Engine failure at 16k??? Why?

Hello guys, Well have a lil, well ok a big problem. Got a 120k sc engine rebuilt 14 months ago. Did some upgrades. So i got it all back and was runnin so puurrtty. Broke it in for the first 3k.. Never going above 4k. What a tease.. Anyway well that was 16k mile ago. I know have a broke engine again. The result was 3 broken top rings. On #3,4,6. Also had the headgasket go out on the #6. I talked to a friend and he says that is very uncommon. I wanted to get a opinion of someone who has built them.. What was the cause of this?? Ok well im almost 19. Could at ANY chance this have been my fault? I know how to drive and i know when it happened it wasnt a misshift or overev. I waited the 4k breakin period, then drove it like normal.. Well ok a lil harder then the normal but we all do. So at 16k why would this engine be pooped? If ya need anymore facts about it ill get back to you. Thanks

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The Kid
NineElevenDrvr

One broken ring is a fluke - three is a distinct pattern. Did you install them correctly? Is the cooling tin around the pistons and cylinders installed correctly. How about the long side of the fins on the cylinders (should be pointing down). Which rings did you use? Did you do the normal 20-min break-in? Have you torn down the motor since and looked inside to make sure it indeed was the rings?

-Wayne

Did you rebuild it or did someone rebuild it for you? Could be a multitude of things that could have caused the problems. Did you correctly gap the rings individually for each P&C? I would venture to say the problem is completely unrelated to your driving habits. I feel your pain.


Dante Oliverio

Agreed, the driving thing didn't have anything to do with this. You only need to stay below 4K RPMs during the first 500-1000 miles while the rings are seating. Did you smog-test (CO meter) the car? Was it burning oil?

-Wayne

Well thanks for the reply.. Ok i didnt do the work. It was an independent.. So to have them installed correctly i wouldnt know.. The wrench has old me he's done a number of engine's. the whole engine looked fine.. i watched the teardown process. it didnt show anything wrong till we saw the headgasket blow out.. i then left and he did the rings.. 3 top broken.. the car had been CO tested and was fine.. no tell tale sign till driving up mountain pass doing about 120ish in 5th.. cruisin.. did that for about 3 miles or so. this morning was cold in the mountains if that has any clue.. but the engine was warm running for an hour prev. so took a long left hander towards the top.. was doing no more then 70 now and made it around and then shifted to 4th.. blip the trottle and vroommm im going.. 3 sec later.. ppoooofff smoke out the back.. so towed it.. long story but friend used his WORK truck for last resort and happened to get caught fired..lol oooppss sorry buddy.. anyway so any more things?

Good advice, but there's more to look for: Pistons don't appear worn. Clearance in bore, within new specs, yet a problem. End gaps correct also, but.......... the ring grooves! A seemingly good p/c may have very worn ring grooves in the piston resulting in a sloppy ring fit yeilding similar results to what you have. Check the grooves on the remaining pistons as well! If all specs. are within tolerances, its too late to check for a lean mixture, overly advanced timing or too low an octane gas. Was there any ping on accelleration? Just be glad a con rod bolt didn't let go due to being reused or a crankshaft cracking due to some nerd neglecting to radius correctly. Ollies! Ollies, or Ollies (and maybe a few others) are capable of doing the machine work properly. Were the heads machined? By whom? (See my post on "How much do you pay your wrench.) Did you know that the guys in the machine shops get less than the garages? Porsche machine shop procedures are special. The machine shop is NOT the place to try to save $.
Sorry about your $ problem. Good luck.

Diverdan

i talked at length with the guy who did the rebuild. i've known him for years. he said the smoking was from being over filled. he ran it for an hour, polluting the neighborhood before it stopped. there was residual oil in the air cleaner area. as hard as you drive it, with all that long hill climbing, i would imagine the broken top rings are from preignition. just cause you didn't (?) hear it doesn't mean it's not there. you had some work done by another shop in seattle, a fuel distributor replacement. apparently you drove 1200 miles on 5 clyinders after the original rebuilder told you it was needed. that easily could have leaned out a cylinder, and made the rest work harder. so others have been messing with his original settings. it's hard to blame the original rebuilder if he has not performed all the work on the car. he has no control over how someone else sets it up. it is out of warranty, it should have lasted longer, and he's trying to work with you. give him a chance. apparently you have been a bit of a butt head with him, so if you want him to fix it for you, you should leave him alone before he tosses you out. sorry to be so blunt.

[This message has been edited by john walker's workshop (edited 04-18-2001).]

John Walker:

You are one great guy taking your time to get to the bottom of problems like this. Like I said, mechanics eat a lot of their work due to abuse, whether intended or not, by the customer. I've screwed up and most of the time I've had to eat, but on occassion I have been helped by shops who go the extra mile. Thank you to all those who have helped me and others in the past for our blunders. Hear, hear for having a continuity in wrenches. One shop to do all is the best!

Diverdan

Well, I like folks who talk plain and I also like good mechanics. Unfortunately both are somewhat rare. So, I talk to myself and work on my car.

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'83 SC

oh boy, stuff like this makes me soooooo nervous considering that I'm thinking about doing this myself....

Is it really that hard to rebuild and set a car up properly?

Adam Roseneck

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1978 911SC 3.0
roseneck@cyberbeach.net