Wanna See Photos of My Cylinders?.. Borescoped

[piscator]

I’m being extra cautious, does anything in these (not great) borescope photos suggest I shouldn’t restart my motor?

I took these with a Teslong “Digital Endoscope Camera” from Amazon. I don’t know how it compares to industrial strength scopes, but for $85.00 it seems to be quite well made!

I’ve never rebuilt a 911 engine, so I don’t really know what I’m looking at. I see carbon on the all the pistons, but I have no idea if it’s a normal amount or a complete disaster! Same with the light scratches on some of the cylinder walls and the tiny bits of carbon or metal -- in some of the photos. I don’t know if that’s normal wear or damage.

This is the 3.0 liter motor in my 1979 SC Targa. The engine ran fine before I dropped it to do a suspension refresh. When I reinstalled and started the engine it developed a rhythmic tapping which sounded like a valve clacking. I did adjust the valves while the engine was out.

On that first restart, the rpms started ‘hunting’ up and down and then the engine would stall. I don’t think that’s related to the ‘clacking.’ I believe I’ve traced that problem to a defective WUR.

In any event, to be safe, I shut the motor down. Seeking advice from the board it was suggested that I drain and filter the crankcase oil to see if any metal showed up. I found none.

A borescope was also recommended, so I picked this one up and gave it a try. I put the Endescope down each of the spark plug ports and took the following photos. They’re not great, but they’re the best I could do.

BTW: Could anyone tell me what the indentation and/or ‘nipple’ on the top of each piston is for?

I sincerely appreciate any comments on or interpretations of these photos!



Cylinder #1




Cylinder #2


Cylinder #3


Cylinder #4




Cylinder #5


Cylinder #6

[jons911]

It's hard to judge, but the carbon build up on your pistons looks similar to what I pulled out of my 3.2 during the rebuild. I have several pics on my rebuild thread if you want to compare. When I asked about the state of my pistons, several others commented that they looked as should be expected and a simple cleaning would suffice to reinstall. Since you haven't disassembled anything I would think you would be good, but I'm by no means an expert and you should wait for more knowledgeable folks to chime in. It also looked like there was some loose carbon bits on the cylinder walls in a few pics. My first instinct is that you would want to clean that out, but I can't see how you could do that with the heads still on.

[patkeefe]

Robert, is your engine the one with the funny shaped pistons? I think the nipple is a marking for top, but I could be wrong. It has been a long time since I saw one of those pistons. I think they all have that marking.

Mahle pistons cast or forged from SC?

[piscator]

Jonathan,

It seems we have the same year SC! Thanks so much for your comments! Your rebuild thread will be a big help, I'll look that up!

[piscator]

Hey Pat,

Who's pistons you calling "funny looking!?!" Yours look better!? :-)

I've never seen my pistons before. They may be funny looking -- but they're mine!

[patkeefe]

They have odd shaped domes on them, I think for flame propagation purposes.
Please don't take it personally

[john walker's workshop]

mmm nipples.

[Trackrash]

The place to look is on the cylinder bores at the bottom or the lowest portion. If any moisture got into the motor and corroded the bores that would be the place most likely to have it occur. The shots you posted look like normal pistons and cylinders. But I don't think you are looking at the lowest point on the bores.

[Walt Fricke]

I don't think that nipple is for anything - an artifact of the casting or forging process.

You could use your scope, probably with its 90 degree end attachment, to check your valves and seats, rotating the engine as you do it. But a leakdown test will tell you if you have a burned valve or seat, or a bent valve, or whatnot.

These are neat tools - I just bought one for $10 which wouldn't run on my Windows 7 computer on which I am typing, but would on my W10 laptop. It has much better light than a 15 or so year old Snap-On. Back then they just had one LED for lighting. Now they have a ring of six or so around the central sensor which does the work. And smaller heads to get into smaller passages.

The carbon bits will blow out the exhaust when you run the engine.

The tapping/clacking post valve adjustment does suggest where that might come from, does it not. And what to check and double and triple check. To be sure, many have been fooled relying on "post hoc, ergo propter hoc" logic.

And yes, some CIS component could choose just this moment to give up the ghost. Though that kind of confounding thing can perplex anyone. The approach to the CIS is through the ignition - is everything fine there? Then by getting the CIS testing gauge stuff (not expensive from JCWhitney back when, and maybe HF now?)and checking pressures.

[pmax]

Pisca,
Those are probably flecks of loose carbon but I would turn the engine over a few times to see if they are gone to confirm.

[piscator]

Walt, I enjoyed your borescope thread in the engine re-building section!

You’re right that these are neat tools, especially for the money! This would have been wonderful to have, all the years I played contortionist marine mechanic!

