500 mile tear-down

[lindy 911]

You may remember my $7500 build of a '78 3.0 SC. I made some high performance changes and the engine turned out very well except for one major issue; the #8 nose bearing is leaking at the o-ring. Yes, I am positive it's the o-ring.

My question is do I just tear it down, replace the seals and gaskets with new, put it back together and call it a day? Or is there anything I should be measuring or checking after 500 miles? It seems the obvious things are the bearing shells and cylinder walls, so I have that covered.

The engine likes to run up near 7,000 rpm. I did not cross-drill the crank the first go round; should I now? What about the stock SC oil pump; should I upgrade now that I know the motor like this rpm range? It's a street car but I drive it pretty hard.

Any and all input is appreciated.

Lindy

[Tippy]

You're going to do a full tear-down for a nose bearing o-ring leak?

That's about the only area mine doesn't leak!

[lindy 911]

It's the only way to fix it. I tried the collar and JB Weld thing and that sucks. I went through all the other stuff too. Mine leaked initially from the gasket between the chain box and cam housing, fixed that, then the through bolts with RTV smeared all over them (blue POS), fixed that, and now the nose bearing o-ring. I think I got the wrong o-ring in my gasket set. I was very careful with the case joining and followed Henry's sealant choices to the "T". Not one drop from the case seal. So now it's time to fix the nose bearing leak.

I guess this is what they all mean when they talk about expertise; "Ones an expert once he makes all the mistakes possible in a narrow field".

Lindy

[Tippy]

Mine leaks from the through bolts and some spots on the cam towers; very frustrating!

I used yamabond on the towers and silicone on the through bolts.

[lindy 911]

I thought it was my towers but it turned out to be the small gasket between the cam carrier and the tower had pushed out during assembly. My through bolts leaked profusely and I too used RTV on the blue o-rings supplied in my gasket set. The RTV will actually push the o-ring out and away from the bolt and it then gets pinched between the case and the washer. I sourced green viton o-rings from Henry Schmidt and used a light coating of grease he supplied and they are as tight as a drum.

Everything is dry now except the nose bearing. The second time around (third time for the top end) should prove to be easier and less stressful (I hope)!

[Eagledriver]

I feel your pain. I've seen an engine that had a small drip cup under the motor mount to catch the oil. He just drains the oil from the cup whenever he needs to. If you do take it apart, I think a visual inspection is all you need. I personally don't think you need to crossdrill a crank or update your oil pump for your RPM range (below 7500). I now install the number 8 O-ring dry. I had one leak when I used silicon grease on the o-ring. I think the grease got between the case halves and kept the case sealant from sealing there. The main thing there is to make sure the o-ring doesn't get pinched between the case halves and the sealant gets all the way to the edge of the case seam.

-Andy

[brads911sc]

I feel your pain. I put about 1000 miles on mine this season. I bought new fuel lines for in the tunel and i have a crimped oil line at the jack tube so i figured its a good time to remove the engine, do a valve job standing up instead of on my back and i have a few small by pesky leaks too that Ill tackle while im in there. I want to wait another month though because this is great driving weather. If you need a hand let me know. Im just right up the road.. good luck getting her sorted..

[Porsche84]

What are you using for oil? I've seen Mobil 1 leak where Castrol 20-50 did not. May be worth a try. A real shame to tear it down!

[Mr9146]

If you pull it apart check the bore at the #8 bearing.

It might be "pounded out" and be too big for a stock bearing but too small for an oversized bearing.

If that's the case you need to bore it and use a larger bearing.