Too Dead Center tool

[Danny G]

Looking for recommendations.

I've seen some of these that have a plunger that goes up and down and others where you get a rough estimate then set a screw rotate one direction then the opposite and halfway between us TDC.

Any preferences?

[Gary Lewis]

I made a simple one by taking the porcelain out of a plug, tapping the hole through the middle, and running a carriage bolt in it along with a lock nut.  It isn't fancy but it works.

So I'd go with the simple one.  Yes, you have to rotate the engine back and forth and find the mid-point for TDC, but it isn't difficult.

[ArdWrknTrk]

That is how I do it Gary.
But dome the end of the bolt so you don't create a burr (hot spot) on the piston crown.
Then slip the wheel around until you get the same degrees either side of tdc.
I have to remember the alternator pulley trick!  😉


Let me see if I can dig mine out of the bottom of my *homemade and specialty tools* drawer....

Edit:

[Gary Lewis]

Jim - I put the carriage bolt in with the head hitting the piston.  But I may have had to turn the head of the carriage bolt down in the lathe to get it through the spark plug hole - I don't remember.

[ArdWrknTrk]

I realized this after I replied....

Facing either way, it accomplishes the same thing.

[Danny G]

I don't have anything to check TDC now but seems like either way is pretty close to the same method, and either are better then a thumb over the hole and feeling pressure to guess.

The stop works by stopping it in both directions and marking TDC.

The plunger you have to watch rise and fall and then mark TDC.

Maybe I'll try both lol.

[ArdWrknTrk]

No, there is a big flat spot (arc?) near tdc.
It's much more accurate to stop on the upswing either side, sum and divide.

[Gary Lewis]

ArdWrknTrk wrote

No, there is a big flat spot (arc?) near tdc.
It's much more accurate to stop on the upswing either side, sum and divide.

Yes!  Don't get too close to TDC.  Stop in the range of your balancer's marks, but as far out as you can.

[grumpin]

Here’s what I used on aircraft.

On a truck I’ve got it on compression stroke then use a pencil and as your moving the piston feel where it stops moving up and starts moving down split the difference and see where you are on the timing mark.

The tool for aircraft has a degree wheel to split the difference.

https://aircraft-tool.com/shop/detail.aspx?id=E25

[Ray Cecil]

grumpin wrote

Here’s what I used on aircraft.

On a truck I’ve got it on compression stroke then use a pencil and as your moving the piston feel where it stops moving up and starts moving down split the difference and see where you are on the timing mark.

The tool for aircraft has a degree wheel to split the difference.

https://aircraft-tool.com/shop/detail.aspx?id=E25

Ive never needed more than a pencil, stick or screwdriver to get close enough. I use my finger to feel for compression stroke.

[ArdWrknTrk]

Ray Cecil wrote

Ive never needed more than a pencil, stick or screwdriver to get close enough. I use my finger to feel for compression stroke.

Close enough for what?

It's certainly not "close enough" for setting cam or ignition timing.

[Ray Cecil]

Cam sprocket and crank sprocket only go on one way. Line the marks up and youve got the crank and cam synchronized. Get the #1 cylinder up near tdc, check the marks on the dampner. O degs there and you are at absolute TDC. drop the dizzy in with rotor facing the correct position. Hook up wires and plugs. Remove mechanical and vacuum advances. Start up engine. Throw the light on it and set base timing. Replace advance mechanisms. Your good to go. All you have to do is get the #1 cylinder "close" enough to get the engine fired up so you can throw the light on it. Ive never done anything else, or ever worried about the perfect timing before first start. Never had a problem get a otherwise healthy engine to run well with that procedure.

[FuzzFace2]

Ray Cecil wrote

Cam sprocket and crank sprocket only go on one way. Line the marks up and youve got the crank and cam synchronized. Get the #1 cylinder up near tdc, check the marks on the dampner. O degs there and you are at absolute TDC. drop the dizzy in with rotor facing the correct position. Hook up wires and plugs. Remove mechanical and vacuum advances. Start up engine. Throw the light on it and set base timing. Replace advance mechanisms. Your good to go. All you have to do is get the #1 cylinder "close" enough to get the engine fired up so you can throw the light on it. Ive never done anything else, or ever worried about the perfect timing before first start. Never had a problem get a otherwise healthy engine to run well with that procedure.

I am with you but .......
I can see their point also.
If the ring slipped on these old dampers when you put it on "O degs there and you are at absolute TDC" it may not be. That is where the piston stop comes into play to check of it slipped or not.
Also when deg a cam you have to be 100% sure of TDC and why the piston stop.

Ray, I have done it your way and never had issues with getting the motor to fire up.
Dave ----

[Ray Cecil]

Yeah, if you are degreeing a cam with an adjustable sprocket....I can see why you should check.

[ArdWrknTrk]

Or if you're looking to apply timing tape to the damper,
or if you're breaking in a new cam on an expensive engine,
you want to be ABSOLUTELY SURE that that timing is on the money.

Because if it's not, you don't have twenty minutes at 2,500 rpm to save it.

There are lots of reasons to do it right.
Look at the pictures Gary posted of Scott assembling Big Blue's shortblock.
If anyone could determine tdc by eye you'd think it would be someone who's won the Engine Masters...

But he uses a dial indicator and a degree wheel. (Held on with a alternator pulley)

[Ray Cecil]

Gotcha