thedsmguy
(Senior Member)
07/08/11 01:30 PM
Very sharp tapping in 4g63

Ok, so here we go.

The car seems to run alrights idles, revs up (a little weak maybe)

150psi compression, the valves seem to work fine when turning the car over with valve cover off. 3g lifters. The sound really sounds like a top end noise. Head was rebuilt fairly recently due to how clean it is and new gaskets.

I've tried disconnecting the a/c unit in hopes it was making the noise, disconnected each injector when running 1x1 and checked that the exhaust manifold wasn't way to cracked and making the weird noises (long shot I know). The oil level is fine, no particles in the oil on a recent drain/refill.

I spent some time with a buddy trying to nail this down. Should we pull the side cover and remove the BS belt to see if thats possibly the issue? Any other ideas?


Terry Posten
(Old Balls)
07/08/11 03:05 PM
Re: Very sharp tapping in 4g63

Shut the car off, remove the VC, and rotate the motor litte by little and just wiggle each rocker arm when they are on the closed side of each lobe.

Compare each one to the other as far as snugness. You may have a bent valve that is causing some lack in the system.

If you can, do a compression test to see if one slug is low. That could show you a starting point.

If you do not install 3G lifters correctly, you will bend valves. You must use a needle and depress each lifter so they are completely soft prior to installation and start-up. If a lifter is jacked all the way stiff, you can shove a valve into a piston top.


curtis
(Space Blanket from NASA plumbed into the attic)
07/10/11 01:38 AM
Re: Very sharp tapping in 4g63

Well if you haven't changed the lifters that maybe the problem. Could be it was refreshed with 1G lifters.

thedsmguy
(Senior Member)
07/11/11 02:38 AM
Re: Very sharp tapping in 4g63

I did not install the lifters personally. But they put these in to try to solve the problem which it did not. I'll have the car in my possession pretty soon. We did a compression test and it was 150 148 150 150. No real issues.

AnotherNewb
(flutterdumper)
07/11/11 05:47 PM
Re: Very sharp tapping in 4g63

Do you think its the top end because of the tempo? If so... rear balance shafts are bad about spinning bearings. I bought a 1g talon that was hammering away because of a spun balance shaft bearing.

FlyingEagle
(Eager Beaver)
07/11/11 08:35 PM
Re: Very sharp tapping in 4g63

Lifters are a highly possible candidate, but I have heard of some people with very loose tensioner assemblies causing the arm to contact it's pad repeatedly.
One of those while you are in there things to check for with the VC off and with a flashlight, engine running.
This is the long shot.


Eaglesfly
(Junior Member)
08/11/11 12:20 PM
Re: Very sharp tapping in 4g63

I had a similar problem about 5 years ago. I swapped lifters, checked compression, pulled the pan just to make sure it wasn't a rod knock transmitting sound up top. I finally ended up pulling the head to find the number 1 piston had a cracked wrist pin. It didn't come out or damage the cylinder wall but allowed the piston to rotate slightly to make contact with the edge of the valves. These were Ross pistons on Eagle rods back then.

thedsmguy
(Senior Member)
08/11/11 12:54 PM
Re: Very sharp tapping in 4g63

Thanks for the info. I appreciate it.


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