3.0 Engine damage...how bad do ya think? (longish)

Vipergrün · 05-18-2002, 10:31 AM

The saga continues with the motor on my 80SC. I had heard some knocking and rattling in the cam housing so I opened things up and replaced the ramps and inspected the pressure-fed tensioners and idler arms. When I fired up the car there was a really loud knocking noise in the engine. I shut her down immediately and opened the cam housing again to see what it was. Some folks on the list indicated that the tensioners may not have been pressurized and I was hearing some movement of the chain and idler arms. So, without removing anything I turned the car over a few times to *prime* the tensioners.

I removed and re-inspected the tensioners. When I compressed the passenger side tensioner to re-install it I noticed that no oil at all came out of it. I thought that was really odd. I checked the oil line that feeds it and found some thick gunk inside the fitting, which was definately not there when I re-assembled everything the first time. Cleaned it out and it worked fine. BTW, my mechanic once received a clogged oil line as part of the pressure-fed tensioner kit!!

So, fast forward to the current time. Everything buttoned back up and tried to fire up the motor. No go. I see spark and am getting fuel. I fear I have flooded her. I remove the plugs to check them and let any fuel evaporate. Then, I come to #6 cylinder plug. Hmmm, not coming out as easily and take a bit more effort. I finally get the plug out and there is damage to the plug. The bottom of the plug has been smashed into the electrode and there is a nick in the base ot the threads. I can only imagine that the piston has hit a valve and jammed it into the plug. In doing some research, I found that the valve train *can* move even if there is slack in the chain and the chain does not have to come off the sprocket, or jump a tooth.

I fear I am looking at a valve job at minimum, maybe piston damage as well.

Anyone else had a similar situation? What was the outcome and what did it cost?

Suggestions and gifts of beer are greatly appreciated

cheers
-Brad
80SC

Harold_89_911 · 05-18-2002, 01:56 PM

I'm so sorry to hear that Brad. I know how I would feel if something like that happened to me. I would go and talk to Jason. He really seems to know his stuff and is extremely reasonalbe with prices. We are lucky to have him in Ventura. Will pay you a beer anytime. Just name the place...

Harold

Tinker · 05-18-2002, 07:34 PM

Turn it over with a wrench on the pulley nut and feel for any binding. If it is ok, then do a compression test and watch how the numbers build. First stroke should be strong with a additional stokes tapering. Compression test should tell the story.

Tinker

Gunter · Gunter's Garage

Your chain may have jumped on the sprocket? It may be time for a good Porsche mechanic to investigate this engine before anymore damage is done. A compression test will show if there is damage to the valves.

Wayne 962 · Wayne 962's Garage

Third time - do a compression check. Although, if only one cylinder was damaged, the car should still run on 5 cylinders. Was it biting (trying to fire) on any of them?

It's odd that you wouldn't get *any* combustion...

-Wayne

Superman · 05-19-2002, 06:54 AM

Do a compression test. In the meantime, you can also turn the engine and watch the valves on #6. A bent valve will not close, which will leave a HUGE valve lash.

Oh and....do a compression check.

Vipergrün · 05-19-2002, 05:25 PM

Thanks everyone,

car is heading to shop for a COMPRESSION test

I'll probably ping ya'll again when I know what's going on.

PS. Superman, car is going in for a compression test!

cheers
-Brad
80SC

Superman · 05-19-2002, 08:36 PM

Now that you mention it Brad, a compression test sounds like a good idea. I wonder why Wayne didn't suggest it.

old_skul · 05-19-2002, 09:04 PM

And I was about to say that maybe you should get a compression test. :\

Sorry about your luck. I can only hope it turns out to be a top-ender for you with no piston damage.

barlowdo · 05-20-2002, 10:45 AM

If there is already evidence of spark plug damage. Why take a chance of causing more damage by subjecting the engine to a compression test ? At least I thought that a compression test required rotating the engine.

