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Discussion Starter #1 (Edited)
Interference, Yes or No?

The F2, F2T and FE-DOHC (FE3) are NON Interference engines.
I know this because
  1. F2 and F2T are basically identical when it comes to the cams, valves, etc.
  2. My timing belt fell off while driving and my engine still works
  3. The Mazda shop manual tells you to turn the camshaft while installing a new timing belt. If the the engine was interference, you wouldn't be able to turn the camshaft 360°
  4. The FE3 pistons have 4 spots for the valves so they don't hit the piston
Basically to check if an engine is interference, just take off the timing belt and turn the camshaft 360°. If you can't turn it all the way, then it's interference. But since that doesn't happen with our engines, then they are non interference. <-- Clay experiment
Fun and closed threads:

Premium Member
1,770 Posts
In addition to the post above:

The test must have at least one piston at exactly top dead center when turning the cam. Or you must test each valve one at a time for one cylinder by turning the the cam until the valve is at full reach and then turning the crank 360 degrees.

If you really want to measure the vavle to piston clearance: Remove the head. Take soft non sticky clay and make a flat disc and set it on the piston while it is at TDC. Reassemble. Turn the cam several revelutions. Disassemble. Use a micronmeter to measure the depth of the clay at the thinest part. That number is you clearance. Remember that the engine was relaxed at that point and when running hard parts do "stretch".

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