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

[Matt Monson]

Originally Posted by proporsche

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

Ivan

You’re right. I scrolled on past when he responded to Suga nuts, and missed his second post.

[jmz]

Once years ago I did this and broke several rockers and bent at least one valve.

I did it a couple of weeks ago while racing ....going for a downshift to 3 on my freshly rebuilt 915 and got 1st. It was oh so brief and it made me **** my pants. So far that is the extent of the damage. I got lucky it seems. I did see some video from the driver behind me. It was a pretty ugly puff of gray smoke that came out of my pipes.

[kent olsen]

Many years ago when Mike Bruns helped me build my 3.0L, he said we will build the crank connecting rods and valve train to turn 8500rpm. Soo my 8000rpm missed shift didn't do anything and it's been running fine since.

[Walt Fricke]

Nick - what do you think is wrong with using a rubber line with an end which screws into the plug hole? That is what most if not all of the leakdown testers come with, isn't it? I wrapped mine with some stiff foam and lots of tape to stiffen it for easier install/removal, and it works fine.

I had made a steel tube line by busting out a spark plug's ceramic and threading its ID to screw a threaded tube in, with an air fitting on the outside end, all to speed up the install/uninstall process. Worked, but because I hadn't gotten the threaded hole fully axial, it wasn't easier to use. Better workmanship ought to do the trick, but again, what's the deal with the rubber? It's not going to expand and give bad readings, is it? Think rubber brake lines.

[cabmandone]

Originally Posted by Walt Fricke

Nick - what do you think is wrong with using a rubber line with an end which screws into the plug hole? That is what most if not all of the leakdown testers come with, isn't it? I wrapped mine with some stiff foam and lots of tape to stiffen it for easier install/removal, and it works fine.

I had made a steel tube line by busting out a spark plug's ceramic and threading its ID to screw a threaded tube in, with an air fitting on the outside end, all to speed up the install/uninstall process. Worked, but because I hadn't gotten the threaded hole fully axial, it wasn't easier to use. Better workmanship ought to do the trick, but again, what's the deal with the rubber? It's not going to expand and give bad readings, is it? Think rubber brake lines.

I got impatient and used the rubber line. I just thought the metal tube would make a positive seal. Story ends with the engine is gonna get dropped. #1 was 90psi/72psi #4 was toast. At this point I'm not sure checking #3 and #5 is necessary since visible inspection with wiggling the rockers indicated that #4 was loose. #6 and #2 were pretty solid at 90/86. The only benefit I can see from finishing is to let Craig know which cylinders to really look at for replacement parts.

[winders]

Yeah, after my last over rev I did a leak down and found that cylinder 3 had 70% leak down. I stopped there as I knew the heads were coming off and going to Xtreme to be R&R'ed.

[Walt Fricke]

Your shop can most likely efficiently remove all the valve springs and valves. Check #1 is to put the valves in a valve grinding machine, or a lathe, and spin them up. If the stem is bent or the head is bent, that shows right up visually. Send them all. Maybe discuss with the shop - odds are decent that the intakes are OK - especially if there are no marks on the pistons showing intake valve contact. You could probably use that approach with the exhausts, but since a couple got dinged, why take the chance?

With the valves out, the shop can test the guide wear better, too.

[cabmandone]

Originally Posted by Walt Fricke

Your shop can most likely efficiently remove all the valve springs and valves. Check #1 is to put the valves in a valve grinding machine, or a lathe, and spin them up. If the stem is bent or the head is bent, that shows right up visually. Send them all. Maybe discuss with the shop - odds are decent that the intakes are OK - especially if there are no marks on the pistons showing intake valve contact. You could probably use that approach with the exhausts, but since a couple got dinged, why take the chance?

With the valves out, the shop can test the guide wear better, too.

I'm going to chat with Craig (cgarr) and see what his preference is. I have no problem with taking things apart I just want to be sure what he'll want.

[Walt Fricke]

Outstanding choice.

[cabmandone]

I brought the heads to Craig last Friday. I also brought the cam towers and rockers along. He's going to do a sonic clean on the towers and inspect the rockers.

Meanwhile, I'm debating rod bolts. Seems there's a lot of talk about the rod bolts being the weak link on the bottom end. I've read that rod bolts have caused catastrophic failure but I have yet to see a thread where a person points to faulty rod bolts (other than one where the original bolts were reused in a rebuild) as the reason for bottom end failure. Oil, or lack thereof, seems to be a more common reason behind a catastrophic failure.

I'm doing all the reading and research I can because I don't want to button this thing up and have a problem later down the road. My first inclination is to drop the $250 for bolts and move on.

[Trackrash]

Originally Posted by cabmando

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.

Check your shift coupler in the tunnel. Mine lost it's bushings and I did the 2nd to 1st shift. Worth checking.

[cmcfaul]

I did the 3\2 money shift. Think I hit 11k RPMs. Valve dropped into the combustion chamber and turned one of the pistons to powder (just gone). Drove it 30 miles home like that. Was an expensive rebuild.

73 911 E

[cabmandone]

Originally Posted by Trackrash

Check your shift coupler in the tunnel. Mine lost it's bushings and I did the 2nd to 1st shift. Worth checking.

My coupler has brass bushings but I will check my shift rod bushing. Once I get the engine back in, I'm going to play around with the coupler adjustment. I'm thinking I have the coupler adjusted on the jagged edge. I never readjusted the coupler when I went from my old transmission to my refreshed transmission. I just bolted everything together and it shifted well enough. But I think I've got some tweaking to do.

Thanks for the suggestion.

[cabmandone]

Just shy of three months and it's back together and running! Merry Christmas to me!! Now to find decent days to drive it for break in.

FWIW, I had 3 bent valves. Cgarr did the work and replaced all valves, guides and seals. I did a few "while you're in there" things like new pistons, rings, and rod bolts.

[sugarwood]

Congrats on the quick turn around.
What was the final bill ?

[cabmandone]

Originally Posted by sugarwood

Congrats on the quick turn around.
What was the final bill ?

I haven't done a final tally but with rod bolts, 12 new valves, new piston rings, gasket kit, and machine work, I think I'm in it somewhere in the $1500 range. Not terrible.

Edit: Just ran the numbers and it came in at $1447.00 for everything listed above. This doesn't include brake cleaner purchased by the dozen along with other cleaning supplies, a new torque wrench because none of mine worked well in the 18-20 foot pound range, oil, oil filter, fuel filter. So all in I was probably closer to the $1800 range.

[yelcab1]

$1500 is extremely cheap. Free labor, I guess.

I drive Ferraris with dog leg shiift gates. You cannot shift back into 1st from 2nd.

[cabmandone]

Originally Posted by yelcab1

$1500 is extremely cheap. Free labor, I guess.

I drive Ferraris with dog leg shiift gates. You cannot shift back into 1st from 2nd.

Labor other than Cgarr's, which was in the total, work was all me. I dropped the engine, tore the engine down, put the engine back together, and put the engine back in by myself.

The frustrating thing about what happened is that I have a Seine gate shift kit in my shifter. I'm going to look at the spring tension and do some tweaking on the shift coupler.

[gomezoneill]

Yeah and not a single photo!

[cabmandone]

I was going to post some pics but I figured everyone knows what a disassembled/reassembled 3.2 looks like. I took PLENTY of pics of the entire process.

One pic I didn't take that I should have was checking ring gap for the new piston rings. I bought a ring squaring tool and checked ring gap which is highly recommended when you're putting new rings in your existing cylinders. Outside of that, I think everything else has been covered here multiple times. I could be faulted for not posting the obligatory pic of me standing in my engine bay after dropping the engine.