Head Bolt Measurement (1 Viewer)

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Looking at the FSM I see a measurement for the Head Bolts of 0.4272 to 0.4331 standard measurement with minimum of 0.417". Where is that measurement taken?

I assume it is the threaded section as noted below for the Main Bearing Cap Bolts but not able to find a diagram specifically stating so.

1684772219616.png
 
Take several measurements noting the least of them. Why not just buy new head bolts or move to ARP studs?
 
Looking at the FSM I see a measurement for the Head Bolts of 0.4272 to 0.4331 standard measurement with minimum of 0.417". Where is that measurement taken?

I assume it is the threaded section as noted below for the Main Bearing Cap Bolts but not able to find a diagram specifically stating so.

View attachment 3329290
You measure exactly where the FSM says to, although the illustration is misleading. Metric threads are measured over the outside of the thread, not in them, so you want to use the flat part of the caliper blade, not the knife edge as the illustration would lead you to believe.

Yes, the measurement is taken over the threaded area.
 
Considering New or ARP, however, the question here is "where to measure"...the threaded section I get 0.428" to 0.429" which is within the spec (assuming the measurement is taken at the threaded section).

The bolt profile I measure (all 14 are as noted below)

Under the head 0.433" (shoulder section)
Middle of bolt 0.418" (undercut section)
Thread section 0.429" to 0.430" (threaded section)

Hence my question...where to measure? If I assume measurement is same as for the Main Cap Bolts (threaded section), I am well within the spec of 0.4272 to 0.4331. If the measurement is middle (unthreaded, undercut section) then I am marginal.

Thanks Baldilocks...D
 
You measure exactly where the FSM says to, although the illustration is misleading. Metric threads are measured over the outside of the thread, not in them, so you want to use the flat part of the caliper blade, not the knife edge as the illustration would lead you to believe.

Yes, the measurement is taken over the threaded area.
Here is my problem...no illustration or verbiage stating to measure the threaded section. I did find your recommendation to be consistent with Main Bearing Cap Bolts and it would make sense that head bolts would follow the same method of measurement. However, nothing definitive so thought I would ask.

Thanks

1684777738611.png
 
Based on my limited experience with failure in these they do stretch/fail in the general area shown with the calipers on it above. I would think that the uncut/smooth section of the bolt is stronger and less likely to stretch than the threaded section. Additionally, the threads that are inside the block when installed are supported by the block so the most likely stretch point is going to be in the threads and not deep in the block. I think you would be safe taking multiple measurements in this general area and then using the smallest of them. I'd assume that if you notice much variance in the diameter of any point of the bolt vs. comparable sections that you should be concerned that the bolt has already started to fail.

If I was inclined to re-use the headbolts I'd still order a few new ones to have on hand in case any fail during the torque process. If/when they fail they feel very different from non-failed bolts so it's obvious and easy enough to replace just the failed bolt and proceed.
 
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The whole reuse of headbolts in my opinion is like taking a shower then chosing to put your manky underwear back on. Sure they will fit but seriously why would you do that...o_O
 
One of the magic properties of metals is that they stretch and return to their original shape and size unless stretch beyond the plastic limit. This is why we use metal for building machines and not wood. There is absolutely nothing wrong with reusing bolts which have not been stressed beyond the plastic limit.
 
One of the magic properties of metals is that they stretch and return to their original shape and size unless stretch beyond the plastic limit. This is why we use metal for building machines and not wood. There is absolutely nothing wrong with reusing bolts which have not been stressed beyond the plastic limit.
But for those of us that are much less edumacated than you....

It's worth my time to just replace them if I'm there so I don't have to worry about if I measured in the right place or if my calipers have been calibrated within the last 6 months......
 
My only concern with TTY head bolts is once installed, no knowing they have yielded. Yes you may notice it felt “different” when installing however no real way of knowing unless you remove the fastener.
 
My only concern with TTY head bolts is once installed, no knowing they have yielded. Yes you may notice it felt “different” when installing however no real way of knowing unless you remove the fastener.
ARP studs.
 
The head bolts were in speck and reused when the HG was replaced on my rig.
8 years later there still holding fine !
 

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