dial indicator adaptor

[russcc]

I know there are several good methods to determine TDC in the flathead with the head on. I was wondering if some one has made an adaptor for a dial indicator that would thread into the spark plug hole, You would need a right angle extension about 1 & 1/2" long to reach from the plug hole to hit the top the piston.

[cmbrucew]

This one will do that. Mag base, or any fixture you might have on hand.
Bruce

[tubman]

You might try an old snowmobiler's trick. Feed enough rope down through the spark plug hole to act as a piston stop. Turn the crankshaft both ways until it stops turning. Halfway between is TDC. You would have to be kinda careful not to vary the amount of rope in the cylinder and rock it back and forth several times to account for the compress-ability of the rope, but I bet it'd be close. I think a dial indicator extension would be tough.

I've done this a lot on snowmobiles, but admit I've never tried it on a flathead Ford.

Bruce, could you explain how that dial indicator set up would work?

[JSeery]

Anything soft enough to be used as a dead stop would work. A dead stop should be more accurate than a dial indicator. The trick is repeatable results, so it needs to be checked several times.

[cmbrucew]

Originally Posted by tubman

You might try an old snowmobiler's trick. Feed enough rope down through the spark plug hole to act as a piston stop. Turn the crankshaft both ways until it stops turning. Halfway between is TDC. You would have to be kinda careful not to vary the amount of rope in the cylinder and rock it back and forth several times to account for the compress-ability of the rope, but I bet it'd be close. I think a dial indicator extension would be tough.

I've done this a lot on snowmobiles, but admit I've never tried it on a flathead Ford.

Bruce, could you explain how that dial indicator set up would work?

You are correct, my bad. You know Chrysler industrial engines had a hole thru the head for that very purpose. Just remove the pipe plug and drop in a welding rod or whatever.
Bruce

[Binx]

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I like the zip tie method. Stick the buckle end in the bore and let it ride up the side of the bore until it hits the head. I think credit for this goes to Bruce Lancaster but the search function on this site is super crappy and getting worse all the time.

Lonnie

[flatjack9]

A dial indicator is not the best tool to determine TDC.

[37 Cab]

You can also make an adapter from and old spark plug that a hose will go on. Add a little oil and turn engine on compression stroke. Oil will travel up the hose and give a very accurate reading. Oh.. Use a clear hose.

[russcc]

Using a dial indicator, if possible, you would get a consistent, and accurate TDC in thousands of an inch by rotating the engine back and forth. The rest of methods I have seen and the ones suggested are not that accurate. Bruce, that was great question about how that dial indicator would be used with the cylinder head on.

[cas3]

i once welded a spark plug base full, then drilled a small hole thru it that fit a piece of rod bent to a 45 degree angle on one end. angled end would hit the piston, straight part slid up an down in the spark plug base with dial indicator on top. this was in a packard straight 8, but should work on the ford too i would think.

[tubman]

I vote for the "zip-tie method" (if it works); has anybody actually done it?

[JSeery]

Originally Posted by russcc

Using a dial indicator, if possible, you would get a consistent, and accurate TDC in thousands of an inch by rotating the engine back and forth. The rest of methods I have seen and the ones suggested are not that accurate. Bruce, that was great question about how that dial indicator would be used with the cylinder head on.

Just the other way around, a dead stop is the most accurate method of establishing TDC. But the real deciding factor is repeatability. You need to repeat the process several times until you come up consistent results. Any process that gives consistent results is accurate. Whichever method you use you do not want to attempt to check for TDC with the piston at the top of it's travel. It needs to be checked a few degrees before and after TDC. These positions are marked on the crank pulley and TDC is halfway between the two marks.

[estout81]

"Zip-tie method" works very well.

[JWL]

Actually there is/was a special dial indicator device made for our Flatheads. I'll look for mine and try to get a picture posted.

However, I agree with dead stop, repeatable, results as mentioned above.

[russcc]

John, that would be great if you could locate that dial indicator adaptor and post a photo. As a former machinist, making one would not be that tough, especially if someone has already come up with one. Thank you.