The 90 degree attachment on this scope didn’t work for me. It’s a tiny polished metal periscope that I couldn’t seem to rotate or maneuver to a distance that would focus. I wonder if a scope with an inflexible arm might be easier. Or how ‘bout one with auto-focus and little servo motors that turn the camera 360 degrees in any direction!

‘Hoc’ this. ‘Hoc’ that. Ya know, this wouldn’t be the first time I got my ‘propter hoc’ confused with my ‘post hoc. In fact, my ‘hocs’ are often out of alignment! :-)

My biggest reason for borescoping this engine is to make sure that the woodruff key that holds the fan-belt didn’t get in there.

Months ago, with the engine out and on a stand, I started dismounting the fan-belt pulley. That little bugger of a woodruff key ‘propter hoc-ed’ itself into the air and landed, no-one knows where. When numerous search parties turned up nothing, I feared that the little key had sprouted wings and flown upward into the engine, instead of downward to the floor; as God and gravity would generally dictate!

Anguishing over the tapping sound heard during the engine’s first start-up, I ‘post hoc-ed’ that I’d found my avian woodruff key. So that’s why we’re borescoping the engine. To make sure that that bloody d-mn key isn’t in there somewhere!!!

[piscator]

Pat, O.K., I won’t take it personally!

John, I wonder what you’ll have to say if we start talkin’ plumbing?! ;-)

Gordon, thanks for the insight. Before I took each photo, I rotated the engine by hand and watched the piston descend to BDC. That’s as low as they would go, for me. If it doesn’t look that way, it may be the camera’s narrow depth of field. This camera seems to focus on a thinner slice of what it’s looking at compared to other borescope photos I found on-line. And then there’s always the operator error!

Pmax, That’s a good idea to see if rotation changes the dispersal of the carbon in the cylinders. Cylinder #4 has a chunk of shiny something on the wall that you can see in the photo. I suspect it’s carbon, but it will be reassuring to see if it moves out of the way when I turn the engine over by hand. Thanks!

[Reiver]

I've borescoped mine for the heck of it and did not see the vertical lines/wear that I see in yours.
I could readily see the factory scuffing of the cylinder walls indicating proper ring work in all of mine.
I don't have alusil jugs tho so they may wear differently but I don't think that is the case.

[jlex]

If you feel the need to clean out those carbon chunks, you could use progressively smaller vacuum hoses hooked up to a shop vac that are small enough to fit inside the spark plug hole. Probably shouldn't worry about them as they'll get blown out anyway.

[piscator]

Good Morning Guys!

Reiver,

Thanks for giving me a point of comparison! I wondered about those vertical lines as well, along with some irregular scratches. Judging their size against the chunks of carbon, they must be pretty small. The 90 degree attachment to my scope wouldn't focus, so it was hard to get a clear view of the cylinder walls. Angling the scope's straight tip revealed only small sections at the bottom of the cylinder.

Jlex,

I like your idea to use vacuum hose to... well... vacuum! I don't think I'm quite that fastidious! I tried Pmax's idea to rotate the engine to see if the carbon dispersed. It did! So I took your advice, stopped worrying, and blew the stuff out by starting the motor!

It ran pretty well and didn't stall, but the idle rpms are still 'hunting' up and down. I'm pretty sure that the WUR needs rebuilding. My rhythmic tapping noise is still there in the area of cylinders #4 and #5, but it seems that's probably a valve clacking.

Every day we make a little progress!

Thanks to all for the help!

[pmax]

Robert,

I think someone else mentioned this a leakdown test and checking the valves would be in order. Don't risk any possible further damage.

[piscator]

Pmax,

I can and will do a leakdown test, it may tell us something about the tapping/ticking noise. It’s a good idea and I can’t run the engine until a WUR arrives, in any case.

I just read that malfunctioning fuel injectors can also cause a ticking sound. That would correspond with the location of my ticking sound, which seems to emanate right at injectors #4 and #5.

If the ticking is an injector, I wonder if that could also be caused by a faulty WUR?

My first suspicion is that a problem is always the result of something I did. And I did adjust the valves. But this ticking/tapping doesn’t sound like what the best of my memory can recall of what clicking valves sound like.

I did the valve adjustment with the engine on the stand and quintuple checked it using my dial gauge in a Stomski jig AND with a feeler gauge. That doesn’t mean I didn’t make a mistake, it’s just to mention that I was awfully darn careful!

Thanks for your cautions!

[Reiver]

I doubt you messed up the adjustment....if they were too tight (bad) they would not 'tick' and if they are too loose you'd note a lack of power.
Better a bit loose than tight.

[glewis80SC]

Pistons from my 80 3.0 during rebuild a few years ago...I've got inverted nipples, just trying to help.

Cylinder

Piston close up and damage from valve hitting it.

[patkeefe]

K-Jetronic injectors clack by nature.