Cam Housing Rear Cork Gasket (and new lifters)
Posted: Tue Sep 27, 2022 11:20 am
I recently supported my engine from above to remove the oil pan to replace the seal on the oil pickup tube (described viewtopic.php?f=12&t=1078). There is a big potential gotcha... the cork gasket at the rear of the cam housing.
Using the engine support bar requires looping a chain through the rear (and front) engine support loops. (I actually used the left side engine support instead of the front engine loop. In hindsight, I should have also tried to use the right side engine support as well).
The rear engine support loop is attached to the rear of the cam housing (sometime interchangeably called the cam tower).
Prior to supporting the engine, I noticed one of the three M6 bolts with 10mm heads that attach the rear engine support loop was loose. So I wrestled a wrench back there and tightened it. Then I supported the engine, worked under it to remove the oil pan, made the repair, cleaned and painted parts (heat shields, oil pan, cross member, sway bar, etc), and put everything back together.
When I started the engine I was delighted to have oil pressure. However, I also had a significant oil LEAK from what turned out to be that cork gasket. Oil was pouring down the back of the engine and onto the exhaust and driveway. Oops.
I decided to remove the cam housing (since I also had a slow seeping oil leak from its base gasket) and some lifters that ticked on startup that I wanted to investigate.
Turns out i had crushed a part of the cork gasket when I tightened the loose M6 bolt with 10mm head. It doesn't take much. I had used a small open-end wrench, so it's already tough to get a lot of torque, and access is cramped, so getting good swing on a wrench is difficult as well.
There is a company that sells a silicone version of that gasket for the 928 (so you get two). They are on eBay and probably have their own website as well. It's probably a good option if you don't want to use the gasket maker method (described below) and you still want to use something other than the factory-specified cork gasket.
I ordered a set of new (rebuilt) lifters from Ian (944 Online), new base gasket, and painted the cam housing and intake manifold.
However, I did NOT use ANY pre-made gasket on the rear cam housing cap. INSTEAD, I used Gray Permatex Gasket Maker. I've used this stuff for years on motorcycle crankcase halves. It works great. It's important to have decently flat and decently pit-free mating surfaces. It's important to be conservative with applying it, since you absolutely do not want little gray stringy gasket fragments to squish out INSIDE that cap and circulate in the oil.
Prior to installing that rear cap onto the housing (still on the workbench), I inserted the cam shaft into the housing. Then I applied a conservative thin-ish layer of Permatex Gray to the rear cap only, making an even layer using the edge of a business card or other similar thin cardboard, credit card, etc.
I attached the cap to the rear of the cam housing, making certain to remember the engine support loop. I tightened the three bolts to spec (7.5 ft-lb iirc). Then I spun the cam shaft a couple times by hand, pulled it forward so I could inspect the rear of the cam shaft through one of the M18 openings, and checked for any gasket maker on the cam. Once satisfied, I finished reassembling the cam housing. (Don't forget the stupidly thin Mylar spacer/gasket/thing that sits at the front of the cam shaft.) I ordered the cam housing gasket kit also from Ian. It contained all the o-rings and seals and even a new cam bolt (the 10mm "triple square" one).
I used spray-on Permatex Copper Gasket Adhesive on both sides of the brand new cam housing base gasket. I had been plagued with a slow leak from this gasket since shortly after I had the engine re-sealed some 40k miles ago. If the car sat for even a couple days, enough oil would seep onto the exhaust header, resulting in it burning off in a stinky white cloud of smoke when the exhaust got up to temp. I wanted to give myself the best chance of remedying that.
Here it is all painted and installed.
Using the engine support bar requires looping a chain through the rear (and front) engine support loops. (I actually used the left side engine support instead of the front engine loop. In hindsight, I should have also tried to use the right side engine support as well).
The rear engine support loop is attached to the rear of the cam housing (sometime interchangeably called the cam tower).
Prior to supporting the engine, I noticed one of the three M6 bolts with 10mm heads that attach the rear engine support loop was loose. So I wrestled a wrench back there and tightened it. Then I supported the engine, worked under it to remove the oil pan, made the repair, cleaned and painted parts (heat shields, oil pan, cross member, sway bar, etc), and put everything back together.
When I started the engine I was delighted to have oil pressure. However, I also had a significant oil LEAK from what turned out to be that cork gasket. Oil was pouring down the back of the engine and onto the exhaust and driveway. Oops.
I decided to remove the cam housing (since I also had a slow seeping oil leak from its base gasket) and some lifters that ticked on startup that I wanted to investigate.
Turns out i had crushed a part of the cork gasket when I tightened the loose M6 bolt with 10mm head. It doesn't take much. I had used a small open-end wrench, so it's already tough to get a lot of torque, and access is cramped, so getting good swing on a wrench is difficult as well.
There is a company that sells a silicone version of that gasket for the 928 (so you get two). They are on eBay and probably have their own website as well. It's probably a good option if you don't want to use the gasket maker method (described below) and you still want to use something other than the factory-specified cork gasket.
I ordered a set of new (rebuilt) lifters from Ian (944 Online), new base gasket, and painted the cam housing and intake manifold.
However, I did NOT use ANY pre-made gasket on the rear cam housing cap. INSTEAD, I used Gray Permatex Gasket Maker. I've used this stuff for years on motorcycle crankcase halves. It works great. It's important to have decently flat and decently pit-free mating surfaces. It's important to be conservative with applying it, since you absolutely do not want little gray stringy gasket fragments to squish out INSIDE that cap and circulate in the oil.
Prior to installing that rear cap onto the housing (still on the workbench), I inserted the cam shaft into the housing. Then I applied a conservative thin-ish layer of Permatex Gray to the rear cap only, making an even layer using the edge of a business card or other similar thin cardboard, credit card, etc.
I attached the cap to the rear of the cam housing, making certain to remember the engine support loop. I tightened the three bolts to spec (7.5 ft-lb iirc). Then I spun the cam shaft a couple times by hand, pulled it forward so I could inspect the rear of the cam shaft through one of the M18 openings, and checked for any gasket maker on the cam. Once satisfied, I finished reassembling the cam housing. (Don't forget the stupidly thin Mylar spacer/gasket/thing that sits at the front of the cam shaft.) I ordered the cam housing gasket kit also from Ian. It contained all the o-rings and seals and even a new cam bolt (the 10mm "triple square" one).
I used spray-on Permatex Copper Gasket Adhesive on both sides of the brand new cam housing base gasket. I had been plagued with a slow leak from this gasket since shortly after I had the engine re-sealed some 40k miles ago. If the car sat for even a couple days, enough oil would seep onto the exhaust header, resulting in it burning off in a stinky white cloud of smoke when the exhaust got up to temp. I wanted to give myself the best chance of remedying that.
Here it is all painted and installed.