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Tricks to clean out head bolt holes in block?


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Finally getting around to re-installing the cylinder head on my tii. I figured, what the hell...I've got a free weekend. And besides, now that all four of my cars are disabled, it is probably a good time to get at least one of them back on the road. The cylinder head install is the easiest of all the repairs, so the 02 moves to the head of the line.

What tricks do you use to clean out the head bolt holes before installing the cylinder head?

I've got the brakekleen spray, blue shop towels, long applicators(q-tips), and safety glasses for when it all sprays up into my face.

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What I do....

Chase the holes with a 12x1.5mm thread chaser....


Blow the holes out with a nice air blow gun.


Only if the oil is very sludgy do I use brake clean to clean the holes. If that must be done I drip a drop or two of fresh oil on the threads in the holes and wipe some on the bolts.


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From the ARP website:

"The Lubricant Is The Key

The main factor in determining friction in a threaded fastener is the lubricant used, and therefore influences the torque required for a particular installation. One of the most overlooked aspects of choosing a fastener assembly lubricant is…the lubricant's ability to "control" the normal function of friction inherent in all high performance engine fasteners. As discussed earlier in this section, friction is at its highest point when a new fastener is first tightened. This "friction" inhibits the fasteners ability to achieve the required preload on the first several cycles. In fact, ARP's in-house Research and Development department has proven that new fasteners using motor oil and other commonly used lubricants such as Moly and EPL typically require 5-7 cycles before final torquing to level out the initial friction and achieve the required preload. Slicker lubricants may reduce the required torque by as much as 20-30% to achieve the desired preload, but compromise in areas of major importance such as preload repeatability, and may yield the fastener prematurely. Typically, the slicker the lubricant, the greater the "preload scatter" or preload error there will be during installation."

Whatever you do, get the holes clean, and DO NOT "put a couple drops of oil down there", as you may crack the block - oil is not all that compressible. Some builders insist on a dry fitment, others recommend wiping an oily rag over the threads after washing and drying the bolts. Chevy guys are dry only - oil bakes onto the bolts, making them impossible to remove. BMW folks are split - whan in doubt, consult the bolt supplier. BMW recommends wash, dry, and a wipe of oil from a rag onto the threads - clean as a whistle bolt hole.

If you are using ARP or other aftermarket bolts, ask them what they recommend for an alloy head on an iron block. ARP has a proprietary lube - anything else and all bets are off.


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I am aware what happens when you try to compress a liquid, which is why I asked for everybody's techniques. It's sorta like bottle washing: how do you get it all clean.

Thanks for the detailed info regarding thread lubes. I became aware of some other info when I moved into the carbon realm of bicycles. Back in the steel days, we would grease the threads and tighten away. Aluminum came along and we started to pay more attention to torque values. With my new carbon frame, not only did they recommend the use of a low break strength thread locker, but they also explained why. (Which I thought was really cool).

Their reasoning was that a fastener needs to be able to be tightened, needs to hold, and should not corrode for subsequent disassembly. They claimed that most greases will be slippery at first, thus requiring a much higher initial torque. Grease will also degrade over time causing the fastener to either become loose or corroded in place. They claimed that purple loctite will dold the fastener at a lower torque, and remain stable over time.

This all sounded good to me. I'll give it a go this time around with this frame.

In the meantime, I'm going to get the 02 put back together this weekend.

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DO NOT "put a couple drops of oil down there"

Sometimes a little dogma doesn't always apply.

The torque for a 2002 head is specified with engine oil as a lube.

If you don't, it'll gall and not clamp enough.

So DO oil the threads of the bolts before installing. And the washer at the head.

It's true that, generically, torques are dry. But not in this case.

And the threads are a loose- enough fit that you'll never crack the block

with oil. Incompressible junk, yes...

So I use a bit of copper tubing taped to the shop- vac hose.

That seems to work really well.

(yes, the inside of my shop- vac is disgusting. )


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I've only done this a few times, but I use WD40 (or similar) to dilute the oil then blow it out with compressed air and a drinking straw ( and lots of rags and safety glasses) repeat as necessary, it's messy but it works.

I would caution against using a shop vac with more volatile solvents like gasoline, carb cleaner, etc.. In large enough quantities it could be an explosion hazard.


So I looked at the internets and apparantly mythbusters debunked this, but I still wouldn't clean my fuel tank with a shop vac.

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