Help!!!! 91 5.0 5.0 Knocking sound?

[niterida]

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?

[WhiteCobra94]

What octane?

[niterida]

out here in colorado, 91 octane is our premium, so that is what I have been running

[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

[dreamstang]

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 ----------

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.

[Trojan Horse]

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?

[niterida]

I did soak the lifters beforehand, but maybe I didnt soak them long enough. As for spark knock, Should I try and retard 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

[dreamstang]

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 retard 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.

[Trojan Horse]

Originally Posted by dreamstang

@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.

[dreamstang]

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.

[niterida]

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,

[Trojan Horse]

Originally Posted by niterida

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.

[niterida]

Thanks for all the tips, i am gonna try and retard 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.

[dreamstang]

Originally Posted by niterida

Thanks for all the tips, i am gonna try and retard 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.