So with a bought of daydreaming or not paying attention etc, I forgot took the car out of 5th on an uphill (losing speed) with cruise on not realizing the clutch pedal doesn't disengage it like the brake does. The engine revved for only about 2 seconds and I panicked and shut the car of (in neutral) and coasted to the side of the road. The tach was stuck at 6000 or 6500 (can't remember which) so I assume that is where it revved to.

My question is....is that bad? I would assume long periods or frequently but can just a few seconds be bad???

I assume anything past 5500 (where the red starts) is bad and that all who go to the track shift before then (never raced before )...

Just a little concerned as it scared the sh*t out of me It started up fine and all but just wondering if damage could have been done?

 

dont worry about it.. lol one time i tried to blow my motor in my old maro.. and i left it in 1st and flored it for like 3 miles and reved the hell out of it.. nothing happend .. btw .. you have a rev limmiter bilt in . so i think your good to go.

 

If it happend for a very short period of time i wouldnt worry about it.

The day we did my v6 to v8 swap i drove my car three blocks, in first gear, floored, redlined all the way. With a cracked block and the damn thing didnt blow up.

It did have a hard time running when i got to the garage though

 

Unless you swapped a T5 in, your clutch pedal should have a cruise disengage switch just like the brake pedal does.

 

I don't have a rev limiter I almost destroyed my engine when I pushed it into 1st instead of second... in my 4 speed auto

 

Right. I don't think the autos came with rev limiters

 

did any 3rd gens come with rev limiters? I thought that was only OBD2???

 

My '88 2.8/T5 has a built in rev limiter @ 6300 rpm.

 

Yeah.. thirdgens have rev limiters.. valve float No thirdgen came with an electronic rev limiter.

 

lol yup.

athough the EFI cars did get a speed limiter..... if you swapped the RPM in place of the MPH variable in the computer, you end up with a rev limiter......

neat lil ECM hack.

 

just out of curiosity, how does this valve float thing work?? Where abouts is it located??

 

Valve float isn't something you look at. What is considered valve float is when the engine spins at a hi RPM, the valve springs are not strong enough to close the valves fast enough for the engine to fire right, so when the valves get stuck open, it acts like a rev limiter. Probably not good to keep an engine in those rpm's to long I surmise.

 

spivey said it..


basicly the crank and pistons are spinning so fast that the weak valvespring doesnt close the valve all the way... the valve stays open..


with the stupidly small camshafts thirdgens came with, the open valve usually doesnt smack the top of the piston... instead, it just lets the pressure out when the engine fires..... the engine doesnt make much power at all, and therefore wont rev any higher.

 

If your engine is old, even a quick jaunt up to redline and back down can be harmful. I did it and destroyed a valve stem seal.

 

i dont have to worry.


by the time i was thru killing the L03, it had no valvestem seals.

 

valve.. seals? wait.. you mean there's supposed to be something keeping oil out of the cylinders? crap

 

Mines an auto and has a rev limiter. Car kept dying whenever I went to stop so finally after the 500th time one day I floored it and started the car. Hit 6k and stopped dead right there, let off, put it in gear and floored it again...That was a yr and a half ago and the car still runs strong. Even stronger now that I've been cleaning the insides a lil.

 

Techsmurf, I have to disagree... I've got a 6300rpm limiter, and it's no valve float... Maybe it's just on the SCs?

 

lets put it this way.

there is no code in the ECM to control overreving.
nothing in the spark control unit to stop it either.

the only cutoffs in the car are the legally required speed limiters for cars that dont have high rated tires. and thoes are fuel cutoffs.


how do you know its not valve float?

btw, if you take your valve spring when it was STOCK BRAND NEW, and placed it in your hand, you could close it when you squeeze your hand... easily.
what in the world makes you think that after all thoes miles and years, that already weak and now weaker spring is going to fully control the valves at 6300?

 

Ok....

1) Has anyone even pulled all the code for the '302 ecu? Not that I'm aware of.

2) Valve float has a distinct feel/sound to it... like the difference between a spun main, and a spun rod bearing. Valve float is exactly as described above, and that's not what my car exhibits.

