Author Topic: DIY - "TDC" Finder from Scrap!  (Read 3823 times)

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Offline goodfellow

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DIY - "TDC" Finder from Scrap!
« on: November 03, 2009, 05:14:53 PM »
Sometimes it's important to know exactly where "Top Dead Center" is on an engine. Many times the timing marks on the timing chain cover or the block are wrong, lost or bent, or the distributor has been removed for service and then finding TDC become essential. There are various ways of doing it -- ranging anywhere from spark plug stops to whistles, but if you really want to be precise, you need a fluid gauge.

Here's one I made this morning for a friend of mine who just serviced his distributor at my shop, but forgot to mark TDC and subsequently turned over the engine a few times -- now he's lost and his '68 XKE won't start. It's just a few pieces of common shop scrap, an old compression gauge hose, clear tubing, brass fittings, a ruler, and some fasteners

I painted a piece of thick plywoood light grey and drilled a 3/4" hole to fit a 90 dgree elbow with two hose fittings





I used hot glue to fix the elbow in the hole and then proceeded to attach 6 feet of clear tubing to the back and also layed out a "U" shaped flow meter on the front of the board with some 1/4" cable fasteners I had lying around.





Next I used an old compression gauge hose and attached it to the 6 foot tubing section. This will allow me to screw the hose into a saprk plug socket and then hookup the clear tubing to the nipple on the compression gauge hose.

Note: if you don't have a spare compression gauge hose, just gut an old sparkplug and hook it directly to the clear tubing.



Here's the completed gauge and the compression gauge hose in the no. 6 sparkplug hole on my engine -- just for testing!!





I filled the "U" meter with a red colored oil (Marvel Mystery Oil) so that it's easier to see, and then I mounted a ruler scale next to the tube (any scale will do)





Once the fluid has reached equilibrium then I proceeded to turn the engine slowly over until the the fluid just started to move in the positive direction. I then marked the scale with a pen and slowly continued to to turn the engine over until the fluid reached it's peak hight. That spot is also marked with a pen on the scale and represents TDC.

To fine tune the setting, I slowly rotated the engine back and forth and observed the fluid level rsing and lowering against my mark-- doing this a few times allowed me to "zero in" on the exact TDC -- when the fluid was at it's peak on the scale.

Any scale will do since you're only using it to set a baseline and then trying to read what the highest fluid level reading is (doesn't matter what the scale is as long as the fluid hight can be readily seen and compared).





It's not "rocket science" -- and it worked real well on my engine. My friend took the TDC finder home and managed to set TDC on his engine within 20 minutes.

Note: if you want very exacting readings, you need to make the "U" meter longer than the one shown in my pics. This one is 1.5 feet long and takes a little fiddling, if it were at 3 feet in length, then the readings would be much more precise.



« Last Edit: November 03, 2009, 08:38:23 PM by goodfellow »

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DIY - "TDC" Finder from Scrap!
« on: November 03, 2009, 05:14:53 PM »

Offline kimetric

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Re: DIY - "TDC" Finder from Scrap!
« Reply #1 on: November 04, 2009, 03:14:47 AM »
Very Professional. Beats using a screwdriver/pencil/stick/straw/ect and "educated feel".

Offline rusty

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Re: DIY - "TDC" Finder from Scrap!
« Reply #2 on: November 04, 2009, 09:37:39 AM »
That is a very neat idea. Hmm I can see mounting on on the wall if you have a dedicated area for that kind of work. Make it movable just in case, but give it a spot of it's own.
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Offline goodfellow

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Re: DIY - "TDC" Finder from Scrap!
« Reply #3 on: November 05, 2009, 09:27:06 AM »
This was quick hack job to help out a friend who had his "panties in a bunch" with worry about his car. If I were to do it over, I'd make a longer tube -- 3ft minimum with a fine mili-liter scale for much greater accuracy, and a tap on the bottom of the "U", so that the unit can also be used for "cc-ing" heads and piston offsets.

Offline rusty

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Re: DIY - "TDC" Finder from Scrap!
« Reply #4 on: November 05, 2009, 10:04:31 AM »
Sounds almost like racing tune prep with your modifications.

Still an excellent idea that I had never thought of. Nice hurry up design as well.
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Offline AaronTycle

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DIY "TDC" Finder from Scrap
« Reply #5 on: September 09, 2017, 10:17:31 PM »
Looks good to me.  Those are some great looking woods. Do you have a shot of the side with the micarta in the middle?
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