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69a · 06-02-2026, 10:30 PM

The Navarro heads that I have, in an engine supplied by H&H have the spark plug area too thick in the casting, about 4 threads to thick. The entire plug including the electrode is up inside the thread. The plugs get fouled every 500 to 1,000 miles. You can't put a longer plug in because the valve is too close. If he hasn't corrected this with the casting you will need to get some material removed.

06-02-2026, 10:30 PM	#2
69a Senior Member Join Date: Aug 2020 Posts: 323	Re: Navarro 8ba Heads The Navarro heads that I have, in an engine supplied by H&H have the spark plug area too thick in the casting, about 4 threads to thick. The entire plug including the electrode is up inside the thread. The plugs get fouled every 500 to 1,000 miles. You can't put a longer plug in because the valve is too close. If he hasn't corrected this with the casting you will need to get some material removed. Last edited by 69a; 06-02-2026 at 10:41 PM.