Airflite40

So, I am soon going to install the rod bearings and nuts, just wondering what type of socket am I supposed to use on the rod nut? It doesnt look like any I have. If someone could verify I believe the correct spec is 55ftlbs for rod nuts. Can I use regular motor oil to lube the bearings and nuts when installing?

GlenL

Those nuts take a regular 12-point socket.

Those should go on dry with a dab of blue toctite. Clean the bolts thoroughly beforehand. The nuts should be replaced with new parts.

Torque depends on nut type. With ribbed surface it's 78Nm. With a flat surface it's 58Nm.

hacker-pschorr

Since the WSM says "lubricate" threads & bearing surface - are you using the loctite as the lubrication? Does this effect the torque?

Where did you find this info - not questioning, just curious. I'm in the middle of a pan gasket job, seamed like a good time to do rod bearings.

Kevin in Atlanta

WSM also recommends replacing the bolts and nuts (I didn't follow those). I used white lub to protect the bearing shells until the oil pressure built up.

hacker-pschorr

I have new nuts - WSM doesn't mention replacing the bolts, at least mine doesn't.

I plan on pre-oiling my engine using a drill on the oil pump, so not sure if I'll use assembly lube vs coat of oil.

Koenig928

The conrod nuts use a 14mm, 12pt socket.

For Torque, look at WSM Vol 1 (Engine), pp. 10-03, and 10-07.
"Conrod nut with smooth bearing surface = 58 + 5 Nm"
"Conrod nut with ribbed bearing surface = 75 Nm"
Also, the GTS rod nuts use a different spec too.

I know the WSM say to lube threads and bearing surface, but personally I did not lube the threads, only the ribbed bearing surface. See picture below. the nuts are designed to 'crush' a bit on the bottem when they're torqued (for the ribbed ones anyway).

I cleaned my threads with lacquer thinner first, and applied RED loctite, only because I don't want that sucker coming loose as the engine is screaming away - but only from my personal choice to do that way. (I discovered a huge 3" hole welded up in my oil pan directly below the 2/6 journal..., but that's a different topic)

GlenL

That'd be the effect. Can't use loctite on oily threads. Just being paranoid.


It's in the Tech Spec booklet; the 81/82 plus 80-84 S version.

Do them early and often. In the future I'll be doing at least 2&6 annually.

Koenig928

I tried sourcing new bolts for my 5.0L rods, but they're not avail. directly from Porsche. There maybe a different source that I don't know of. But, this is what I learned about the stock bolts. Apparently, Porsche designed the bolts to not yield when torqued properly, the nut is the one that crushes slightly. Bolt hardness is 12.9, nut harness is 12.0.

If a bolt has a crack in it, then you'll feel it when torqueing (soft turn).

If your really into getting new bolts, then ARP makes a matching bolt/nut set for the 944 rods (which are exact fit for the S4 5.0L rod). But, they are heavier and have a higher clamping force, which will distort the rod large end. So you'll have to resize your big end to make them work properly.

Pre-oiling with the engine pump is a great idea. I did that too. I used assembly lube directly on the rod journals/bearings and then drizzled oil on top when it was put together (but that's with the motor upside down on a stand).

Also, A note on the rod bearings. The Porsche bearings should always be spot on for size. But I've heard some say that the Glyco bearings tend to run 'slightly' smaller, approx. ~0.001 inch, for their "standard" size bearing. Which could work out perfectly for a crank that has slight rod journal wear.

Either way, I would recommend measuring the rod journal first. And use Plastiguage (red and green) to determine your exact clearance. Practice measuring and torqueing with your old rod nuts first, so you don't burn-up your new ones.

hacker-pschorr

Cool, thanks guys - first time rod bearing job here (on any car) so I'm checking everything over and over.

I need to pick up the 81 spec book.

Guest 928tt

You need to use oil on the threads to get a true torque on the rod and main nuts and use plenty of assembly lube on the crank and rod bearings. And use a good torque wrench.

6.0-928S

I cleaned my threads with lacquer thinner first, and applied RED loctite, only because I don't want that sucker coming loose as the engine is screaming away - but only from my personal choice to do that way. (I discovered a huge 3" hole welded up in my oil pan directly below the 2/6 journal..., but that's a different topic)

Bill,
RED loctite is the 'permanent' stuff. Not trying to be a critic but I used RED on rods once & I'll never do it again. Years ago I built a 427 Ford tunnel port NASCAR motor. After cleaning the surfaces, I applied a small dab of the loctite on the backing of the rod bearings where they seated against the crosshatch on the inside of the rod's big end to help prevent any spun bearings since the motor would be spinning well over 8000 rpm. We never spun a rod bearing. But when I went to disassemble the motor, some rods were scratch damaged trying to get the old rod bearings off. The heat really reacts on the red & it wouldn't let go. It took hours. I'll never do it again. It's even more effective on threads.
Hammer

Koenig928

Hey Hammer,
Not a problem at all, I appreciate your insight with the loctite, I'll have to be careful with that.

Personally, I've never had a problem getting Red Loctite to let go on threads. And yes, I know I'm deviating from the WSM's on this, but I've got reasons for it. Something flew apart on this motor and made one hell of a hole in the oil pan some time in the past. The pan was welded up, but I suspect it was a conrod nut that did it. Usually when a nut or bolt lets go, it does more damage to the cradle and block as the rod comes apart too. but I've got no damage to either, just the pan, so its hard to tell... I'm just trying to ensure the darn thing doesn't do something similar again. Call me paranoid...but I've had bad experiences with bolts breaking on this engine....

H2

Great information guys...for when I tackle an engine refurbish. Thanks.

Harvey

SwayBar

I find it very amusing when people knowingly deviate from the FACTORY workshop manuals. The guys who were paid to design and engineer the engine essentially wrote the manuals, and here are some of you deciding to out-engineer the Porsche Powertrain Engineers. Do you really think you out-thunk Porsche?



By the way, Loctite is NOT a lubricant. And if a non-lubricant is used in an application requiring a lubricant, then the item will not torque as deemed necessary by the engineer.

svp928

I have to agree with sway-bar...The torque spec for rod bolts is generally arrived at by measuring how much the bolt stretches for a given amount of torque, applied with a known lubricant. This spec stretches the bolt to a percentage of its yield strength. If you change the lubricant, the amount of stretch for a given torque value can vary wildly, allowing the bolt to either be insufficiently tight, or stretch into yield, at which point it won't stay torqued. Both conditions result in failure. The racing shops I work with actually use dial indicators to stretch rod bolts to the spec provided by Carrillo, or whoever supplies the bolts. This takes the torque variable out of the equation.
So, you should know and be able to measure how much the bolt should be stretched if you want to change the friction characteristics of your assembly.
And I have never seen red loctite used on a rod bolt...
Not trying to be negative, just hoping to stave off a possible failure.