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Today’s post is a quick set of important facts about lapping compound.
I have discussed valve lapping in the past – in particular, what it is meant for and what it isn’t. I realized after the fact (or after the post) that there were a few important facts about lapping compound that everyone should know.
Important Facts About Lapping Compound
#1 – Lapping compound is either water-based or oil-based. The stuff you get at your local hardware store or order online is generally oil-based and requires no mixing. Water-based lapping compound requires mixing before usage.
#2 – The base is important because it impacts cleanup. Water-based compound can be cleaned up with water, while an oil-based compound really needs to be cleaned up with an oil-based solvent (like paraffin). If you have every tried to clean up an oil-based compound with water, you will know that it doesn’t really work. It is VERY important after valve lapping to make sure you cleanup thoroughly. The tiny abrasive particles will migrate through your engine if not cleaned up thoroughly. Just because you can’t see them, doesn’t mean they aren’t still there. Many mechanics recommend using an ultrasonic cleaner after valve lapping to make sure all the compound and abrasive is truly gone. This may not be practical depending on the size of the valve head and the size of your ultrasonic cleaner.
#3 – The hard abrasive mixed with the base can be a variety of things from silica (sand) to glass to aluminum oxide. Just like with media blasting, the harder the abrasive, the more cutting action the compound will provide. You need to pick your lapping compound based on your required need, which will depend on how bad the valve seat surface is in need of cleanup.
#4 – There are also many grades of lapping compound, just like steel wool and sandpaper, ranging from coarse to fine. You want to use coarse compound first, then finish with fine.
That’s it for me and my important facts about lapping compound. Like I said, this was just a quick little post to educate people further on lapping compound. The process of lapping itself is very easy and straightforward. I think the reason for the follow-up is to make sure the DIY mechanics out there are also cleaning up thoroughly.
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