Good Morning, I'm hoping someone out there can feel my pain this morning. So this past weekend i spent my time rebuilding the Carburetor then I went on to work on the timing as it runs pretty rough right now and the carb rebuild helped but its definitely not in time, no top end power it just bottoms out hard to get above 35mph. Anyway so I don't seem to have a make or an indent on my main pulley I can see the little pin (8BA) next to the pulley but there is no mark. so I tried taking out a spark plug and then turning the main shaft so that i could feel the rod go up and down on the number one, no louck thought as the rod i have in the spark plug hole is sitting on the valves.

Long story short how do I find TDC on my Flathead 8BA

 

There are a couple of ways to go about this task, one is to use a TDC finder tool. It consists of a spark plug threaded tube with a spring loaded pin in the center. When inserted into the #1 plug hole, the pin will rise and fall with the motion of the piston. When the pin is out as far as it will go you know that the piston is at TDC. The other method is to use a piston stop...this tool can be purchased or easily fabricated from an old spark plug. The tool has the metal body of the spark plug with a threaded pin through the center. The tool is screwed into the #1 plug hole and the engine hand-turned over until it stops. The engine stops turning over when the #1 piston contacts the tool, at this point a mark is placed on the harmonic balancer. Then turn the engine over the opposite direction until the piston once again contacts the tool and the engine stops. Make another mark on the harmonic balancer. Now you have two marks on the balancer...TDC is the halfway point between these two marks. If my description is not clear, go on the internet and search for TDC, etc and you will find many YouTube videos that show these procedures much better than I can describe them here. Good luck...


Here is a link to one product...

and here is another

 

Those generally don't work on a flathead, because the piston isn't under the spark plug hole.

You can get pretty close by bending a wire into a "Z" shape and working it thru the plug hole. The leg that goes over the piston needs to be short, maybe 1/8", so it won't get caught between the piston and head. Make the "handle" long enough there is NO chance of it falling into the combustion chamber!

Turn slowly, watching the tool. You'll see the handle move as it comes up on TDC. At that point, take the tool out and look in thru the plug hole, you can see the piston coming up.

 

Assuming that the crank and cam gear marks align perfectly, wouldn't #1 TDC be when damper timing mark is aligned with the timing cover pointer?

JB

 

His damper doesn't have a mark or the "bump" on it.

 

Got it, thanks for the clarification, sorry to derail the thread.

 

I use the old method, hold my thumb over the plug hole until it blows my thumb off of the hole. That will get you close.

 

Jpyles - I had the same issue, my damper did not have the bump. So I found TDC as described here, I actually watched the piston from the oil pan top out ( my engine was dissembled on a bench ) looked at the damper at the timing cover pointer, and could see the faintest round circle. I guess it was chipped off at some point during a clean up. I just punched it with a set punch and now that's my new damper timing mark. See if you have the same thing.....

JB

 

Using a vacuum gauge here to set ignition timing sure seems tailor made to avoid a lot of confusion and hassle.

 

Good method. Have a helper actually turn the engine for you and you should be able to find TDC within a few degrees. Close enough for setting pre-start timing.