3.2 with cam tower oil leak - while I'm in there

[Evans968]

My '88 911, purchased with 78k on the ODO, now 25 years later has, 160k. I had a mechanic repair some bad rings at 129k and he did the crank bearings at the time (said the heads were OK). All was well until the timing chain case leak occurred about 5k miles ago, repaired/sealed and cam timing adjusted by a different (competent) mechanic who discovered some sloppy work by the first guy. Recently during a hard DE run, new evidence of oil leak, on the right bank, cam tower to head area. I have removed the valve cover on that side and confirmed that the rocker shafts are not leaking and appear to be in the proper position, possibly never touched by the 129k dismantlement.
So I plan to remove the engine, take it to my current mechanic to remove probably both cam towers for re-seal. The question is how far is it prudent to go down the "while you're in there" path (truly a dangerous path). I have read numerous Pelican threads on this and believe i understand the rocker shaft issue (rebuilding this area on a high mileage engine may require additional machining, RSR seals, etc.
I would like to end up with a reliable engine to a) maintain the value of the car (other wise, very nice), b) OK for autocross and maybe one DE/year, c) leak free. A complete rebuild (new cylinders/pistons) would add about $4k to the cost, so if original pistons check out ok, would lean toward keeping them in. But moving to at 3.4 set is tempting. Head rebuild seems appropriate now.
Any advice you can give would help.
Thanks

[brighton911]

A compression test and if possible, a leak down will give you a good idea of the engine's health. How is your oil consumption? If the heads have not been touched, I would say it is definitely the time to do them, you are in there anyway.

[Evans968]

Oil consumption has been very low, even during HPDE's. Leads me to believe the heads have been done by a PO. Regardless I will have the heads renewed and the cylinders/pistons checked. If there is significant wear on cylinders/pistons, I believe these can be reconditioned, correct? Is this advisable or am I in for a new set?
Next question is if the rockers look OK after removing cam towers (no leaks, as they appear to me now) is it advisable to leave them alone or do these get refurbished at this point?
Thanks

[KTL]

A leak between the cam tower and the heads is rather uncommon, unless someone did a poor job of sealing the two machined surfaces. There's no oil pressure occurring between the heads and the towers. it's just splash/drip oiling. So that's why it's surprising to me that there would be an actual leak between the two. As long as the nuts are all tight (uniformly) and the sealant was applied OK (not uncommon for WAY too much sealant to be used here), then I question if there's actually a leak there.

On the other hand, the pesky circular three bolt gasket between the cam thrust plate and the cam tower is a notorious leaker. Over time that gasket degrades and allows for a good leak to run down the chain housing or the engine case. It also doesn't help that the sealing surface on the cam housing is not as flat as it should be. Plus that location is definitely subjected to pressurized oil (cam housing providing pressure to support cam bearing/journal) and therefore oil is trying to force its way past the gasket. The only way to fix it is to replace the gasket. My recommendation is to coat the new paper gasket with a sealant like Permatex copper spray gasket sealer to prolong its next life.

[Evans968]

Yes, I thought at first that it was the 3-bolt gasket as well. That happened on the left side 2 years ago. Fixed with the help of my mechanic (long experienced Porsche race wrench) who does use a sealant on the paper gasket. I have less confidence in the guy who did the 129k piston ring job in 2005 that gave me the first chain case leak. So two weeks ago at VIR when I saw oil drips under the right side chain case, I was sure that was it. But when I took it over to my guy, he quickly diagnosed the oil beneath the cam tower joint an(photos attached). And it does worry me that this went from a dry engine to dripping oil over the course of two DE days. .

[amg55driver]

Thanks for the info!

[Evans968]

Does it look like this is a cam tower to head leak? If yes, it would seem that the sudden occurrence would point to a stud break. I have removed the valve cover to check for this, but all seem to be OK. I placed a socket on each and gave them a light twist.
I had planned to replace the valve cover and proceed with normal use (but no DE's for now) then remove the engine and take it to my mechanic address the leak plus WYIT item (still not finalized, thus the questions).
Thanks

[KTL]

I myself would clean the area really good and then run it to see where the oil is leaking. Seems to be wetter around the oil return tube bores than it is up higher near the fins at the bottom of the heads

[Evans968]

Great idea! will do as soon as my parts order with cover gaskets arrives.
Thanks!

[boyt911sc]

Originally Posted by KTL

I myself would clean the area really good and then run it to see where the oil is leaking. Seems to be wetter around the oil return tube bores than it is up higher near the fins at the bottom of the heads

Evans,

You worry too much. When was the last time you degreased the underside of your engine? Spend some time cleaning your motor and observe the areas after a couple hundred miles. You will be fine.

Tony

[Evans968]

Tony, you're correct about my worrying! But in answer to your question, I have had the engine out within the last three years (about 10k miles) for fuel and vacuum line replacement, de-greasing engine, pressure washing engine bay, clutch work, etc. Had headers off then as well. Until the right side chain case leak, it had been pretty dry. Chain case leak fix made it really dry. In the pre-DE tech check just weeks ago, my mechanic had commented "ah, dry". So whatever happened during the DE last month resulted in a collection of drips found only after a run (no new drips while garaged).
So this started the worrying. If it's the chain case, I can deal with that. If it's the oil return tubes, I can deal with that too. If it's the cam tower, that brings up the big choices.
I've expected for a while (given the 160k mileage plus DE's and autox's) that sooner or later, I'd have to do (or have done) a full rebuild, but really don't want to do it now. Maybe this winter, or maybe in a year or two.

[Walt Fricke]

A rocker shaft walking out of its holes will produce a leak pretty quickly. I just had to deal with this at a race. Easy to check the intakes, not so easy to check the exhausts.