After two years finally started working on replacing the head gasket on the boosted ’85. Last year I had a chance to pull the intake and yesterday re started working on it. Got the distributors/wires off and the driver side valve cover. The PS pump bolts are removed and will be pulling the pump and brackets probably tonight. Only worked on it for an hour but it was nice to finally get a chance to do so. When the PS/Alt bracket is off, the driver side timing belt cover can come off, followed by pulling the cams and disconnecting the exhaust manifold at the H-pipe. After that the head can be pulled. I’m anxious to see if the modifications to the last stud (shortened by a couple mm), during the last time the heads were off, will make pulling the head, with the engine in the car, much easier that the first time. If everything goes well, the head should be off in a couple hours. Then I can finally see what happened in there. I hope the HG damage is clearly visible.

Since most of the top of the engine is apart, I’ll try to re do the crank venting and build some baffles for the oil filler neck. Maybe re do some of the old vacuum lines and hose and re design the catch can to dup the oil back into the crank. I’d really like to seal up the engine as much as possible cause even the smallest leaks become a real gusher when the engine starts to see boost.

 

Hey Imre,

I know you modded that stud so you don't have to pull the engine, but from all accounts, pulling the engine isn't really a big deal in these cars and it makes working on other stuff WYAIT MUCH easier. Have you considered that option?

I can't speak from experience, but from what I've ready it's really only a few hour job either way, and then you're not working inside the bay. I'm almost tempted to do it just because my cam covers could use new gaskets and I'd like to clean everything up nice and shiny .

Good luck and keep us posted! (It feels good to finally get your hands dirty after a long delay, doesn't it?)

 

Do all boosted motors have these oil control problems, or was yours exacerbated by the leaking head gasket or blow by past the rings?

 

Mike,

I'm only pulling one head so the engine will stay in. I know its' not that bad to pull the engine but it's much easier for me when only one head is being removed. It takes up less room in the garage when the engine stays in. I haven't had the time to fully disassamble the parts car so space is somewhat of a premium in my 2.5 car garage. It was nice to finally work on something that I really enjoy. Till now it has been cars that I flipped for a littel profit but, since the last one is done and in the paper, I figured to use that time to re start the work on the 928.

I don't know if I would yank the engine just change the valve cover seals. They are easily accesable when the engine is in the car.


As for the blow by issue, some 928 have more than others, but yet to see any that didn't require some modifications or form of oil vapour control after they were boosted. The unique design of the cylinders lands itself to larger tolerances that normal iron sleeved blocks so the blow by is more too.

 

In just about any NA engine that you add boost to, I would think you will have some blow-by that will need to be dealt with. I'd say one of the big issues withthe 928 is that the crank can throws oil up at the oil filler neck which is also the path to releive the crank case pressure. Without something to stop the oil, it quickly accumulates in the breather tubes and can cause a buildup of excess crankcase pressure.

So some type of baffle in the oil filler neck is certainly preferred over nothing at all, but in most, if not all, cases you will also need some type of oil/air separator.

 

If you had a blown head gasket and let the engine sit like that for 2 years i would be very careful about checking for ring damage especially if the coolant was leaking to the cylinders.. I would also recommend pulling the other head to check for problems. the block may be toast

 

Don't worry, the coolant was drained a long time ago but I will have a closer look at the rings. The HG blew because of a slowly failing injector and not because of a detonation or high boost. Just before I noticed something was off, I replaced the injector on one of the cylinders. As opposed to failing open or shut, this one slowly opened less and less so it created a lean condition in this cylinder and took the HG out. I'm very certain that's what happened cause the cylinder that had the injector problem ended up having the steam cleaned spark plug too. At least that's my theory but as soon as the head is off, I'll know more. Both head gaskets were changed when I bought the car so they are not that old. That's why if the damage is clearly visible on the driver side I'll leave the passenger side alone. The timing belt is only a couple years old too so this HG should be a simple job. Should be is the key word here.

 

if the sparkplug had a steam cleaning then the rings in that cyl are probably toast after sitting for 2 years

 

The driver side timing belt cover came off last night. It was a little tight to get it off without removing the alternator bracket (the PS pump tensioner had to be unbolted to give enough room) but with some creative manoeuvring it came out. Marked everything up on the cams, crank and passenger cam sprocket so I don’t have to move the crank at all and still have plenty of reference points to get the t-belt back into alignment. When the t-belt came off the driver side cam pulley, nothing moved. That’s good cause it will be that much easier to re set everything during re assembly. Before it got too dark I removed the front and back cam caps, the ones that are not load bearing (they are cast together, intake with exhaust). Tonight I’ll pull the cams and over the weekend I’ll disconnect the exhaust, remove the steering shaft coupler/shaft, then the head can come out. So far has been straight sailing, let’s hope it stays that way.








Always the optimistic aren't we! I’ll post exactly what I find as soon as the head is off (should be sometime this weekend). I have the spare engine sitting in the garage from the parts car so in the worst case, I’ll use that as a replacement.

 

Yep.

 

On that note.......some of the S4 guys upgrade to 951 rings since they are stronger then stock S4 rings. Do these fit in the 85/86 motor? I cannot think of any reason why they wouldn't, but you never know.

 

I can provide pics of what he describes. Ive got an 87 block with a cracked #1cyclinder it sat for a while and besides the obvious crack, the block is toast becasue of some nasty corrosion or something on the cylinder walls. Everything else on the motor is fine, heads look perfect!

 

I'll take and post pics as soon as the head is off. You guys are more than wellcome to look and comment on it.

 

Hopefully you wont find this...or the whats in the bottom pic!
just took it a minute ago.

 

Tony-
That's not your motor, is it?