25 psi.The lifter we think that is giving trouble is pumping oil at idle (no tap)But seams to stop pumping at higher rpms TAP TAP TAP.ie no oil at rocker arm. But only this one seams to be doing it. TAP TAP TAP!!!
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post #11 of 18 (permalink) Old Feb 5th, 01, 05:45 PM
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Hey TAP TAP TAP you dont have one of thoes goofy oil baffels under the intake?TAP TAP TAP I had one of thoes and the push rod was hitting it,would only do it at higher RPM.I know what you are going thru,I can still hear it TAP TAP TAP, aaaarrrrgh.No wonder I have no hair.

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post #12 of 18 (permalink) Old Feb 6th, 01, 04:54 PM
 
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Years ago, I worked on a Firebird with a 305
that was noisy like that. We ended up pulling the heads. The valve guides were
worn out!
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post #13 of 18 (permalink) Old Feb 7th, 01, 08:00 PM Thread Starter
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Hey guys Well?? we bit the bullet and pulled the engine So far we have not found the tap Going to the machine shop with the block & heads.( Heads were rebuilt in Nov!) Having crank checked an new cam bushings put in block. Also checking the cam for proper run out ! THANKS!!! for all your help. will let you know what we find THANKS Again, Mike
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post #14 of 18 (permalink) Old Feb 8th, 01, 07:47 AM
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wow, I would have said hell with it myself, but good luck on the hunt. hope its not too expensive..

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post #15 of 18 (permalink) Old Feb 8th, 01, 01:18 PM
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I think that almost every small block chevy engine I have ever had made a ticking or tapping noise. I've accepted these noises by now since I've never lost an engine. Makes me wonder if there isn't something in the small block's design that makes it common. Fuel pump or oil pump maybe. It never seems to be the lifters though, that's too easy.

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