Hilton

Ryan, another useful tip for drilling the first hole on center is to make a drill guide using a bolt of the correct size.

See attached pics below - thats from getting a water pump bolt out, but same principle. Depending on how deep the sheared shank is, you may even be able to leave a thread on the guide to hold it in place rather than having to use vise-grips.

Just cut the head off an appropriately-sized bolt, leaving enough shank to hold it in place (and possibly a thread or two), then on the bench, center punch it and drill through it.

Then when drilling the first thin hole with the left-handed drill bit (using plenty of cutting oil too), just use the guide to make sure its centered.

Pics attached are:

1. Guide, and the extracted M6 shank
2. Holding the guide in place with vise-grips for drilling

Hilton.

Landseer

That's a great tip! Thanks, Hilton.

JHowell37

I've got a stupid question. I've removed and reinstalled the valve covers on my '85 5 or 6 times over the years. I've never broken one of those bolts. FWIW, I've never tried to remove the lower portion of the bolts. How do you all keep breaking them?

Fabio421

Try removing the lower half and you will see what all the fuss is about. Horrible design.

To the OP. Use one of these and it will save you alot of WYAIT's and fguture headaches. Your problems will be over.

Landseer

Mine appear to have been serviced once and possibly overtightened and/or loctited at that time.

The car then sat 10 years. I was knowledgeable of the potential problem of breakage but despite best efforts one broke.

Also, another one backed-out with the top portion (on the lower passenger side against the firewall).

There was no way to reach the underside with a counterhold wrench. And it wouldn't clear the camshaft, effectively pinning the cover in place. I had to unbolt and move the motor itself. Looks like the upper was loctited into the lower.

Getting them on and off now is easy.

JHowell37

Why on Earth would I want to remove a lower one?

jon928se

Re "not as deep as the original"

I realise your post is a few months old. I wouldn't worry about it. The original scenario was a steel bolt into aluminium. hence lots of threads needed as the alu is soft. You now have a steel bolt into a steel thread thus only 5 or 6 threads needed to generate the full strength (or thereabouts) of the bolt. Re the helicoil into the aluminium. The outside of the helicoil is approximately an M8x1 thread thus is 8/6 times stronger than the original for the same number of threads. Combine this with the benefit of not turning a steel female thread into a male alu where the aluminium can be easily damaged/gall etc. I'ld say it is better than the original.

Sailmed

The main problem is when the upper one freezes into the lower one, or when you want to do machine work on the heads - now - get the cover off without removing the lower one - and remember - we are all watching.

Tails

Interesting thread.

When I was a young lad learning at "the knee of the master", if you had a drill run off centre at the beginning, get a nice sharpened centre punch and chisel out a small groove on the side of the hole where you want the drill to move towards, and then carefully start drilling and the drill will track towards the centre. If you do it in small incremental grooves you can gradually get the drill to the centre.

The best method is to use a centreing guide at the start.

When reassembling parts I was also taught to apply an "anti-scuffing past" to endure that the nuts, studs etc., are easy to get out in the future. This procedure was "hammered home" even if you knew that you would not be diss-assembling the equipment in the future. Remember do not use carbon based products on aluminium.

Easy outs are a pain if they fracture, as described above. Heat, penetrating fluid and if necessary "freezing" and especially left handed rotating drills are all good method to get broken studs out.

Tails 1990 928S4 Auto

Glen McCartney

When I refinished my cam covers last year, 175K on the engine never opened, I bought the newer bolts and was going to replace the two piece design., All the original bolts came off without a hitch, tried to loosen the first stand off piece from the head. It wouldn't budge, so thought the better of it, left them alone and sold the new style bolts. Used anti-seize on reinstall and shouldn't have any problems when I have to remove them again in 175K miles.

Lizard928

A few notes on this.

If you have broken off bolts get the proper tools for removal.

I use the following extractors, and have never broken one,




All of those are IRWIN in the pictures, I also use craftsman.

Although my first choise is to weld on them as the heat helps to break down the bond.
That said the 2 piece bolt design shown by the OP is not a good one. I would strongly recommend that if you break one of the 2 piece, or need to remove the base that you buy new (upgraded from Sharky) style bolts.
On the same hand, if you need to remove them, use a small propane, or butane torch and heat the area up around the bolt BEFORE attempting to undo it. Do not heat the bolt, just the aluminum casting.
Then use a small electric or air, LOW POWER impact driver. The repeated hammer motion is much easier on the bolt for getting it out.
And again if you remove the early style bases (85/86) then throw them away and buy the new style bolt.

I have yet to get any left hand drill bits, but I will be getting some soon.