3) Weak already and now weaker spring? I've got dual coil valve springs, with enough pressure to hold the lifter/rod to 7000+ rpm. IIRC, it's something like 243 lbs of pressure @ .444" lift, with about 10000 miles on them.

 

why ... if the auto had it, would it allow it to go so much higher than the redline? 6300?

I've never taken mine over 5200... just to be safe

 

what are the rev limiters set at? where does it stop u????

 

I take that back, I have gotten it over 6,000k, but only that one time on accident... before I had my motor rebuilt.. hell maybe that was the reason I had a spun bearing...

 

Interesting little side note. The 2.8's in the z-24 cavaliers have a rev-limiter. It's set for exactley that 6300 RPM. As for over revving an engine, even just for a quick blip, you really have nothing to worry about.

Stupid kid I was took my Z and held it floored for about 3 minutes, down 3 quarts of oil and not a singel problem. Continued on for a couple more years of that abuse daily. Car had over 170,000 miles on it as well. these little 2.8's are nearly indestructible. And i know the 2.8 in a cav is different that a 2.8 in a maro. But same principle.

 

I know for a fact my motor won't go above 6k. I floored it in neutral it hit 6k and stopped dead right there. Car just held 6k so either there's a limiter, fuel cut off, or magic to keep stupid fools like me from blowing up a motor when really really really really through the roof too the moon ripsh*t.

 

man.. I don't even see the point, because you lose all your power at what... 4500 rpm? It feels like you aren't even moving anymore! If I want to go fast, I let it shift automatically... with the accelerator all the way to the floor, but I let it up just a tad before 4000, then it shifts, and I keep it near the floor... then when you gain some more speed, you can floor it again... but I'm not saying you'll go fast, just faster...

 

Just curious, what does a spun bearing feel like (i have never experienced it before). Will the engine still run....is there a vibration but it can still be driven?? Horrible noise?

 

holy crap man! it is really scary! the motor will only go to like 2000 RPM no matter how you use the pedal... and the car sounds like KANG KANG KANG KANG really embarrasing.. my car got so LOUD that I had to put on my emergency flashers! The sound starts out faint, you can hear it in your oil pan. For me it took about 3 weeks from the time I used motor flush on my freshly purchased car to start making the sound.... then about 2 more weeks until total meltdown... after it got louder than my flowmaster 80... I had only about 2 miles in it left, I literally rolled into my driveway and it died...

* it went from sounding like a small bottom-end engine noise - to a complelely breath-taking cracking smacking banging screaching screaming crying sound in less than an hour of driving... Once it gets to the end, you don't have much time left...

All this happened because my oil pump got clogged with shi* from the motor flush, and my pressure started reading zero at stop lights... everyone I talked to said my gauge was screwed up, so I didn't think twice... well you know what happens now! you get faced with the situation, that you just bought a car, and now you can sell it for almost nothing, or get the engine rebuilt for a little bit less than what you paid for it! What a dilemma... I got the shaft if you asked me! I was even thinking of a v-8 but I settled on the 6 for some reason... damn my judgement, don't trust me on anything.

 

Mine seems to fire, rev, wont fire, fire, rev, wont fire, fire, all at 6150-6300, and sounded like a Spark related rev limiter.

87 Firebird

Still trying to blow my motor

Want to do something scary, open the hood, and open the TB all the way and jsut sit at the "limiter" for 2 sec, and listen to everything howling, and spinning

 

I bet that would be scarier with a scarier motor! hehe

 

yes its not pretty, once its starts knocking get it home fast, and get ready to pull the engine. Both times this happened to me I had maybe an hour from a slight ticking to major banging.

 

And that's all from a spun bearing? What exactly happens that makes it a spun bearing - it just unseats from it's location and rotates in the seat some - thus screwing up oil flow or is it somethign else? I could see how a lack of oil would screw up reciprocating components.

 

dunno exactly... but apparently people can fix a spun bearing easily... I just didn't know anyone that was an expert on this ( at the time )... but yeah, in about an hour, it goes from a "maybe this is a big-time problem"... to "oh crap, my engine sounds like a vw bug"... to "KANK KANK KANK KANK KANK.... thud!" (thats what happens the hour before the death of a 60 degree v6... a very painful hour I might offer...