Mechanical over rev. What did you find when it happened to you?

[cabmandone]

So... I went and did a 1/2/1 shift at 60 mph last weekend. I still can't figure out how I did it since I have a kit installed that creates a 1/2 gate and spring centers the shifter in the 3/4 shift plane... but whatever.

I thought I got away with one since there are no odd mechanical noises coming from the car BUT my #4 cylinder is cold and a bore scope appears to show valve contact with the piston. From research my brother and I have been doing, it appears the top end is the primary concern. The valves, springs etc, being the "sacrificial lamb" in a mechanical over rev situation. Naturally if the valve and piston come into contact repeatedly you'd have piston issues but my bore scope inspection only shows a "half moon" on the side of the piston. I'm going to try to get some decent pics but my bore scope isn't the best out there (Harbor Freight cheapo).

I'm waiting for a extension tube to arrive to perform a leak down test. I'm thinking while I wait for the tube to arrive I'll drain the oil, pull the valve covers and see if there's any visible damage.

I'm curious, since there's seems to be limited info on this site regarding the "money shift" and what exactly happens, what others found when they took things apart. I'm not looking for "I did this while I was in there". I'd like to know what damage you found internally. I'll be posting as I learn more about what happened to my engine. My symptoms so far are cold #4 cylinder and the engine is running lean. I'm in the 15-16 range on AFR at a cold start when I'd typically be in the 13's. The engine runs like I've got the oil cap off.

The worst part of all this is that I had the car for sale! I told my wife I should have been driving it like I was selling it rather than driving it like I stole it. Oh well!

Some threads I've found on the "money shift" I'm going to try to make this thread the "one stop" for issues related to the money shift. I probably should have included money shift in the title.
How much damage from a 5-2 shift?
Money shift woes
Missed a shift, broke some rockers, what else?
Broken rocker arm need advice
5-3 Miss Shift on a 3.2, what are we looking at here?

[stownsen914]

A leakdown or compression test should reveal a leaky valve if it's bent. You may also hear the bent valve banging against the seat since it wouldn't be sitting flush anymore. This assumes the rocker is still actuating the valve, i.e. rocker not broken.

Bad overrevs often break the rocker arm. If that cylinder is cold, it could be that the valve isn't moving at all anymore due to the rocker being broken. Pulling a valve cover as you mention will reveal that.

[Manda Racing]

Broken crank pulley…

[manbridge 74]

Leak it. It’s the only way to know...

[Matt Monson]

Cabmando, post this in the engine rebuilding forum. You’re likely to get more people who’ve been through this versus armchair diagnostics.

[cabmandone]

Originally Posted by Matt Monson

Cabmando, post this in the engine rebuilding forum. You’re likely to get more people who’ve been through this versus armchair diagnostics.

Good point. I'll ask the mods to move to the rebuild section.

Meanwhile, I'm going to try to pull all the plugs today and get a look at each piston with the bore scope.

[Bill Douglas]

Good luck Nick.

Hopefully it's something small like the distibutor/lead/sparkplug.

[3rd_gear_Ted]

The valve train is the weakest set of components.
I've seen a broken valve train repaired @ race track and back out the next session

[TimT]

The last time I did it... all the rockers on one bank were broken, cast rockers..

If you have forged rockers, you may find more internal damage.. valves bending and cracking the heads where the valve stem passes because the valve is meeting the top of piston, and the (forged) rocker wont yield. The valve stems looks like odd pasta shapes

No armchair BS .... IRL experience..

Oh, mine and Bills butt cracks were pictured on the cover of the Suncoast Regions Club Racing newsletter a few years ago while we did a engine in top end rebuild, in the sandy dusty Roebling Road infield

[cabmandone]

Seems the early cars, up to 69, had the forged rockers. Knowing that and from having my engine apart my car had cast rockers. Seems that would make any damage to the bottom end unlikely. As mentioned I can see a smile on my #4 piston. I pulled the plugs and it appears each was kissed with some showing more contact than others. I'm going to drain the oil, pull the valve covers and do a visual inspection while turning the engine over by hand. I figure by the time the extension tube I ordered gets here, I'll no longer need it because I will know if the valves are moving and have some idea if any are bent because if they aren't making full travel, my gap will be wrong.

In one of the threads I linked, it was suggested that the head of the pistons be buffed to remove the imperfection made when the valve met the piston. I have six good pistons at my disposal so I'm thinking I might just put those in if I have to do a teardown.

[winders]

What usually happens on the 2nd to 1st money shift is one or more exhaust valves hit pistons. What happens next depends on the rocker type and how much you over revved the engine. I have done two 2nd to 1st money shifts and both times the engine was at 8,000 rpm when I made the shift.

My 3.6L race engine has cast rockers. In each incident a single rocker was broken. If you have a spare rocker and the broken piece stays in the valve cover area, you can fix that in 30 minutes. Valves might or might not get bent in this case. Put the new rocker in, adjust the lash, and start the engine up. If she sounds good and runs right, you are probably good to go. I broke a rocker at the start of a race. I replaced the rocker and won the next and final race of the day.

But, other things can go wrong. For example, it would appear that in one over rev incident, the passenger side chain tensioner had a retaining ring come off and it disassembled itself. This caused other valves to get bent. A leak down test will help inform you if any valves are bent.

