Today , I overrevved my C3 L48. The story, which I will omit, is not pretty. The tach stuck at 7,000 rpm. The car ran perfectly during the parade I was in. I then drove it home, the tach went back to normal, temp was in normal range, oil pressure at 40. It was in the 80s today. As I started to climb the last hill toward home, the car bucked a couple times, power went down and then the engine quit. After about ten minutes, I was able to restart it and Grt it home. Any ideas on what damage I might have done and how to check it out? Thanks, philgran

 

Pull the valve covers and look for bent or broken pushrods.....if you find one it's going to be expensive

 

Is it running on all cylinders? If so, and oil pressure is the same as before, I would assume all is good.

When you got it started, was it running ok? In a parade, it gets hot, and perhaps you had vapor lock?

 

How does it idle? meaning does it shake, miss etc

Did you downshift or miss a gear?

Almost sounds like a coil got hot or your fuel pump was going out.

 

Are you saying that the L-48 engine was actually turning 7,000 RPM, or was there a glitch in the tachometer / ignition? If the engine was actually turning 7,000 RPM, what was the length of time for this event?

 

When I bought my low mile 1980 L82 that had been in storage for almost 2 decades, it had a very interesting overev story.

The original owner, who I bought it from, had a shift kit put in it when it was brand new. It would go into whatever gear you shifted it into no matter what speed or rpm it was turning. A around 43,000 miles, he had a freind ask to borrow the car for some special ocassion, so he let the guy use it. The guy was zipping down the interstate, floored it and downshifted all the way to first gear. WIZ-BANG! Most the rods were sticking out of the block.

This is the way I bought it almost 20 years later.

Was it something along that nature that you did to your car?

Mike

 

The story: As I was sitting in the Independence Day parade line with the the other Vettes, I was waiting to go as our line had been called to move out. The line started to move and then stopped. I was in "D" and idling.

What I think happened was that I was pushing hard on the brake and my foot slipped and I stomped on the gas pedal. The car leaped forward and in those milliseconds before the crash into the Vette 30 feet in front of me, I, thinking I was still standing on the brake, quickly, first, shoved the shifter into "P" and secondly shut off the ignition key.(should have been the first move). Everything stopped. Then I took a breath and tried to assess what had happened. I restarted the car, then I checked the gauges (normal) except the tach was pegged at 7000 rpm. As I said, it was in the mid-80s and I was walking around the parking lot in my Tevas.

I was in the parade running at low speed for over an hour. I was in a state of agitation as the guy in front was tossing out candy and kids were darting out in front to pick up his short throws and I was worried about the engine. I had turned the newly repaired A/C off as I thought it was making the engine temp rise (220), when off, the temp lowered fractionally. I completed the parade and headed home over city streets up into the Berkshire Hills where I live and the air temps outside got lower. There were no hiccups during the parade and on the ride home until I was about 5 miles from home where it stared to lose power going up a hill and then quit. After about a half hour, i started it up and slowly drove home with one "hiccup" on the way home. Now it sits in the garage awaiting my pulling off the valve covers. All along all the gauges were fine. The tach returned to normal on the way home. The temp and oil pressure were normal for what I thought was a hot day. I think once I was running for home, I did turn the A/C back on and felt a slight measure of tepid air flowing out. I might have turned it back off before the "incident". I'm not sure. This car is almost 40 years old and survived many California summers before it came to New England. The sn bleached out rugs in back are a testament to those summers in La La Land.

The good here is no one was hurt and the Vette in front still has a rear end. I hope my baby is OK too, but I'm worried...

Thanks to all who offered advice.

Philgran

 

Ran fine during the parade.

 

Since it was in "P" for a few milliseconds (the time to move my hand from the shifter to the key), I think it did get up to or either over 7K.

 

No, I was at the helm and screwed up myself. No one else to blame.

 

Hopefully there's no major damage from a 7K rev for just a few miliseconds. Since it ran fine during the parade, I'm going to bet that the engine is OK. Your subsequent loss of power on the drive home may be ignition or fuel related to the long near-idle times in the parade, as a previous poster said.

If the engine starts and runs OK today, I would probably not even bother with removing the valve covers.

Good luck!

 

Biggest danger is a piston hitting a floating valve at that RPM. For such a short duration I doubt it happened. If it did you should be hearing a clattering or ticking from the engine.

For future reference, I find it much easier to use the left foot for brake and the right for throttle in the C3 corvette. Not sure how many guys do this, but there is not a lot of foot room down by the peddles vs modern automatics.

 

Don't drive in Tevas, In fact, don't do anything in Tevas.

 

Could be coincidental and unrelated to the previous incident.

 

over revving damage normally does not go away. If engine is stock it unlikely to have piston to valve contact. Timing chain , valve springs, distributor rotor, spun bearings more likely. I suggest to have HEI checked out. Module and coil. Pick up coil checked for weak wires, the vacuum advance can work harden wires over time breaking them within insulation. It will cause a cut pop out or stall on as vacuum advance applies and releases. Module failing hot then working when it cools is common. Remember dielectric grease if module is removed or replaced

 

I guess I am wondering if you think the engine actually went to 7000 RPM....?

Note to self....based on this, I will never consider driving my 77 in a parade. But, I wouldn't have anyways......cause I am a grumpy old man. Ask around on the forum, and Ed427. Oh yeah, and I am not sensible either. Unrelated rant off.

 

You're alright with me - I don't care what everyone else says!

 

id be that guy after about 10 min would bust a U turn and take off in the middle of the parade. People arent on my "like" list in general

 

You have an electronic tach, I believe you experienced a tach error.
A stock L-48 would go into valve float way before it hit 7K.
When you had this 7k reading was the engine roaring it's guts out, you could actually hear it revving?

 

The engine looks and sounds fine now. Doesn't seem to be any lingering damage. No unusual noises. I've yet to check the coil. The parade and the travel to and from it were the longest period of time I have been continuously running the car since I bought it. It was also the hottest trmpeature day I had ever driven it during. It was the first outing since I had the A/C condenser and drier replaced. I had just replaced the power antenna, the steering box and the rag joint. I also tried and failed to fix the horn and somehow did something that stopped the headlights from rising (they go up with the manual override). Perhaps there is a clue there as what actually happened. Maybe I was focused too much on the overrevving (sp.) and missed another clue? Again, thanks to everyone who offered advice. I tried to thank everyone individually but might have missed someone. Philgran