Does shaving a bolt head make it weaker?

So, I found out the issue with my Subaru:

http://grassrootsmotorsports.com/forum/grm/need-subaru-clutch-help-no-love-from-nasioc/82648/page1/

The issue is the flywheel bolt heads are ever so slightly hitting the clutch disc It is a known issue on early 2002 WRX's as they use a "slightly" thinner clutch disc that is no longer available/sold.

I'm not too keen on grinding down the current bolt heads to make it work... but I order LOTS of specialty hardware at my day job and I have never heard or saw thin headed bolts.

Suggestions?

Just talked to my old man who mechanically tests bolts for strength for his work and he says cutting the head down a bit won't affect the strength much. I don't think it would matter, get out the file/grinder and cut the head down. The stressed portion of a bolt is in the shank and threads. As long as you can torque the bolt head and not strip it out I wouldn't worry about it.

Common on 2.3 fords too. Call ARP and get better bolts with thinner heads, then you'll sleep at night not wondering if the flywheels going to peak out and saw your foot off.

Shaving a bolt head does make them weaker, but as this is not the weakest spot, it's a moot point.

It would only be when you shaved so much of the head off that the head becomes the new weakest point that it would matter.

While you can certainly do it, you'll always worry. Thin headed bolts do exist. If you can in fact get them from ARP without breaking the bank, you would sleep easier using those. McMaster Carr might also have some.

I would speculate the head height of the bolt is driven more by having adequate engagement and strength to prevent rounding off during installation/removal then to keep the head from popping off from tensile stress. How much head height you need for installation/removal then would be dependent on how good the tools you are using are.

My concern wouldn't be strength of the bolt; it would be the strength of the 6-point head. Less surface area for your socket wrench to grab onto seems like it would increase the likelihood of rounding off the bolt.

I would look for new bolts, it seams that there would be some ready to kit out there if this is a common issue.

A lot of flywheel bolts are thin 12-point heads, get some that fit your application. 12-point gives you more contact area on the thin head.

Point seems lost here. With out the head, the bolt holds nothing.

That said, shaving the head just enough for clearance should not cause a problem.

option 1: http://www.summitracing.com/parts/arp-254-2801/overview/

option 2: http://www.mcmaster.com/#96144a263/=rhpo0f <-- will need to compare head heights and also threaded length. that's the 30mm and there is a 20mm as well

I suppose the answer would depend on what "ever so lightly" means as it could mean different things to different people. What percentage of the head material is to be removed compaired to the overall thickness of the head itself. If it approaches 10% percent I wouldn't do it. As others have said ARP might be the answer. They have an online catalog where you might be able to match up what you need even though it may not be the bolts specified for your application. Their technical folks will also answer questions about bolt specifications or at least used to.

Even this cheapskate would buy ARP bolts if available.

Let's look at the problem from a practical standpoint.

Have people done it in the past without issue? Yep.

Have people done it in the past WITH issue? Probably not.

You could run into vibration issues if you shave them down, unless you get them all exactly the same height.

If this is a known issue, isn't there a Subi forum that has this solved?