M8 bolts for head coolant passage.

[Volhv]

The two bolts at the forward coolant passage, the ones that go through the head and into the block, have been a pain.

The fwd (long) one decided it would strip its 6mm hex hole, so I pounded a 12mm 12point socket over the round head which is 13mm, and removed it that way.
The aft (short) bolt sheared its head. After much profanity, I double nutted the remaining shank, froze it, blasted it with Kroil, shocked it with a hammer, as well as the block.......etc etc... I finally got it out. Why was it so tight? The bolt threads were stripped, and that destroyed the threads in the block also.

Anyone know where I can get a cheap timesert? Or would a helicoil do? Think those bolts take 15ft/lbs..... And for those that have used timeserts, are the taps for them proprietary, or can I just buy some inserts, and put them in with the tools I allready own. I have a 100 degree countersinking tool, drill bots, taps......

Measured the old bolts, and they are M8x35, and M8x55... grade 8.8, maybe I can find some stainless ones.

Pictures to follow....

[Volhv]

An incredible amount of force was needed to get that shank out.... stripped a few nuts in the process.

Pretty tight fit on the socket, that's why it works! haven't managed to get it off yet.



A bit hard to see, but the threads in the aft hole are mangled.

[Gawernator]

O_o

[jeffrsmith]

I had the same thing happen when I pulled the head on my '87.

I helicoiled mine, pulling 15 ft lb was not an issue. I also used copper anti-seize, hopefully if I ever need to pull the head again I won't have a repeat.

Ian at 944Online was able to provide new hardware of the proper size for a reasonable price, you will have to give him a call, the bolts are not listed on the website.

[honerboys]

probably could drill it out next larger size and re-tap - watch for drilling filings falling into water jacket

[krystar]

napa sells helicoil kits.

[Volhv]

Just ordered a timesert kit.
Not too pricy, a bit more than what helicoils go for locally.
While I have used helicoils before, and they are generally fine, I have seen them back out when removing bolts at later dates, and they do sometimes break or bind.
I guess now I'll give the timesert a try since it seems to be highly recommended. Once you get the initial installation kit, replacement inserts are quite cheap... as long as you need the same size.

As far as going to a bigger size, like a M10, I think there isn't much meat around the hole in the head, so I'd rather not weaken it.

I also have an exhaust stud hole that could use repairing.

[Volhv]

The timesert kit hasn't arrived yet, but the replacement bolts are here.
Found some titanium ones. A great way to shed some weight. If my calculations are correct, this should free up about 44 HP.
But seriously, they won't corrode, and will be really fun to drill out if I need to take the head off again.

Here's a quick comparison between the new titanium, and the old steel. It might be hard to see in the picture, but the old bolt is slightly bent.

[Volhv]

Finally got the timesert kit...... and installed.

[Guest765]

Respectfully, its a waste of time and money to retap, coil, or replace that bolt in any way. They're not necessary in my experience and when mine sheared off and the ez out broke in the remaining shaft, I just left them both out. They don't see any pressure whatsoever.

You did a good job with the coil though, I guess.

[Gawernator]

Do not question the mighty and powerful Volhv!!!!