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Reusing old engine bolts

joe smith

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I understand the "replace it" mentality if there is any question..
After cleaning and wire wheeling my Clutch plate, and flywheel bolts, I notice the very out side of the threads have " bits" missing.. Very Very small, almost like a file or hacksaw nicked them..

I would think they were small rust spots, and I cleaned out the rust when I wire wheeled them???
Anyone know exactly what these marks are? Any thoughts on what I should replace and what not?? I realize these bolts are 50 years old, but at least they were probably good American steel and not the "taiwan" replacement stuff...
 
I dont see why they need to be replaced. Unless you can see stretch marks or cracks in the bolts.

Just my take on it.
 
No idea without seeing them at to what caused the marks. And even after seeing them. Probably would only have a guess. Certain applications have a torque to yield rating, some have high shear. I tend to replace spinning parts, head bolts internal engine bolts with ARP American made. More expensive than the hardware store, but worth it.
 
Most if not all clutch/flywheel manufacturers will recommend new fasteners. These bolts are subject to a lot of heat and stresses of rapid acceleration "G's" on their threads /shoulders.
When you torque a fastener you weaken it be cause you are stretching it to the torque spec. Stretching eventually cause fastener failure. Just like rod and head bolts should be replaced at a minimum. Current cars are built with single use fasteners called "torque to yield" that are discarded each time they are removed.
New, high quality fasteners should not even be something to think about. Or you can install your old ones and...they might work, or not.

 
No idea without seeing them at to what caused the marks. And even after seeing them. Probably would only have a guess.

I don't think the marks would show up with an attached pic.. They are almost like the very edge of the thread has crumbled in spots...
 
age old question, if your car is a cruiser and not a drag car I feel you can reuse them. Many will disagree with me but Im fine with that.
 
I use ARP. There are sources for high quality (USA) hardware, however ARP is excellent and easy to get. There is "Fastener Warehouse" in Portsmouth NH if you need "big" stuff or rigging supplies. They supply the Portsmouth Naval Shipyard.
 
age old question, if your car is a cruiser and not a drag car I feel you can reuse them. Many will disagree with me but Im fine with that.
I've never read in a service manual to replace the bolts. My only exception would be if someone else worked on it and overtorqued them.
 
Clutch and flywheel bolts are in a very stressful spot. For whatever it costs to replace them wouldn't you feel more comfortable with new ones. In the long run it may be cheap insurance to keep things together. As you can see everybody has a different opinion and do what you feel is best. Sometimes saving a dime can cost more in the long run.
 
I wish I could see small stress cracks, I would have saved a lot of money having parts Magna-fluxed.
New fasteners are just a form of insurance policy. Ask yourself if the potential savings are worth the potential loss if they fail.
It is your car and if it fails nobody who said just use them again will step up and help pay for damages, because it was just their opinion. They will say....
 
Clutch and flywheel bolts are in a very stressful spot. For whatever it costs to replace them wouldn't you feel more comfortable with new ones. In the long run it may be cheap insurance to keep things together. As you can see everybody has a different opinion and do what you feel is best. Sometimes saving a dime can cost more in the long run.

I was helping a friend with his clutch replacement on his Ford 390/3 speed. Went to bolt up the pressure plate, and with very little torque, one of the heads sheared off. So little torque, I was able to back the threaded portion out with my fingers.

I'll reuse head bolts, flywheel bolts, torque converter bolts, with no problem. But the pressure plate bolts have intense heat cycles. They are readily available at parts stores.
 
I use new (ARP) for rods, mains, heads, clutch, flwheel and damper bolts. All else I reuse the factory bolts for that OEM look. Except on my Hemi I studed everything that I could.
 
Most if not all clutch/flywheel manufacturers will recommend new fasteners. These bolts are subject to a lot of heat and stresses of rapid acceleration "G's" on their threads /shoulders.
When you torque a fastener you weaken it be cause you are stretching it to the torque spec. Stretching eventually cause fastener failure. Just like rod and head bolts should be replaced at a minimum. Current cars are built with single use fasteners called "torque to yield" that are discarded each time they are removed.
New, high quality fasteners should not even be something to think about. Or you can install your old ones and...they might work, or not.
Ugh
If a bolt is torqued to yield the first time, it means that it gets a permanent stretch. In that case, it will still hold the load up to that torque without further stretching. However I cannot see why a manufacturer would specify such action, which metallurgically makes no sense. I can see the reason not to reuse them in that case.
 
I've never read in a service manual to replace the bolts. My only exception would be if someone else worked on it and overtorqued them.
I agree that no FSM recommends replacing flywheel bolts, but the bolts in question are 50 years old. Replacing them now could save a problem later. One bolt "walking" out could be a disaster. ARP for the win.
 
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