split second mechanical over-rev
10-21-2018, 08:38 PM
#1
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split second mechanical over-rev hey everyone.. so recently I was dicking around in my 6 speed 01 z.. cammed with supporting valvetrain.. and I missed a gear bad for the first time in my life. Except I don't think this missed gear was the typical neutral rev limiter scenario.. I think I actually somehow yanked 2nd instead of 4th. It happened very fast and I clutched in immediately (or as fast as I could) because the car spiked VERY high rpm and started wheel hopping real bad.. which made me think it had to of been 2nd. still can't believe it.. but anyway here's a video. I drove it home fine, no weird noises from engine or trans that i can tell, the cars got a dumped X pipe off long tubes so can't really hear every little thing, but i really think I might have fucked something up. Anyone ever do this and your car has been fine since? I'll be pulling heads to check for valve dings on the pistons. It sounded like ~8500 rpm...
10-21-2018, 08:46 PM
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I actually did this for the very first time recently lol. Best that I can tell eveything sounds the same, except for maybe a slight increased vibration around 80 mph. The vibration was there before after the torque arm install, but i swear it's just a tiny bit worse now.
10-21-2018, 08:49 PM
#3
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Hey, you might be totally OK. I didn't hear any weird noises in the video. How does it sound idling? That's when you will hear naughty noises. LS engines are amazingly tough. The occasional wing-it to high RPM's can usually be handled.
10-21-2018, 08:51 PM
#4
If it’s running fine you’re probably ok, just dodged a bullet. It wouldn’t hurt to remove the valve covers and inspect for damage. You can bump the engine with injectors unplugged and make sure all the valve movements are smooth and get a visual on the springs/rockers/retainers. I would invest in a cheap borescope instead of pulling the heads if there are no other signs of damage.
10-21-2018, 08:52 PM
#5
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If it’s running fine you’re probably ok, just dodged a bullet. It wouldn’t hurt to remove the valve covers and inspect for damage. You can bump the engine with injectors unplugged and make sure all the valve movements are smooth and get a visual on the springs/rockers/retainers. I would invest in a cheap borescope instead of pulling the heads if there are no other signs of damage.
10-21-2018, 09:01 PM
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Money $hift. Yikes. I highly recommend pulling a couple spark plugs and looking for eyebrows.
You mighta lucked out, depending on the valvetrain. But thirty minutes to check cylinders 1,2 is worth it. If you see eyebrows, my condolences.
You mighta lucked out, depending on the valvetrain. But thirty minutes to check cylinders 1,2 is worth it. If you see eyebrows, my condolences.
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10-21-2018, 09:32 PM
#8
Don't pull the heads, Buy or borrow a bore scope and you should be able to see the piston tops easy enough. Since it was wheel hoping you may not have revved as far as you think. I put a brand new LSA supercharger with an new LS3 drive by wire throttle body. First time I turned the key and it fired up and idled fine. I shut it down to check for leaks and fired it a second time, RPMs shot through the roof instantly. Looked at the logs and it spiked just over 7,800 with no load at all. Checked everything over and it was fine. Long story short this happened twice before I figured out the cause and it still runs it's *** off a few thousand miles later.
Edit: I didn't see the borescope was mentioned already lol
Edit: I didn't see the borescope was mentioned already lol
10-21-2018, 09:43 PM
#9
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Thanks for the advice so far guys. I will try a Borescope first. Believe me this is embarrassing to post lol.. I’ve never done anything close to as stupid as this. The on-ramp is a slight right turn which is the only reason I can think of myself yanking it toward second. ******* stupid and I am sick over it. Worst case I do have another ls1 ready to drop in haha
Last edited by dan.b; 10-22-2018 at 07:08 AM.
10-21-2018, 09:52 PM
#10
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Don't pull the heads, Buy or borrow a bore scope and you should be able to see the piston tops easy enough. Since it was wheel hoping you may not have revved as far as you think. I put a brand new LSA supercharger with an new LS3 drive by wire throttle body. First time I turned the key and it fired up and idled fine. I shut it down to check for leaks and fired it a second time, RPMs shot through the roof instantly. Looked at the logs and it spiked just over 7,800 with no load at all. Checked everything over and it was fine. Long story short this happened twice before I figured out the cause and it still runs it's *** off a few thousand miles later.
Edit: I didn't see the borescope was mentioned already lol
Edit: I didn't see the borescope was mentioned already lol
10-21-2018, 10:22 PM
#11
Trust me I couldn't turn it off fast enough, Log showed it made 7lbs of boost also, It ended up being a defective throttle body. After the second time it happened I triple checked everything and then used a camera to watch the throttle body while just turning the key on and off and sure enough every so many cycles the throttle blade would go wide open and stay there, I tried another throttle body and it never did it again. First starts always worry me but I wasn't expecting that lol.
10-21-2018, 11:00 PM
#13
Trust me I couldn't turn it off fast enough, Log showed it made 7lbs of boost also, It ended up being a defective throttle body. After the second time it happened I triple checked everything and then used a camera to watch the throttle body while just turning the key on and off and sure enough every so many cycles the throttle blade would go wide open and stay there, I tried another throttle body and it never did it again. First starts always worry me but I wasn't expecting that lol.
10-22-2018, 06:43 AM
#15
That sounded high but didn’t sound bad. Honestly it just sounded like you heel-toed it for a down shift. If it’s running fine I wouldn’t even worry about it, the valvetrain clearly kept everything in control - you’d definitely know if it didn’t because there would be no “I drove it home” part of this story.
10-22-2018, 08:25 AM
#17
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That sounded high but didn’t sound bad. Honestly it just sounded like you heel-toed it for a down shift. If it’s running fine I wouldn’t even worry about it, the valvetrain clearly kept everything in control - you’d definitely know if it didn’t because there would be no “I drove it home” part of this story.
10-22-2018, 12:21 PM
#19
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