OK, Richard uses 5-40 bolts to attach the header. I notice that the bolts are just long enough to grab 4 or 5 threads. Maybe 5/8" long. The hole is maybe 3/8" deep down to the liner. Any reason I can't use a bolt just a little longer so it grabs a few more threads?

Wayne,

See, now you asked a question and I have to give an embarrassing answer. I'd hoped no one would ask.

I overtorqued one of the screws and stripped out the last couple of threads. The choices seem to be go to a longer screw (3/4" versus the 5/8" long that comes with the engine), tap out the hole to a larger size (surprisingly, I have some 6-48 screws that would work - even have a tap), or send the engine back to Richard to be repaired. I'd hoped that just using a longer screw would work OK. It's only the last 2 or 3 threads.

Hmm, maybe a helicoil?

sigh.... Now the cat's out of the bag.

I would suggest a Heli-Coil. Who knows what you will run into with a longer SHCS.
Wayne

Bill,

I was just concerned that the screws were the length they were for a reason. I didn't want to distort the case or something.

Bill,

I was just concerned that the screws were the length they were for a reason. I didn't want to distort the case or something.

Hi Randy,

I can understand that.   As we all know, the full strength of a bolt is already achieved at the length which equals the diameter of the bolt.  So a shorter bolt is as *Strong* as a longer bolt.  There should be no problem as long as you run both bolts the same length.

Oh Bill:

That's in a perfect world where the thread size is optimum for the material and the material is as strong as the screw!!  Unless that is some super alloy, neither is the case here!



Curt

Hi Curt,

What are you saying here?  As far as the *strength* of the *bolt*, itself, I have always been told by machinists, engine builders, and all, that the maximum strength of the bolt is reached at that point. 

I was not referring to the strength of the joint that is created. 

Have I been misinformed all these years? (this even goes into racing engines when I was doing that. )

Thanks, Randy.   After I read it a few times, I believe you are right.  Curt is talking about the strength of the *bolted joint*.

I was just referring to the tensile strength of the bolt, itself, not the joint created by it.