I have a Rennshift shifter. The spring that pushes the shifter away from the 5th/reverse plane has 3 spacers underneath neath it. This provides the max spring pressure. The spring that pushes the shifter away from the 1st/2nd plane had no spacers underneath it. It still provided a push toward the 3rd/4th plane, but it was not all that it could be. I put two spacers underneath the spring and now the centering pressure is much stronger. I believe this will help prevent the money shift as shifting from 2nd to 1st requires much more effort to overcome the spring and keep the shifter in the 1st/2nd plane.

[cabmandone]

I have a Seine gate shift kit installed. This is why I can't figure out exactly how I did what I did. I don't grab the shifter coming out of two. I push with my palm out of two to allow the spring to move the shifter into the 3/4 plane.

Leak down test is coming. I just have to wait for the metal extension tube. I want to be sure I've got positive contact and a good seal. I know I could use the rubber hose but I think it will be easier to do the test properly once I've got the metal extension tube. Meanwhile I'll keep playing around and doing any visual inspection I can. Hopefully my mistake will help others in diagnosing if the same thing happens to them.

[sugarwood]

How did you get it into 1st going 60? G50 or 915 ?
Really sorry about the bad break, and hope you get it sorted

[cabmandone]

Originally Posted by sugarwood

How did you get it into 1st going 60? G50 or 915 ?
Really sorry about the bad break, and hope you get it sorted

915!! That's what new dog teeth and brake bands and sliders will do for ya I guess
I'm really missin my old transmission right now. It would have let me know I was trying to go into 1.

[cabmandone]

On the inspection front, I drained the oil and removed the valve covers. Nothing fell out so that's a BIG plus. I put the engine at #1 TDC and felt valve play. I then went around as if I was doing a valve adjustment... 6,2,4,3,5. Not sure if it's just in my head but the #4 exhaust valve felt loose. Not enough for an "Ah ha" moment but I'm going to put the feelers in #4 and see what it looks like. I had my son turn the engine by hand while I watched the valves move and everything appears to be moving. Next up is a leak down test but that's gonna be a while unless I just decide to use the normal rubber tube. I'd really like to wait till this metal extension tube arrives because I want to see how much easier it makes the job or whether I waited and wasted $22.

[winders]

Originally Posted by sugarwood

How did you get it into 1st going 60? G50 or 915 ?
Really sorry about the bad break, and hope you get it sorted

I use 1st in at least one turn at every track I race on.......it's easy to shift into first gear!

[Walt Fricke]

I think I did the 1st instead of 3d upshift once, at a track at my 2d DE back when. Subconsciousness I think I was trying to impress my instructor that though my line was pretty bad, I was super good at making quick upshifts. Car ran rough thereafter. Tried to reset/check ignition timing. Was all wacky. Found the crank pulley locating pin had sheared, which explained that. Fixed it. Car started to seem to be running pretty much as before after a while. Two years later, with my lap times much improved, after transmission repair the mechanic, who drove it to be sure he had got things right, said it appeared to be down on power. Oh? I did a test (probably compression), and things didn't look so good. So I pulled the engine, and removed the heads, and gave them to the shop. Got a call - mechanics rolling around on the floor laughing. 6 exhaust valves bent into a sort of S shape.

What had happened is that the valves sawed grooves in the valve guides so the valve heads could seat again fairly well.

Lap times got even better after the engine went back in. Not something I would suggest as a long term fix, though. But one never knows. The head of one of the new valves from the rebuild broke off on track without the benefit of a missed shift, and there had been no such overevs in the interval. This time all sorts of things were destroyed, though the case could be welded up where the rod had sawed a new slot.

Without a broken rocker, my guess would be a bent valve head. That could lead to larger valve lash before anything started to readjust. The leakdown will tell you what is going on. Can you do your own engine removal and teardown and reassembly? Not so hard if you like puttering, and the head goes off to a shop which does that kind of thing.

[cabmandone]

Originally Posted by Walt Fricke

I think I did the 1st instead of 3d upshift once, at a track at my 2d DE back when. Subconsciousness I think I was trying to impress my instructor that though my line was pretty bad, I was super good at making quick upshifts. Car ran rough thereafter. Tried to reset/check ignition timing. Was all wacky. Found the crank pulley locating pin had sheared, which explained that. Fixed it. Car started to seem to be running pretty much as before after a while. Two years later, with my lap times much improved, after transmission repair the mechanic, who drove it to be sure he had got things right, said it appeared to be down on power. Oh? I did a test (probably compression), and things didn't look so good. So I pulled the engine, and removed the heads, and gave them to the shop. Got a call - mechanics rolling around on the floor laughing. 6 exhaust valves bent into a sort of S shape.

What had happened is that the valves sawed grooves in the valve guides so the valve heads could seat again fairly well.

Lap times got even better after the engine went back in. Not something I would suggest as a long term fix, though. But one never knows. The head of one of the new valves from the rebuild broke off on track without the benefit of a missed shift, and there had been no such overevs in the interval. This time all sorts of things were destroyed, though the case could be welded up where the rod had sawed a new slot.

Without a broken rocker, my guess would be a bent valve head. That could lead to larger valve lash before anything started to readjust. The leakdown will tell you what is going on. Can you do your own engine removal and teardown and reassembly? Not so hard if you like puttering, and the head goes off to a shop which does that kind of thing.

Oh yeah, that won't be a problem. I've had the engine apart before when I had to do head studs. Waiting on this extension tube is going to feel like an eternity. I think I'm just going to go at it and see what kind of results I get using just the rubber adapter.

[Matt Monson]

Pull the valve covers and check the rockers while you wait.

[proporsche]

Hi Matt ..he did post #15......i do this all the time;-)....that i overlook.....

Ivan