How To Find TDC The 'Easy' Way -EricTheCarGuy

Here's another great use for your vacuum gauge. If you're trying to find TDC (Top Dead Center) compression stroke say for a leak down test, this is an 'easy' way to do that. Also, if you are doing a leak down test you're already set up to do the test once you find TDC. This method could save you quite a bit of time. Just be sure to use a gauge that's capable of reading pressure as well as vacuum or this method won't work. Here's a link to a video on how to perform that leak down test should you need that information.

Stay Dirty

ETCG

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[oldschoolchevy]

This is the same method I use just remove the guage and zip tie a balloon to the end of the hose. You'll for sure know which one is the compression as it'll blow the balloon up almost the size of a 3-4" PVC pipe with a single turn of ur ratchet. Love the videos Eric! U sir have saved the day for me on numerous occasions. After watching my first video of urs I subscribed instantly and literally have found myself on more than 1 occasion coming on here & hunting for ur videos on parts I already know about or how to remove just to see your methods and techniques on how to do it! To me that says a lot about a mechanic! I'd let u work on ANY of my vehicles with the upmost confidence! Keep up the awesome work plz!

[robertclymer]

I know this video is over 7 yrs old, BUT FINALLY a super easy understanding way to find TDC. Those videos with the piston stops, balloons, screwdriver, wood dowels, plastic straws in the spark plug hole were confusing and not very accurate. Thanks Eric, glad I found this video.

[kurtiscalmsetccdwell]

I love finding TDC this way. I dont do it often but when I need to I always look for this video because I always need the quick refresher.

[Chubbypickletickler]

This is a great way to find TDC on a particular cylinder.  For those saying use your thumb or finger and wait for compression to push your digit off, that's great too.  Assuming you can reach it.  I have both gauges but never used them in this manner as a shade tree guy.  I'm working on doing a Timesert insert for a blown sparkplug on my nephews V10 powered Excursion.  Try reaching a rear spark plug hole with one arm and rotating the crank with your other.  No easy task.  Especially as his has 8" of lift and 35" tires.  The hood is at my shoulder and I'm 6-4.  Regardless this worked great as I need the piston on #9 at TDC to cut new threads and install the insert.  Thanks for this.  Always learning, always going farther.

[project]

This was a huge help. Thank you! Grabbed a $14 fuel pressure/vacuumed gauge from Harbor freight, worked perfect and came with connections for the spark plug hole.

[RevDogg]

This worked perfectly on a '98 Chevy 350 Vortec. Needed to replace a distributor that had broken it's plastic base and jumped timing while trying to start on a -33 degree F morning. Being out in that cold, and with 20+mph wind for this, I was really trying to find a way to save time and avoid tearing everything out to see the harmonic balancer...

Thanks for the GREAT tip!


PS: To all those who mention having these tools laying around or not and whatnot.. I didn't have either the vacuum gauge or the compression tester already. Spent 60 bucks for both. ( Could have gone much cheaper on the comp tester, but I'll use everything again, and it's been on my purchase list for a while.) In my situation, that $60 was well worth my time and agony saved.

[MudRFunR]

Great tip, Eric! It's guys like you that keep guys like me informed to be able to accurately share what we learn, in our own way. Thanks for sharing!

[dancroteau]

Works great, and pretty accurate. As long as the gauge moves in one direction or the other the cylinder is on the compression stroke otherwise it cannot since one or the other valves will be open. Going back and forth slowly until you find the point were the gauge doesn't move and that's TDC. I checked this method with a piston stop and the difference was unmeasurable.
Very helpful not to have to remove a valve cover to observe the rockers to confirm your on the compression stroke and find TDC.

[ericthecarguy]

That's a great idea and better than the 'screwdriver' method I've shown in the past. Just make sure you clean it off before you put it back in the engine. This method is great if you're already doing a leak down test as the hose is already in the cylinder and ready for compressed air.

[tomslover]

Mucho thanks. Saved me sooo much work as I am working on a BBC (454) in a motorhome with poor access to everything! You are the man! ❤👍

[APrintmaker]

Thank you for posting this video. I needed to find the beginning of the compression stroke in order to install a Time-sert spark plug thread repair. Having the gauge hanging next to me under the vehicle while I turned the crankshaft worked well.

[TriodeLuvr]

I like Dave Farden's idea (below) to just use a hose without a gauge and put the end in your mouth. In my case, I only need to get each piston to the approximate top consecutively in order to replace valve seals (small block chevy). Both rocker arms will be removed before I position each piston, so it doesn't even matter which stroke it's on. Anyway, thanks for the video, it was a big help. I've used a dial indicator in the past to confrim accuracy of TDC on no. 1, but it's a huge PITA. Your method is much easier and quicker for what I need to do.

[tpk]

for the shade tree mechanic you can put a balloon on end when inflated tdc, if you pass it deflated

[dextermorgan]

The most accurate way of finding TDC that I have found is to do as Eric has done and then to fine tune it, push on some clear tubing and allow it to droop in a "U" shape. Put a little liquid into the tube and then work the crankshaft back and forth a bit. The liquid will move in the tubing up and down on each side. The point at which it changes directions is exactly TDC.

[travisvossler]

Got to say for someone who has talked down on this channel this is a great video

[edgrrickett]

Wow bro that is a great tip on how to get to TDC easily! Thank you I have the 30.00 timing light from hobofright gonna get me a 14.00 vacuum pressure tester and Im set!

[chuckcregger]

Dude, I've been around gearheads for awhile, never seen it before. Real Cool.

[switchest]

So let me get this right...( pencil in mouth, wondrous look)

I need:-
Compression gauge and hose to suit..
Manufacturer relative, hose to cylinder block adapter ( spark plug hole bit)
Vacuum gauge with PSI and vacuum markings
Schrader valve remover
Reduced ID vacuum hose
Socket and ratchet/strong arm for crank
The love of Christ

Is that right?

[ericthecarguy]

How are you going to find marks for more than just #1 cylinder?

[freddievilla]

Tks 🙂🙂🙂🙂🙂🙂🙂. I don’t know if I’m learning disabled but had to watch a lot of videos until I finally understood with your video. Tks