Re-use rod bolts?

[EngineerDoug]

Hope everybody is having a Merry Christmas...got a question about rod bolts. I'll be starting to re-assemble my budget 383 this week. To give you an idea of the intended RPM range of this build, I will be using the Summit K6400 cam, which is fairly mild. This will not be a max-effort, high rpm screamer.

My question is, should I re-use my rod bolts? Is there any way to tell if they have over-stressed or stretched? None of the rod bearings appeared to have lost their crush, nor were any of them spun. There was some marking on the back of the bearings and rod bores, if that means anything. I do see signs of valve float, however, as the tips of some valves were beat up.

Let me know if I would be penny-wise and pound-foolish to re-use them. Your advice is appreciated; thanks.

 

[Lionized]

I wouldn't.

 

[66chargerpat]

On my 66 383 the rod bolts yield every time I recheck the toque. I just couldn't sleep that nite. Next day I change them out with a set of ARPs. that was 160k miles ago. 50$ for peace of mind and I have drove and beat the hell out of this engine.

 

[cdr]

If you change rod bolts the rods will need to be checked & probobly be resized. on your build if they torque good just put it together .

 

[Xp29h]

I wouldn't either. Go ARP for sure!

 

[747mopar]

The 3 things I always replace in any type of performance motor is rod, head and main bolts. Cheap insurance, to me rod bolts are the most important to replace seeing how they're under extreme stress and a failure can completely destroy a motor.

 

[miller]

As long as the bolts, and nuts, have no visible damage, and are not loose in the rods, I've never had a problem re-using rod bolts. They stayed glued together this long, right?
Tried a set of those ARP bolts on my current build...didn't like the idea it would take a big hammer (or other means) to get 'em in the rods, and re-used my originals.

 

[69L48Z27]

On a stock rebuild, or close to it, I have no issue reusing stock hardware. Inspection and condition dictate what gets reused.

 

[65-440]

Reuse ... I'm big on cheap insurance but sometimes things are not necessary. If the nuts and bolts are good then torque them down and move on. I assume you'll be having everything balanced ? If so let the machine shop look at them.

 

[PRND21]

For a mild rebuild, probably not. In your case you state that you suspect the engine had been abused (valve float), I'd at least have the rods checked. If they are in need of being resized, then definitely replace the bolts. And use a press or a vise to replace them.

 

[moper]

If they look good and the rods are not going to be rebuilt then leave them alone. Your use is mild. If you do replace, then you need to properly resize the rods. The better the replacement bolt, the more important is it that they be cycled and resized.

 

[Cranky]

It isn't the rod bolt that gives up so much....it's the nut. We dealt with bolt torque a lot where I worked and one time we had a company come out to 'teach' us the proper way to check torque, lubes to use and why nuts and bolts give up. On one test, a new cap screw (a bolt is made up of a threaded stud and two nuts. A cap screw is a fastener with a head on one end and is screwed into an object with threads or is used to clamp something together using a nut on one end) was installed into the torque tester with a new nut and tightened up to the proper spec and measured. Then it was loosened and torqued again to the same measurement and the fixture showd it was about 10% less clamping force. Did it again and it was about 15% less. One more time and it was 20% and then it didn't yield anymore. Then a new nut was used and toque readings were right back up within a percentage point. I brought in some new and used rod bolts with new and old nuts to test and they did the same thing with the same results. Even new rod bolt with a used nut showed things were not up to snuff. If you look at the rod fastener you'll see that the main body looks pretty beefy while the nuts are kinda thin. The thicker the nut, the better they hold up to being retorqued but a rod nut is somewhat thin and testing heavier nuts showed it. I also asked about reusing the old nut but adding 5 lbs to the torque reading even though some say you can do that, these people showed it actually didn't add any torque...other words, the nut kept yielding.

