I have the spark plugs out and the driver's side valve cover off to watch the valve springs/rocker arms. How do I verify that the #1 cylinder is at TDC?

 

As the intake valve starts to close, you are getting close to TDC. With your finger on the spark plug hole, turn the engine over. The compression will try to push your finger off as the piston approaches TDC. That will get you close enough to start looking for the line on the balancer.

 

Thanks! I'm off to the garage.

I think the harmonic balancer has rotated and is no longer lined up.

 

I rotated the engine until I felt the puff of air push my finger out of the #1 spark plug hole. At that point, the timing mark on the harmonic balancer is pointing to about 11 o'clock.

So, what is the correct way to re-align the timing mark on the harmonic balancer with the timing tab?

 

With a new balancer....

Chuck it in the trash or clean it up and use it for a frisbee.

Brett

 

Keep rotating till you get there, you are close...Use a wrench on the center balancer bolt.

 

Apparently flathead fords do not have timing marks so those guys have come up with many ways to accurately find TDC. One of the most popular seems to be to take an old spark plug, make a hole down the middle, attach a transparent hose and put the other end of the hose in a bottle of some kind of transparent oil (or water if you are very careful). As you crank the engine -- using a breaker bar on the the center bolt of the harmonic balancer -- the oil will bubble as the piston comes up and will start to suck oil into the hose as soon as it has past top dead center. To find exactly TDC, make a mark on the hose, go past TDC until the hose has sucked up the oil to the mark. Mark the harmonic balancer at that point. Crank the engine backwards. The piston will come back up, push the oil out of the tube, then start sucking it back up as you back up past TDC again. When the oil comes back up to the mark on the hose, mark your harmonic balancer again. TDC will be 1/2 way between the 2 marks you have made on the HB. If you use water, try not to let it suck it all the way into the cylinder.

Just this past weekend I did the spark plug with a hole in it and was able to verify by listening to the air coming out that the mark on my balancer was at least pretty darn close to TDC. You can probably do the same by just putting your finger over the spark plug hole if you can do that and turn the engine at the same time.

Oh yea, I'm sure you've figured this out already but it is much easier to turn the engine with all of the spark plugs out (at least as many as are easy to get to).

 

All the spark plugs are out to make this easier. I also removed the flex fan so I wouldn't cut my hand up.

When I feel the puff of air, that is really close to TDC, correct? At that point the mark on the harmonic balancer SHOULD be at 0 on the timing tab. With the distributor cap off, the rotor should be point at the #1 cylinder also, shouldn't it?

If all the above it true, my harmonic balancer has slipped and my distributor is off one tooth.

 

If you want to know exactly where TDC is, you need a screw-in piston stop available from speed shops like Jegs. It costs around $10 or so. You screw it in the spark plug hole and rotate the engine untill the piston hits the tool and the engine will not rotate further. Then put a mark on the balancer that lines up with the zero on the timing tab. Then rotate the engine in the opposite direction and stop again when the piston hits the tool. Mark the balancer again where it lines up with the zero on the timing tab. Now, exactly half way between the 2 marks you made is where the timing mark on the balancer needs to be. Chances are good that the factory indicator will be in the middle of those 2 marks you made. If yours is not there, you have a problem.

-Mark.

 

Screw a piston stop into the plug hole and bring the piston up turning it clock wise until it stops than put a mark at 0 on the harmonic balancer now turn it counter clock wise until it touches the stop again and put another mark on the harmonic balancer at 0 now find the center between the two marks and that is TDC.

Neal

 

Lars found TDC simply by sticking a socket extention into the spark plug hole and moving the piston gently until it jammed. Mark it, then back the other way and mark. Exactly similar to the piston stop, but no special tool required. Two person job though.

 

During the compression stroke, the piston should be pushing quite a bit of air out the spark plug hole as the piston comes up. Exactly when it stops pushing air is TDC.

The rotor should be a little past #1 at that point depending on how much advanced timing you actually have. It actually doesn't matter so much if the distributer is off by a tooth as long as it is rotated to get you the correct timing.

Using air and your finger will get you in the ballpark -- to get exact you will need to use one of the methods people have posted here.

 

Lars has this all explained here . . . found it from a previous post.

http://www.corvettefaq.com/listing.asp?group=1&sub=11

gonna have to meet this guy one of these days!

 

To find TDC I had this written down from Lars somewhere but here goes.
- the line on the harmonic balancer, line this up to 0 degrees on the your timing tab
- remover your distributor and check to see if the rotor is pointing to the no #1 cylinder, if it is you are at TDC for no #1 cylinder compression stroke.
- If the rotor is not pointing at the no #1 cyclinder then you are likely point at the no #6 cylinder. If this is the case then turn the engine one full rotation to have the line on the harmonic balancer line up to 0 degress on the timing tab again and the rotor pointing at the number one cylinder.

I also have the Haynes manual and they do have a page or to on how to determine TDC. Hope this helps

 

Basically, turn engine over till the straw stops rising-mark 1, then reverse it and turn it over till the straw stiops rising-mark 2. Then measure between the 2 marks and that is zero. Hopefully you will find an existing mark right there.

 

I used the tool from Eastwood to find TDC - Top Dead Center Indicator - it worked great and I didn't even have to take my valve covers off.

http://www.eastwoodco.com/shopping/p...emType=PRODUCT

 

Crane makes the best piston stop I have seen. I ordered one from Jeg's and it was a cheap import that I couldn't screw into the head without messing up the threads

 

Jam a bolt into the plug hole and crank the engine over until the piston rams up against the bolt. Make a mark on the balancer where this happened.

Next, reverse the polarity of the cables going to the battery to cause the engine to crank backwards until the piston again rams up against the bolt. Make a second mark on the balancer where this happended.

Next, divide the distance on the balancer between the two marks. This will be TDC.

Of course if you use this procedure, you'll have found TDC but will most probably have trashed your engine and burnt up some wires.

Of course I'm not serious. I agree with the above posts on the procedures they've suggested.

 

Uhm...you should use a socket wrench on the harmonic balancer bolt to turn it manually. You already have the spark plugs out. If you don't have a finger small enough to feel the intake valve (my pinky just barely touches it when it's open all the way), then remove the valve cover so you can watch the valves in the #1 cylinder. By hand...turn the engine until you see the intake valve open then close, next...use your pinky or insert a screwdriver part way into the spark plug hole...if you push it in all the way then you may damage the spark plug hole threads when the piston tries to reach the top. You want the screwdriver in the hole just enough so you can detect when the piston is moving up or down. Since the intake valve had just closed then the piston will be at the bottom of the intake stroke, so when the piston reaches the top of that stroke it will be at TDC. It's easy to turn the engine past the TDC, so you may have to back the engine off a bit to make sure you are perfectly lined up with TDC. At that point check your marks on the balancer. If they don't line up at this point then the key must have snapped on the balancer...you must remove the balancer, front cover, timing chain and gears, then replace the key...also go ahead and replace the timing gears and chain while you are at it...I think $30 or something like that for stock parts. If the key broke, then there could have been something that caused it...scares the heck out of me!

 

One of these may make it easier to find TDC. A lot cheaper than a new balancer.

http://www.jegs.com/cgi-bin/ncommerc...30&prmenbr=361

BigBlockk

Later.....