Was talking with my mechanic tonight who did the top end on my car about a year and a half ago to arrange some routine maintenance. We happened to touch on, what else, the subject of the valve guides.

He mentioned some discussions he'd had with other 993 mechanics he knew who have seen multiple incidences of cars that required more than one top end job in fairly short order. Kinda makes me paranoid. He said his suspiscion is its more prevalent in cars that see alot of stop and go in traffic, not something my car sees much of as a weekend toy.

Anyone here had to have more than one top end job done or heard of others who have experienced this? Just curious...

 

Have not heard this is a problem. Perhaps the repeats are jobs done with Porsche valve guides, which are known to be fast wearing....I am on my first top end and running strong, virtually no oil consumption.

 

102K miles. 0 top ends. Leakdown numbers at 101K miles:

1 - 2%
2 - 1%
3 - 2%
4 - 2%
5 - 3%
6 - 2%

The only way I see a second top end shortly after the first is if the shop used sub-par quality materials or they didn't do a good job the first time around.

 

No kidding.

If it's done right, with the right materials, you should be better than new. If it needs to be done again, it wasn't done right the first time.

Or so I have been told...

 

Had mine done at 92k~ miles. My guy told me I had a little bit left in the exhaust valve guides but not a lot. I was burning a quart every 800 miles or so, so it was still within spec at the time. "Within spec" cracks me up. The car has 116k miles on it now and hasnt burned a drop of oil, doesnt hiccup, make odd noises, nothing... I do drive my car hard too but I also take very good care of it with lots of prophylactic maintenance. A buddy who works in a shop is always amazed at the condition it's in (except for the bumper cover which has a raging case of "rockpox") and how well it runs. The car looks only mildly used.

I will admit it's not as squeeky clean as Andreas' car. Then again, no ones car is.

 

I've never heard of this on a 993 or any other Porsche. Valve guides, when properly fitted, should last around 150K. The top end in my car was done at 74K and I've got 111K on it now and it doesn't burn a drop of oil.

 

My silver C4S had 7k mi on a top end when I bought it. Within a few months, I got a CEL. Took it to my p-car indie and he said it needed at top end again. When I asked why, he said "that's just the way it is with these cars". I did some research here and then took it to another tech to have the O2 sensors checked. Sure enough, that's what it was.

Always get a second opinion and always question what those "p-car specialists" say. Techs make a lot of money on top end jobs. Telling you he's seen multiple cars that required more than one top end sounds like he's trying to make you comfortable with that idea of bending over. I can't ever recall anyone on this forum needing more than one top end.

 

A properly done top end doesn't need to be done over again for 100K+. One of the keys is using good quality guides (not OEM) that have been correctly installed and fitted. Valve seats should never be ground, only machined with cutters that have been properly maintained.

There are several more details involved in this operation but those are the big ones.

 

Not really.

Granted the overall bill may be high to the customer, but what of that does the shop actually make? When it's all said and done, how much have you beaten the/your flat rate? What's the back end liability if anything is glitched, say even a small oil leak?

I ALWAYS would prefer to do the equivalent labor hours on general service work, brakes, alignment. Things that get a car in and out in one day, and provide instant cash flow.

Now, if you're struggling and need all the work you can get.........different story.

 

I'm at 133k miles and doing fine - not top end rebuild needed yet!

 

A top end is mostly labor and that's how techs make the bulk of their pay. My comment was made on the basis of hours billed. Aside from that simple, salient point, I'm not in the business of fixing cars so I don't know the economics of that business.

 

Hi Louis,

I would be very cautious about generalizations here. The profit in a top end varies by marque, the parts bill and local shop rates.

Most people outside of this business have no idea how many hours it takes to extract the powertrain, disassemble the top part of the engine, do all the requisite machine work properly, reassemble, and reinstall everything.

Done correctly, its not slam-bam job and VERY few people get rich in this industry.

 

+1 mine hardly burns a drop 67k I think the 993 valve guide issue is blown out of proportion. Of the 10's of thousands built I'm sure the failure is much less than people think. were only hearing about a small percentage. imho of course..

 

Hi Steve,

Sorry if I was unclear. As I stated before, I have no idea what the economics (profit margins) of your business are. I said my comments were based on hours billed and you seem to agree that it takes many hours to do the job. Maybe I should've said "Techs bill a lot of hours" instead of Techs make a lot of money".

I guess it's all in how you define rich. If you get as much satisfaction from working on Porsches as I think I would, then you sir, are a wealthy man.

 

Keep in mind that most shops bill on "book" not real hours. Book for a brake job is far more than real time. Many mechanics go home every day after working 8 hours with 14 hours in the bank. Some of the shorter straight up jobs "book" well and some of the larger ones such as a top or bottom end might not.