Ok, need help...err advice,

highboost951 · 03-21-2006, 09:52 AM

Here's the situation...a friend buys a new set of cheap autothority chips off of ebay for a stock '87 951 w/ a lindsey boost enhancer, he installs them and was enjoying them until a 4th gear pull, 130mph, poof, white smoke, blown headgasket.

Car is now dropped off for me to fix.

To my surprise, the headgasket is blown at the #1 cylinder, I'm used to it being the #3/#4. Oh well, moving on. Everything looked good in the cylinders, pistons had even clearance around the bores, no scratches, yadda yadda. The head checks out good, even the exhaust guides were good, just needed to lap the valves a bit and install new seals. Skimmed the head just to clean it for the headgasket. All is back together and this thing is a mosquito fogger! The 1st cylinder is loaded with oil, even crawling up the threads of the plug and on the washer; #2, #3, #4 plugs a white as can be, looking a bit lean & hot. This was just last night at 1:00 A.M. so I didn't spend too much time looking at it, ready to go home. Due to the volume of oil, and how it was crawling up the threads of the plugs I'm thinking the oil control ring was damaged when the headgasket let go. I really don't think a valve guide seal would put out that much oil. Guys.....your opinions? I'll do a leakdown and compression test tonight, I wasn't going to mess with it last night since I could see a little oil pooled on the piston top. It would throw my readings off anyways. Ooh, I just had a thought...if there is even more oil on top of the pistons maybe it could be the valve guide seals...

Alright guys, sorry for rambling, I typically have the answers not questions. This is a first for me, I've never had this type of thing happen. Anyone blow out the oil control ring when they blew a headgasket? I've seen a bent rod because of it but not this, errr.

highboost951 · 03-21-2006, 09:56 AM

Hell, I wonder if it is just the oil control ring if it will even be detectable by the leakdown and compression test. The compression rings are good I'm sure, hmmm...

nynor · 03-21-2006, 02:11 PM

turbo blow by? (i know, sounds dumb...)

highboost951 · 03-21-2006, 05:43 PM

nope, it's just the 1st cylinder.

I don't think I'm going to mess with it tonight, but I had a thought. I'm going to run it for a bit, shut it down, rotate #1 to TDC, I'll pull the fuel rail and wait to see if oil pools on top of the intake valve, if not it's probably the oil control ring...yikes

sayporsha · sayporsha's Garage

Hmm . . . I'm confused. You said you replaced the valve seals, but you are thinking it may still be a valve guide seal. Is there more than one seal per valve?

It does seem unlikely that a bad valve guide seal could soak a cylinder like that. However, these cars have been known to blow the seals off their perches if too much boost gets up the valve guides. I heard that Porsche issued a TSB to use Loctite when installing the seals to help hold them down.

You may want to confirm the integrity of the hose from the cycling valve to the wastegate. If it's broken or plugged it will overboost. I would also confirm the setting on the Lindsey Boost Enhancer.

Best of luck,

highboost951 · 03-22-2006, 02:22 PM

Valve guides seals were replaced, just thinking that it may have come loose or was damaged. Car hasn't been boosted at all yet, I took it for a 5 min. test drive to clear out the coolant out of the exhaust. The hose and the setting are good, I just replaced the hose when I put it back together. Hopefully I'll have an opportunity to work on it tonight but after I change my 1/2 shafts on my car. I broke the drivers side one last night!!!

ae1969 · 03-22-2006, 03:36 PM

I have had exhaust side valve stem seals pop off..........

IT SMOKED LIKE IT WAS GOING OUT OF style............ the oil was pooling quite a bit.......

Were the guides notched? I have seem some of the original heads have no notches on the guides. The stems were glued in to place. I made the rookie mistake of not swapping the guides or at least glueing the seals.

Pull the intake to get a peek. I discovered mine when I pulled the header........

highboost951 · 03-29-2006, 05:50 PM

Just an update, and Alex thanks for the tip. I'm determined it's the rings. I ran it, cranked #1 to TDC, no oil in the intake port, piston was coated w/ oil, if it was the guide seal it would be out the exhaust, not in the combustion chamber. compression is down about 7#'s compared to the rest, oh joy. that's definitely not good when that cylinder is "wet" and the others are dry.

nize · nize's Garage

cool. keep us updated!

highboost951 · 05-30-2006, 04:15 PM

sorry guys, I forgot to give an update.

Well it's been about a month and a half and all is well.

I pulled the fuel rail and it was definitely not coming in from the intake, and if it was the exhaust it would have been smoking but not pooling on top of the piston.

I checked, double checked, and had some one else check the rod and it was straight as could be. Scary enough, I buttoned it back together with a new set of rings. I took it for a test drive, seated them, and presto, no more oil smoke.

I forgot, what's even scarier which I failed to mention in the first post is that the car was attempted to be re-started after the headgasket let go (which I didn't know till after putting it back together). The cylinder was full of water and he attempted to start it. It actually physically broke the aluminum nose casting of the starter. It was a more than a "little" noisy when I went to restart it. I for sure thought that the rod was bent and I overlooked it, but apparently the rings didn't like compressing water too much. All is well with the new ones.

nize · nize's Garage

wow good to hear!