teddysam1

I just had a top end rebuild due to my SAI ports being clogged. I was wondering if anyone could tell me what is the likelyhood of this happening again? and if so, is there a time frame? and how do I prevent this in the future? 1995 993 95,000 miles

mpruden

I can't remember reading of someone doing 2 top end rebuilds on a 993 street car's engine. I'm sure it happens, but the likelihood of going in there again must be pretty darn low.

Just curious, what were the reasons you decided to do a top end rebuild on your 95 beyond an SAI malfunction?

Foxman

A top end and rebuild on a 1995 with OBD 1, just for clogged SAI ports? I'd just leave it alone unless there was some other problem. I have a 1997 with a piece of electric tape over the yellow warning light. This is not a performance issue. That said, I've seen clogged ports like that on garage with queens with fewer than 30,000 miles. Possibly they weren't driven hard enough, but the odds are very good this will repeat itself. You are lucky to have a 1995 with OBD 1. Drive and enjoy it!

teddysam1

In reference to "mpurden" comments........it failed Ca. Smog....thus led to a series of other fixes

ricks993

I just finished a total rebuild on my 95. After asking what others have done, I decided to plug my SAI so I never have to worry about it. I removed the complete system and plugged then cleaned and saved the parts for future if ever needed. It frees up a lot of space in engine bay.

nine9six

Teddysam,
Do you have a list of issues that were addressesd/replaced in the top end rebuild?

Failing smog could be a number of singular or simultaneous issues that do not require a top end rebuild...You could have a stuck SAI check valve and a slight over fill of oil, which would cause high HC from oil in the exhaust and eventually lessened life and failure of O2 sensors. All of which would fail CA smog.

Were you burning excessive oil (1qt-600 mi)?

teddysam1

Nine9six,
Yes, I do have a list, which included bad compression.......I believe in 4 cylinders.......so I think it was due........I got new rings, seals etc....a new top end basically and then some. I'm just hoping not to have this problem for awhile, thus the question. I've heard from people saying this problem will come back, to you should be fine for another 100,000 miles. I figured rennlisters would know the best........any advise would be welcomed....

mpruden

We like to debate this around here, but based on what I've seen, the root cause of the problems that lead to a top end rebuild is worn valve guides.

Some pros on this forum have commented that both the guide material and the original fitment from Porsche was of questionable quality on many 993s. If true, then using better materials and more attention to detail when assembling should greatly reduce the chances of this happening again.

Overall, I wouldn't worry about it. The new valve guides should last longer than the originals, and being a 95, it's unlikely it would get bad enough to cause an emissions failure again. Remember, with your OBD I car, the passages could be completely clogged, and you, and your smog tech would have no idea. That's the benefit you have over the 96+ OBD II cars.

Drisump

I believe if you search you'll find reference to a few gurus who aren't impressed with the guides Porsche shipped the cars with. Some extremely low mileage cars have had their heads stripped and analyzed and found to have excess clearance between the guide and the valve.....and that is from the factory. That being said, unless your car had extreme amounts oil getting past the guides causing a build up of carbon on the valve seat thus creating a compromised seal, it would be hard to explain the compression problem. A friend of mine, that builds engines, changed out the factory guides for silicon bronze ones in a clients 993. He feels that these non OEM guides will never be an issue again. Anyway, good luck

teddysam1

Thank you for your advise/knowledge........I hope with the work I had done it will be like driving a new 993......

NYC993

From reading many posts:
1) use non oem valve guides
2) dont overfill oil
3) drive hard

teddysam1

NYC993,
I believe they used Canyon valve guides........

vincer77

On a 95, clogged SAI ports should not be a problem. As mentioned before, it will not cause performance issues, and will likely not affect ability to pass smog. Also, it does not trigger a fault code.

Supposedly the replacement guides should not wear like the original ones, so if it is the case that worn guides contribute to clogged ports, then it should be minimized.

My sense is that not replacing the SAI valve often enough is more likely the culprit. When I changed mine out, it was within the recommended interval, but the valve would flow both directions. When the valve operates properly, there should be no flow from the exhaust ports, with oil residue or not. I have decided that I will change mine every 15,000 miles.

Steve Weiner-Rennsport Systems

Valve guide life is all about two things:

1) Using the proper material.

2) Fitment; the factory did a poor job and especially on the exhaust guides. The machine shop must ensure they are installed correctly so the valves are perfectly centered on the seats and the guide bores are honed (NEVER reamed) to size.

teddysam1

Im hoping that CANYON valve guides are the right material and as far as installed correctly, my fingers are crossed