something's knocking on (or in) the engine
Thread Starter
Burning Brakes
Joined: Oct 1999
Posts: 1,047
Likes: 1
From: Arlington Texas
something's knocking on (or in) the engine
Drove the vette to work this morning (6 miles, no highway).
About a quarter of the way there I noticed a little noise from the engine compartment.
I thought maybe I had a header bolt working loose and I was hearing a small exhaust leak.
As I continued, I noticed that the severity didnt increase when I got on it like a normal exhaust leak. The tapping/knocking/rapping sound sped up with the rpms but did not change volume, except to slowly increase in volume the longer I drove.
I pulled into work, shut off the engine and popped the hood. I couldn't see anything obviously wrong.
No leaks, fan wasnt hitting anything, nothing loose.
I started it back up and man the knocking was loud with the hood up.
I still couldn't pinpoint the location, but it sounds like it is slightly louder on the drivers side. It's hard to tell if it's coming from the front or back.
Oil is full and has good color.
Oil pressure is good (good as it ever was, around 40 when driving around town).
Running super unleaded.
Temp gauge showed about 180 or so.
Engine runs and pulls strong, just sounds terrible.
Any ideas?
About a quarter of the way there I noticed a little noise from the engine compartment.
I thought maybe I had a header bolt working loose and I was hearing a small exhaust leak.
As I continued, I noticed that the severity didnt increase when I got on it like a normal exhaust leak. The tapping/knocking/rapping sound sped up with the rpms but did not change volume, except to slowly increase in volume the longer I drove.
I pulled into work, shut off the engine and popped the hood. I couldn't see anything obviously wrong.
No leaks, fan wasnt hitting anything, nothing loose.
I started it back up and man the knocking was loud with the hood up.
I still couldn't pinpoint the location, but it sounds like it is slightly louder on the drivers side. It's hard to tell if it's coming from the front or back.
Oil is full and has good color.
Oil pressure is good (good as it ever was, around 40 when driving around town).
Running super unleaded.
Temp gauge showed about 180 or so.
Engine runs and pulls strong, just sounds terrible.
Any ideas?
Last edited by Shrike; Oct 4, 2006 at 11:09 AM.
Thread Starter
Burning Brakes
Joined: Oct 1999
Posts: 1,047
Likes: 1
From: Arlington Texas
Probably close to never. Or al least since '73 when the dealer replaced the original block.
I replaced the carb and intake and replaced the valve seals, but that's pretty much it as far as engine work.
It could definitely be a bearing, but it just seems odd that the oil and oil press seem fine.
I'm going to go over it tonite with a stethoscope (i.e. a wooden stick) when (if) I get home and see if I can pinpoint the sound location.
I replaced the carb and intake and replaced the valve seals, but that's pretty much it as far as engine work.
It could definitely be a bearing, but it just seems odd that the oil and oil press seem fine.
I'm going to go over it tonite with a stethoscope (i.e. a wooden stick) when (if) I get home and see if I can pinpoint the sound location.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Originally Posted by Shrike
Probably close to never. Or al least since '73 when the dealer replaced the original block.
I replaced the carb and intake and replaced the valve seals, but that's pretty much it as far as engine work.
It could definitely be a bearing, but it just seems odd that the oil and oil press seem fine.
I'm going to go over it tonite with a stethoscope (i.e. a wooden stick) when (if) I get home and see if I can pinpoint the sound location.
I replaced the carb and intake and replaced the valve seals, but that's pretty much it as far as engine work.
It could definitely be a bearing, but it just seems odd that the oil and oil press seem fine.
I'm going to go over it tonite with a stethoscope (i.e. a wooden stick) when (if) I get home and see if I can pinpoint the sound location.
If it's anywhere below the heads it's most likely a bearing. I would say the sound you hear is likely a rod slapping on a worn bearing on the crank. It may also be a worn pin, and the piston head is slapping around.
Also pull a valve cover and see that all your valves are opening and closing properly.
Melting Slicks
Joined: Aug 2003
Posts: 2,135
Likes: 2
From: Dayton Oh
Could be lots of things. The first I'd check would be timing. The second thing would be to pull the valve covers and have a look at the rockers.
Is your's a manual. Maybe just a throwout bearing about to pop.
Is your's a manual. Maybe just a throwout bearing about to pop.
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Melting Slicks
Joined: Mar 2006
Posts: 3,342
Likes: 7
From: Connecticut
Originally Posted by Shrike
I'm going to go over it tonite with a stethoscope (i.e. a wooden stick)
Good luck.........Hope it's not too serious
Thread Starter
Burning Brakes
Joined: Oct 1999
Posts: 1,047
Likes: 1
From: Arlington Texas
I'll check timing and pull the valve covers and see what I see.
Hydraulic lifters.
I'll drain the oil and see what it looks like (metal shavings, etc)
It is a manual. Clutch was replaced about a year ago.
Hydraulic lifters.
I'll drain the oil and see what it looks like (metal shavings, etc)
It is a manual. Clutch was replaced about a year ago.
Thread Starter
Burning Brakes
Joined: Oct 1999
Posts: 1,047
Likes: 1
From: Arlington Texas
Originally Posted by Bob Onit
A 3 foot length of old garden hose has worked better than a wooden stick for me
Good luck.........Hope it's not too serious
Good luck.........Hope it's not too serious
I hope so too, but I am prepared for the worst.
Scott
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
If nothing else this could be a great chance to upgrade everything. New timing set, maybe bore it out and get new pistons. Hotter cam, re-work the heads, and tune or replace the carb. This knocking could get you some extra ponies...
Thread Starter
Burning Brakes
Joined: Oct 1999
Posts: 1,047
Likes: 1
From: Arlington Texas
took the valve covers off, nothing obviously wrong.
Did have several loose header bolts. I tightened those up and started it up.
I could still hear a noise, but I only let it run for a few seconds- before I noticed gas spraying everywhere!
The (fairly new) fuel line had split where it was attached to the carb and when I flexed it to get the valve covers on/off it developed a leak.
I had to do some work on the wife's car, so I just left it (after cleaning up the fuel). I will replace the line tonite and see if I can determine where the noise is coming from.
Did have several loose header bolts. I tightened those up and started it up.
I could still hear a noise, but I only let it run for a few seconds- before I noticed gas spraying everywhere!
The (fairly new) fuel line had split where it was attached to the carb and when I flexed it to get the valve covers on/off it developed a leak.
I had to do some work on the wife's car, so I just left it (after cleaning up the fuel). I will replace the line tonite and see if I can determine where the noise is coming from.
Le Mans Master
Joined: Feb 1999
Posts: 8,351
Likes: 75
From: Tampa Bay FL
Originally Posted by big_G
Also consider a lifter. They can get plugged up with debris, they usually work themselves clean after a while.
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Marvel is amazing stuff. Used it once or twice and it worked wonders. But, if you're gonna get serious with the motor if this is a bearing...the Marvel oil will do little for a freshly rebuilt engine...
