A whole summer rebuilding, and it leaks

[targasc1980]

Hi. I just want to share the story of my summer long undertaking, and where it stands now. I'm a student, and I go to school 300 miles from home. While I was home for Thanksgiving, I discovered some broken head studs in my Dad's 1980 SC that he hasn't touched for years.

So I decided that when I came home for summer I would take it down to the case and do a top end overhaul, as the engine had 130,000 miles. The process was really great fun, and I enjoyed it the entire time.

I ended up having to split the case, because as my machinist(he did a full valve job for me) and I were removing the studs together, one of them broke right at the case, so he had to drill it out. My machinist said the bearings looked great, so I reused them and left the rods on the crank.

Assembly went pretty smoothly, except for one thing: I used a brand new torque wrench when tightening down the case perimeter bolts, and I didn't realize how subtle its click is. I overtightened one of the nuts right next to the sump, and totally stripped it, so it wouldn't hold any torque, and I couldn't get it off because it just spun on the stud. I called a local Porsche mechanic I know, and his opinion was that if we replaced the stud and nut and torqued them down, that it wouldn't leak. In retrospect, I should have just separated the case halves, and started again. But instead, the mechanic welded the nut to the stud so we could take them both out, and replaced it with a new stud.
My goal was to be able to drive the car before I went to school, and I was really set on it. After so so much effort trying to finish the thing before I left, when I started it up, it started leaking from the whole section of the case parting line near the stud that wasn't torqued when it sealed.

I was pretty disappointed, as now I'll probably have to do pretty much the whole process over again before the car is ever ready for the road. I kind of feel like I failed, after putting in so much time, but it doesn't help to think like that. I did have a lot of fun, and I'll probably do a lot more of an actual overhaul this time rather than just a repair. I found myself wishing I did these things as I was finishing up the project. New bearings, rod bolts, check all the con rod bushings and rocker arm bushings, etc...

Anyways, thought I'd share. Does anyone have any ideas of how to fix the problem without taking the whole thing apart again? I know I could try snugging up the nuts a little tighter but I'm not very confident that that would work. Either way I won't be able to try anything until I go home for Thanksgiving.

[75 911s]

First off, I'm glad you enjoyed the process. Think of everything you learned. The experience is a big part of the value in my opinion.
I think you answered your own question, which is that you have to take it apart and do it right. It should go a lot faster now that you've done it once.
There exist a 'temporary patch' that I read about with another forum member who had a similar problem. And that is you can create a temporary plug. Essentially you don't engage the threads on the outer half, you simply plug the hole on one side. So if it's leaking out the stud, it will temp fix it, but if the halves are leaking more drastic, it's take it apart again time. Hey gives you something to do on Xmas break! :-D

[gtc]

Just curious, what sealant did you use for the case halves?

[911truther]

no doubt sealant type could lead to more leakage during your stub repair process

[targasc1980]

It didn't look like it's leaking out of the stud hole, I think it was just leaking from the whole section of the parting line. But thanks for the idea! I'll take another look at it and maybe give it another shot. I used Loctite 574.

[gomezoneill]

We've all been there it's part of the learning curve. Don't let it slow you down you'll get there. There's a thread on the board that the op asks (okay admit the mistakes you've made in the past) it makes for some good reading. I'm not sure of the thread title so I'm paraphrasing.

[tobluforu]

That sucks. Years ago I built my first 911 motor, was putting in different pistons with longer skirts and did not realize that I was supposed to cut the case. oops. Granted, it's not as bad as yours as I figured it out after installing one piston and manually spinning it. It was still a bummer none the less as I had to take it apart and bring it down to machine shop which cost me another 3weeks, more money, yada....
Good luck though, second time is always easier.

[Neilk]

Is there a sump plate on your car? I rebuilt my engine too and had a leak along the seam as well. I gave up trying to fix it and brought it to a mechanic and he noticed that the sump plate was not completely flat and was letting oil seep out. Since the car has a slight rake toward the front when parked, and air pushes oil backwards, it appeared as if the whole bottom of the case was leaking.
He sanded the sump plate against a piece of glass to get it completely flat and engine is now dry as can be. Give that a try first before taking everything apart. It worked for me.

[Flat6pac]

When you're sealing the case with 574 you have to seal inside the stud perimeter
The bottom rear corner of the case doesn't match seams so you need to apply extra.
Bruce

[manbridge 74]

I think if this was just a parting line leak I'd be tempted to to get all the oil out the way and use some sort of good modern epoxy to try and seal it. While maybe not the most correct way, what do you have to lose?

[targasc1980]

@Neilk, thanks for the heads up. I'll definitely check that out the next time I go home.

@Flat6pac, I made sure to apply sealant in all of the necessary areas. It seemed to me like I applied a fair amount, and there was a decent amount of squeeze out.

@Manbridge 74: That was my idea too, but my local Porsche guy expressed a lack of faith in this plan. If I were to try it, do you have any recommendations for what to use?

[Jack Olsen]

The Toyota Black Sealant.