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Fri Nov 21, 2008 6:05 pm

Probably a really stupid question but I could not find the answer . I have a nice used set of scat h-beam rods . I read all about the proper stretch and such with the rod bolts . Are the ones I have reusable ? Or do I need to purchase a new set of bolts ?
Are rodbolts for one time use only ? Thanks, Jerry

Fri Nov 21, 2008 6:12 pm

I reused the bolts in my 42 year old Corvair engine, and I'd imagine the Scat rods have better ones. Wisdom says replace or at least use a stretch gauge, but I say use 'em if you're not going crazy on the engine.

Fri Nov 21, 2008 6:27 pm

You can reuse them.

Fri Nov 21, 2008 7:49 pm

Thanks . the rods are scat and the bolts,although they "look" just like arp bolts they are stamped scat on them.

There to be used in a 2276 I'm building for my dune buggy. It will only be a toy and not a racer but I dont want it to fail .
I will have someone who has built plenty of vw engines before helping me out so I guess if they dont torque or stretch out right I will replace them before I continue .

Fri Nov 21, 2008 8:10 pm

:? ............Another $70 for a fresh set of bolts, or thousands of dollars because one $8 questionable rod bolt let go.
I'll let you do the math.

Sat Nov 22, 2008 4:28 am

Quote: ............Another $70 for a fresh set of bolts, or thousands of dollars because one $8 questionable rod bolt let go.
I'll let you do the math.

Not trying to skimp on such an important part,just didnt really know the answer . I'll go new . Thanks

Sat Nov 22, 2008 6:48 am

If you knew the history of the bolts, maybe.
IE how many torque cycles they had been through or whether or not the engine had spun a bearing.
Without that information, I'd do as SRP1 suggests and replace them.

Sat Nov 22, 2008 7:27 am

Not only do you need to know hole long the bolts have been used, you need to know if they were tightened properly.

Many people don't realize this, but an under tightened bolt will fail faster from stress fatigue than an over tightened bolt. Not simply fail faster, but it can fail prematurely.

All bolts will eventually fail from stress fatigue. But if everything is designed properly, the engine will wear out long before the bolts fail.

Harder high strength bolts are more susceptible to stress fatigue failures due to nicks or scratches on the bolts. The harder the bolt is, the more polished it needs to be. They don't make high strength bolts shiny just to make them pretty. It gives them greater resistance to stress fatigue.

Rust is one of the worst things that can happen on high strength bolts. It creates thousands of micro stress risers where a crack can propagate from.

I'd agree with the others that new rod bolts is cheap insurance.

Scott Novak

Sat Nov 22, 2008 12:23 pm

I have been building engines for 17 years and I have never had a rod bolt break ever. I have also taken apart at least 1000 engines and have never seen a broken rod bolt. I have numerous connecting rods that have literally ripped apart and the rod bolts are still in one piece. The only time I haven't reused rod bolts is when they are rusty and pitted. Everything that everyone has said so far is correct, I am not disagreeing, but in a street engine the chance of a rod bolt breaking is about the same as winning the lottery.

Sat Nov 22, 2008 12:27 pm

roy@mofoco.com wrote: I have been building engines for 17 years and I have never had a rod bolt break ever. I have also taken apart at least 1000 engines and have never seen a broken rod bolt. I have numerous connecting rods that have literally ripped apart and the rod bolts are still in one piece. The only time I haven't reused rod bolts is when they are rusty and pitted. Everything that everyone has said so far is correct, I am not disagreeing, but in a street engine the chance of a rod bolt breaking is about the same as winning the lottery.

Very true with stock German rods and bolts. I have only had one of those break and that was while torquing it down, and on the bench.

Sat Nov 22, 2008 12:35 pm

SRP1 wrote: roy@mofoco.com wrote: I have been building engines for 17 years and I have never had a rod bolt break ever. I have also taken apart at least 1000 engines and have never seen a broken rod bolt. I have numerous connecting rods that have literally ripped apart and the rod bolts are still in one piece. The only time I haven't reused rod bolts is when they are rusty and pitted. Everything that everyone has said so far is correct, I am not disagreeing, but in a street engine the chance of a rod bolt breaking is about the same as winning the lottery.

Very true with stock German rods and bolts. I have only had one of those break and that was while torquing it down, and on the bench.

You are right, I should have clarified that. I was referring to stock German rod bolts.

