Have a Knock
Thread Starter
Team Owner
Joined: Jan 2003
Posts: 21,234
Likes: 19
From: Freestate Corvette Club! Elkridge, MD
St. Jude Donor '17
Have a Knock
Hi Everyone!
I have a 1971 454 with solid lifters. The car has a serious lifter type knock. I tried to adjust the lifters and that (and new plugs and wires) helped the shake at idle, but the knock is still there. The car also smokes like heck from the passenger side exhaust pipe when i rev it up and a few minutes after i let it off - from the SAME side I THINK the lifter knock is coming from. I will pop the covers off tomorrow to look for a broken spring or what not, but any thoughts? BTW - it does not clatter a lot (some to be exepected I assume with solid lifteres) at start up and only smokes under load and 5 min there after. The facory oil pressure gauge reads 30 lbs ish at idle so i think that is ok. Tach does not work so i do not know the idle.
The owner (the 2nd owner) I bought it from said it has not been run in 5 years - could this be the trouble?
ANY suggestions are GREATLY appreciated as always!!
I have a 1971 454 with solid lifters. The car has a serious lifter type knock. I tried to adjust the lifters and that (and new plugs and wires) helped the shake at idle, but the knock is still there. The car also smokes like heck from the passenger side exhaust pipe when i rev it up and a few minutes after i let it off - from the SAME side I THINK the lifter knock is coming from. I will pop the covers off tomorrow to look for a broken spring or what not, but any thoughts? BTW - it does not clatter a lot (some to be exepected I assume with solid lifteres) at start up and only smokes under load and 5 min there after. The facory oil pressure gauge reads 30 lbs ish at idle so i think that is ok. Tach does not work so i do not know the idle.
The owner (the 2nd owner) I bought it from said it has not been run in 5 years - could this be the trouble?
ANY suggestions are GREATLY appreciated as always!!
Last edited by Ragtop_Rob; Oct 19, 2007 at 06:26 PM.
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
How did you adjust the lifters without removing the valve covers? That would be the first thing is to inspect the valvetrain. The smoking could be minor or something major. It will take some more diagnosing to find out.
Thread Starter
Team Owner
Joined: Jan 2003
Posts: 21,234
Likes: 19
From: Freestate Corvette Club! Elkridge, MD
St. Jude Donor '17
I had them off to adjust, it was fine at the time, but i was wondering if a spring broke after the adjustment. I used to have a cut away cover that allowed me to watch everything on my old LT1 while it was running. This car has double springs, i was thinking maybe an inside spring let go? Sorry for not being clear - I guess I am working two problems at once here...
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
This is the 71 you just bought off E-bay? Really nice looking car!
Have you changed the oil since you got it? a tapping or clicking is probably valvetrain related. Have you been driving the car hard? If it is an original solid lifter big block that is a 71 LS6. They used forged pistons and sometimes have a slight knocking sound before they warm up (Piston slap). Always let the car warm up good before driving, especially if you are driving it hard. The forged pistons have to expand to reduce piston slap. A long wood dowel is the tool of choice here. Use it to locate to tapping by putting it against the valvecovers and listening to the end. If it is not in the valve cover, deep in the engine, gets worse when warm and is a deep knocking sound. DON"T DRIVE THE CAR LIKE THAT!!! If your car had a knock the previous owner could have changed to a thicker oil and added STP or Motor honey, something like that to sell the car. Hope this is not the case but have heard of it happening before.
Have you changed the oil since you got it? a tapping or clicking is probably valvetrain related. Have you been driving the car hard? If it is an original solid lifter big block that is a 71 LS6. They used forged pistons and sometimes have a slight knocking sound before they warm up (Piston slap). Always let the car warm up good before driving, especially if you are driving it hard. The forged pistons have to expand to reduce piston slap. A long wood dowel is the tool of choice here. Use it to locate to tapping by putting it against the valvecovers and listening to the end. If it is not in the valve cover, deep in the engine, gets worse when warm and is a deep knocking sound. DON"T DRIVE THE CAR LIKE THAT!!! If your car had a knock the previous owner could have changed to a thicker oil and added STP or Motor honey, something like that to sell the car. Hope this is not the case but have heard of it happening before.
Last edited by 63mako; Oct 20, 2007 at 10:51 AM.
Thread Starter
Team Owner
Joined: Jan 2003
Posts: 21,234
Likes: 19
From: Freestate Corvette Club! Elkridge, MD
St. Jude Donor '17
This is the 71 you just bought off E-bay? Really nice looking car! Have you changed the oil since you got it? a tapping or clicking is probably valvetrain related. Have you been driving the car hard? If it is an original solid lifter big block that is a 71 LS6. They used forged pistons and sometimes have a slight knocking sound before they warm up (Piston slap). Always let the car warm up good before driving, especially if you are driving it hard. The forged pistons have to expand to reduce piston slap. A long wood dowel is the tool of choice here. Use it to locate to tapping by putting it against the valvecovers and listening to the end. If it is not in the valve cover, deep in the engine, gets worse when warm and is a deep knocking sound. DON"T DRIVE THE CAR LIKE THAT!!! If your car had a knock the previous owner could have changed to a thicker oil and added STP or Motor honey, something like that to sell the car. Hope this is not the case but have heard of it happening before.
Have you changed the oil since you got it? a tapping or clicking is probably valvetrain related. Have you been driving the car hard? If it is an original solid lifter big block that is a 71 LS6. They used forged pistons and sometimes have a slight knocking sound before they warm up (Piston slap). Always let the car warm up good before driving, especially if you are driving it hard. The forged pistons have to expand to reduce piston slap. A long wood dowel is the tool of choice here. Use it to locate to tapping by putting it against the valvecovers and listening to the end. If it is not in the valve cover, deep in the engine, gets worse when warm and is a deep knocking sound. DON"T DRIVE THE CAR LIKE THAT!!! If your car had a knock the previous owner could have changed to a thicker oil and added STP or Motor honey, something like that to sell the car. Hope this is not the case but have heard of it happening before.I have not actually driven this car yet, I can't until I get the tilt tele column installed (tomorrow).
THANKS FOR THE HELP!!!!!!!!!!!!!!!!!!!!
Thread Starter
Team Owner
Joined: Jan 2003
Posts: 21,234
Likes: 19
From: Freestate Corvette Club! Elkridge, MD
St. Jude Donor '17
BTW - Missed this in mt reply. The car has the original motor, but it was rebuilt by the previous owner. FOr whatever reason that is FAR beyond me, he put solid lifters in it. Maybe he liked the clattering noise or relentless maint. The car is a 365 horse LS5 with a slightly modified original motor.
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
Yes, this is the "Ebay find"..... I found the problem today, it broke a rocker arm. I picked up a new set from Lad's, and just finished replacing them. It runs great now - I can't wait to drive it! I now have to wonder if I misadjusted it and caused the problem. I double checked everything this time around.
I have not actually driven this car yet, I can't until I get the tilt tele column installed (tomorrow).
THANKS FOR THE HELP!!!!!!!!!!!!!!!!!!!!
I have not actually driven this car yet, I can't until I get the tilt tele column installed (tomorrow).
THANKS FOR THE HELP!!!!!!!!!!!!!!!!!!!!
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski