Top End and Reseal

[gregwils]

Originally Posted by cstreit

There's no feeling worse than finding an oil-pump seal laying on the floor after you've sealed the case and wondering if it's an extra, or if you forgot to put it in.

I know that I have read about laying stuff out, but understanding why it was so important escaped me....until now. Great tip, thank you.

[marcsalleras]

Good luck to you, I started my tear down on my 86' 3.2 like last week, I'm about to split the case today

[gregwils]

Thanks marcsalleras - good luck to you too. You're a head of me.

More progress today, but need to stop after just a few hours - 13 days before Christmas with lots of non-Porsche stuff to do. Like I said, I am slow, but this is really a fascinating project.

Left timing chain cover is off along with 1,2,3 cam tower and head bank.

Sprockets look pretty uniform to me, so I will plan to reinstall along with the chain.





Cross-hatching visible on all three, but cylinder walls most exposed on #2. I don't know what to make of the carbon patterns on my pistons, but #1 has coast to coast coverage. #3 carbon appears thicker.



Close up of #2, but the photo doesn't do a good job of showing the cross-hatch marks.



Heads look OK to me based on my vast experience with Porsche engines. Seriously, I was afraid the valve faces would look worse. Is there any way that I can examine the guides, I am just curious about the oil consumption?

[Flat6pac]

The guides are measured as side movement of the valve and the seals on the guide also wear. I leave the decision of the guide wear to the machinist.
The last set of heads, I told the machinist to replace the 12 and he called and said they were already changed and in very good condition, he honed them slightly so he was happy with them and put them back together.
another at 90K needed all guides replaced so its a crap shoot when you take it apart.
Bruce

[shbop]

A small hole guage and a mic will let you gather the info you want.

[gregwils]

Ok, a little more work this weekend, but with just a few days to Christmas, there hasn't been much time at all for the engine. I did get the chain and heads off 4,5 & 6. #4 was my low compression, high leak-down cylinder, but there is no visible evidence of any possible cause. I can only see an inch or so of the cylinder wall, but it looks perfect - cross hatching clearly visible top, sides and bottom. I have to assume one or both of the valves weren't fully seated. I'll never know if it was my valve adjustment or some carbon.





close up of #4, can't see much in photo

[gregwils]

If my piston ring end gaps are in spec, I intend to reuse. Once I clean the cylinders, my plan is to coat the walls then just a light coat of oil, essentially replacing what is currently on them. No deglazing or any other prep. Does that sound correct for reusing rings?

Also, what is the best way (safe) to remove that carbon ring at the top of the cylinders? Thanks.

Having great fun.

[Flat6pac]

Thats a carbon deposit not a ring groove in the cylinder so you really dont have to do anything with it. Are the cylinders nikisil or alucil? Looks like youre really moving along on the engine.
Bruce

[gregwils]

Bruce - The cylinders are nikasil - 11 ribs and slightly magnetic. The ring of carbon deposit seems like oily tar with some carbon mixed in for good measure, it tells the story of my high oil consumption. Actually, it seems to be cleaning up with a plain paper towel and some rubbing alcohol.

[Flat6pac]

You want to pull a cylinder, especially the one that was the worse, then one to see for comparison. Then you will see the blowby down the different rings and down the skirt. The last post I did on the restud you can see the rings and blowby which was negligible .

Bruce

[gregwils]

Ok, a little more progress this weekend. Cylinders off and and dilvar exhaust studs are out. I discovered it's all about technique when it comes to removing the studs. Wayne's book is clear, but the written word is always subject to interpretation. In the end, I heated only inside the cylinder spigot and they came out pretty easily, heating any other part is a waste of time.

The cylinders look good and my bore gauge indicates about .005" out of round on #4, which was the cylinder I was concerned about. I will measure the others, but looks well within spec. I still need to measure the piston ring side clearance. It appears like very little blow-by on the pistons.

However, here is my big issue. I did shove the top compression ring in cylinder #4, made certain it was level at approximately where the cylinder and case meet. End gap was .65 mm. The wear limit is .8mm. Assuming that the end gap started at .3 (mid point of new according to book), then the ring is 70% of the way from new to wear limit. This translates to another 30k miles before it would hit the wear limit.

Does any of this make sense? Should I re-ring at the risk of new rings seating properly or keep the old rings and not worry too much about the end gap? Decisions, decisions....

Back to work tomorrow, but will steal some time next weekend.

#4 piston


No mas dilvar



Better shot of cylinder

[Flat6pac]

Greg, As I was saying about blowby, you have no tarnishment below #1 ring so I can believe the rings are still doing their job. There will be nearly no wear on the nikisil and doing the rings now along with the valve job you will be putting too much stress on the bottom end. Recommend you open the bottom, reseal, inspect, change out the intermediates, new chain rails, close it up for the next few years.
Bruce

[gregwils]

Bruce - thanks for the quick feedback. I only put 3 - 4k miles a year so even if I only get another 30k to 40k miles from the existing rings, that is ten years of driving. Plus, I won't need to worry about the rings seating or causing undue stress on the bottom end as you suggest.

I will do as you suggest regarding the crank. I'll check the mains and if they look good, I won't touch any of the rod bolts. I do have the intermediates.

One more question. I was thinking about replacing the valve springs just because it seems like the get fatigued, but you thought the existing ones would be Ok for street driving. Does that still seem reasonable? I don't mind replacing them if you think they are at risk for breaking. Thanks again.

[Flat6pac]

All you do is drive the car, just build to spec, the springs will support your driving. If you want them replaced, theyre not terribly expensive but you ll never feel the difference just Sunday driving.
Bruce

[gregwils]

Bruce - Thanks. I am going to stay with the existing springs. I continued to search the forums and while I know there are failures, it mostly seems to be from stress.

I removed the heads and rockers from the cam towers. The only mark I saw on one of the camshaft lobes was on #1 intake, but there was no marks on #1 intake rocker.

Does the lobe need repaired? I can feel it with my fingernail. Can it be polished or does it need reqround? Also, are the radial marks on the camshaft bearings normal?

I also found pitting on one rocker - #1 exhaust. Does this need repaired?

Hopefully, this doesn't translate into regrind and polish of both cams and rockers, but if it does, it does.

#1 intake lobe


#1 exhaust rocker

[gregwils]

A little more progress today. I split the case. One point worth noting, the case is far easier to separate once all the bolts are removed.

My bearings and crank appear Ok when I compare them to the photographs others have posted. The intermediates are showing copper as expected. For me, the benefit of splitting the case is 1) to know the condition of my bottom end, 2) to replace the intermediates, and 3) to make sure that no crap got in the bottom when I was doing the top.

I will probably spend the next few weekends cleaning - sloppy job, then begin the process of reassembly.

Here are my photos - comments welcomed.

[Flat6pac]

Greg, it is looking good. If you pull the beariings off the case, bag them with the exact location such as 4 L or 6R so they go back exactly where they camr from. The back of the bearing should have a 930 part number on it.
Bruce

[rcaradimos]

Greg,
Have you identified the cause of your oil consumption?

[gregwils]

Bruce - Thank you once again. I plan to do exactly as you say 1L, 1R, 2L, etc. I will check the part number on the back bearing - not sure if " back" translates to #1 or #8, but I am sure one of the bearings will have the part number.

Bob - I have not as yet. I am guessing it is the guides, but the heads are no disassembled yet, so can't confirm. I will post as soon as I know.

[Flat6pac]

#8 wouldnt count but #1 use left and right as it shows the most wear of the mains
Bruce