engine knocking...HELP
Thread Starter
Intermediate
Joined: Feb 2008
Posts: 39
Likes: 0
From: Foley Alabama
engine knocking...HELP
1977 l48 4 speed with 85k original miles
Ok, after setting the timing at 3,500 rpms the engine starting making a strange noise like the a/c compressor clutch needed to be oil, then it developed into a "rattling" sound like a valve dropped and then started knocking (all of this in just a matter of minutes).
I checked compression and didn't see anything unusual. Pulled the valve covers and found a very loose push rod on #6. Pulled the intake manifold to inspect the lifters and found the lifter seemed to be stuck, so I thought I had found the problem. Changed out all the lifters, put it back together, and it actually seems to be worse.
I can't tell where the knocking is coming from: Checked compression again and this is what I have:
#1 - 160 psi #2-155 psi
#3 - 150 psi #4 -155 psi
#5 - 155 psi #6 - 155 psi
#7 - 150 psi #8 - 160 psi
Just not sure where to go next..... I did take off all the belts and crank the engine just to be sure it wasn't from something belt driven, no difference. Oil pressure is 40 psi.
Thanks in advance for any suggestions...
Ok, after setting the timing at 3,500 rpms the engine starting making a strange noise like the a/c compressor clutch needed to be oil, then it developed into a "rattling" sound like a valve dropped and then started knocking (all of this in just a matter of minutes).
I checked compression and didn't see anything unusual. Pulled the valve covers and found a very loose push rod on #6. Pulled the intake manifold to inspect the lifters and found the lifter seemed to be stuck, so I thought I had found the problem. Changed out all the lifters, put it back together, and it actually seems to be worse.
I can't tell where the knocking is coming from: Checked compression again and this is what I have:
#1 - 160 psi #2-155 psi
#3 - 150 psi #4 -155 psi
#5 - 155 psi #6 - 155 psi
#7 - 150 psi #8 - 160 psi
Just not sure where to go next..... I did take off all the belts and crank the engine just to be sure it wasn't from something belt driven, no difference. Oil pressure is 40 psi.
Thanks in advance for any suggestions...
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
Possible wiped cam lobe(s) ... particularly at stuck lifter(s).
pull out lifter & inspect lifter face & cam lobe.
Possible collapsed lifter.
a vacuum gage in knowledgable hands can help diagnose wiped lobe and/or collapsed lifter ... a cheap essential tool.
pull out lifter & inspect lifter face & cam lobe.
Possible collapsed lifter.
a vacuum gage in knowledgable hands can help diagnose wiped lobe and/or collapsed lifter ... a cheap essential tool.
Melting Slicks
Joined: Mar 2008
Posts: 2,023
Likes: 6
From: Austin Tx
Racer
Joined: Nov 2006
Posts: 491
Likes: 5
From: Tampa Bay Area, U.S.A. (Zombie Nation)
I think you're talking about a SB but on two separate occasions my BB suddenly developed a horrendous knock. The first time I tore it down, expected the worse, but found nothing wrong. Put it back together, sounded fine. Many months later, same thing again. This time I just took it out and ran the pee out of it. Ran great, knock stopped. Never happened again. Always suspected valve train as culprit. Still a source of wonderment.
Safety Car
Joined: Oct 2005
Posts: 3,570
Likes: 1
From: Algonac Michigan
