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Evolution of the 5.0 HO
I came across this article that was talking about the evolution of the Ford Windsor (aka SBF) and I found something almost disturbing. They were talking about crankshaft bolts and how the bolts that come with flexplates should never be used with flywheels because they aren't long enough. On my existing Explorer 302, I reused those bolts.

If you don't want to read the entire page, here's what they said:

When converting from automatic to a manual transmission, be sure to use the correct flywheel bolts. Those specified for use with an automatic transmission flexplate and stiffener are not long enough.
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Current Ford Master Parts Catalogs specify part # D2AZ-6379-B bolts for both flexplates and flywheels. They are not long enough to properly clamp a manual transmission flywheel to the crankshaft. Don't trust 'em.

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Obsolete but still available part # B8AZ-6379-A is the correct grip length. These bolts come with thread sealant pre-applied.

I'm fairly sure the bolts that came in my Explorer engine are the 1st ones. I don't drive the thing hard and never plan to. Although it does, on occasion, get over 5000 RPMs. Should I be worried or will the bolts I have be just fine for the light duty I run the engine?

For the 331 build, I'm thinking I'll upgrade to the longer B8AZ-6379-A bolts. I just thought I'd ask here just to get opinions, but more importantly, hear if disasters have actually happened BECAUSE of using a shorter bolt and under what conditions those disasters occurred.

Chris, I have always used the correct lenght bolts, usually even get new ARP ones from Summit. Same goes for the ones attaching the clutch. Real cheap insurance. Just don't want to risk reusing those bolts. Other than that, how's it all going down there with the 331 and everything else I'm sure you got going on?
Dave

Hopefully you'll be fine. Obviously you don't have as many threads catching so you risk them snapping or threads being over loaded and stripping. However you don't hammer it at the drag strip and wail on it all day so I'm sure you'll be fine.

I always heard 4 threads will hold as good as 8. But person telling me that only thought it good advice when we were working on my junk

I bought the ARP flywheel bolts at the same time I bought ARP head bolts and valve cover bolts. The flywheel bolts were only like $8 for a set...cheaper than FRPP. The head bolts where what was expensive.

Soul wrote:I always heard 4 threads will hold as good as 8. But person telling me that only thought it good advice when we were working on my junk

Well,
The old rule of thumb is to use a bolt long enough to get one full thread dia of engagement if going into steel and 1 1/2 times if going into aluminum. 1/2" bolt would need half an inch engagement into steel as a minimum. 40 years as a mechanical designer with a lot of fastener background.
Chris,
I have usually found Summet/Jegs lot cheaper than the dealer. Most of the engine bolts today are the "torque to yeild" type and have to be thrown away after using. ARP's just good insurance, don't know the price comparison to Ford bolts.
Dave

I didn't even price out what TTY head bolts would be for that very reason. And now that they are bought, I'm not even a little curious. The ARP bolts are reusable (to an extent) and aren't designed to yield. You torque them to spec, not to yield. They are also 12-sided heads so you get the unmistakable aftermarket look of the head bolt from the engine bay...that is if someone knows what they are looking at. To the laymen, my engine will look just like a stock Explorer engine.