More specific rebuild questions

I've been reading quite a bit in preperation for the reassembly phase of operation: "get my damn car back together so I can drive it" and I have a few questions that aren't clear in the things I've read.

Ok, here goes.
In B.A's (Bruce Anderson) book pg.118 he talks about checking the layshaft gear clearance. But he dosen't get really into what that means and how to perform the measurement, and later on, in the engine rebuild chapter, he mentions that the layshaft gear clearance is supposed to be checked upon DISASSEMBLY! Oops! I didn't do that so what now?

Next, I hear all of this talk about weighing pistons and con. rods to make sure they all weigh within the same amount and for proper placement in the engine. Ok, first off can someone please tell me how these weights can change from when it was first put together, and secondly, whats the best way for me to weigh them if, it is in fact, necessary?

When B.A talks about measuring the crankcase bores, how exactly do you do that? Do you put the case halves together and reach inside with a caliper? That dosen't sound right to me. I can't find any diagrams or pictures of these measurments being taken.

I think it was Beetos who had the harry incident with the overtorqued rod bolts...
My question is,... everyone said that B.A was "vauge" or "misleading" when he discusses putting assembly lube on the rod bolt threads. I have re-read through the rebuild chapter numerous times and I can find 2 or 3 times he Blatently contradicts what has been discussed on this bbs about NOT putting anything on the threads of critical torqued bolts. Am I to understand that B.A is just plain wrong?
Final answer??? NO lube on threads?

B.A also says to use motor oil on the main and rod bearings but to use assembly lube on the camshafts and rocker arms. Why is this? If, (from what he says about assy. lube) assy. lube has the capability of standing up under extreem conditions (like a first time started engine) why wouldn't you use assembly lube on ALL moving surfaces?

And finally, (for now anyway) On page 127 B.A makes note of lubing the pilot bearing b/f mating the engine to the tranny. I am assuming that the pilot bearing is the bearing on the flywheel right? He says if not lubed that it will friction weld to something and the clutch won't disengage.
I thought the pilot bearing just centered the flywheel on the end of the crankshaft...what gives?

Oh, and in my Haynes manual it talks about measuring the layshaft end float and adding a certain number of shims under the layshaft cover. Where can I get these shims...I sure don't remember seeing any when I took it off.

Thanks a million guys,
sorry this is so long...
at least I know where my ignition switch is located now...


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Leland Pate

___79 SC Targa

[This message has been edited by Leland Pate (edited 03-23-2001).]

Leland,
Welcome to the land of uncertainty. I too struggle with these issues from time to time and find that alot of the debate to lube or not to lube is a matter of preference, experience, comfort and piece of mind. ( Man does that sound rather filthy) Anyway, in a previous lifetime I rebuilt alot of stuff. There are actually charts for material specifications and torque, alot of this documentation actually gives dry and lubricated torque values for the same materials. In experience I have found that there is interpretation in these values. I have actually torqued bolts to their yeild point to measure the differences between dry or lubricated values. (there is a difference). I choose to torque bolts dry as I feel the results are more repeatable.

As for the layshaft gears, I would not worry about not having measured it upon disassembly, it has to be right when you reassemble and if you are using the same pieces that came out it should at least be close. Shim stock is available at many places such as Grainger supply, I made my own shims for my valve adjustments after the seats were cut.

As for assembly lube over oil, I tend to use assembly lube on bearing and journal areas as I feel it stays where you put it better than just oil, and if you take your time to reassemble things it may be awhile before you actually crank things up. I would use oil on rings and such in that I wouldn't want any residue in the cylinders from the assembly lube if burnt. Again it's just my preference.

FWIW, I'm sure B.A. is a fine person and is quoted on this board by many quite religiuosly, but even fine people are misquoted and even worse make mistakes. Good Luck. May the force be with you...

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78 3.0L/3.2L CIS 911SC

I can't answer all, but can help with some.

1. Layshaft: can't help, could look in the Bentley, but I'm confident you'll get a quality explaination.

2. Rotating weight: Balancing this is something best done by a quality machine shop. Useing chevy as a referance. The factory builds so many engines and the parts all weigh within a certain tolerance, so they run well. However, balancing gets all of the pistons and rods very close, usually within .5 gram. Everything that rotates should go to the shop for balancing: crank, rods, pistons w/ rings, rod bearings, flywheel, pulley, washer, bolt, everything behind the clutch. Engine life will be extended from running smother, and you will gain some control over RPMs. I know I noticed a difference w/ chevys. Porsche is so well engineered you may not notice a great improvment.

It has been awhile since I ballanced an engine, but it used to only cost $110, I couldn't justify not doing it.

3. Bore Micrometer, I think it is called. stick it in the bore and expand it to the diameter of the bore, carefully remove it and then measure it with your calipers.

4. Rod bolts, I always use the red Loctite. On high tension bolts, like main bearings I use the engine oil that will be used in the engine. My understanding is the high torque bolts will not come loose, and the oil will let you get very accurate torque readings, without the poping you find with dry bolts or even loctite.

While we are talking engine oil that is the only thing you want in your cylinders and on your pistons, DO NOT USE WD-40, it will slow the ring seating proccess.

