David Salama

Well, yesterday I blew out another cam housing gasket only within 2 months of repairing it with the use of Yamabond. I know I have alot of blow by (piston rings, I believe), so I turned down the maximum boost to 15 psi. Well in my fiddling with the blow off valve recently, apparently I blew out the gasket. It leaks out onto the fourth exhaust manifold pipe. Smoke !!! I've ordered another gasket from Jason at Paragon. Since the car runs so great when the gasket is holding up, I hate to undertake the big rebuild at this time. I plan on replacing the gasket again, turning down the boost a little more and crossing my fingers. Any other tips ?? I was actually wondering if I could put a camhousing vent in one of the cam housing plug sites which would open if the pressure gets to high. Is this safe. I see american muscle with cam vents, can I ??
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Danno

hmmm, oddd... Due to surface-area differences, for any given crankcase pressure, you would probably blow out the oil-pan gasket before you blow the cam-cap. Odd.... Perhaps you're getting too much oil-pressure in the cam housing? Is there a pressure-regulator for that?

David Salama

Is there any possibility of a mismatch between the exchange head from Powerhaus I have and my cam housing. Was there any changes in the oil passages over the years??
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WillyC4S

David,

You might want to try not using a cork gasket and going directly with the Yamabond or other gasket-maker.

When I re-did my timing belts, water pump and all the seals (including the oil filter housing seal), I used 3Bond 1211. When I replaced the rear camhousing seal (near the engine hook loop) I didn't use the cork gasket, but just went straight with the 1211. I figured the cork material is a weak point in the system. No leaks so far.

Hope this helps.

*****

Danno

Hey *****, did you make it out to Willow Springs a couple of weekends ago?

Paul C 944

What tool are you using to tighten the bottom bolt?I can only reach mine from underneath.Any tricks/tips or special tools?

David Salama

The bottom camhousing bolts can be reached with a long extension and a universal joint in the back corners. I am able to do the entire job from the top. Any other thoughts on the cam housing vent to atmosphere?
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Ahmet

Crankcase pressure (or the amount of boost you're running)and cam housing oil pressure don't have a whole lot to do with each other. The gasket usually leaks because of improper torqueing of the bolts not from excessive oil pressure. Porsche switched to a thinner gasket at some point I also know that. I personally use Porsche glue instead of the 'yamabond' stuff (Loctite 574 if I remember correctly). There is an oil pressure valve in the head and the block (from memmory). The one in the head seems to be your culprit. I'll double check this by friday if I have time and get back to you.
Ahmet

David Salama

I'm still waiting for my replacement camhousing gasket to arrive, but have been developing a plan to alleviate another gasket failure. I obviously have alot of blow by past my piston rings. I know I have developed high crankcase pressure since I have blown oil up the oil dipstick tube at the track, dislodging the dipstick upwards. With everything tightened down, the pressure has to go somewhere and simply blows out gaskets. I have ordered a K&N filter to fit on top of my oil fill tube instead of the cap. This hopefully will vent any excessive crankcase pressure. In response to Ahmet's comments, I have examined the top of the head with the camhousing off. There are two drain ports which drain oil back from the camhousing to the oil pan. I blew some air in the hole and could feel it coming out the oil fill tube. If I have positive crankcase pressure, it would be refered directly up the the camhousing. In addition, the oil pressure relief valve is keeping oil pressure into the same housing. The result is gasket failure. This is my theory. The local Nascar race shop tells me that anyone who modifies a turbo car for big Hp gains needs to vent their crankcases. He stated this like it's a well known fact, but I don't see any comments from the Porsche Modifiers. What gives? I will let you know how the K&N works once I get the car back together. Any comments?
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Ahmet

David, If I follow your post correctly, you're assuming your cam housing gasket leaks because of too much crank case pressure. The crankcase could get pressurized because of blowby from the rings, but this pressure (if the crankcase vent is working properly) should be very insignificant compared to the 5+bar oil pressure thats in the oiling system. Now if the oil pressure relief valves are working correctly, I don't think there's enough exposed surface area on the cam gasket to actually have it break because of excessive oil pressure.

After my rebuild (just last month), I blew one oil pan gasket, and two cam seals. This is with as new compression, running at less than 5psi of boost. Since my initial repairs with the correct gasket/sealents, and the correct torqueing sequence I've turned up the boost to 19psi and put over 600 miles on the car. Not a drop from anywhere.

Just trying to help.
Ahmet

David Salama

Ahmet,

Point taken, however, I have already been properly torquing my camhousing. I believe actually that the oil pressure probably is unrelated to gasket failure. The oil pressure is measured in a closed narrow channel, not in the crankcase. Once the oil reaches the camhousing , I can only imagine that it sprays through or over the cam and then falls by gravity to the oil pan. I still believe my positive crankcase pressure from by blow by, MAF, big turbo overwhelms the stock crankcase vent tube and build tremendous crankcase pressure. Why else would the pressure shoot the dipstick up, and blow out gaskets. I have developed several other oil leaks as well.
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keith

Wait a minute - what are you guys using Yamabond or 574 on during a camhousing gasket repair?

David Salama

I read about it here, and decided to give it a try. Do you have a problem with using Yamabond?
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keith

No, I just want to know where you are using it...

David Salama

I put the Yamabond above and below the entire edge of the camhousing gasket. That is what I plan to do again this time.

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