in distress

This is a 96 C4 LT1 at start up it is very quite, after 15 or 20 sec. a slight tapping appears and get's louder, when it gets louder it sounds like it's metallic. mainly on the drivers side. after the motor get's hot the tapping sound get lower and lower to a point after about 15 or 20 minutes it is barely noticeable. Turn the car off let it sit 10 or 15 minutes, start the motor a slight tap appears, then seems to go away.
Replaced al lifters with Delco push rods are straight appear to be ok. When listening to the motor underneath behind drivers side tire it is extremely louder. Also tapping sound seems to be in rhythm with the of the exhaust. Can any one point me in the right direction.

3D-Aircrew

Don't stress ... you'll find plenty of help here. You can take a yardstick and place it on the motor where you hear it and put you ear on it (carefully) and narrow down the noise to a certain area. Check also that your exhaust is not touching anywhere on the frame or that the exhaust hangers have their rubber. Welcome to the forum

cadmaniac

Not much info, but here goes...If your are sure it's internal...
Check the rocker arms. Could be one cracked, or galled from the pushrod. Look at the valve stems while the rockers are off for excessive wear also. Keep in mind you will have to adjust the valve when you put the rocker nuts back on.
If that checks out, and you're sure it isn't a lifter, unplug 1 spark plug wire at a time on the noisy side . If the sound goes away or changes, that is likely the cylinder to examine. Bearing could be going, but it doesn't sound like it. Sounds like the metal is expanding once the engine gets warmed up, and tightens the engine tolerances on the offending parts..

Is it a high mileage engine?

biggiefl

Does it go away if you rev it 100rpm?

in distress

I only had the car a little over a year the speedometer was 47,347 not really sure if that is true. Thanks I will try the spark plugs wires. I also was told that you can replace the dash.

in distress

[QUOTE=in distress;1596055779]I only had the car a little over a year the speedometer was 47,347 not really sure if that is true. Thanks I will try the spark plugs wires. I also was told that you can replace the dash.Also it does not go away at higher RPM

Kevova

Any work prior to noise? Oil pressure? If oil has some miles drain oil and cut open oil filter check for metal with magnet. Look for silver or gray material in filter. Bore scope would be handy to look at cylinder walls and top of piston. If piston is shiny on the outside and dark in the center, bearing could be on the way out, piston maybe contacting head. It could be an exhaust leak, they can be pesky and have a tapping sound. A stethoscope with a tube in place of probe works pretty good. Make sure bolts are tight. I would hope for exhaust leak.

drcook

a cardboard wrapping paper tube works wonders for listening through, as the above folks have mentioned to use a tube. it is long enough to put in places and won't seriously hurt you if you bump a moving part. if you don't have a partially empty roll you can steal the tube from, go to the dollar store and sacrifice a dollar.

in distress

Has been tapping since I bought it, oil pressure seems ok , This is 96 collector addition LT1 I ran the motor pulled spark plug wires 1 through 7 one at a time I can not get to # 8 in the rear cylinder passenger side, any suggestions. so far none of the cylinders have made a difference.

in distress

Oil has been changed a couple of times did not think of looking for metal. still trying to figure out how to get # 8 spark plug wire off so I could check that cylinder.

dc6902

#8 will come off. I recently replaced all rockers on passenger side and it cured my ticking. That was only after replacing all lifters and the passenger exhaust gaskets.

in distress

Can not seam to get to # 8 spark plug wire at the very rear of the motor on passenger side this is 96 LT 1 any suggestions.

biggiefl

I put 2 wire ties on the cap and my bud and I pulled the ties with pliers.....bitches were in there.

in distress

Thanks for the idea I'll give it a try

cadmaniac

Sounds like a valve train noise from what you describe. I'm still leaning toward the rocker arms....

jetskibruce

I agree get a listening device. I use a plain broomstick. I was just checking for a slight morning knock myself and I can hear everything spinning nicely with the stick and then wow, a couple of injectors are loud. (relatively)

in distress

Thanks for the info, I am ordering rockers and pushrods this morning hopefully that will do the trick.

topfuel67

Have you ruled out an exhaust leak? On one of my first cars, a 67 Mustang, I had that exact issue. I replaced the lifters, changed to roller rockers, plugs, etc. My friend came along and pointed it out right away. The exhaust heats up quickly and the gaskets flex.

in distress

I already ordered the rockers & pushrods If that doesn't do the trick before go after valves I will check the exhaust. If I had a carburetor I used to pure some STP in it and watch for smoke, don't know if I can do that with a throttle body.

biggiefl

"don't know if I can do that with a throttle body."


Try Seafoam in the TBI...she'll smoke like its on fire.