So, for something really mild, I would say it's ok and I've done it plenty of times but for something you have a some money in, I would say no. On a performance build when it starts out with new rod bolts and nuts, new nuts go on on the first tear down. New nuts also go on if they've been torqued one time and have to come apart for any reason. ARP used to sell fasteners but now I think they only sell to other companies? Used to buy rod nuts in bulk from them years ago. On your engine, you will probably be safe enough reusing the stock nuts but if it's been apart before, I might go with new nuts on it. They used to be cheap but it's been years since buying any.

 

[67belvedere/225]

arp all the way

 

[mmissile]

Always replace rod bolts. I always upgrade, as well. While the stuff is apart for a rebuild[even a stock one] I have the rods resized, and polish the beams.

 

[Cranky]

Always replace rod bolts. I always upgrade, as well. While the stuff is apart for a rebuild[even a stock one] I have the rods resized, and polish the beams.

If the rod needs to be resized then I do it but if they are round already, why do it. And the replacement of the bolts doesn't always distort them. Measure them at 10-12 and 2 o'clock to make sure they are round. A real tight press fit on the bolts can and usually does distort the rod but in most cases, the fit isn't tight enough to do it. Most auto machine shops don't want to bother checking them because it's not going to make them any money. Same way when it comes to align boring and square decking. It takes time to check it and just going ahead and machining it all is the easy way out to make money.

 

[EngineerDoug]

Great inputs, guys. I understand what resizing means, but if the bearings have not spun, help me understand why resize. What is it about fitting new bolts that would mandate resizing - do the new bolts somehow affect the shape of the bearing bore? I was under the impression that resizing was done when the bearing bore was "stretched" due to over-revving or a spun bearing.

I am leaning toward new bolts, because this looks to be the last added expense, and they are relatively cheap. I just want to completely understand the resizing issue.

Thanks.

 

[Cranky]

Popular belief is that whenever you install new rod bolts, you "have" to resize but that's not always the case. If the new bolts are very tight, then they will probably distort the size but if they fit like they should, it's usually not necessary so long as the big end was true to start with. A good sign of the rod being true is having even wear on the bearing. Fretting on the back side is usually a sign of the bearing that didn't have enough 'crush' in the rod. Could have been the bearing being on the small side or the size of the rod being a bit too big. Ping issues can also beat the bearings to the point of them losing all crush. If you've ever pulled an engine apart and saw pistons that looked like crap on the top and the bearings just fell out of the rods when you pulled the caps, that's usually a good indication things were not right.

 

[EngineerDoug]

Aha! Fretting is the word to describe the wear patterns I saw on the back of the bearings. Also had noticed some of the rod bolts came out of the rods easily and some were pretty tight. I learned something new today - I like that.

I'll go with new ARP bolts and have the rods checked/resized when I pick up the block. Had I not seen the aforementioned signs of over-revving and odd wear patterns I might have re-used the bolts/nuts.

Thank you!

 

[Fran Blacker]

If you use a vise to change rod bolts be sure to use flat 1/8" thick brass in vise to protect rods.

 

[dvw]

I agree if the bolt fits properly the rod bore will change very little if any. Was it proper to start with? Without the proper tools who knows. Therefore if you trusted the rod with the old bolts there would be no reason not to trust it with new bolts. Pro-Stock engine technology is great, but it's not necessary for most builds. Any engine build is a compromise on cost and time. Most street strip builds could probably get away with plenty of stock stuff with no machining. Look at the old bearings. Were they wearing properly? If so the rod is probably round enough and there was enough bearing clearance for that current power level. What are the consequences if the rod is out of round? If the clearance is tight the bearing could grab the crank. Another reason to run bearings loose. If it was mine I'd swap the bolts. Carefully check the bolt holes for burrs and deburr SLIGHTLY as necessary. Carefully press the new bolts in using a press or use an aluminum block with a hole in it as a receiver and press the bolt in using a vice. Heads up the wave-loc bolts fit far to tight for my liking. To go as far as resizing, polishing the beams, and new bolts? I'd buy a new aftermarket rod before I spent that kind of cash on a 30 year old rod of unknown history
Doug