I was taught to apply LuberPlate[sp] a lithium type lube on the rod and main bearings, it melts quick and blends in to the engine oil, the bearings receive pressurized oil, the cams and rockers do not, that is why you want that stickey adhesive type assembly lube on the cams.

Last the pilot bearing. Yes lube it. Yes it does center the tranny input shaft to the crankshaft. The crankshaft and the tranny inputshaft turn at different speeds when the clutch is engaged. Only when you release the clutch peddle is the crank and tranny input shaft turning at the same speed.

BA refers to an extreme condition, but if there is no lube those parts can become friction welded together, and applying the clutch will not allow the two shafts to rotate at different speeds.

Back to the lay-shaft: still can't help.

PS. On the layshaft.

Haynes book also said to take measurements when I was in the tranny, Bentley did not. Bentley explained how to. My point: When the fine folks at Porsche first assembled the parts they put them where they belonged, they had a criteria. They could not put something BACK together that had never been together. Get a quality manual, I believe the Haynes book is for an experienced wrench. The Bentley is much better.

[This message has been edited by GT911 (edited 03-23-2001).]

Leland,

Regarding balancing of parts, forget it! I assume you know which pistons & rods came out of locations 1-6 in the firing order, so just put them back the way they were, and everything will be fine. Porsche balances them much better than most other mfrs, and you are right ... they haven't changed! So, don't worry!

About the rod bolts ... use red Loctite, two drops per bolt, on opposite sides with one drop near the bginning of the threads, and the other near the end. And make sure the threads are very clean and dry before you apply the Loctite! Clean all of the rod bolts and nuts very carefully with spray brake cleaner/degreaser no more than one hout before final assembly! Use Loctite 'Locquic' N Accelerator 7649 ... if you can get some. It works on the thread locker and also on the sealants 574 and 518 that you use on the crankcase and heads/cam towers!

Use moly assembly lube on cams, rockers, rod & main bearings, intermediate shaft gears and sprockets, chains, idler sprockets, cam sprockets, etc.

You are a ways away from needing to worry about the pilot bearing, but Swepco 101 or other high-quality hig-temperature moly grease is the thing to use.

Check your email!

Good luck!

------------------
Warren Hall
1973 911S Targa

Thanks guys,
Last night Paul made a good point about using plastigauge on my bearings. Ionly remember this stuff from watching my father put the motor back together in our old 2002.
Why haven't I seen anything in any manual about this stuff? Like I said before, there are holes in my knoweledge...
I guess I'm just confused about the sequence of events here.
Let's just say for instance that all of my crank journals are within spec and I have the crank micropolished. Do I assemble the rods onto the crank using the old bolts with this plastigauge stuff then tear it apart and read the "spread" of the plastigauge?
Or, is the fact that I'm using standard size bearings and the fact that my journals are good ok, and just reassemble the rods with the new bolts and loctite period. same with the main bearings... can someone explain this?

Also in regards to measuring the bore of the crankshaft...am I supposed to assemble the case halves minus the crank and layshaft, torque it down with the bearings installed and then measure the the bores? I don't understand how I'm supposed to reach inside the case and take measurments from the main bearing bores.

And finally, what is the point of this layshaft clearance measurment? I'm guessing that I'm trying to check for play between the crank and layshaft gears? Is this the right idea?
Thanks again,

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Leland Pate

___79 SC Targa

The Porsche machine shop I talked to told me that they will bolt the case back together without the crank and measure the case bores. They didn't say how, but I figured that those measurement machines are so expansive that only machine shops had them. Take it to whoever did the rest of the measurements (fluxing etc.). Good luck and be sure to keep us (me) posted because I'll be doing this soon enough.

Just as an aside, it is always so reasuring to hear Warren's advice. God knows, I was nervous taking the engine apart, nevermind when I go to put it together. Hopefully I'll be working at a dealership by then...

Good luck Leland!

Adam Roseneck

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1978 911SC 3.0
roseneck@cyberbeach.net

Did they mention whether or not those measurments were taken with the bearings installed or not?
Thanks!


[This message has been edited by Leland Pate (edited 03-24-2001).]

Hello

layshaft end float = ? can someone descripe the part. is it relatet to the camshaft ?

To mesure out the bores and several other things you need some basic messurment tools:


















Well I had the oportunity to get such tools direct from the manufactorer in Stuttgart and spend over 1000$ back then ( 1984 ). Today the same grade and quality will cost 2000 $, they prices for mechanic droped slightly but precision is allways hard to manage.


Better visit a shop with the pre mountet empty case ( tourqued down to specs ).

I do allways messure all including the delivered bearing´s : I also recomen a perun with the crankbearings in the case. You can feel any problems by turning the crank. Well lubed and oiled it shud turn smooth with no spots.


Disasembling the engine is marking all parts. Allways put them back on the same spot and direction. The slightly heavier rods and pistons go to the flywheel. The parts have diferent wightgroups and within that a tolerance from 3 - 6 grams. You also can find the lightest part and match the others by little grinding. But i hope you know how to messure the correct moving wights on the rod.

Most borespecs have tolerances from -0,008 to - -0,016 mm. say field is 0,008 mm
Crankcasebore gets oval and has sometimes undersize in piston movement direction
while geting oversize on the other driection. Just rebore to standardsize will work.

Grüsse

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