Help!!!! 91 5.0 5.0 Knocking sound? - Mustang Evolution

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Old 06-04-2012, 02:31 PM   #1
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Help!!!! 91 5.0 5.0 Knocking sound?

Hello,
I just finished rebuilding the 5.0 in my 1991 LX, It has the following mods bored .30 over, speed pro forged pistons, ARP rod bolts, balanced, Edelbrock performer cylinder heads, Cobra intake manifold, E303 camshaft, Comp 1.6 roller rockers, new ford racing lifters, new harmonic balancer, 24 lb/hr injectors 65mm tb, 73mm mass air.
After Priming the system with a drill, I installed the distributor,I started up the car and let it get to operation temperature, checked for leaks set the timing to 12 degrees, adjusted the idle and decided to take her for a shakedown run. the first 15 miles of my cruise went just fine, as i was about a mile away from home, I noticed that there was a rapid tapping sound that only came out at 2,000 plus RPM, but went away any RPM lower than this. I babied the car home and let it sit over night. After consulting some friends, I started the car up the next day, checked the timing and revv'd it to 2k, no tapping sound, so I hopped in and drove it, 5 miles, no tapping, 10 miles, still none, at about 20 miles, I finally heard the tapping that occured above 2k rpm. I Checked all my bolts, checked for exhaust leaks, and I don't suspect it is a rod knock, as it doesn't exist at idle, any ideas on what it might be?? I have plenty of oil pressure, the temp is fine, the car runs smooth, just noisy, I am stumped?
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Old 06-04-2012, 02:35 PM   #2
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What octane?
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Old 06-04-2012, 02:44 PM   #3
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Re: Help!!!! 91 5.0 5.0 Knocking sound?

out here in colorado, 91 octane is our premium, so that is what I have been running
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Old 06-04-2012, 04:58 PM   #4
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Re: Help!!!! 91 5.0 5.0 Knocking sound?

Any Ideas? I am lost, I have been told I can take a timing light and hook it up, if the sound matches the light, its probably valve train, if its a different speed, it could be bottom end, does this actually work? Thanks in advance
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Old 06-04-2012, 05:26 PM   #5
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i would pull the valve covers and make sure your rockers are tightened down properly. you are sure this isnt spark knock?

---------- Post added at 05:26 PM ---------- Previous post was at 05:25 PM ----------

Quote:
Originally Posted by niterida
Any Ideas? I am lost, I have been told I can take a timing light and hook it up, if the sound matches the light, its probably valve train, if its a different speed, it could be bottom end, does this actually work? Thanks in advance
yes tif the noise matches the light its in the valve train.
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Old 06-04-2012, 11:17 PM   #6
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Re: Help!!!! 91 5.0 5.0 Knocking sound?

You may have a bad, collapsed or partially collapsed lifter.Does it miss or sputter?
Did you soak them in oil and get them primed up before installing?
Did you check all of your pushrods and make sure none were bent?
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Old 06-05-2012, 07:41 AM   #7
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Re: Help!!!! 91 5.0 5.0 Knocking sound?

I did soak the lifters beforehand, but maybe I didnt soak them long enough. As for spark knock, Should I try and ****** the timing from 12 to 10? with the pushrods, I checked each one for straightness on a piece of mirror glass and blew through them with carb cleaner as I took them out of the package. The strangest part is that the noise doesnt come on till 2,000 + rpm, thanks for all the tips, i'll have to try them when I get off of work
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Old 06-05-2012, 07:53 AM   #8
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Quote:
Originally Posted by niterida
I did soak the lifters beforehand, but maybe I didnt soak them long enough. As for spark knock, Should I try and ****** the timing from 12 to 10? with the pushrods, I checked each one for straightness on a piece of mirror glass and blew through them with carb cleaner as I took them out of the package. The strangest part is that the noise doesnt come on till 2,000 + rpm, thanks for all the tips, i'll have to try them when I get off of work
Well I don't think 12 is to much timing. Especially if your running premium fuel. But whenever I am trouble shooting something like this, I like to set it at base timing just to be sure.

@trojan
If the lifter wasn't properly primed, would it eventually prime after running for a while? I am asking cause I don't know. But I was under the impression it might. And still doesn't mean that its not the problem either.
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Old 06-05-2012, 11:16 AM   #9
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Re: Help!!!! 91 5.0 5.0 Knocking sound?

Quote:
Originally Posted by dreamstang View Post
@trojan
If the lifter wasn't properly primed, would it eventually prime after running for a while? I am asking cause I don't know. But I was under the impression it might. And still doesn't mean that its not the problem either.
Yes, No, Maybe.


It depends on whether or not the lifter internals were damaged before it recieved oil.
I soak mine and use an old pushrod to "pump" them up while submerged in oil, just to be sure.

It's also very important to prime the oiling system good in a newly rebuilt engine before starting.
It helps prevent issues with any components not receiving oil quick enough.
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Old 06-05-2012, 11:18 AM   #10
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Quote:
Originally Posted by Trojan Horse

Yes, No, Maybe.

It depends on whether or not the lifter internals were damaged before it recieved oil.
I soak mine and use an old pushrod to "pump" them up while submerged in oil, just to be sure.
Gotch. That makes sense.
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Old 06-05-2012, 11:48 AM   #11
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Re: Help!!!! 91 5.0 5.0 Knocking sound?

I used an oil can to inject oil into all the lifters after they had soaked in oil overnight, even though the lifters were brand new, i suppose it could be a faulty lifter,
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Old 06-05-2012, 12:19 PM   #12
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Re: Help!!!! 91 5.0 5.0 Knocking sound?

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Originally Posted by niterida View Post
I used an oil can to inject oil into all the lifters after they had soaked in oil overnight, even though the lifters were brand new, i suppose it could be a faulty lifter,
It sounds like you took all of the proper precautions, but yes, a faulty lifter is a possibility.
It is a bit strange that it does not happen until 2000+ RPM, but that could mean that at very low RPMs the lifter will pump up, but it is unable to hold as the RPMs rise.


If you don't see any obvious signs of damage and it is just rattling or clattering a bit I would be tempted to just drive it a while and see if it worsens or improves.
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Old 06-05-2012, 01:10 PM   #13
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Re: Help!!!! 91 5.0 5.0 Knocking sound?

Thanks for all the tips, i am gonna try and ****** the timing to 10, check my rocker adjustment and try and drive it some more, drained the oil trough a paint strainer like some on aother had suggested, no shavings/coppery residue, oil looked clean, didnt look inside the filter though as I had no way of cuttinging it open that wouldnt produce its own metal shavings.
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Old 06-05-2012, 01:25 PM   #14
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Quote:
Originally Posted by niterida
Thanks for all the tips, i am gonna try and ****** the timing to 10, check my rocker adjustment and try and drive it some more, drained the oil trough a paint strainer like some on aother had suggested, no shavings/coppery residue, oil looked clean, didnt look inside the filter though as I had no way of cuttinging it open that wouldnt produce its own metal shavings.
That sounds like the best next steps to me.
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