Detonation at High Speed?
Thread Starter
Burning Brakes
Joined: Feb 2005
Posts: 752
Likes: 1
From: Tulsa OK
Detonation at High Speed?
Went on a 2,000 mile road trip last week and on the way home it was pretty hot - 98 to 100 degrees F.
Car was running good - steady drive, all interstate, for about 11 hours at 75 to 85 mph, stopping only for gas and fast food. Oil temp was 226, coolant temp was 199 and trans temp was 184.
Decided to have some fun on an open stretch of interstate, no traffic and the radar detector was quiet. Ran it up to about 120mph at WOT. Got there pretty quick but it was pinging pretty heavy so I backed off.
Car has LT's, Hiflow cats, Corsa, Blackwing and a custom dyno tune. Gas was 93 octane.
Was it just the hot conditions or do I need to think about a retune?
Car was running good - steady drive, all interstate, for about 11 hours at 75 to 85 mph, stopping only for gas and fast food. Oil temp was 226, coolant temp was 199 and trans temp was 184.
Decided to have some fun on an open stretch of interstate, no traffic and the radar detector was quiet. Ran it up to about 120mph at WOT. Got there pretty quick but it was pinging pretty heavy so I backed off.
Car has LT's, Hiflow cats, Corsa, Blackwing and a custom dyno tune. Gas was 93 octane.
Was it just the hot conditions or do I need to think about a retune?
Race Director
Joined: Oct 2002
Posts: 16,477
Likes: 26
From: Gone
CI 6-7-8-9-10 Veteran
St. Jude Donor '03
Not sure 11 hours of run time at <2000 RPM really warrants new valvesprings or lifters. 
Let's see, 11 hours times a 75 mph average speed, equals 825 miles. Most folks easily do 7-10 times that amount just between routine oil changes.
EStreeter, if you can still duplicate the results, having someone that can scan/tune it is probably the next step. Might be a classic case of too much timing, or too leaned out. WOT at higher speeds puts the greatest load on the engine...if it's ever going to ping, that is when it will occur.
If you can't make it do that anymore, then maybe simply a bad tankful of gas, or perhaps the high ambient temp was just enough to make an aggressive tune go over the edge.
Let's see, 11 hours times a 75 mph average speed, equals 825 miles. Most folks easily do 7-10 times that amount just between routine oil changes.
EStreeter, if you can still duplicate the results, having someone that can scan/tune it is probably the next step. Might be a classic case of too much timing, or too leaned out. WOT at higher speeds puts the greatest load on the engine...if it's ever going to ping, that is when it will occur.
If you can't make it do that anymore, then maybe simply a bad tankful of gas, or perhaps the high ambient temp was just enough to make an aggressive tune go over the edge.
Burning Brakes
Joined: May 2008
Posts: 1,147
Likes: 1
From: Mohegan Lake New York
AU N EGL 75-85mph@11hours I'm a little confused whats so bad about that? rpm's should be around 2500 to 3000 should handle that with out breaking a sweat you mentioned springs/lifters???? detationation/how do they tie in? suspect valve float??don't think car would detonate bad springs/lifters car would just go flatwhen he ran it up to 120 did temp. jump up? would indicate lean or too much timing OR the real possibility or contaminated gas or regular sold out of premimun pump gas sold today w/ 10%alky if contaminated with MINUTE amount of h2o octane drops 3to 4 points recommend he pull plugs examine porcelain of plugsto make sure it was indeed detonation he heard if so porcelain will be spotted like pepper but its pieces of the piston flaking off. be advised detionation very bad check tune first.cloogged cats/exhaust would cause that also was fuel mileage bad or worse than previous telltale sign of clogged exhaust but can be partially be clogged and still get acceptable milage.. AU N GEL don't doubt you just not sure what you mean
Team Owner
Joined: Sep 2003
Posts: 43,084
Likes: 33
From: Raleigh / Rolesville NC
It was the sound that you described. Personally if I head that sound, I would want to look or at least listen to the springs and lifters.
If I am wrong so be it. But worked with too many LS6s and recently many LS3s that have made that sound describe right before they dropped a valve.
If you have a stethoscope have a listen above each valve. If not just a solid piece of steel rod will do. Let the engine idle and put the stethoscope or steel rod above each valve spring. Of something is off, you will hear a difference between the good ones and the one that isn't
Running 11 hours at 80 mph should not be a problem even with poor fuel. Just burn right up.
Good Luck
If I am wrong so be it. But worked with too many LS6s and recently many LS3s that have made that sound describe right before they dropped a valve.
If you have a stethoscope have a listen above each valve. If not just a solid piece of steel rod will do. Let the engine idle and put the stethoscope or steel rod above each valve spring. Of something is off, you will hear a difference between the good ones and the one that isn't
Running 11 hours at 80 mph should not be a problem even with poor fuel. Just burn right up.
Good Luck
Thread Starter
Burning Brakes
Joined: Feb 2005
Posts: 752
Likes: 1
From: Tulsa OK
Thanks for the responses.
When I was cruising as those speeds it was only at about 2300 rpm. The car has a 3:42 rear. It will run all day like that. Average mileage was about 25mpg. Instant mileage was usually between 22 and 28mpg depending on the grade of the road.
The car is hardly ever driven very hard. Never been to the track. Once in a while I pull a hole shot just for fun. The engine is pretty quiet and idles smooth. Runs strong. I didn't mention that if you run up to high speed without just smashing the peddle (WOT) it doesn't make any detonation noises. It just keeps on pulling.
I have had it up to 140 and that was at a little over 4,000 rpm. No problem.
When I was cruising as those speeds it was only at about 2300 rpm. The car has a 3:42 rear. It will run all day like that. Average mileage was about 25mpg. Instant mileage was usually between 22 and 28mpg depending on the grade of the road.
The car is hardly ever driven very hard. Never been to the track. Once in a while I pull a hole shot just for fun. The engine is pretty quiet and idles smooth. Runs strong. I didn't mention that if you run up to high speed without just smashing the peddle (WOT) it doesn't make any detonation noises. It just keeps on pulling.
I have had it up to 140 and that was at a little over 4,000 rpm. No problem.
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