Engine knocks when ambient temps around freezing or below

[sneakingfart]

Hi all, quick question. Have a 1999 Suburban with 185k miles. Runs very well, makes good power from what I can tell, but I only had this truck for around a year. Now that it's colder outside, I'm hearing a light knocking noise on initial engine startup in the morning. Lasts for about a minute, quiet enough to where you may not even notice it if you aren't paying attention, does get a little louder and faster with increase in RPMs. But really, by the time I pull out of the driveway, it's gone. This morning was about 27 degrees outside and it was more noticeable. No issues at all when ambient temps are warmer. I read on here that similar issues attributed to piston slap and seems fairly common. Is this anything to worry about? Thanks.

Edit: forgot to mention, oil pressures are normal, oil is Amsoil 5w30. No issues at all about 30 seconds to a minute after starting.

 

[Schurkey]

Yep, that's classic symptoms of piston slap.

Somewhat unusual to have slap on a small-block, but not unheard-of.

GM says it's harmless. Probably is, if it goes away when warm. I've got a pair of Luminas that piston-slap all damn day long, and the gas mileage suffers due to the knock sensor getting confused between "detonation" and "GM Engineering Cheapness".

My 'Camino has Keith Black hypereutectic pistons, it has piston slap for about ten seconds then quiets-down.

 

[JOHNGAAA1]

Schurkey is 100% correct. All my regular drivers knock at start up. If it aint broke dont fix it.

 

[sneakingfart]

Ok, that's good to know. Thanks guys. I'll leave it alone

 

[df2x4]

My '97 K1500 Suburban with the 350 has started doing this in the winter time in recent years. Same deal, always goes away in 30 seconds to a minute. I haven't bothered to do anything about it and it's been fine.

 

[sneakingfart]

Thank you, that's great to hear. I figured it was probably normal, or at least OK, but just wanted to make sure.

 

[RichLo]

Change the oil regularly and I would add a quart of Lucas also.

 

[yevgenievich]

If frequency higher than rpm often in cold weather lifters take a bit extra time to pump up.

 

[Keeper]

Horizontal oil filter. Make sure your filter has an anti-drainback valve.

One of my 454's has had a cold rod knock since new. It has 330+k on it now. Normal.

 

[chasw44]

I once built a International scout 2 for a deerlease truck but it turned out so good I brought it home for regular trips around tx. When I started on the motor it was stuck from rust in a cylinder no 6 I think. I decided to just hone the pits out on that cylinder hone all the others and re-ring it along with new cam bearings and mains and rod bearings and seals and etc. It always had piston slap until it warmed up. Still got it but its been resting for quite awhile now that I've gone back to chevys. In the early 70s I had a 62 panel truck with a 327 with corvette fi pistons in it and the block had a lot of miles on it. It started cracking piston skirts one by one till the last time in it I did the last two that were on the same bank. I could always hear each one as they cracked.