How To Find TDC the ‘Easy’ Way

[EricTheCarGuy]

There are a lot of uses for a vacuum gauge but this one is seldom used. I think it’s a neat trick.

Topic

[Agustin Alfonso Cesar Charles]

Eric, do most engines/car parts get so rusty? I mean (from me that I live down SouthAmerica( is the first time I see an engine like that; maybe body panels but not the engine itself, that’s rough.

[Doug Haas]

Eric,
I appreciate the Subaru videos. I have 3 now, and tips like this are very much appreciated because the usual techniques often don’t work well with the boxer engines.

I have one question for you: Wouldn’t TDC be achieved when the pressure was at it’s maximum positive pressure instead of when it goes from positive to negative?

[W00DBar0n]

[quote=”djhcolorado” post=44284]Eric,
I appreciate the Subaru videos. I have 3 now, and tips like this are very much appreciated because the usual techniques often don’t work well with the boxer engines.

I have one question for you: Wouldn’t TDC be achieved when the pressure was at it’s maximum positive pressure instead of when it goes from positive to negative?[/quote]Yes, but once you pass it pressure drops right off, why he went back and forth till he got zero.

I did this on an 289 small block engine a few years ago, the timing marks were damaged so we had to find tdc another way, this happened to be the way. We also did it with a depth gauge, but you can’t tell if you are on compression or exhaust stoke.

[EricTheCarGuy]

[quote=”CarDoog” post=44278]Eric, do most engines/car parts get so rusty? I mean (from me that I live down SouthAmerica( is the first time I see an engine like that; maybe body panels but not the engine itself, that’s rough.[/quote]

Yea, there’s plenty of rust in this neck of the woods. It makes for some challenging repairs sometimes.

[EricTheCarGuy]

[quote=”djhcolorado” post=44284]Eric,
I appreciate the Subaru videos. I have 3 now, and tips like this are very much appreciated because the usual techniques often don’t work well with the boxer engines.

I have one question for you: Wouldn’t TDC be achieved when the pressure was at it’s maximum positive pressure instead of when it goes from positive to negative?[/quote]

As soon as the cylinder reaches TDC it starts to move downward thus creating a vacuum. This is the point I try to show in the video to indicate where TDC would be.

[college man]

That was a nice tip.Your a tricky guy. 🙂

[cbriden]

I had a spark plug blow out on my 5.4L Triton motor and I went through a procedure to find the top dead center of cylinder #4. I needed the valves closed so I could drill out the hole and install the Timesert thread repair insert.

This TDC procedure is so easy, but I would not have thought of it in a thousand years on my own. I had a duhhh moment… I really did it the hard way & was never absolutely sure where the piston was precisely.

Really great video.

[Michele Pensotti]

Nice trick Eric!

I didn’t know there were these gauges which measure both pressure and vacuum, they are very useful indeed.
It seems in every video I watch I discover a new useful tool to do new interesting and useful things!

And thanks for also linking the leakdown test video, very very interesting too!
I would not have imagined an engine’s compression was so…evanescent, I mean, I would have thougth the piston rings would hold the pressure a little better…and instead it escapes fairly quickly!

Wow!

Thanks for all the learning experience you give us Eric! :woohoo:

Live long and prosper (and stay dirty!)

10nico

[Author]

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