The thread size is the same as the Injector; M24x2.0

Another issue with the Harbor Freight Injector hole adapter is that it has a hollow area in it that causes the reading to be slightly lower.

However, if you buy the adapter by it self some place like eBay that adapter alone is around $30 without shipping; and you have to round up your own fittings and compression Gauge.

So the Harbor Freight one is still they way to go if you want to do the test cheaply.

If the Harbor Freight Adapter is having trouble sealing in the Prechamber area you could us a Copper Washer inplace of the Heat Shield. To soften the Copper washer after use heat it read hot and let it cool.

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84 300D, 82 Volvo 244Gl Diesel