I STUPIDLY let my cousin drive my MN6 today, as he had never been in a vette - has/had stick experience, but was really rough on the clutch.

After he got the hang of it a bit, out on a backroad, let him run it through the gears. From 2nd to what SHOULD have been 3rd, went back into first, and before you could say OH S*it, RPM's ran off the scale - no idea how high they went.

Now, it burbles blue smoke out the exhaust and feels like there is just nothing there. No low end power/torque at all.....once revs get to 3000 or so, it's kicks in but is still very sluggish, and a whispy trail of blue smoke is noticeable especially during "normal" downshifts.

Me thinks dropped valve or something, but engine seems to run OK but idles a little rough, but not much. At idle smoke is less.. Shut it off, wait a few minutes, then start it up... big puff of smoke.



HOW MUCH IS THIS GOING TO COST ME?

 

You mean how much is this going to cost your cousin

 

Blue smoke usually means oil burning, you might have blown a gasket or worse a piston Im sure someone with more experience will chime in. Good luck

 

Moved to C5 Tech...

 

Blue smoke is always a bad sign.

 

blue smoke = burning oil.....

VR

 

Boy, that really sucks. Hopefully it won't cost too much to get fixed.

 

Anyone got a clue where to start looking? Something that I can do?

Check compression? I've got a gage for doing that. Or would something be more obvious to look for?

Let it sit about 6 hours and just tried it again, Big puff of blue smoke on start-up then just a faint whisp at idle. Nothing leaking from underneath?

***GEESH*** This is haunting me thinking new motor - NO

 

OMG! bub

 

Ok, sounds like you over revved the engine on a downshift, which is where the rev limiter can not help you. Disconnect the battery, pull the valve covers. If you dropped a valve, well, you know what that means. If not take the rockers off and check the pushrods. Bent broken pushrods happen often when this happens (been there done that). Next drain the ol and take a look in it to see if you have any metal in it. Bent broken pushrods shouldn't cause you to burn oil, so it looks like maybe something worse, but if you find some, and nothing else wrong, you could replace them and see what happens. I would definately do a compression check before starting the car again.

Well if all else fails and you have to do something costly, at leat make sure you get an upgrade with it, even if it costs more. The big poo-eating grin you will get later will help the medicine go down.

Hopefully some more qualified people will chime in. Make sure you post this on ls1tech.com also.

Not an expert, just my $.02.... Good Luck!

 

At what speed was this 1st time Corvette driver shifting from 2-3? Seems to me he should've been shifting at about 30 (taking it easy for a first timer) in which case a jump to 1st shouldn't be that rough.

 

Blue smoke=Rings=Pistons, 90 percent of the time.
A mechanic told me that one time.

 

Definately oil. The big puff on start up typically means valves, Start with the spark plugs. Pull each one out and mark which cylinder it belongs to. The condition of the plug will tell you which cylinder died. Then pull the valve covers and check the springs. Check for debri around the vavle stems and a bent valve stem. You may have just damaged a stem seal. If all looks good, then do a compression check. Check your engine oil for coolant as well. My guess is that, if you continue to drive it blowing out oil the cats will be ruined.

 

$20.00 says bent rods.

 

We were approaching 60-65 MPH when shift from 2nd to 3rd...uh.. I mean 1st occurred. Even as I was yelling to push in the clutch, it was like information overload to him. Just backed down until that soaked in. BTW - doing that REALLY slows the car down in a hurry

Thanks guys. I'll start with the least invasive - remove plugs and take a look, followed by compression check and check oil to see if it's PINK. Anyone know what the pressure reading should be and acceptable differences between cylinders is/should be?

 

Yeah, downshift to slow was how I was taught to shift. Of course I learned to drive a stick on a Chevy C30 Tow Truck, heh! Unfortunately it's always been a habit of mine, and eventually cost me a set of pushrods on the vette. It's a habit no more, but I didn't do anything as radical as your buddy.
Your plan sounds good. I can't find my compression test results, but I seem to remember it either being around 95 and around 6-8% leakdown on each cylinder, with #8 being a little below the curve. I can't find my little cheater notebook with all the good facts in it right now, will look again tomorrow. Hopefully someone else will post something more definitive.

I think I would pull the valve covers and rockers and check the pushrods regardless. Even if it isnt a big problem now, you could have bent one slightly, which could pack a nasty surprise for you later. Pull them out. Use some system for remembering where each one came from. I use a valve train organizer, or you could just do this one at a time. Wipe the pushrod clean, and roll it on a flat glass shelf, mirror, whatever. If any are less than perfect, replace the whole set, good cost/insurance ratio here.

Tell your buddy you'll sell the bent ones to him for a souvenir, for whatever price it costs to fix this... :

Also, I have found that broken parts make excellent conversation pieces at work. My super duper DTE 300m hardened half shaft from the set of used 4.10s I bought in the beginning of the year are the current favorite. Seeing the twist in the teeth of something that beefy is mind boggling! Just trying to add some levity to the situation, I know that knot you get in your gut when your pride and joy is in the hurt locker. Like I said, make it an opportunity to upgrade!

Good Luck!

 

Mine acted like this when I broke a valve spring, the spring did not look broken but was cracked and when removed it fell into 3 pieces, I have light rings that I did not request in my shortblock that probably make a few horsepower but use oil and the smoke is deff blue--I would think your bottom end would be fine unless you dropped a valve, but the valve train took a beating and removing the valve covers will very likely tell the tale.

 

Bent push rods and or bent valves not seating.

 

I can understand the bent pushrod concept....but how does that explain the oil burn? If anything, a bent rod would keep the valve seated longer, no?

I will be pulling the push rods out and take a look at them. It's been a while since I did some top end engine work. I've worked on 4 and 6 cylinder aircraft engines which use solid lifters and a specific torque and gap method. How do you tighten the rockers back down and is there a specific sequence and gap? Engine running or not while setting valve litters?

Geesh - I've got all the tools to do this job, just need a touch of guidance to refresh the procedure again.

 

Very easy to do. Now get going. I've got money riding on the verdict.