A little piston slap on late small blocks is not unheard of. I have seen a couple high mileage stock engines and have a vortec myself that were pretty loud on cold mornings and got quiet after a little warm up. Especially since you don’t know the specifics of the internals on your engine, that is entirely possible. The sound going away as it warms up is pretty common for piston slap, but definitely not exclusive to it. The mechanics stethoscope suggested by others should help you narrow it down. If you send off the oil sample you should get an idea of bearing health.
Oil pressure Question
- Thread starter Aidan Kesler
- Start date
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1. Have you verified that your gauge is accurate? Connect a different, mechanical gauge to the oil port; see what a different gauge reads.
2. You should be running 5W-30, not 10W-30. 40 psi at hot idle is WAY more than typical.
2. You should be running 5W-30, not 10W-30. 40 psi at hot idle is WAY more than typical.
Aidan Kesler
OBS Enthusiast
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Well here is a video of it, I took a screwdriver like suggested and went to the oil pan, and didn’t hear anything abnormal, just moving parts like normal. But the “knock” sound did appear to be from the exhaust leak I have in my headers. Still kind of in question though because I've never heard an exhaust leak sound like a rod knock before. When it warms up, it pretty much goes away 90%.
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Aidan Kesler
OBS Enthusiast
Well my motor is supposedly a super low mileage fresh rebuild with tight clearances (supposedly lol) and plus I’m running at 10w30 with Lucas so the high oil pressure is expected, just didn’t know if it was safe. Which I’m sure it is.
Get the oil analysed at the next change.
Constituents of 'white' metal - bearings.
Iron/hard steel alloys - shafts.
Aluminium - piston skirt.
Iron/steel etc can be from rings or valve gear but tend not be so noisy as you describe.
Constituents of 'white' metal - bearings.
Iron/hard steel alloys - shafts.
Aluminium - piston skirt.
Iron/steel etc can be from rings or valve gear but tend not be so noisy as you describe.
Excess pressure just puts extra load on the distributor gear and cam gear. Thick oil takes longer to flow thorugh the oil passages and oil filter, meaning it takes longer to reach the bearings and rocker arms, leading to additional start-up wear.
Knock off the Lucas crap, too. If you needed it, it'd already be mixed-into the oil.
Knock off the Lucas crap, too. If you needed it, it'd already be mixed-into the oil.
kenh
I see nothing I hear nothing
The knock you hear when cold could simply be an exhaust noise. I had a Colorado with the 4 cylinder. It had a cold knock, really loud. It was simply the exhaust in the cold manifold. Headers can make this worse. I had a friend with a Dodge p-up. Same thing, cold knock and it was confirmed exhaust "knock".
Ken
Ken
kenh
I see nothing I hear nothing
You last paragraph describes a loose rod bearing. Rod bearings will knock in a float condition as when the engine is not in acceleration or deceleration. Main bearings usually knock under load. Exhaust leaks can sound like a knock. Fix that first then see what you have.
Ken
