Inliners International Forums General Discussion Engines Finding TDC with the head on.

Morning all, certified numb skull here!
Well this 302 build is the first one where I'm spending the time and $$$ to build it the way I always wanted and thought it should be. This includes decreeing the cam. Gotta find TDC first right? Well had the usual brain fart and already put the head on and torqued it down. Then I realize I can't find TDC the way I seen it done with a piece of flat bar bolted across the deck with a bolt and couple nut on it? Like always being thoughtless causes me to be thoughtful later on. I can use an old plug or a "anti fouler" with a nut welded on it? Screw it in no.1 plug hole, rotate crank til ball on flywheel line up with pointer in the bell housing? Screw piece of all thread into anti fouler til it touches piston, then rotate opposite direction and adjust according to what the pointer on degree wheel says? Iirc you can buy a piston stop tool like this? Of course being cheap hard headed and insisting everything take forever I'll make mine. How bout it guys will this work?

Yes. You need a positive-stop spark plug adapter, easy to make:

1. make sure the piston is close to bottom dead center. Screw the modified spark plug in. Turn the bolt in pretty far to make sure it protrudes deep inside the combustion chamber. Now turn the crank over slowly by hand (all other plugs removed to reduce resistance).

2. when the piston hits the tip of the bolt, stop turning immediately and make a mark on the crank pulley where the TDC indicator is. this is not your TDC yet, just the first reference mark

3. turn the crank the opposite direction, it will make almost a full turn until the piston once again touches your plug bolt. Make another reference mark on the pulley at TDC indicator.

4. Your true TDC is exactly half way between your reference marks, so measure the distance between them and divide by 2, and make your TDC mark. If the distance between reference marks is really big, you can turn the plug bolt OUT a little and repeat the whole procedure, the piston will then move higher up in the cylinder before it stops against the plug bolt, and then your two reference marks will be closer together.

I used a jam nut on the bolt because you want the bolt-to-plug relation to stay 100% rigid, no wobbling. I threaded the inside of the spark plug after I knocked the porceline out. Cant remember sizes off the top of my head.

Jan

Thanks!

If the timing cover is not yet on, and I am assuming this is true for the 302, if you line up the marks on the timing gears, that is tdc for no 6. Rotate around so the cam mark is opposite the crank mark and you should be tdc for no 1.

The 37-62 stovebolt Chevy & 39-59 GMC's had a hole in the bellhousing with a pointer in it. There was a little shiny ball cast into the flywheel which when lined up with said pointer was supposed to be TDC. I'm assuming it's probably a bit off but a good place to start. I don't know whether the marks on the gears line up or not at TDC but the cover is not on so it will be easy enough to see. Thanks for your responses.

As one who found out the hard way do not trust the marks on a cam or crank gear........Good Luck