New Piston Rings WITHOUT Opening the case
 

Hey all. I've been tearing into my 1978 SC and a few heads studs were broken below the cylinder line, so i took them off.

Sadly..one the piston rings broke while doing so.

A friend told me they've heard of people having sealing issues when installing new rings on the old cylinder heads. Any input or suggestions on this dilemma that i'm in?

PFAhttp://forums.pelicanparts.com/uploa...1647463615.jpg

Cylinders in these engines can usually be re-ringed without problems but the procedure has to be done properly. You would start by finding out what kind of cylinders they are. Alusil or Nikasil? They say Nikasils are better for re-ringing but I successfully re-ringed my Alusils.

Other questions are raised here also. If several head studs were broken, then your cylinders and heads may have taken a beating and will not seal properly when you reassemble the engine unless you have machine work done. Also, this is a good time to just have the heads re-done with new valves. Exhaust valves particularly. And guides and seals.

THIS... I mean, if you've already gone this far....

They're stamped Mahle and are magnetic, so Nikasil.



That's the plan. I'm sending the heads off to competition engineering here shortly to be rebuilt as needed. I was originally planning on leaving the pistons and cylinders alone, but here we are.

Nope. Mahle make both Alusil and Nikasil but KS always Alusil.

I'd like to do anything and everything without touching the inside of the case

Also magnetic

I'm not following you. Why would there be sealing issues installing new rings in old cylinders? What is that supposed to do to the heads sealing to the cylinders?

As long as the head stud issue wasn't a long standing issue and didn't create any hot spots on the cylinder mating surface, I don't see why there would be an issue. I don't see any evidence of carbon blowing by the mating surface at the cylinder/head mating surface on the picture attached.

All good! Typically my "go-to" guy for advice told me he has heard stories of people having issues.

Seems like my best option here will be to get a set of new rings and when having my heads rebuilt, i'll have the cylinders honed as well.

You might want to look more into that. It's recommended that you "deglaze" at the most if I'm not mistaken. Honing can cause friction which causes premature wear on the rings. When I did my new rings, several builders recommended I simply deglaze the cylinders, check the bores, check ring gap, then install new rings. If installing new pistons they recommended checking the skirt gap I think.

I just read the title of this thread and realized how dumb it was. Swapping the piston rings without removing the heads...psh - what an idiot.

I meant to ask about changing piston rings without splitting the case. As I said, I haven't done this before, but I've only seen pistons & rods installed from the tops of the cylinders and then attached to the crank from the bottom.

I found this video and it gave me the confidence I needed. (https://www.youtube.com/watch?v=jd82Hg9BbuA&ab_channel=KlassikAutomotiveTr ainingSchool)

I'm going to speak to the machine shop that works with these early 911s and get their opinion (price). Thanks for all the input everyone.

take the cylinders off, checkout the piston skirts and look for cyl scoring etc. If they look good, you can measure them for roundness and deglaze them and get your new rings and go to town.
Remember to place the ring gaps spaced out and with the gaps on the up side. (i think that was recommended in wayne's book.)

But you are at this point, why not do the bearings too?
Post a pic of the cyl walls when you can. I'm curious what the factory nik cyls look like because the alusils were quite unique looking that almost look like a gray paint.

Kevin, I understood you had already removed the cylinders. Good to hear you are planning the things you should do while the engine is apart. I went ahead and replaced the rod and main bearings but golly, I wonder if anyone has ever worn out the main bearings in a 3L. I think these engines have seven main bearings, right? I might, if I were you, wiggle the rods back and forth to see if one is looser than the others.

If the machine shop fly-cuts your heads and cylinders, then deck height will be reduced and compression increased. Your choices include thicker cylinder base gaskets to raise the deck height again. Your choices could also include simply allowing the higher compression. You might want to do the math and consider higher compression. In a nearby thread, Jeff Higgins says his engine is 11:1 and he uses pump gas. Hmmm....

John Walker measured my cylinders at rebuild time. 186,000 miles. The most wear he could find was .0015". Miniscule. My cylinders are Alusil, and I did nothing to them except wash them very aggressively using parts solvent. It changed the color of the business surface from dark grey to light grey. The new rings seated just fine. Engine never made smoke. Bruce Anderson advised me to start it with my driver's license in my pocket, then drive it like I stole it. Force those rings against the cylinder wall with compression. Nikasils are a complete different animal, and I think they recommend a slightly more aggressive 'roughing' of the business surface. You can NOT use an abrasive on Alusils. Nikasils are different. Again, others know much more than I.

Now I see your car is a '78. You could consider better pistons. 8.6:1 CR pistons leave a lot of performance on the table.

They are perfect for turbocharging though... :D.

Okay so all you have to do is get one of the circlips out WITHOUT dropping it into the cylinder bore of the case, then push the piston pin out. I put the piston I'm working on at the top of the stroke then slide the cylinder up until I can see the piston pin. Then you CAREFULLY remove one of the circlips and push the pin that holds the piston to the rod out far enough to remove the assembly. On the bottom of the cylinder there's a half moon shape that allows the piston pin to slide out. This is how I take the cylinder and piston out as one unit. Make sure you bag and tag pins so you know which cylinder they belong to and make sure you mark the cylinders so you know where it goes. And buy a sleeve type piston ring installer. It makes the job SO much easier. I'll post the one I used later. Oh and you install the piston back into the cylinder from the bottom because the cylinders have a taper.

