Kocking when first starting
Thread Starter
Heel & Toe
Joined: May 2006
Posts: 22
Likes: 0
Kocking when first starting
I bought my 82 Vette about 3 weeks ago and this was the first week, where she was not started up at least once. Yesterday, when I started her up, I heard a loud knocking from the engine for about 20-30 seconds but it went away and when I start her up after that I don't hear any knocking at all. I put 89 octane fuel in her and did an oil change about 2 weeks ago with 10-W30 and a standard ACDelco filter (short one, not the longer one). Is this something that I should be concerned about? The only thing that I can think of is that the oil is not getting distributed fast enough (I am still in the learning process when it comes to cars). Again, this only happened after she has been sitting for a week.
Thanks for any input.
Thanks for any input.
Le Mans Master
Joined: Jan 2004
Posts: 7,399
Likes: 75
St. Jude Donor '14
I'm guessing piston slap. The lack of oil from sitting combined with a slightly loose piston clearance causes the skirts to slap until the piston heats up and expands a little to fill the bore. Essentially harmless. Engines can run a long time with this condition without damage, I would just wait for the knocking to subside before getting on it hard.
Drifting
Joined: May 2005
Posts: 1,629
Likes: 4
From: Somers CT
It could also be excessive wear in the rear main, when the engine is first started there's no oil flow to fill the gap and it'll make some noise. As soon as the pressure gets up the oil cushions it and it'll quiet down.
Thread Starter
Heel & Toe
Joined: May 2006
Posts: 22
Likes: 0
Thanks for the input. There is no ping when she accelerates or going uphill. She runs strong but slightly rough but I still have to change the plug cables, distributor cap and rotor. As long as it is harmless, I can live with it. Gonna pull the motor next year anyways (has 74,000 miles on it) and put in a crate engine. I don't want to put too many miles on the original motor or run it hard.
Thanks again.
Thanks again.
Le Mans Master
Joined: Jul 2005
Posts: 5,752
Likes: 4
From: Austin Texas
Originally Posted by SIXFOOTER
Was it Knocking or was it Valve clatter? Sometimes on older engines the valvs will clatter for a few seconds until the oil pressure gets up. Not a big deal
Sometimes a lifter will bleed down if an engine sits for a while. No biggie.....
Team Owner
Joined: Jul 1999
Posts: 26,545
Likes: 46
From: Huntersville NC
Originally Posted by smangs
I heard a loud knocking from the engine for about 20-30 seconds but it went away and when I start her up after that I don't hear any knocking at all.
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Thread Starter
Heel & Toe
Joined: May 2006
Posts: 22
Likes: 0
Originally Posted by PRNDL
Although we commonly use the term "knocking" to mean pinging or detonation, I don't think that's what he means here. My understanding is "knocking" like someone knocking on a door.
Yup, it was an actual "knocking" sound.
