Bill Ball

I'm just an amateur, so you pros please correct me, but the way I undestood it is that Porsche specifies torque to angle because it is a more accurate to get to even fastener tightness or clampload as it eliminates variable thread friction that can lead to errors if you torque to a spec. Torque to spec on other fasteners is acceptable. So, I don't expect to see the same torque value on all head bolts after using torque angle.

I'm not suggesting I fully understand this, as torque angle is usually used on "stretch" bolts to provide a specific amount of stretch to generate the clampload, and stretch bolts are single use. But the WSM does not specify the head bolts as single use. Head bolts for many other engines are single use stretch bolts. If they aren't stretch bolts then periodic retorquing is usually called for.

Regardless, I've taken the WSM at face value in this case, and so far that has worked. The only time I have varied from the WSM head bolt torque procedure is with non-OEM gaskets, such as Cometic multilayer metal head gaskets. Those clearly need a different approach despite Cometic saying to just follow the factory procedure.

Bill Ball

Oh, one other thing...the thing about the washers not turning - I think that only applies to the engines with head studs. There are intructions to rough up the underside of the washers on re-use. I've only seen this in a service bulletin. Again, please correct me if wrong.

hacker-pschorr

What this covered yet? What do you use (if anything) to lube up the studs / bolts?

I remember many years ago watching an engine builder put a dab of motor oil on every bolt (not a 928).

blown 87

Correct in that the goal is to produce "X" amount of bolt stretch, and the torque to get "X" will be different, usually depending on friction losses.
Like high end rod bolts that you use a mic on to measure length on.

As far as the need to replace them every time, yes, if they are torque to yield they need to be replaced, but the question here is do the latter 928 bolts get stretched enough to yield, that I do not know, but for the price of a set of bolts I am going to replace them.

Cometic is so full of it I bet they wear brown pants.

blown 87

For reason I have stated, and other things, I do not agree with that.
Do not let them turn.

GregBBRD

"Cement head" refers to how stubborn we Germans tend to be. Not how smart. A huge amount of the technology we have today came directly from WWII. They were, at least, 20 years ahead of everyone else....probably still are.

blown 87

One thing is for sure, they understand both ends of brute force.

mark kibort

I agree. just look at the ME262 when we were flying around 150mph slower in our state of the art mustangs! sure they handled better, but ......
They do know technology and can make quality stuff. thats the reason I race it. no other car would put up with my abuse for over 10 years, starting with a car that was already 15 years old to begin with!

the piston offset design and build, might be stupid, or they just might have been stubborn to think that it didnt matter, or matter much. simularly, the new TB adjusting tool on the old belt might be the same kind of thing. in the end, you dont hear of too many failures or slipped belts if they are tigntened using anything that has been used in the past.

by the way, when did the porsche engineers start using the steel cam pulleys vs the aluminum ones??

blown 87

If you like the ME 262, they are building 5 new ones and restoring one original one.
Here is the home page, look at all the links including the past years, be warned it is very long.

http://www.stormbirds.com/project/index.html

GregBBRD

Stop thinking.

Technical Bulletin #8703 (Book D pages 26-30) tells exactly how they want it done.

Note that the early 16 valve engines get torqued and only the "later engines with head studs" get angle tightened.

Note that there are specific washers that need to be used. Note that there are specific head gasket part numbers.

Note that they are very specific about the washers not spinning, when they are tightened....for angle tightening.

Mark Kibort: Note that you can re-use head bolts. That doesn't mean that you can just re-use every fricking bolt you ever see, That means you still need to look at them and determine if they are good....just like every other thing you look at, on a vehicle. I've personally seen a fair amount of broken head bolts and head bolts that yield too far, when tightened. So....I have a "method".

Here's how I figure it out: If the heads botls have the original gold coloring on them and have had no water touch them, I re-use them. If the head bolts are black or stained, I replace them....all of them...so that I can get the best head gasket compression possible. If I get one bolt, in a set that doesn't tighten properly....has less torque for a given angle....the whole set gets replaced.

I think using/combining steps from other sources is a huge mistake. No where, except on the very early engines, and in the "early instructions" does Porsche ever mention angle tightening the head gaskets, loosening them, as then doing it over again. (Note that Porsche says nothing about doing this, in these "replacement" instructions...even for the early engines....and these instructions "replace all previous instructions in repair publications regarding the tightening of the cylinder heads on the 928".) (Also note: 928 head gaskets have been superceeded several times, since the "original' instructions were written....and Porsche is very specific about what head gasket part numbers the "new" instructions apply to.)

These specifications were designed to get the proper amount of tension onto a head gasket. Allowing the head gasket to compress for several days is certainly going to compress the gasket. They have already taken this into account. Loosening the hardware and tightening it again is going to make the hardware over-torqued and the head gasket over compressed.

All this being said, I don't really care how you guys do it...you can tighten the botts with a 3/4" impact, for all I care. I'm going to continue doing things my way. Every engine that I build seems to work pretty well....which is a good thing....because when they don't, I would be fixing them on my "own dollars". I have noticed that the majority of "home" rebuilds never run or never last for many miles..... go figure. I have noticed that Mark Anderson buys up a fair amount of "home project" cars that never ran or worked....go figure.

Bill Ball

Argh! I'm missing 8703. 8603 covers the studs. Thanks for the further comments.

jeff spahn

I am missing 8703 as well. Not in my entire file. I see it in the table of contents. No page though.

GregBBRD

I'm not much of a "model to model" guy....I react to stuff that is in front of me, without much regard to what year....but I think that they put steel gears in for the fisrt couple of years, then switched to aluminum gears, for a couple of years. Then they switched to aluminum gears with the HTD belt for a couple of years, before the 32 valve engines.

I've got an original '82 Euro, in the shop, with early belt and aluminum gears.

Leon Speed

Just wanted to say thanks to Greg (and Greg) for your info. I learned a ton, very valuable.

mark kibort

I cant keep it straight, even if you knew!
I got the aluminum gears from my first experience with the euro stuff (also 82 euro) and those are the pictures I posted. i never posted the oil pump pulley, but it was about twice as grooved as the cam pulleys. (and those were really bad! ) once thing i bet, the belt didnt wonder much to the edge!!!