New guy, about to pop my engine rebuild cherry
10-20-2016, 05:13 PM
#16
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Been sick for the past week and a half so progress on the tear down has been slow. However, I have made progress and continue to chip away at it a little at a time. Along the way I've discovered (I know it should have been obvious early on but I still have a lot to learn about this car) that I already have the carrera chain tensioners. So the good news is I don't have to worry about buying the updated covers or the oil lines but given that the porsche brand tensioner kit on pelican parts is the same price I'm probably better off buying the whole kit and getting new gaskets and oil line "for free". There's a part of me that wants to just reuse the existing tensioners but I have no idea when they were installed so that strikes me as a bad idea.
On the bad news side of things one of the cams has pitting on the lobe surface that is visible with the cam still in the engine. I'm assuming that means I'm in for at least one new cam which has me thinking about swapping for something other than stock despite my intention to keep the rebuild basically stock. I'll know more in a day or two when I get the cams out and will post pictures so hopefully you guys can chime in on my options.
On the bad news side of things one of the cams has pitting on the lobe surface that is visible with the cam still in the engine. I'm assuming that means I'm in for at least one new cam which has me thinking about swapping for something other than stock despite my intention to keep the rebuild basically stock. I'll know more in a day or two when I get the cams out and will post pictures so hopefully you guys can chime in on my options.
10-20-2016, 06:32 PM
#17
the carrera chain tensioners should last a loong time - am I missing something? the OP indicates > 80k on the motor
OTOH, what caused the cams to get pitted? and could it have affected the chains/tensioners as well?
OTOH, what caused the cams to get pitted? and could it have affected the chains/tensioners as well?
10-21-2016, 08:52 AM
#18
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The car has 78k on it now. I would assume that the tensioners should last a long time but without knowing when they were installed I have no way of knowing when the clock on "a long time" was started. Not that tensioners can't be replaced with the engine in the car but it seems like a lot of effort rebuilding the motor only to have the tensioners potentially fail soon after.
10-21-2016, 03:27 PM
#19
I'd just check them out carefully - even 78k should not be a lot of miles for them. The oil used could be a more important consideration.
Maybe Steve W. will see this thread and give you a more experienced opinion - or ask a good shop near you how long these usually last. One that has seen hundreds of older 911s.
Maybe Steve W. will see this thread and give you a more experienced opinion - or ask a good shop near you how long these usually last. One that has seen hundreds of older 911s.
10-21-2016, 08:48 PM
#20
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For the OP - and I just can't resist the temptation on a Friday evening - when you say you're about to pop your engine rebuild cherry an alternative phrase comes to mind: "Prepare to gab your ankles!"
One of the most challenging aspects is to find a competent machine shop which is VERY experienced doing Porsche 911 engines. I would put that at the top of my To-Do list before dropping the engine.
FWIW, a bunch of years ago when I overhauled many 911 engines, a relatively simple and cost-savings solution to the rocker arms was to rebuild them installed rotated 180° from their original position (and this was done in conjunction with rockers which had been rebushed/refurbished to original specs). In their original position virtually all of the wear is on one side of the rocker shafts. With a 180° rotation on reassembly they can start wearing on the other "as-new" side.
One of the most challenging aspects is to find a competent machine shop which is VERY experienced doing Porsche 911 engines. I would put that at the top of my To-Do list before dropping the engine.
FWIW, a bunch of years ago when I overhauled many 911 engines, a relatively simple and cost-savings solution to the rocker arms was to rebuild them installed rotated 180° from their original position (and this was done in conjunction with rockers which had been rebushed/refurbished to original specs). In their original position virtually all of the wear is on one side of the rocker shafts. With a 180° rotation on reassembly they can start wearing on the other "as-new" side.
Last edited by Coloradocurt; 10-21-2016 at 09:49 PM.
03-03-2017, 09:40 AM
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Been a long while since my last post on this. Mostly because very little has happened thanks to life getting in the way as it frequently does. With the exception of removing various studs for replacement, the engine is completely torn apart. Major issues that I've found are the pitting on the cams as well as more (and more severe) pitting on the con-rod journals of the crank (mains are perfectly fine though). The only thing I can think of that could have caused the pitting is the time it spent sitting in the garage when my dad still had the car. There was more than one occasion that I am aware of when the car sat for 6+ months without being started or driven. Based on input from others moisture in the oil or high acid levels from older oil being left in it during those periods are the most likely causes.
In the meantime I have found a couple reputable shops to do the machine work based on suggestions from here and a few porsche buddies I have so that's not much of a concern anymore.
Unfortunately the total broken head stud count ended up being 7. More unfortunately, only 4 of those were willing to come out. Even more unfortunately, the remaining 3 have resisted every effort I have made to remove them from heating, oiling, various gripping methods, left hand threading and wrenching with a left handed bolt, various extractors, and finally drilling with a left handed bit to just a hair under the minor diameter of the threads, followed by more left hand threading/extractor attempts. At this point I have managed to avoid touching the threads in the case itself so no permanent damage has been done but I have exhausted every option I can think of so it looks like inserts are in my future. REALLY unhappy about my failure to get these things out but at least hope is not yet lost that I can recover from this without any major drama.
In the meantime I have found a couple reputable shops to do the machine work based on suggestions from here and a few porsche buddies I have so that's not much of a concern anymore.
Unfortunately the total broken head stud count ended up being 7. More unfortunately, only 4 of those were willing to come out. Even more unfortunately, the remaining 3 have resisted every effort I have made to remove them from heating, oiling, various gripping methods, left hand threading and wrenching with a left handed bolt, various extractors, and finally drilling with a left handed bit to just a hair under the minor diameter of the threads, followed by more left hand threading/extractor attempts. At this point I have managed to avoid touching the threads in the case itself so no permanent damage has been done but I have exhausted every option I can think of so it looks like inserts are in my future. REALLY unhappy about my failure to get these things out but at least hope is not yet lost that I can recover from this without any major drama.