12a Rebuild: One Tension Bolt with Short Threads
08-12-14, 06:44 PM
#1
12a Rebuild: One Tension Bolt with Short Threads
Setting up for the stack assembly.
I noticed when pulling the tension bolts one had short threads compared to all the others. Its at the very top, #15 in the tightening sequence (image).
Is this correct to have one short-thread bolt and it is #15?
I've searched but came up empty here and in the documents (could be I missed the reference).
I noticed when pulling the tension bolts one had short threads compared to all the others. Its at the very top, #15 in the tightening sequence (image).
Is this correct to have one short-thread bolt and it is #15?
I've searched but came up empty here and in the documents (could be I missed the reference).
08-12-14, 09:06 PM
#2
that's a new one on me. i've never seen that before.
can you snap a photo of the head? maybe someone just bought something from a hardware store to replace a lost or broken bolt. sometimes they snap in use (presumably due to vibrations) or when removing them.
can you snap a photo of the head? maybe someone just bought something from a hardware store to replace a lost or broken bolt. sometimes they snap in use (presumably due to vibrations) or when removing them.
08-13-14, 02:12 AM
#3
I've never had a bolt snap in use or during removal, and I've torn down some 30 year olds whose tension bolts didn't want to budge.
That is a bolt from the '70s! They are supposedly slightly more likely to snap during use if you rev to the moon where they could resonate (like past 10 grand which you will never do) so Mazda started making the threaded section longer.
Once you engine is assembled, tap the outside bolt with a finger. It'll ring at a certain frequency. Match that in revs, and you know how an opera singer can break a wine glass?
To make a long story short (no pun intended), don't worry about it. Use it and I guess you can put it back in the same hole. It won't break
until the fat lady sings.
That is a bolt from the '70s! They are supposedly slightly more likely to snap during use if you rev to the moon where they could resonate (like past 10 grand which you will never do) so Mazda started making the threaded section longer.
Once you engine is assembled, tap the outside bolt with a finger. It'll ring at a certain frequency. Match that in revs, and you know how an opera singer can break a wine glass?
To make a long story short (no pun intended), don't worry about it. Use it and I guess you can put it back in the same hole. It won't break
until the fat lady sings.
08-13-14, 03:52 AM
#4
so far, i've never pulled an engine where a bolt was already broken, but i have had 2 break on as many engine while removing them. one of them my friend (at whose shop i was working that day) had to heat it with his torch in order to get it out the front housing.
08-13-14, 06:13 AM
#5
Correction: The bolt is exactly the same length as the others except the long one on the outside bottom.
The threads are just shorter.
(But I did have the broken dowel pin lower right.)
I'll put it back where it came from.
(This is an Atkins rebuilt from 1997.)
The threads are just shorter.
(But I did have the broken dowel pin lower right.)
I'll put it back where it came from.
(This is an Atkins rebuilt from 1997.)
08-13-14, 09:35 AM
#7
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08-13-14, 12:35 PM
#9
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I'd be more worried about the effects of a bolt hitting the backside of the flywheel at XXXX rpm...
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