Walt's got those descriptions reversed. Pauters have locating dowel sleeves and use a "free" bolt that does not have it's shank aligning the rod and cap. Stock Porsche rods use nuts & bolts with shanks that lightly press into the rod and cap to properly align them.

I'm of the opinion that anything you can measure is worth checking when you're messing with the inner workings of the engine. People have proven you can do the new bolts w/out measuring stretch or resizing the rod. Great.

I still like to know that whatever i'm throwing in the engine is measuring up properly. I think throwing some new bearings, new rod bolts on old rods w/out checking is a bit risky. Not necessarily from the new bolts alone. Bearing clearances are pretty easily futzed by various issues, including the bearings themselves.

If the higher applied torque distorts the bore slightly and that closes up already tight clearances, that could create a problem some time down the road. That's the rationale behind doing the rod resizing.

I wish I still had some spare stock rods and some ARP rod bolts on the shelf or else i'd supply the testing info to add to the discussion. Maybe I can borrow back a rod from Frank since he owes me a tool returned in the mail......

Same point for resizing on the VR6 that is proven as not required. It's standard cover your ass language so you can't place any blame of failure on ARP.

http://arpinstructions.com/instructions/204-6006.pdf

The concept of “while you’re in there” has a whole new meaning when it comes to 911 Porsche engines.

It costs about $200 to resize the big end, rebush the small end and balance the rods. Why not? It seems like cheap insurance.

With Porsches like any other replicating engine, the rods deform during every rotation of the engine. This deformation in the form of elongation of the big end is expected and with normal operation conditions, well within the abilities of the rod to accept.

The problem is, when Porsche went to the 55mm journal (3.2, 3.3 and 3.6) they were forced to reduce the size of the rod bolt (from 10mm to 9mm) in order to preserve the rod to oil pump clearance.
This reduction in rod bolt size resulted in a reduction of bolt strength and in turn increased the rod deformation during standard operation.

With a high quality rod, the material can resist this deformation to a much greater extent.
Higher quality rod bolts do the same.

What we find in the Porsche engine is that the big end becomes oval shaped and needs to be resized.
The ovality seems to increase when the rod bolt tension is released then retorqued.
I have measured ovality in excess of .0025 in engines that ran without sign of rod failure.

The other issue with Porsche rods is the fact that Porsche is generally unconcerned with rod balance.
The general spec is about 4 grams from one to the next with many rods in the same factory assembled engine having end to end difference in excess of 6 grams. We shoot for .5 grams.

For these reasons, we rebuild all connecting rods where the engine is of unknown origin.
Remember, if the rod fails it’s quite often more than just a bearing that is damaged. Usually you’re looking at buying a crank, a rod and trying to figure out how to deal with the magic window in your case.

The original poster asks if he needed to modify his rods in any way? I would say no as long as big end is within specs after the new bolts are installed and torqued. This would require measuring. If you have the tools, you win.

That's a pretty cavalier attitude toward assembling an engine, but it's yours. YMMV. Do you also undertighten your wheel nuts?

BTW, the factory spec for tightening torque on a 911 rod is 35 ft.lbs. ARP uses a different spec on their rod bolts/nuts (50 ft.lbs.). Does it make a difference in clamping force? Yes. Does it make a difference in the big end dimension and engine life? That's up to you to find out.

Sherwood

Nothing under-tightened here.

Sorry if it came across as cavalier - the reality is I've worked on a lot of different car types where the same myths have been busted already. Seems this is a lone corner of the internet where myths prevail in abundance like buffalo on the open plain. It's hard to see them all under the sun chomping on grass and not put a few bullets in them.

There's more than one torque spec out there for "factory spec" is my understanding. 35-45ft lbs per Bruce Anderson... 17 ft lbs plus 90 degrees per our host here. Who's feeling lucky here? :cool: 6 of one, a half dozen of the other.