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How often does a 993 typically need a top end rebuild?

 
Old 01-30-2012, 12:08 PM
  #16  
IXLR8
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Originally Posted by gonzilla View Post
Sounds like you may be able to get some from Steve.
I like to have several options available and get some feedback before deciding with which guides I am going with. I have lots of time for that and will check the Euro scene as well.
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Old 01-30-2012, 12:19 PM
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TheOtherEric
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Originally Posted by Steve Weiner-Rennsport Systems View Post
Yes it can, however it requires removal of the valve covers and an accurate measurement of side play in the valve assembly. This takes an experienced tech to do this to get reliable results.
Alternatively, could you remove the intake and the headers and visually inspect the valve guides for carbon buildup? I'm not saying that's any easier, but would it be sufficiently accurate?

Maybe you could snake a long boroscope in there? Just a thought.
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Old 01-30-2012, 12:48 PM
  #18  
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Originally Posted by TheOtherEric View Post
Alternatively, could you remove the intake and the headers and visually inspect the valve guides for carbon buildup? I'm not saying that's any easier, but would it be sufficiently accurate?
Not really,... You need to assess/measure valve stem-to-guide clearance. The only two ways to do this is either measure side-play (which is a little bit of "Kentucky Windage"), or disassemble everything and measure the stem OD & taper of the valve stems and the ID of the guides.

Maybe you could snake a long boroscope in there? Just a thought.
That's useful for checking the condition of the cylinder surfaces, however it will not tell you anything about the guides.
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Old 01-30-2012, 01:31 PM
  #19  
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Thanks Steve. I was just wondering if we could devise a more practical and non-invasive alternative to the wiggle test. The wiggle test seems to be pretty rarely done.
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Old 01-30-2012, 01:41 PM
  #20  
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Originally Posted by IXLR8 View Post
I like to have several options available and get some feedback before deciding with which guides I am going with. I have lots of time for that and will check the Euro scene as well.
I'll be interested to hear what you find out. I know it's in my future. It seems as these things are getting older, it's not a question of if, but a question of when they will need new guides.
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Old 01-30-2012, 03:48 PM
  #21  
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Originally Posted by TheOtherEric View Post
Thanks Steve. I was just wondering if we could devise a more practical and non-invasive alternative to the wiggle test. The wiggle test seems to be pretty rarely done.
Hi Eric,

I wish there was one that offered the same qualified results,...

I think the reasons why this isn't done more often is simply due to the time it takes to pull the lower covers and the lack of experience in assessing the degree of movement.

We don't perform PPI's any longer, however when we did do those, that was an integral part of that service so a potential owner knew precisely what the engine needed or not.
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Old 03-03-2012, 11:12 AM
  #22  
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Originally Posted by Falcondrivr View Post
From what I can tell from years of reading, oil consumption is the only real indicator of wheather or not a top end is need on a '95. Mine has no rebuild, and the oil consumption is minor. I'll pass 160,000 miles next month. It's my daily driver and does track duty several weekends a year.

That is greatness! 160k impressive!
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Old 03-03-2012, 11:54 AM
  #23  
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Originally Posted by shadow993 View Post
That is greatness! 160k impressive!
How about we see what they look like when they come out?

I've done a dozen or more engines that went close to 200K (granted, 3.0L and smaller, and a major miracle they didn't puke tensioners along the way), and the stem-to-guide clearance is silly. Not to mention intake stem taper itself. Not anything I'd want to subject to track use. But I can do it myself, and I'm funny that way.

The 3.2L I'm putting in "Ruby" (Ed Hughes Targa that I just bought) will get an engine that was done by Bob Grigsby at ~170K original. Came from Hank Watts (Secrets of Solo Racing) '86 cab that was wrecked. That car/engine was bought new, driven into submission at autocross and on track for a dozen years, and held up fine. But it was religiously maintained. So there's the flip side if you want to just keep going and going.

Personally, I've never seen a factory guide on any air cooled that didn't warrant replacement. I've had my hands in 3.6L engines with as little as 20-30K miles that I was in to change rod bolts.
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Old 03-03-2012, 12:05 PM
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Originally Posted by gonzilla View Post
I'll be interested to hear what you find out. I know it's in my future.
Don't wait for me as it'll be a long ways away, time-wise.

I'm not one to go off the deep end because I am using an almost immeasurable amount of oil. Its an air-cooled engine, so is my BMW R100 GS and it consumes some oil when filled to the "max" line on the dipstick. The other air/oil cooled motorcycle I have also consumes some oil if filled to the max level...and everyone complains there is a problem, yet they continue making the same mistake...over filling...there is a red dot in the center of the oil level sight glass which is where the oil level should be...not at the top of the oil level sight glass.

Originally Posted by gonzilla View Post
It seems as these things are getting older, it's not a question of if, but a question of when they will need new guides.
As with any wear item, any car make and model included. On my daily driver, I consume zero oil between very long oil change intervals and that is at 135K miles.
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Old 06-20-2012, 02:36 PM
  #25  
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My late 1995 C4 has 350K miles. Oil consumption has increased slightly over the years, but not much. Daily driver.
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Old 06-20-2012, 06:46 PM
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350k miles could be the RL record holder! Nice.
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Old 06-20-2012, 09:24 PM
  #27  
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I have a 1995 993 with almost 103K on the odometer, original valve guides, zero oil consumption between oil changes, and it runs great. Cheers!
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Old 06-21-2012, 05:12 AM
  #28  
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Hi

I had my guides changed at 185k miles. They were worn, the valves themselves were fine. They only got changed because the engine was part for a broken piston ring. We do not have smog tests in the UK though. The engine did not use much oil and never smoked befor the guides were done by the way.

All the best

Berni
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Old 06-21-2012, 04:29 PM
  #29  
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I'm at 95K miles and use about 1 qt oil every 5K miles.
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Old 06-21-2012, 06:27 PM
  #30  
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This really is a perplexing issue. When I sold my last 993NA it had 53,000 miles IIRC and passed the leakdown with a above 98%. When I had a PPI done on my present tt with only 24,000 miles, one valve guide was badly worn yielding about 70% or so on that cylinder.
The heads went off to Steve and now all is well for many years I'm thinking. The lesson is always have a leakdown performed and keep a cash reserve....Chris
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