587 rotary valve clearance

[Jetman454]

I was wondering which method is best for measuring the rotary valve clearance. When I measure with .031" solder the gap is good. However when I measure with feeler gauges the measurement is bad.

 

[AKnarrowback]

Use soft solder with the valve in place.

Measure at 4 points, quadrants of the rv cover.

The min should be .010", the max is .014".

Under .010" can cause hot running, over .014" can cause hard starting when the engine is warm.

 

[etemplet]

When you check with the feeler gauges you are checking AT the PORTs. Those points are always going to be worn more than the rest of the cover. Here is a picture of me machining a cover plate. Note they excessive wear at the ports compared to the rest of the cover? This is typical. If you are reading good in the middle (topand bottom) you should be OK. Use a straight edge across the cover to determine how bad the plate is wrong at the ports. (.005") is OK.

NOTE: This cover was really bad. I probably took (.015" +) off the cover. Then of course you have to machine the other landings and equal amount. As @AKnarrowback states they start a lot better when the clearance is correct.

 

[JC-SUPERJET]

Has a Nikasil Coating ever been tried on the Rotary Valve friction surface?

Wouldn't wear and is also oelophilic (retains lubrication). Reduces friction load and heat.

 

[Jetman454]

I ended up measuring the crankcase side and rotary valve cover with a depth caliper in multiple places. Measured the rotary valve with a regular caliper. Did the math and the math matched what the feeler gauges were seeing.