Unsolvable tapping sound 94 LT1
07-26-2024, 02:35 AM
#21
TECH Resident
I had a loud tick once, hard to figure out, and and it turned out to be an exhaust leak between the header flange and the header tube where there was a small spot where the tube wasn't welded to the flange thoroughly, allowing a leak on the under side and one of the pipes near the back of the driver's side where its hard to get in there. I only found it after taking off the header and doing a close inspection. Easy to fix, hard to find.
Another time I found that the copper gaskets I was using weren't the correct port shape to seal completely on the bottom. They were LT1 copper gaskets, and I can't remember the brand name, but it wasn't something that I expected to find when I took them off and saw what was happening. They were all borderline along the bottom where the sealing edge was really thin.
Another time I found that the copper gaskets I was using weren't the correct port shape to seal completely on the bottom. They were LT1 copper gaskets, and I can't remember the brand name, but it wasn't something that I expected to find when I took them off and saw what was happening. They were all borderline along the bottom where the sealing edge was really thin.
07-26-2024, 11:30 AM
#22
I did have an exhaust leak from a couple loose header bolts but sounded a bit different. This really makes a metal on metal tap. But I’ve heard this suggestion a couple times so I’ll pull the headers and take a look. They are smacking the ground quite often so quite possible they developed a crack
07-27-2024, 01:44 PM
#23
Village Troll 
iTrader: (2)
I did have an exhaust leak from a couple loose header bolts but sounded a bit different. This really makes a metal on metal tap. But I’ve heard this suggestion a couple times so I’ll pull the headers and take a look. They are smacking the ground quite often so quite possible they developed a crack
07-27-2024, 09:01 PM
#25
Definitely thinking it could be a lack of oil to the lifters for some reason. Any ideas on this. Oil pressure is good. The noise is loud at low rpm then stops mostly at mid range then gets loud at high rpm again
07-30-2024, 05:23 PM
#26
New timing chain and sprockets still tapping.. listening very close sounds to be coming from the back of the motor. Almost like it’s something with the flex plate or clutch. Pressing clutch and loading the clutch has no affect on the noise. Or oil pump drive gear but I looked all over haven’t found anybody naming that as the source of a tapping sound
08-04-2024, 08:21 PM
#28
Today I picked up a stethoscope. Which I must say works way better than I expected. Put it on each rocker nut and #7 intake is definitely the culprit. This is the same that collapsed at the beginning of this. I replaced that lifter when It collapsed and now replaced all of them including that one again. Figuring the cam was damaged I just pulled everything out today. Roller Rocker is tight with no flat spots, pushrod is straight, lifter looks good, and cam looked and felt good. Only thing to note is most of my pushrods are apparently rubbing on the head. Anybody ever have a tap from this? Not sure if I should change length or open the holes up. They are self aligning rockers
08-05-2024, 12:52 PM
#30
This is the worst one. 1 valve over from the valve I heard the most noise from. But most of them have at least some rub marks. I assume if this was making a tap it would be from either getting pushed off center in the rocker or lifter, or snapping the rocker sideways
08-05-2024, 02:29 PM
#31
TECH Fanatic
Those look like old 918's with the blue stripe. Slide those rockers off and inspect the springs in the picture. Look at the valve tip to make sure the retainer does not hit the rocker alignment tabs.
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cpenrose (08-05-2024)
08-05-2024, 10:32 PM
#33
TECH Resident
Are you absolutely sure you have self aligning rockers? I wonder if you ended up with NSA rockers and need guideplates. Pull the pair off #7, flip them upside down, take a picture, and let us see the roller side of the rockers that contacts the valves.
SA on the left, NSA on the right.
http://www.97transam.com/gm847cam/install/IMGP2796.JPG
I'm looking to see if you have some kind of guide flange on the bottom of the rocker body at the roller tip end. The rollers themselves sure don't have any guides.They look like my NSA pro mags from the top.
SA on the left, NSA on the right.
http://www.97transam.com/gm847cam/install/IMGP2796.JPG
I'm looking to see if you have some kind of guide flange on the bottom of the rocker body at the roller tip end. The rollers themselves sure don't have any guides.They look like my NSA pro mags from the top.
Last edited by ACE1252; 08-05-2024 at 10:41 PM.
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jmd (08-10-2024)
