Any time you interface dissimilar metals, there can be a corrosive reaction. In this case for aluminum it's best to use an anti-sieze.



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Thread locker - Used to "lock" a bolt in place when it's critical the part does not come loose, or is not easily re-tightened. Example: Flywheel bolts. Replaces set screws or snap rings and locks against vibration loosening. May require heat or special tools for removal. I've also used it on the occasional stubborn bolt that keeps coming loose. There are both permanent/heavy-duty (red) and non-permanent/medium-duty (blue) thread lockers. Interestingly, Permatex Blue comes in a red tube, and Permatex Red comes in a blue tube! Go figure?!?

Thread sealant - Typically used on metal tapered pipe thread fittings where you might otherwise have used Teflon tape or pipe dopes. Prevents galling and protects mated threaded areas from rust and corrosion, and usually contains PTFE. Thread sealing is achieved as the anaerobic adhesive cures when confined in the absence of air, and between close fitting metal surfaces.

Anti-seize - A highly refined blend of aluminum, copper and graphite lubricants. Used during assembly to prevent galling, corrosion and seizing due to weathering or chemical reactions, such as occurs with dissimilar metals. Anti-Seize assures easier disassembly. I always use anti-seize on spark plug threads going into aluminum heads. I've also used anti-seize on sway bar bushings to prevent squeaking, and it doesn't squeeze out over time like grease will.

So to answer your question, I'd use anti-seize on the three studs that hold your AC compressor to your aluminum heads, as well as on your spark plug threads. This will help protect the threads in your aluminum heads from being pulled out or destroyed when you try to later remove those studs (or plugs).

 

Thanks @Garth66 . What about the water pump bolts? Sealant on the threads and anti-seize on the shaft?

 

I use a LITTLE Teflon (ptfe) thread tape on stuff that seals water, but not on areas where oil is circulated. If a giblet of the stuff went into a crevice of a radiator, no big deal. If it hung in an oil screen or made it to a bearing or lifter...oh Lordy.

 

These products are a good reason to have a set of taps/dies to chase and clean the threads and bolts before reassembly.

 

After fighting with I don't know how many rusty water pump bolts over the years, these days I put antiseize on the threads of the bolts that got into the block and paint the rest of the bolt shank with sealer. After seeing way too many bolts stuck pretty hard in the block that probably would have come out had not the shanks snapped from being weakened by corrosion.

 

I use Antisieze on just about everything. I use thread lock if it's specifically required

I even use Antisieze on gaskets. I haven't used gasket cement in at least 25 years. I've never had a gasket leak with Antisieze and the next time you take it apart, the gaskets come off cleanly!

 

I replaced my water pump and timing cover bolts with stainless steel and coated them all with anti seize. Didn't use it on any gaskets, but like Huskinhano, I used anti seize on just about everything when I put the car together.

 

How about sensors screwing into the manifold? Anti seize ok?

 

just a very small amount, and never any Teflon tape. The tape has a propensity for interfering with the grounding of the sensor.