[GrayLT1]

So I'm working on breaking in my 2021 LT1 (just changed oil at 500ish miles today), and I heard what sounded like valve rattle while I was pushing on it a little.

Basically I was doing a 2nd gear pull and running it up semi-aggressively (1/2 peddleish) to about 4500 rpm then letting off.

When I was starting to let off the transmission shifted and for a second I hear what sounded like valve rattle. I did this 3 times and it happened all 3 times.

I run Costco 93 and/or Shell 93 in the car so hopefully I don't have low octane/bad gas. Normal driving it runs fine and has plenty of pep.


So since I'm new to the car I wanted to know if others have experienced anything similar with these cars, etc.

Only thing else I think it could be is the DI pump when I let off the gas.. but that is just a pure guess.. b/c it sounds like valve rattle.


FYI: In high school I had an 86 trans am with an engine my father built that was really sensitive to octane.. with that car I could tell you what stations had the best gas... wondering if this car is similar..


Thoughts/experiences?

Thanks

[95 imp]

If you get an OBD2 plugin module you can monitor the KS to see if it is an octane issue.

https://www.amazon.com/Veepeak-OBDCh...o%2C296&sr=8-6

[Petrol Head]

Valve rattle? Might be the valve spring issue. There was a batch of bad valve springs in the LT1s that have been breaking within about 500 miles of new. May want to bring it to the dealer.

[LT4Greg]

That’s what I’m thinking too. Maybe a valve spring that is failing.

[GrayLT1]

Sorry, when I say valves rattle I’m trying to say pre-ignition(I guess valve rattle is an old school phrase I picked up from my father). What is strange is that it is only doing it when I go over 4000 rpm and start to let up on the gas peddle.

Thx for the feedback.

[LT4Greg]

If you can Gray, run 93 octane gasoline in your LT1. That is, if you don’t. I use Shell V-power in my ZL1 and used it in my long gone 2016 2SS. It is rated 93 octane and our big V8s love it!

[ember1205]

Do you have the performance exhaust (NPP)? There used to be an issue where the valves in the bypass pipes would start to rattle (but that should have largely been repaired in the more recent cars).

[GrayLT1]

Originally Posted by ember1205

Do you have the performance exhaust (NPP)? There used to be an issue where the valves in the bypass pipes would start to rattle (but that should have largely been repaired in the more recent cars).

I do have NPP. The sound seems to be pinging from the engine bay but who knows.. maybe it is echoing and it just sounds like it is coming from the engine bay. I just ordered the blu-tooth device to use OBD Fusion as suggested to see if it is ignition/detonation issues.

Thanks

[GrayLT1]

Originally Posted by LT4Greg

If you can Gray, run 93 octane gasoline in your LT1. That is, if you don’t. I use Shell V-power in my ZL1 and used it in my long gone 2016 2SS. It is rated 93 octane and our big V8s love it!

I am running shell 93 and/or Costco 93.

Maybe I got a bad batch of gas...

Thanks

[ember1205]

Originally Posted by GrayLT1

I do have NPP. The sound seems to be pinging from the engine bay but who knows.. maybe it is echoing and it just sounds like it is coming from the engine bay. I just ordered the blu-tooth device to use OBD Fusion as suggested to see if it is ignition/detonation issues.

Thanks

If you have someone that can help, you might be able to identify if it's in the NPP by having them rev the motor while you're listening at the exhaust tips.

[ctrlz]

Originally Posted by GrayLT1

Sorry, when I say valves rattle I’m trying to say pre-ignition...

Your car won't keep pinging (the sound of "knocking" or pre-ignition) unless the knock sensor is bad, which would likely throw a CEL.

I think there were some other threads on people getting used to the start up sound of a direct injection engine, which I guess comes off as "metallic" to some people.

[GrayLT1]

Originally Posted by 95 imp

If you get an OBD2 plugin module you can monitor the KS to see if it is an octane issue.

https://www.amazon.com/Veepeak-OBDCh...o%2C296&sr=8-6

Good idea.. ordered it this morning.

[GrayLT1]

Ok went for another test run and it did not do I it 3 out of the 4 times.

I think I got some low octane gas in it from a shell station (it is half Costco and half shell in the tank now)

It wasn’t doing it when I only had Costco gas.

Thanks everyone for the replies/suggestions. This car is new to me and I’m learning it’s characteristics... so GM wasn’t kidding when they say use 93 octane

[ember1205]

Originally Posted by GrayLT1

Ok went for another test run and it did not do I it 3 out of the 4 times.

I think I got some low octane gas in it from a shell station (it is half Costco and half shell in the tank now)

It wasn’t doing it when I only had Costco gas.

Thanks everyone for the replies/suggestions. This car is new to me and I’m learning it’s characteristics... so GM wasn’t kidding when they say use 93 octane

FYI... The Costco / Kirkland gas is Top Tier Gasoline as designated in the manual. It's pretty much all I run in mine (unless I'm out of town and there isn't a Costco nearby) because the price is so much better than anywhere else and I have never had an issue with it. I also run it in my truck and she runs it in her SUV (also premium) and results have always been very good.