About to close case. Two important questions?

[MBradbury]

Hi,

Getting ready to finally close the crankcase halves tomorrow. I have two important questions before I do.

Q1. What kind of washer sits beneath the 15mm nut in the LHS chain housing? If you look at picture 3-27 in Wayne's rebuild book, it looks like a bevel washer. I have attached a picture showing the stud I am referring too, it's rooted in bearing journal number 7. This stud has some of the characteristics of the through engine bolts and the studs that clamp bearing journal number 1. All these other bolts and studs have beveled washers and o-ring seals, does the stud under the 15mm nut require same or does it use a flat washer without an o-ring? Wayne's rebuild book says there are 24 beveled washers and o-ring seals. The through bolts and the two studs clamping journal number 1 would account for all of these.

Q2. I am planning to seal the case halves with Loctite 574. Wayne's rebuild book says you should apply this to the RHS case. However, this case has all the components already fitted, i.e. crankshaft, and intermediate shaft. This will make it difficult to apply the sealant evenly on all the mating surfaces. Why can't I apply the sealant in the LHS case which is free of obsticles, etc? Related question regarding loctite 574. When does the clock start ticking on the 45mins cure time? When the sealant is dispensed, or when the metal to metal contact is made?

I'm counting on you all for guidance. Putting this engine together is a nerve racking experience when you're standing over it alone in the garage.

Regards
Mark

[Wayne 962]

There's a small spring washer that goes underneath that nut. Part number 900.028.023.02. That's that special nut that only seems to fit that stud.

Applying the sealant to the other case half is also an option - it's far easier to apply it to the case half that is mounted in the engine stand, in my opinion. When you lower the other case half down, you will know where the sealant is, and where the case is going - doing it in reverse is doing it a bit blindly in my opinon, but again, it's personal preference here...

The 45 minute clock starts ticking as soon as the case halves are mounted together. However, as soon as you put the sealant on, you will start getting airborne particles and dust in it, so don't leave it out and exposed for any length of time.

-Wayne

[ChrisBennet]

I can't remember if Wayne's book mentions this but just in case it doesn't... The "trick" to sealing the case is to tighten the perimeter bolts first after you put the case halves together. Steve Weiner told me this. Greg Brown also mentioned this in one of his articles.
-Chris

[MBradbury]

Wayne,

Thanks for the reply. It looks from the part number you supplied that this spring washer is the same one used on the front engine mount frame (N-012-242-3). The Pelican Parts supplied engine hardware kit contains 4 spare washers of this type.

Chris,

Actually, the directions in Wayne's book instruct to torque the through bolts before the perimeter bolts. The Bentley manual sequence agrees with Wayne's book. Obviously, I don't want any leaks, but I don't want to create any adverse internal case stress by tightening in the wrong sequence. Any further comments?

Regards
Mark
Regards
Mark

[Wayne 962]

The factory procedure is to tighten the inside bolts first. Many other rebuilders also assemble the engines this way. I doubt there would be too much of a difference either way, as long as you finish within about 45 minutes...

-Wayne

[Jim Sims]

Do a "dry run" assembly first if not actually screwing on items at least go through the motions. Doing this will ensure that you have all the parts and tools needed. This is also the last time to ensure you have everything correct inside the bottom end. Are all the oil pump seals, nuts and lock washers in place? Is everything correct with the intermediate shaft? Are the crank seals in place? If the crank and intermediate shaft were polished did you clean out the oil passages well? Yesterday, I helped a friend take apart a rebuilt pickup engine that appeared to have had grinding/polishing compound left in the crank oil passageways. The engine failed in less that 2000 miles (bad rod knock). All the crank journals are scored and will require grinding to first undersize. Good thing it was cheap to buy; previous owner sold it as he didn't want to deal with fixing it again.

In the 911 assembly it is really helpful to have a 2nd person putting on fasteners with a speed wrench with you following torquing to the correct torque. There is actually room for a third person if everyone knows their role. I was taught it was best to have everything done within 15 minutes of bringing the case halves together. After a dry run and under the direction and with the assistance of our Porsche mentor my son and I had his engine together and buttoned up in 10 minutes. No leaks. Good luck, Jim

[Wayne 962]

Originally posted by Jim Sims
Do a "dry run" assembly first if not actually screwing on items at least go through the motions.

This is actually a good idea if you haven't done one of these before...

-Wayne

[cstreit]

I always wondered if you tightened the perimeter bolts first, if the case would line up as well around the crank had you tightened the through bolts first...


Wayne, any thoughts about that?