Just curious, Don

Vipergrün · 05-20-2002, 11:06 AM

barlowdo,

you bring up a very good point. If I rotate the motor by hand it binds right before #1 is TDC according to the rotor position and the Z1 mark. Since 6 fires right after 1, I'd bet it is #6 hitting a valve on the up stroke. A comression test will no doubt continue beating the heckout of whatever is binding, possibly causing more damage.

Will a piston give out before there is damage to the crank, connecting rod, bearings, etc?

I can almost guarantee I am out a major valve job and would like to limit further damage. Should we just start teardown?

Thanks for your input.

-Brad

Kurt B · 05-20-2002, 11:29 AM

When I changed my tensioners, I got the plastic zippers and zipped the chain to the sprockets on both sides in two places. This kept it from spinning, and it also kept the teeth on the gear in the right places.

Superman · 05-20-2002, 11:31 AM

According to my understanding, the world may not yet know what it would take to injure a 3L crank. This is an exaggeration of course, but apparently they are pretty darned tough. One very experienced mechanic I know once said that he has seen engines destroyed to the point that only one part is reusable....the crank.

I confess I do not recall your earlier stories, and I am wondering what happened to this motor recently. Was it rebuilt? Was it worked on? I know that the chain ramps were replaced, but this is not likely to produce this kind of problem. I wonder if something (a nut or something) could have fallen into the combustion chamber. If so, you will likely have to take it apart to retrieve the item.

Again, if it were my engine, I would take the valve covers off and rotate the engine to see if any valves have EXCESSIVE clearance. If a valve stem is bent then there would be excessive clearance since the valve would not close. If a head snapped off, there would be no clearance at all. You could also back the adjustments off and see where physical contact is being made.

mikequig · 05-20-2002, 11:32 AM

Since a teardown is a foregone conclusion, just get on with it and hope for the best case scenario - a bent valve and no piston damage.

Further running of the engine can subject it to more damage!

Treat it as an opportunity - to make topend performance upgrades of your choosing.

barlowdo · 05-20-2002, 11:45 AM

I would take it to someone who has knowledge of these engines and tell them what is happening. The reason I say this is , I have gotten two different answers as to how much damage one can inflict by doing nothing more than turning a 911 engine over by hand after a in-proper timing chain mishap.

One expert states that indeed damaged can be inflicted. Another expert who I just recently asked the question of at a tech session and who is the head Porsche Mechanic for a local Porsche dealer felt that "no just turning a 911 engine over by hand does not put enough torque on the internal components of an engine if indeed one stops the minute resistance is felt".

Not having done this myself all I can do is repeat what I have heard.

So what do other "Experts " out there think ?

-Not an expert, Don

Vipergrün · 05-20-2002, 11:46 AM

Hey Superman,

It appears this indicent may be partially self-inflicted and partially a fluke. I did not turn the motor over prior to starting it to get pressure back to the tensioners. Also, the oil line feeding the passenger side tensioner was clogged and it appears that no amount of *priming* would have pressurized the tensioner.
This whole job started due to slight knocking and some chain rattle. In doing some research there were a couple references indicating that slack in the chain could cause damage, even if it didn't come off the sprockets, or skip a tooth.

Kurt B,

believe me, I tied off the chains and used a wooden wedge between the case and sprockets to assure no movement.
With both tensioners removed, I was able to create the necessary play in the chain (minimal) to replace the ramps.

mikequig,

already been in contact with EBS racing to spec out parts and check on head jobs. Now I gotta decide if I want to triple the cost with my mechanics labor charges, or tackle at least part of this myself. I have been truely inspired by Leland Pate and others who have taken on rebuilds.

Thank you all for your replies

cheers
-Brad

dickster · 11:26 PM

sorry about your situation

just a thought before you go stripping things down.

how about a leakdown rather than compression testing, don't have to turn the motor over (well only by hand) and gives more accurate info??

don't think its been mentioned yet?

btw - you'd have to be pretty heavy handed to damage the engine turning over by hand. you'd feel a very metalic resistance on point of contact, and its obvious something is wrong.

good luck

Wayne 962 · Wayne 962's Garage

A leakdown test doesn't require rotating the engine repeatedly. You can check for bent valves using this test without further damaging anything...

-Wayne