Re-use Connecting Rod Bolts?

[Exodus_2pt0]

rod bolts have far less stress on them than head bolts do. ive re used connecting rod bolts before.

This is very far from the truth. Rod bolts bear the full force of each piston firing.

[bmwstudent]

I've banged dirty chicks with no rubber before. Just because i've done that doesn't make it okay or safe. I don't' recommend it. Throwing a rod is like getting herpes, its permanent.

[aventari]

This is very far from the truth. Rod bolts bear the full force of each piston firing.

This is actually not true--the crank bears that force, but the rod bolts do take a lot of force slowing the piston/rod down on the upstroke.


Regardless I'm reusing them and I hope I don't have to post in here again in a few months

[nando]

okay, good luck buddy.

"the bentley doesn't say you can't" is about the dumbest thing I've read here in a long time.

[reelizmpro]

You can and will probably get away with it but it's not advised and if one fails, you will have a big mess to deal with because you didn't take the extra precaution. That's too big of a gamble...just change them for peace of mind.

[acolella76]

They can be reused just enough to torque down the bearings so you can measure bearing clearance. That is about all that I would reuse them for... after that buy new ones. There's nothing more depressing than spending a shit load of money rebuilding an engine and getting rod knock 100 miles later. Ask me how I know!

[Exodus_2pt0]

This is actually not true--the crank bears that force, but the rod bolts do take a lot of force slowing the piston/rod down on the upstroke.


Regardless I'm reusing them and I hope I don't have to post in here again in a few months

It is true... You are wrong.

Each piston is attached to the crank. When one piston is on its power stroke, another will be on its intake stroke. The force generated by the piston on its power stroke, will transfer to the piston/rod assembly that is on it's intake stroke, through the crank. Therefore, the connecting rod bolts attached to the cylinder that is on the intake stroke must bear the full force in order to pull that piston/rod down.

Get it yet? It is a tremendous mistake and misunderstanding to assume that connecting rod bolts aren't under extreme pressure.

If another person attempts to tell me i'm wrong again, I suggest you go and take some classes on Internal Combustion Engines.

[aventari]

Oh yeah you are correct sir, I withdraw my previous comment. I wasn't thinking about the other pistons.

I'm also not terribly worried about a 250,000 mile engine in a $300 car blowing up. I'm just throwing in new bearings while I have the pan dropped to eek a little more life out of it because it's going to be hard miles on the track from now until it lets go. The car is getting built for 24 Hours of LeMons / Chumpcar.

If it blows I'll drop in an $80 junkyard motor over a weekend, no big deal.

See you guys on the track :)


edit:

"the bentley doesn't say you can't" is about the dumbest thing I've read here in a long time.

Really? Following the instructions in a factory manual is the dumbest thing you've read on an message forum? I don't know which internet you're on, but I'd like access, please.

[mikeedler]

Really? Following the instructions in a factory manual is the dumbest thing you've read on an message forum? I don't know which internet you're on, but I'd like access, please.

factory manual??????????? If you would read an actual BMW factory manual, almost every single fastener that you remove from ANYTHING on a BMW is supposed to be replaced.

best of luck

[nando]

Oh yeah you are correct sir, I withdraw my previous comment. I wasn't thinking about the other pistons.

I'm also not terribly worried about a 250,000 mile engine in a $300 car blowing up. I'm just throwing in new bearings while I have the pan dropped to eek a little more life out of it because it's going to be hard miles on the track from now until it lets go. The car is getting built for 24 Hours of LeMons / Chumpcar.

If it blows I'll drop in an $80 junkyard motor over a weekend, no big deal.

See you guys on the track :)


edit:


Really? Following the instructions in a factory manual is the dumbest thing you've read on an message forum? I don't know which internet you're on, but I'd like access, please.

lol. IT'S NOT A FACTORY MANUAL.

there are many errors in the Bentley. It's a nice resource but it's far from the "end all" source.

[Exodus_2pt0]

Oh yeah you are correct sir, I withdraw my previous comment. I wasn't thinking about the other pistons.

I'm also not terribly worried about a 250,000 mile engine in a $300 car blowing up. I'm just throwing in new bearings while I have the pan dropped to eek a little more life out of it because it's going to be hard miles on the track from now until it lets go. The car is getting built for 24 Hours of LeMons / Chumpcar.

If it blows I'll drop in an $80 junkyard motor over a weekend, no big deal.

See you guys on the track :)


edit:


Really? Following the instructions in a factory manual is the dumbest thing you've read on an message forum? I don't know which internet you're on, but I'd like access, please.

I guess you don't care then if the motor lets go in the middle of a race?

That being said, I reused rod bolts on one of my cylinders when I got my engine. Just wanted to inspect the bearings, I haven't had an issue. Then again, I rarely take my car past 4.5k

[CarsSuck]

^^ you guys got 'em good, but let's get to the real point. OP isnt building a motor for a cheap-skate, shit box, challenge race. From what I gather he wants a reliable street motor that will be driven strenuously. My rule of thumb is this: if the part is cheaper than the labor to access it, replace it when you're in there. Not that I pay for labor, but it's logical.

[ForcedFirebird]

It's a must, period. Throw away all of those used bolts.

If I were you I would drop the extra money on ARP bolts, that's what I did.

Says the guy that tells people to use an impact on the crank bolt. :p

lol. IT'S NOT A FACTORY MANUAL.

there are many errors in the Bentley. It's a nice resource but it's far from the "end all" source.

Bentley says to tighten the valve cover nuts to 11ft/lb and they will snap every time lol. BMW says 6ft/lb.

Take this with a grain of salt, but I have re-used TTY bolts in a pinch, second time only, never a third (except once on an iron head engine, re-used the head bolts a 3rd time) and never had any issues. Not doing it on customers' cars, but my Triton V10 in the haul truck has been 22k miles towing a race car and trailer all over the country after changing out the bearings and re-using the TTY rod bolts.

It's a gamble, if you don't mind tearing it apart again to save $100, go for it. For me it's different, I'll change a motor out fairly quickly with a shop at my disposal, but wouldn't even think about it working on a home garage floor, or for an engine I was going to run high RPM's on a track.

[aventari]

Thread Update
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One year, lots of street miles and 5 track days later, motor is still running superbly and connecting rods are still safely inside the engine block.

[SkiFree]

Thread Update
================================================

One year, lots of street miles and 5 track days later, motor is still running superbly and connecting rods are still safely inside the engine block.

Over the same course of time I can point you to at least 5 M20's and more M10's who did not replace them and have had them fail. I'd go buy a lottery ticket.