Cylinder Review please

[NEWFIE 69 911E]

Hi all,

Recently dropped engine in my 1980 911SC RoW Targa with 200K Kilometers due to broken lower head studs. Engine is now dissembled, and heads will require minor polish / flycut. My plan is to leave the crankcase and P&Cs alone, due to low mileage and excellent operation before the stud issue(s) + my low annual mileage history (20K KM in 8 years)

All but one cylinder have no scoring, but #5 has one minor score:



How does it look to cylinder experts out there? Thanks

[zedsn]

If that is all of it for that cylinder I think that you are ok by still using it.

[DRACO A5OG]

Prior to disassembly, did you do a compression and /or leak down test?

[NEWFIE 69 911E]

Originally Posted by zedsn

If that is all of it for that cylinder I think that you are ok by still using it.

Thanks for reply, I am thinking the same

[NEWFIE 69 911E]

Originally Posted by DRACO A5OG

Prior to disassembly, did you do a compression and /or leak down test?

No, I did not

I know I should have, but did not have the equipment for leak-down, and was not sure that compression readings would be legit with so many broken head-studs.

My bad

[DRACO A5OG]

I would post on the engine rebuild section, they may know more but I agree that cylinder looks fine.

When you put your finger nail on it, can you actually feel the groove?

[NEWFIE 69 911E]

Originally Posted by DRACO A5OG

I would post on the engine rebuild section, they may know more but I agree that cylinder looks fine.

When you put your finger nail on it, can you actually feel the groove?

Thanks. Yes, I did post on the engine forum but no replies yet.

Yes, you can feel the groove, but just barely, if that makes any sense!

[turbo owner]

That scratch could be from a broken ring.

200,000 kilometers? Never rebuilt before? 40 year old seals.

Now is the time to dig a little deeper if you plan to keep the car.

[GaryR]

Originally Posted by turbo owner

That scratch could be from a broken ring.

200,000 kilometers? Never rebuilt before? 40 year old seals.

Now is the time to dig a little deeper if you plan to keep the car.

I agree, I would absolutely be splitting that case, replacing all bearings, seals, timing chains and ramps, etc...

[NEWFIE 69 911E]

Originally Posted by GaryR

I agree, I would absolutely be splitting that case, replacing all bearings, seals, timing chains and ramps, etc...

Many thanks for advice,

According to Wayne's book, and other posts here, the crankshaft etc should be ok for another 200K KM (not miles), so I am inclined to leave the case alone, except for replacing seals and chain ramps.

[boyt911sc]

Originally Posted by NEWFIE 69 911E

Many thanks for advice,

According to Wayne's book, and other posts here, the crankshaft etc should be ok for another 200K KM (not miles), so I am inclined to leave the case alone, except for replacing seals and chain ramps.

Since this is your first engine rebuild, I understand your apprehension about doing a top and bottom rebuild. I did the same for my very first one too. It is a decision you have to make yourself. But after several engine rebuilds, the additional bottom rebuild work should be included because it does not take much time to do it. It feels very intimidating when you have not done one before. Once you done one, you will understand why people encouraged you to do the top and bottom rebuild even with a 200Km.

Tony

[NEWFIE 69 911E]

Originally Posted by boyt911sc

Since this is your first engine rebuild, I understand your apprehension about doing a top and bottom rebuild. I did the same for my very first one too. It is a decision you have to make yourself. But after several engine rebuilds, the additional bottom rebuild work should be included because it does not take much time to do it. It feels very intimidating when you have not done one before. Once you done one, you will understand why people encouraged you to do the top and bottom rebuild even with a 200K miles.

Tony

Thanks Tony,

Please note engine/car has ~200K kilometres = ~ 124K miles , and the engine has not been opened before.

Re top-end: I will send the heads to a machinist experienced with Porsche air-cooled here in Canada for inspection and assessment.

Re bottom-end: I will think it over and decide; in the meantime, what do you think of the cylinder as noted above?

Best,
Tom

[Nine9six]

Originally Posted by NEWFIE 69 911E

Thanks Tony,

Please note engine/car has ~200K kilometres = ~ 124K miles , and the engine has not been opened before.

Re top-end: I will send the heads to a machinist experienced with Porsche air-cooled here in Canada for inspection and assessment.

Re bottom-end: I will think it over and decide; in the meantime, what do you think of the cylinder as noted above?

Best,
Tom

Exactly! I wouldnt touch the very robust bottom end that can typically go 250-300k mi. So 124k is basically half-life.

Leakdown test is gennerally performed to che..ck valve seal integrity. Compression test for cylinder compression check.

Generally speaking, if you can hang your fingernail on the groove, its .003-.005" deep. Cleaning up cylinders with a hone certainly wouldn't hurt overall compression...

[NEWFIE 69 911E]

Originally Posted by Nine9six

Exactly! I wouldnt touch the very robust bottom end that can typically go 250-300k mi. So 124k is basically half-life.

Leakdown test is gennerally performed to che..ck valve seal integrity. Compression test for cylinder compression check.

Generally speaking, if you can hang your fingernail on the groove, its .003-.005" deep. Cleaning up cylinders with a hone certainly wouldn't hurt overall compression...

Thanks - we agree re half-life

Only one cylinder (#5, above) has a score, and cross-hatch pattwrn is still seen in all cylinders.

Not sure I can hone these cylinders; they look like Alusil to me...

Happy motoring!

[NEWFIE 69 911E]

Hi thread followers

Ok, for peace of mind , I decided to pull the piston out. Happy to find no broken rings. Still wondering, what could be the cause of this score? You can see a corresponding mark on the piston skirt...

[Discseven]

Newf... Suggest measuring cylinders for taper and ovality (according to Porsche specs.) Cylinders can look fine to the eye but if our of round, performance is lost.