Oddjob

So when having to wet sand/oil stone the oil pump mating surface after bolting the cradle back onto the block, how much of a mismatch is common?

Ive got a pretty good lip prior to any sanding. Not sure if removing the sharp edge will accomplish much, the oil pump still will never seat flat, unless the surface was machined. Normal?

Chris Prack

Your not supposed to have a lip at all. After sealing the crank girdle with 574 you torque the studs to the first step. Then use a mallet or compothane hammer and tap the girdle so the surface at the oil pump mounting is flush. Then finish torque the girdle.

If you already have it finish torqued and still have a lip, I would pull it back apart and do it again.

Oddjob

I already did the plastic hammer trick and this is the best it will get. Manual states right in there to use an oil stone after assembly to sand it flush. Local 944 shop told me the same thing - they never line up after reassembly and expect a time consuming effort to sand it down.

My concern/question is the amount of material that will need to be removed to make it flush, seems excessive. For those that have had to sand the surface, how much of a lip did you have?

Chris, by your reply, Im assuming you had none - it was perfectly flush?

R.B.

Make sure this step is done correctly. The shop that did my crank, also installed my crank and oilpump. I did not check this when I put my motor back together and when it was installed and I started it. Yup I have oil coming from the front oil pump and the rear main seal. Although not a huge amount of oil, but enough to give me a couple of drops the next morning. Not exacltly what you want to see after you have rebuilt your engine.
Live and learn (and pass on the knowledge)

-R.B.

Chris Prack

Jim, how much of a lip do you have? I have done 30+ 944/51/68 engines in the last five years and have never had to sand any down. I am a Porsche tech by trade so I have some experience with this kind of thing. I have had to torque the studs less initially to get the gridle to move.

Have any pics?

Ski

Chris, ever done the freezer thing a time or two?

Oddjob

Chris, it will be a little hard to measure, but I will put a feeler gage up to the lip to get a ballpark estimate. I can definitely hook my finger nail on it.

I saw someone mention the freezer idea before, but I had some concern about doing that. When the block and cradle are at the same temp, the cradle will be trying to expand against the studs. Probably not a big deal, but I did not like the idea.

AlexE

Throw the girdle in the freezer works perfect. It will shrink a 1-2 thousands no problem.
Install and torque...........and all is well.

Chris Prack

No, never tried freezing it. Maybe I have just be lucky.

I may give it a try next time to how it works, sounds reasonable.

JDeitz951

Go to loctite.com and read the specs for 574. It fills gaps up to a certain number. If you are within that spec, you might be OK. Feeler gauge should be up to the task to measure the gap.

Tom M'Guinn

When I dissassembled my 968 block, the cradle was dead on flush. A staight edge would sit flat against it with no gaps on either side.

Ski, how does the freezer trick work? When it warms up, doesn't it just expand back? Didn't someone make up a jig to align the cradle when torquing?

Oddjob

Lip is between 0.008 and 0.009". Seems too much to me.

Spoke with one of the engine builders at the local shop and he didnt seem too concerned about a noticeable lip (although I had not measured it yet, when I spoke with him) and said its not uncommon to spend 1-2 hours using an oil stone to sand it flush.

Chris Prack

No jig that I have heard of, once it warms up it's already torqued so your golden. Dietz, the oil pump has to sit flat, it's not just a matter of sealing but also wear on the pump drive and rotor. It will create a side load on one side of the pump and it will end up gauling the housing.

Chris Prack

If it's 8 thou. I would do it again. I would not let that go and I would not sand it flat either, that's a large area to have to be certain it's flat. FWIW.

Oddjob

Alright, I took it apart and reinstalled it by pounding the hell out of it. I started off with the bolts tightened to 10Nm, pounded for awhile, then went up to 15Nm, pounded, then up to 20Nm and pounded some more (factory manual says to tighten between 10-20Nm when pounding on it).

I got the lip down to 0.005-0.006" doing that.

So I pulled it off again and threw the cradle in the freezer. Went through the hole sequence again, and did some more pounding after the 1st stage torque sequence. Got the lip down to 0.002-0.003".

But I have some concerns about the freezer method: moisture condenses all over the cradle and the loctite 574 does not spread evenly and seems to not adhere very well to the cold surface. And the water droplets in the bearing assy lube, make the grease almost gritty. I hope that the moisture will find its way out of the bearings and the sealing surface/loctite but Im doubtful that it will. Im thinking about putting some heat on (heat gun) it to evaporate it out of the bearings. But that still wont help the sealing surface.

Ive thought about different approaches with the freezer method, but any sequence of steps will still likely encounter similar problems with the condensation. Go ahead and use this method if you want, but do it in a dry place next to a dehumidifier....