Sometimes....when you are removing one of those circlips....it suddenly enters another dimension. One moment it is there, and the next moment it is gone. It travels through a wormhole, visits other dimensions, and sometimes comes out at the other side of your shop. Sometimes. Or in the engine case.

Yep! That's why I stressed carefully. Lucky for me, my brother bought the tool that installs the circlip which takes a lot of stress out of installing them.

The piston ring tool is a Wiseco ring sleeve.
summitracing dot com/parts/wis-rcs09500

The circlip tool
https://www.pelicanparts.com/More_Info/STOMSKISR072.htm?pn=STOMSKI-SR072&gclid=Cj0KCQjwuMuRBhCJARIsAHXdnqOofx7ORGq1ei 9R16_3eF3xhMjnMGIIecw8YV6iqCXsj7HfJBgLqUsaAhEUEALw _wcB

BTW, do you have Wayne's book? It's a HUGE help.
https://www.pelicanparts.com/catalog/accessories/rebuilding-porsche-911-engines.htm

Really hoping to change the rings without removing the pistons. Seems like each time I take something apart, something new goes wrong:rolleyes:

Thanks everyone.

Dropping the assembled heads (cam towers, cams, etc) and cylinders to competition engineering later this week. He's going to inspect and instruct me on what all is needed, but when I asked about "honing" he said he does it all the time. Seems like changing out the rings without removing the pistons is no big deal with the proper tool. Thanks for the help everyone. Jumping back into my "build" thread here -> https://forums.pelicanparts.com/porsche-911-technical-forum/1108632-1978-finally-out-storage.html

Gotta clean the carbon from the ring grooves w/new rings, so pistons off for that. And don't hone the cylinders!

I did the same job a couple years back. Removing/reinstalling the pistons is no big deal. I did wrap plastic wrap around the block, and around the rods so the circlips couldn't wormhole their way deep inside the case. Good cheap insurance 👍

Soaking in diesel is an easy way to decarbon your pistons.

Kevin,

Your post above does not make sense. How could you change the rings without removing the piston/s from the cylinder/s? Were you referring from the connecting rod? Or this is another typo?

Tony

Yes i was referring removing them from the connecting rod

Each time I have failed to listen carefully to John, I have come to regret it.

I used an old, broken ring to clean the ring lands.

The carbon mostly just flaked off my pistons due to the moisture in the air, once they were out and sitting on the bench. I live in a humid place.

In for a penny…
Clean the pistons, if something goes wrong it needed to be fixed anyway!

Pistons are off and ready to be cleaned

For pistons, I found WD40 good for dissolving carbon buildup. I replaced my pistons but I cleaned a few to see what kind of damage the valves making contact with them did. Hopefully you marked each piston so it goes back in the original cylinder and kept the pins in their original order as well.

Scotchbrite pads with soap and water is what a few recommended for deglazing the cylinders. John W, Henry S, and Bruce P all recommended no honing, just deglaze. Again before you install the new rings, you should check ring gap which means putting the ring in the cylinder and using a feeler gauge to check the gap. I bought a cheap ring squaring tool on Amazon for the job. And when you go back together, make sure you oil the cylinders lightly before you install the pistons with new rings and have some assembly lube on hand to lube the rod and pin.

https://www.amazon.com/ProForm-67652-Piston-Ring-Squaring/dp/B003IN3ZEY

I ran my Alusil cylinders through John Walker's large industrial automatic parts washer. I suspect it washes parts with some sort of solvent. In any case, it changed the color of the insides of those cylinders from a dark grey to a light grey. I think it removed the carbon buildup between the silicon chips which are the actual business surface. Alusils are made using aluminum mixed with silicon, and then the aluminum is etched from the business surface as the last step in the manufacturing process, leaving the silicon poking out for the rings to ride on. I think the parts washer re-exposed those silicon chips.

Yes, light oil on the cylinders. Yes, assembly lube. Your newly assembled motor will make quite a few revolutions before those parts will be bathed in pressurized oil. Assembly lube on cams too!

Once again, I see no particular need to split the case but if this were my engine, I would at least wiggle the conrods just to see if one is looser than the others. If they all wiggle about the same (not much at all), then condition the heads and cylinders, reassemble and drive it like you stole it. Combustion chamber pressure presses the new rings against the cylinder walls. This improves the chances of the rings getting properly seated. Don't baby the engine in the first few minutes. Full throttle.

Honestly I think the rod bearings would have to be trashed to feel any wiggle.
When I had the heads rebuilt last fall, I put in new ARP rod bolts because John and others highly recommended it. I didn't split the case, I just took each one out, inspected the bearings for any wear signs, sprayed with Molykote and let dry, then reinstalled each bearing in its original orientation with assembly lube and tightened things down.

I replaced main and rod bearings, and all fasteners. But I did not recondition rods. When everything was half-assembled I noticed one rod bearing had more movement than the others. I did nothing about it. That was many years and miles ago. I even accidentally touched 7000 rpm a few months ago. Everything seems fine, but I will always regret not having the rods reconditioned.

If it blows up, I will see it as a signal from God to upgrade to a 3.6.

I've always been under the impression that some side to side wiggle is fine but it's the up & down motion where you don't want any play..

Rods will turn easily in the direction perpendicular to the line of the crankshaft, since that is their job. But rods should not wiggle much in the direction of the line of the crankshaft. And again, I am mostly just suggesting you wiggle them all, and see if they all wiggle about the same. "The same" being not much.

There is a proper lapping procedure using paste and felt pads developed by Sunnen for Alusil bores. Have had this done many times by a local machine shop with the correct knowledge and tools. 100% results to date.