The Stovebolt Site Forums The Shop Area Engine Shop 235 flywheel timing question

Hi - I'm guessing this question has been asked, but I'm not finding answers with the search feature.

I have a '59 235 engine and I'm ready to time it. My #1 cylinder is on its compression stroke and I see several marks on the flywheel. There is a triangle, followed by the number 10, followed by the number 20. The number 20 has a steel ball in the center of the zero. I believe the steel ball represents top dead center on #1. Is this correct? If so, then what is the triangle? Is it 20 degrees before top dead center?? The triangle mark does not seem far enough away from the steel ball to be 20 degrees.

My HEI vendor recommends timing 10 to 18 degrees BTDC. Where is this point relative to the marks I described above? Thanks!

Usually the steel ball is the timing mark for that model/year engine. It could be before TDC or after TDC, depending on the engine. The triangle is usually the TDC mark.

What make, year, and size engine?

The truck is a '49 Chevy 1/2-ton. The engine is a '59 235. I don't know whether the flywheel is a '49, '59, or something else.

My 1958 Shop Manual tells me to time the engine 4-degrees BTDC, but it doesn't tell me which mark is TDC. As the flywheel rotates, the triangle mark reaches the pointer first, followed by the 10 and then the 20 (with the steel ball). If the triangle is TDC, wouldn't this mean the steel ball is AFTER top dead center?? And if the steel ball is AFTER top dead center, then it seems like I'm timing my engine in the wrong direction if I use the steel ball as the timing mark.

The triangle is a point on the flywheel used to check for timing gear wear and doesn't relate to ignition timing. The ball is your factory timing mark, probably at 4 degrees BTDC as your shop manual states and is a good place to start.

You're gonna have to play it by ear a little on this one. The timing can be advanced until pinging is heard, then backed down just below that point. On my HEI the timing ball is not visible in the window unless I look downward into it. If you knew the diameter of your flywheel I would think a guy could mark it off in 5 degree increments pretty easily but who knows where your engine's "sweet spot" is. Happy hunting!!

Cool. Thanks!