A Little Spark Knock

[32valvZ]

Wasnt really hot outside nor was the engine "hot"... it was normal...Noticed from a dead stop, when letting the clutch out, and keeping the rpm relatively low, I can hear a brief spark knock gurgle. A/C off and I can only hear it with my window open. If I give it a little more throttle on take off, I dont hear it, but not sure if thats just because I cant hear it over the exhaust.

Im hoping its just a bit of gasoline thats not quite up to snuff... If it isnt poor gas, how would I start troubleshooting?

I havent made any recent changes to anything and other than that the engine is running perfectly... I have a bottle of octane booster, but Im a little skeptical on using it from reading up on it here and on the forum.... Thoughts?

[Paul Workman]

Some knock may be normal, especially with computer controlled ignition where spark (knock) is constantly being monitored and advance adjusted to optimize performance (LT5s included).

IIRC, the octane in Colorado is typically 91 - not 93. In spite of this, knock is somewhat mitigated by the fact that atmospheric pressure, e.g., in Denver being "the mile high city" where atmospheric pressure is lower than it is in (say) Chicago where AMSL is only 600-700 feet and octane is typically 93 for premium fuel. (IDK if that matters in your case, but thought I'd mention it for the record.)

Knock or piston slap?? The only way to know for sure is to record the knock sensor or knock counts on a scanner. That way you don't come to an erroneous conclusion(s).

Something else(?): IF you combustion chambers get filled with too much carbon, knock can result. As Dave McLellan said once (in effect): "An occasional blast to 7000 rpm is thrilling, and the LT5 will thank you for it!"

NOTE: One of the never-ending questions from the "untutored" that never seems to go away: "Will my engine make more power with higher (e.g.,93) octane compared to regular?"

Well, it depends! Is the question relating to the energy capacity for a given volume of fuel

Several variables come into play: mainly speaking: actual changes in compression (pressure), ignition timing, fuel-air mixture, temperature, and (here's a biggie), whether or not the tune can be modified automatically in accordance with detected/recorded knock event density.

In short: engines with computers w/ programming that can analyze knock density feedback and automatically adjust timing (spark advance) and/or air-fuel mixture to contain knock within tune, may result in higher (engine) output power, and benefit from higher octane (like our LT5s).

[viper107]

I have noticed on earlier models some had a little piston cluck like pulling into a drive way from a stop, normal cause I have seen a few do it