Anybody done it? Internets is coming up with no results.

Simply cut them down to the correct length.

The spiral center design helps keep the vibrations/harmonics from snapping the bolt.

I silicone the centers of my 12a bolts, and you can also silicone the centers of the 13b's for even better protection.

Any reason not to do it? My engine's back apart, so now's the time.

Thanks.

 

What are you talking about, Willis? Care to show what these "spiral center" bolts look like?

Every 13B I have worked on has had the same tension bolts 12As have, just 20mm longer.

 

he's talking about the S5,13B-REW and 13B-MSP tension bolts used after 1989.

but the shorter 12A doesn't snap tension bolts, even in the 13B engines they don't snap tension bolts. i have only seen one bolt failure in hundreds of engine rebuilds. if he is breaking bolts that easily then he is doing something severely wrong.

the later tension bolts are slightly better, but they won't fix what you are talking about. the ONE single bolt failure i had was actually an S5 tension bolt with the ribs.

 

I wonder if the problem coincides with people severely overtightening the bolts. I've never seen a tension bolt issue and I use some pretty hefty sustained revs. I also torque to 23ft-lb.

Like tuning a guitar string, changing the tension on a bolt will change its natural fequency. Interesting, isn't it?

 

most likely, i generally torque them to 37 ft lbs, but those are generally turbo engines. n/a engines require less torque to keep the engine from twisting. even with the higher torque the failure rate is low (1 in 6,300ish). even in engines that twisted and cracked irons, the tension bolts survived.

 

Thanks for the replys.

Not breaking any bolts. And it seems its not as big as a deal as the internet makes it seem.

Its not from the engines twisting. Its from the vibrations over 8.5k. Thats why the silicone helps. It dampens the vibrations.

Just wondering if the newer designed bolts where better.

I cut down/installed the spiral ones anyhow, as no one replied for 9 months!

I actually plasti dipped the entire bolt, and then siliconed the center. Did it do anything? Probably not, but its done, and it cant hurt anything.

Thanks again.

 

I've heard of people putting heat shrink on the bolts.

I've always put silicone on the bolts, more inadvertently than anything - I am too cheap to buy new tension bolt washers, so I clean up the old ones and silicone them in place. A bunch gets on the bolts too, I figure it won't really hurt anything by letting the bolts get goopy.

It takes a lot more work to make a 12A happy with sustained revs over 8,5 than it does with a 13B, surprisingly enough. If you use 2mm seal, 12-pin rotors.