Sat Nov 22, 2008 12:55 pm

roy@mofoco.com wrote: SRP1 wrote: roy@mofoco.com wrote: I have been building engines for 17 years and I have never had a rod bolt break ever. I have also taken apart at least 1000 engines and have never seen a broken rod bolt. I have numerous connecting rods that have literally ripped apart and the rod bolts are still in one piece. The only time I haven't reused rod bolts is when they are rusty and pitted. Everything that everyone has said so far is correct, I am not disagreeing, but in a street engine the chance of a rod bolt breaking is about the same as winning the lottery.

Very true with stock German rods and bolts. I have only had one of those break and that was while torquing it down, and on the bench.

You are right, I should have clarified that. I was referring to stock German rod bolts.

Roy your so right about rod bolts. Steve I raced the Porsche 912 5.3 rod on my 84mm crankshaft with 20% load and no problems with the same bolts. The KB motor that Keith runs is 20 years old. That was a 426 until they cut it in 1/2. 309 and still running. But where old school.

Sat Nov 22, 2008 1:09 pm

ARP...nothing else.

I measure the bolts and replace the nuts. Rarely have I ever had to replace an ARP bolt because of stretch.

Sat Nov 22, 2008 3:18 pm

Thanks for all the great info !!
I don't know the history other then what I was told by the seller so take that for what it's worth.
Said it has less then a thousand miles on the build. Most of the parts look like it but I'm sure there were a few reused things.
Pistons/cylinders,cam,lifters,rods ,all look perfect. Crank looks nice but has some very minor marks from maybe low oil pressure , could probably be reused with just a polishing but I'm going bigger on the crank anyway . Heads were probably from another motor but no way to really be sure .
I have no reason to doubt the low miles on the rods/bolts , and the whole shebang came from a vw guy here on the samba .

The engine will not be beat on , I dont drive my stuff hard at all. Just some low speed spurts once in awhile .
If new is needed, I will buy them without thinking twice but if it is just a waste of money for my objective and what I already have will work fine then I would rather spend that cash somewhere else.

Sat Nov 22, 2008 9:18 pm

Just making a funny here!

Quote: in a street engine the chance of a rod bolt breaking is about the same as winning the lottery.

Dude buys a quick pick at lunch time, is driving home after a late day and some OT at work. The radio station announces the daily lotto numbers. Just as you realize you won the damn thing, BAM the engine expires. The $1100 YOU JUST WON GOES TO A NEW REBUILD.

Remember this is just a joke. I am in now way shape or form a person that can weigh in with an educated answer so I just come into a serious confab and fart in the room. :lol:

Sat Nov 22, 2008 10:01 pm

[quote="jbreddawg"] Quote: Thanks for all the great info !!

I don't know the history other then what I was told by the seller so take that for what it's worth.

That right there should have answered your question, but there are two things you can check:
1- If your rod bolts say Scat or ARP 8740 on the bolt head then throw them out, you really want a bolt that says Scat or ARP2000 on the head. 8740 is fine for most mild builds but I would not re-use them. Also ARP2000 is a much better material.

2-Install the rod bolts using the torque over stretch method. Any rod bolt that stretches past it's max stretch limit at it's specified set torque is fatigued and looking at failure.

Hope this helps, new bolt are the best but it sounds like your looking for more of a factual reason to buy new bolts. No crystal ball on this stuff so that's the best advise I can give you.
Good luck

Sun Nov 23, 2008 7:46 am

8740's should be more than enough for street engines, you just know they're a step up from stock ones. I'm pretty sure my Unitech rods have those bolts. 2000's for high-stress apps for sure.

Sun Nov 23, 2008 8:13 am

Thanks again guys . Thats why I love this forum.
I've decided to just buy new and not chance anything. I'm too new at all this to play russian roulette with my motor lol !!
I guess if new bolts were 4-5 hundred it "might" be worth reusing them for what I need but less then a hundred bucks it's a no brainer. Especially when it's a part that can make your engine go boom !
I really appreciate the different opinions , they really help out alot ! Jerry

Thu Nov 27, 2008 6:38 pm

You know I'd get in on this.

Just split my case after two years of use. ARP2000 bolts were used, torqued correctly during the one and only build.

Never spun a bearing. Was sure hoping to reuse the bolts.

Thu Nov 27, 2008 7:41 pm

I wouldn't lose sleep over it. Like I said, if I can get away with reusing 42 year old OEM bolts, I doubt you'll have any problems.