Rod bolts

[Roslin]

When i am torquing my rod bolts (genuine Porsche) with red 271 loctite, i wondered if it is necessary to lubricate the surface on the nut where it mates the rod cap, with asm. lube to achieve the right torque level ??



Roslin

[AFJuvat]

DO NOT use loctite 271.

You are supposed to lightly oil the threads prior to torqing them.

Follow proscribed torque procedure.

AFJ

[Henry Schmidt]

Many qualified engines builders have been using Loctite on rod bolts for years.
In some cases it makes sense but light oil is the prescribed method.
We general use Wurth CU800 anti seize. We generally don't use stock bolts and never use stock nuts.

[Scott R]

Originally posted by Henry Schmidt
Many qualified engines builders have been using Loctite on rod bolts for years.
In some cases it makes sense but light oil is the prescribed method.
We general use Wurth CU800 anti seize. We generally don't use stock bolts and never use stock nuts.

Which rod bolts do you use Henry?

[Henry Schmidt]

ARP bolts and a special order 12 point, serrated flange nut.

The nut is the same nut we use on the Supertec head stud kit.

[Ken911]

red loctite has the same lubricating properties as 20w- 50 oil so that tourque specs will still be accurate using red loctite. part of the design of red locktite

[afterburn 549]

now there's one for me. Ken911 do you know where that info comes from ?? I can remember countless arguments against this idea...

[Eagledriver]

I don't use loctite on these but it probably won't hurt. I think factory bolts are fine in this application (3.0 SC engine) as long as RPM is limited to 7500 or less. Rod bolt failures are rare on this engine. The torque spec from my book shows 25-29 ft/lbs. I used the higher number on my latest engine. Basically it felt like the nut was still turning a lot at the lower spec and was slowing down dramatically at the upper end. Obviously you don't want to go past the elastic limit of the bolt.

-Andy

[snowman]

Always follow the manufactures recommendations, period. If you use factory parts, use factory specs. If you choose ARP, follow what ARP specs, exactly. Failures are typically caused by people following proceedures not recommended by the people that designed the stuff, people that know more than anyone else in the world about the stuff.

Rod bolts are held in by their clamping force and friction. Locktite does NOTHING to improve this situation. If a bolt, any bolt is cycled, that is the force acting on the bolt exceeds the clamping force, it can only last for a few hundred cycles, max. At that point it breaks.

Locktite works for wagon wheel fasteners, for planks on an 1800 vntage Canastoga Wagon, but it does not work on a modern engine. Locktite does nothing to strengthen the bolt or its clampling force. If the bolt is cycled it breaks, the nut still is in place, with or without the locktite.

Suspension parts are usually differen't. The bolts loosten up due to vibrations and fall out. Locktite prevents this. Even at this point the bolt is not subjected to serious forces, just more vibration. Actually if the bolt is properly tightened to begin with, it will not fall out even without the locktite. In the case of a connecting rod, if the bolt ever loostens to the point that only the locktite is holding it in, it is cycling, and it is going to break, period. How long is a couple hundred cycles at 3000 RPM?? About 1/3 of a minute.

A common problem with techs is that they think they know more than the people that designed the stuff to begin with. They do not. Often times they think they are right, usually for the wrong reasons, but that is the opinion you will be most often exposed to. Engineers DO know what they are doing. OF course there are exceptions, but they are rare and much less frequent than the typical tech will admit to. Always do what the people that designed the stuff recommend. In doing so you will fail much less frequently than people that do not follow those recommendations.

[Henry Schmidt]

Here we go again.

The Loctite won't hurt but it may help.

When the rod bolt is over stressed [overrev] there is no guarantee that is will break. If it stretches, the nut can loosen and come off. Once the bolt has stretch (overrev) failure is eminent.
The loctite can prevent a more catastrophic failure.
Less damage to ancillary parts. (oil pump, case, cylinders and so on)

One prominent off road builder uses Loctite on their rod bolts in type 1, type 4 VWs and 911 based engines. As far as I know they are among the best off road engine builders in the country.

[cstreit]

Originally posted by snowman


[snip]
Locktite works for wagon wheel fasteners, for planks on an 1800 vntage Canastoga Wagon

[snip]

Presumably those gnawed on by a rod-munching beaver?

[afterburn 549]

yea - my beaver, get er done

[Roslin]

Thank you all of you, for these wery interesting replays ! Now it is up to me to decide to use Loctite or not.. :-) I think i like the way with no Loctite on the std. street engine.

Roslin

[snowman]

Henry,

You are a good tech. Become an excellent tech by understanding what the engineers are talking about. You DO NOT KNOW MORE than the engineers do, You only lack the understanding that they
do. So learn from the engineers, do not try to become something you are not, ie an engineer. Once you lean what they are talking about your advice will become worth much more than it is now. Thats bucks in your bottom line.

[AFJuvat]

Henry,

FWIW, I use the ARP nuts and bolts as well.

IMO, using loctite (particularly red) on a rod bolt is just bad form.

As an aside, after torquing the bolts down; either be computing stretch or the three stage method; what are your thoughts about peening the nut and bolt (i.e. center-punching the junction between the bolt and nut)

AFJ

[AFJuvat]

Edited.... post removed

AFJ

[afterburn 549]

I would not be so quick, and your a moderator ?? There has been a lot of good info here despite the stone throwing

[Henry Schmidt]

Originally posted by AFJuvat
Henry,

FWIW, I use the ARP nuts and bolts as well.

IMO, using loctite (particularly red) on a rod bolt is just bad form.

As an aside, after torquing the bolts down; either be computing stretch or the three stage method; what are your thoughts about peening the nut and bolt (i.e. center-punching the junction between the bolt and nut)

AFJ

I was under the opinion (perhaps mistakenly) that Roslin was using stock (genuine Porsche) rod bolts and nuts.
The poor quality/design needs all the help they can get.
If he would have said ARP bolts I would have said that Loctite was not a good idea.

Over the years I have seen peened /punched rod nuts and always wonders why? Might help, but I really have no personal experience with that technique.

[Turbo_pro]

Originally posted by AFJuvat
Snowman,

I'm sorry, but after reading this post and your "so full of propaganda I'm now convinced you own stock in Carrillo rods" post; I am forced to conclude:

1. That you see yourself as some sort of engine rebuilding Moses calling down your commandments from up high to us, the unwashed who do this as a hobby, or perhaps in Henry's and my own case, someone who actually does this for a living.

Amazingly enough, we have managed to thrive and succeed for years before you graced us with your little vignettes of wisdom.

2. Or you are one of the most pompous, arrogant, equine sphincters I have ever read.

AFJ

__________________
Es geht nicht darum wie schnell man faehrt, sondern wie gut man schnell fahren kann.

Ihr Brunnen der nutzlosen Porsche Information


AFJ

A little harsh but well put.

[Scott R]

Originally posted by AFJuvat
Edited.... post removed

AFJ

Edited or not, over the years you have never given me bad information, not once. So let me beg another question... I ordered stock rod bolts to rebuild my stock 3.0L Sunday driver. Should I return them and go ARP?