armin922 Posted May 16, 2003 Report Share Posted May 16, 2003 My friend has a stock 2000 camaro z28, and he said that he hears a slight knock whenever he just starts up the car or when its cold. Also sometimes at idle. But he said that he took it to the shop and asked the guys and they said that, that sound is a normal sound for a stock LS1. My friend also uses 87 octane for his car. Does anyone happen to know what the problem is? Or is it just normal for a bone stock 00 camaro z28 to have a slight knocking sound? Quote Link to comment Share on other sites More sharing options...
smokinHawk1647545499 Posted May 16, 2003 Report Share Posted May 16, 2003 I have heard piston slap on start up is normal in an ls1. Athough i dont have this problem. ONLY 87 OCTANE WHAT IS HE THINKING. the CR of a stock ls1 is 10.1:1, you should be using around 91 octane or greater. Quote Link to comment Share on other sites More sharing options...
Guest wishihadafastcar Posted May 16, 2003 Report Share Posted May 16, 2003 i agree... he should be running a higher octane for sure Quote Link to comment Share on other sites More sharing options...
armin922 Posted May 16, 2003 Author Report Share Posted May 16, 2003 but he told me he read the owners manual and it said its ok to put in 87 octane, but the higher the octane the better peak performance? He said that he doesnt really care about peak performance so he just uses 87 octane. Quote Link to comment Share on other sites More sharing options...
BIG SHAFE Posted May 16, 2003 Report Share Posted May 16, 2003 Lower octane=Knock especially with a higher compression ratio, I'm pretty sure on the Vettes it says that Premium should be used, should be the same for any LS1 maybe LT1??, not positive though. Quote Link to comment Share on other sites More sharing options...
SamZman Posted May 16, 2003 Report Share Posted May 16, 2003 I've also heard piston slap happens in some LS1's, so I'm pretty sure that's what he's hearing. He may want to take it to a dealer if he's really concerned. It's not detonation, and I don't think it's being caused by the lower octane gas. If the car is detonating upon startup and when the car's idling and cold he's got serious problems. Originally posted by smokinHawk: ONLY 87 OCTANE WHAT IS HE THINKING. the CR of a stock ls1 is 10.1:1, you should be using around 91 octane or greater. I know Lee Howie recommends that people run 87 octane in LS1s... He said that's all he runs in his daily driver C5 and claims to gain a tenth or two.. Quote Link to comment Share on other sites More sharing options...
BIG SHAFE Posted May 16, 2003 Report Share Posted May 16, 2003 You live and learn. Quote Link to comment Share on other sites More sharing options...
Guest stevil Posted May 17, 2003 Report Share Posted May 17, 2003 Piston slap in cylinder #1, cold start, it's very common in LS1s. Not that big of a deal though, I don't think dealers will do anything for it, no recall or anything. The octane isn't causing it, but I wouldn't reccomend 87 either. Quote Link to comment Share on other sites More sharing options...
Nitrousbird Posted May 17, 2003 Report Share Posted May 17, 2003 The goal with any car is to run the lowest octane you can WITHOUT detonation/needing to pull timing. The LS1 PCM I believe has a table (my OBD-I LT1 PCM does, so I'm sure it does as well) that basically detects low octane by knock counts from the sensor, and just pulls a large amount of timing. I tried running 87 in my car when it was stock. Doesn't hurt anything....BUT, it was down on power where you want it (down low for crusing and up top), and got worse gas mileage. The 20 cents/gallon cost savings between 87 and 93 was ate up in the lower gas mileage. Of course, my car is 10.5:1 stock. With a stock LS1, I'd probably stick to 89 at least. No need for 93-94, but 87 is probably a bit low. Quote Link to comment Share on other sites More sharing options...
Ryoga Posted May 19, 2003 Report Share Posted May 19, 2003 Originally posted by Nitrousbird: The goal with any car is to run the lowest octane you can WITHOUT detonation/needing to pull timing. The LS1 PCM I believe has a table (my OBD-I LT1 PCM does, so I'm sure it does as well) that basically detects low octane by knock counts from the sensor, and just pulls a large amount of timing. I tried running 87 in my car when it was stock. Doesn't hurt anything....BUT, it was down on power where you want it (down low for crusing and up top), and got worse gas mileage. The 20 cents/gallon cost savings between 87 and 93 was ate up in the lower gas mileage. Of course, my car is 10.5:1 stock. With a stock LS1, I'd probably stick to 89 at least. No need for 93-94, but 87 is probably a bit low. Yup, they all said it right. I'm 99.99% sure it's not your gas that is the problem. The LS1's can run 87 if you don't mind getting into the 'Low Octane' table, Ideally-at least in my application at Lee Howie's near demand, I finally put 89 Octane and ran it through a coupe tanks then tested at the track. I had no more knock than normal (under very similar weather conditions) and actually put down my best times ever. My heads are even milled down an extra .20 as well so I don't think that's the problem. When you said he only (or at least mainly) hears the noise on a cold start up (in the colder weather being worse) then that pretty much sealed it. It's a very common condition for LS1's and has become one of the accepted characteristics of the beast. I've heard of no seriously negative impact due to this condition and even have the same thing on my TA. I wouldn't worry about it if you aren't throwing lights and have no major 'ride' changes that have been noticed. Quote Link to comment Share on other sites More sharing options...
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