Over-torqued connect rods...what should I do?

[virusdoc]

I'm starting to assemble a mostly stock 1600 rebuild, and as I was assembling the lower end I misread Wilson's rebuild guide and accidentally torqued my connecting rods to 32 ft lbs. These are stock, refurbished rods with nuts (not cap nuts), and the correct torque should have been 24. They all have loctite on them and the entire lower end is assembled on the left case half and timing set. Should I just loosen the nuts to 24 ft lbs before assembly, or have I fatigued the bolts/nuts? The rods all spun smoothly on the crank, dropping in a uniform rate with no hangs.
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1976 Convertible Super Beetle, "June Bug".
FI-->34PICT3 carb conversion-->now dual 40 IDFs
Self-rebuilt 1904 (after totally botching a 1641 rebuild, cussing a lot, and throwing lots of cash in the fire)

[67rustavenger]

It's only 8ftbl tighter. You can leave it as is. Since the rods are loose and falling at the same rate as gravity pulls them downward.

Or back the rod nuts off till loose and start again. What likely happened when you tightened to 32ftlb. Is the bolt stretched a bit. That's normal when tightening rod bolts.

In the technical section above. There is an "Engine Blue Printing PDF." You can down load that and print a copy of the torque value sheet. I taped that sheet to the garage wall above my workbench for quick reference.

Good Luck
_________________
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[modok]

I do not think you have stretched the bolts.
Rod bolts of that size can usually take 32, 36, up to 38 ft-lb


Clean off the locktite, apply oil, tighten to the correct value, or....
IMO 25-26 ft-lb maybe ok.

[johnR]

I would [definitely] leave it as is. The loctite is set. It's not a significcant amount and you may create more problems trying to get them perfectly to spec.

[vwracerdave]

mostly stock 1600....I'd leave it alone and move on.

I read an article by a major hi-pro V-8 engine builder. He said 90% of all catostropic engine failures are falsely blamed on broken rod bolts.
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2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK

[virusdoc]

Thanks for the quick replies, all. Looking at my machinist’s notes I see he checked all the bearing clearances at 28 ft lbs. And one of the four was at the tightest permissible clearance. I think I will pull off the nuts and retorque to 26-28 and be done.
_________________
1976 Convertible Super Beetle, "June Bug".
FI-->34PICT3 carb conversion-->now dual 40 IDFs
Self-rebuilt 1904 (after totally botching a 1641 rebuild, cussing a lot, and throwing lots of cash in the fire)

[vwoldbug]

I would not touch them.

[Cusser]

[rosevillain]

Wait, Locktite on rod bolts? I thought just oil and torque?

[raydog]

[virusdoc]

[Cusser]

3 years ago I used brand-new connecting rods from CB Performance on my 1600cc rebuild, and used CB's torque instructions.
_________________
1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297

[DesignBuild]

Years ago and I guess it would still apply to the manufacturers that used them, rod bolts and nuts where torqued using oiled threads and then pal nuts were applied as the locking feature to prevent the steel nuts from backing off the bolt.

A pal nut was a stamped nut that was heat treated. Studebaker was one engine manufacturer that used them as a lock nut on connecting rod bolts. Studebaker did all of their own casting using a unique formula containing 30% recycled steel for their iron castings. Crankshafts were forged steel as were connecting rods. This what was done for even their lowly six cylinder engines.

[modok]

[modok]

It has been proven nearly impossible to get a rod bolt to vibrate loose.

Just because somebody wrote it in a book it will be forever repeated.

We need a sticky for BOOK CORRECTIONs.

These charts for torquing a faster dry are a new thing, for these new "once use only" fasteners. In fact if you want to maximise the life of your fasteners, try LUBE.

How would you even make a connecting rod otherwise?
It has to be bolted together to machine it. Then assembled in the engine. then on rebuild time you bolt the rod together to check the size, if out of spec then take apart to cut the parting, then assemble and re-hone, then disassemble, then assemble in the engine. How many is that?
Wanna go dry? NO, zero advantages to it.

[virusdoc]

Apparently I kicked a hornet's nest. Wasn't aware there were such divided schools of thought on how to fasten a connecting rod! The Loctite did seem like overkill to me, but I assumed the oft-cited Wilson book knew what they were talking about.

However, in the same section he did mis-cite the orientation of the timing marks on the main gear at #1 TDC by 90 degrees, and I knew enough to suspect that was wrong and confirm it on these forums. And at no point in the book does he tell you to reinstall the oil slinger on your crank before dropping it in the case, and I knew that was wrong. So I will take the remainder of his rebuild instructions with a grain of salt and compare other sources.

Regardless, my lower end assembled nicely and spins smoothly after all the case bolts are torqued down.

Now to find a way to hold that beast in place while I torque the gland nut and set end play...
_________________
1976 Convertible Super Beetle, "June Bug".
FI-->34PICT3 carb conversion-->now dual 40 IDFs
Self-rebuilt 1904 (after totally botching a 1641 rebuild, cussing a lot, and throwing lots of cash in the fire)

[raydog]

Here is a generalized table I found having to do with dry vs lube. All I am saying is using lube should absolutely be taken into consideration if you should be torquing dry. If virusdoc's manual says to lube thread, that's fine. Lock tite would not have been my first choice.

It's not about the fastener spinning off of the stud, it has to do with bolt stretch and tension pulling on the bolt. Rather go through a couple of cheap nuts than having a bolt snap in a critical application.

Virusdoc, I would leave well enough alone at this point. Again, this isn't rocket science.



Lubricant Torque Reduction
No lube 0
Graphite 50% - 55%
White Grease 35% - 45%
SAE 30 oil 35% - 45%
SAE 40 oil 30% - 40%

[rosevillain]