Top Dead Center: How to determine?

monk302

Founding Member

Apr 18, 2001

742

2

16

New Jersey

Jun 29, 2006

#1

• Jun 29, 2006

• #1

Hey everyone,

Was wondering if you could all explain the best way to determine Top Dead Center (TDC) in my engine. I have a 302 with the older firing order. I believe that my #1 cylinder would be on the passenger side, closest to the radiator. If you could all help me out it would be appreciated.

Many thanks,

Mike

 

Shakin66

Founding Member

Jan 19, 2001

628

1

19

Waycross, Ga / Lake James, NC

Jun 29, 2006

#2

• Jun 29, 2006

• #2

You can wet a paper towel and stuff it into the spark plug hole and then jump across the solenoid. When that #1 cylinder (your correct, front passenger) comes up on TDC it will pop the paper out. While this is not going to be at exactly TDC I then shine a flashlight down and use a 15/16" socket on the crankshaft/harmonic balancer bolt to roll it back & forth.

 

D

D.Hearne

New Member

Sep 29, 2000

11,730

6

0

south louisiana

Jun 29, 2006

#3

• Jun 29, 2006

• #3

Better yet stick a wood dowel down the plug hole and rotate the crank. This won't get it exactly on TDC because of the relatively long dwell time of the piston at the top of the stroke, but it'll be close. You can fine tune it some by judging TDC from the movement of the dowel up, til the point it starts back down, by moving the crank back and forth.

 

SoCalCruising

Founding Member

Jul 25, 2000

2,437

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47

SoCal

Jun 29, 2006

#4

• Jun 29, 2006

• #4

If you want TDC power stroke: mark on dist. body the position of #1 plug wire; remove dist. cap and rotate engine until rotor is pointing toward #1 plug wire mark on body of dist. (the one you made). You are now close to TDC, power stroke. Use D.Hearne method of placing sm. dia. dowel or screw driver (Phillips) inhto spark plug hole; rotate damper (using ratchet or breaker bar on damper bolt) until you feel piston is at TDC. This all assumes that you cannot find TDC on your damper, or do not trust the damper marking, and want to use another method.

 

monk302

Founding Member

Apr 18, 2001

742

2

16

New Jersey

Jun 30, 2006

#5

• Jun 30, 2006

• #5

Alright, so what if I have the distributor out and the engine currently is not running? I am doing the Stock Ford Mustang Mass Air EFI conversion. so I want to find TDC then line up my distributor correctly.

Thanks,

Mike

 

A67StangMaster

New Member

May 4, 2005

401

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0

San Jose CA

Jun 30, 2006

#6

• Jun 30, 2006

• #6

I just put a screw driver in the spark plug hole and turn it over untill it reaches the top. works for me.

 

B

BillyD65

New Member

Jan 31, 2006

4

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0

Mesa, Arizona

Jun 30, 2006

#7

• Jun 30, 2006

• #7

Use the paper towel method or get a friend to put their thumb over the #1 sparkplug hole while you bump the starter. You can feel the compression as the piston comes to TDC. Fine tune it with a 15/16 socket by aligning the timing mark. The dowel method will tell you TDC but not whether you are on the compression or exhaust stroke. You need to be on the compression stroke. Point the roter at # terminal on the dist.
Bill

 

ozstang65

Founding Member

Jul 13, 2002

313

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Queensland, Australia

Jul 4, 2006

#8

• Jul 4, 2006

• #8

You can do this with either the head on or off. You need to get something solid to stick down into the bore. Either weld an extension onto a spark plug or rig up a bolt on a piece of angle to bolt across the bore if your heads are off.

The stopper doesn't have to go far down into the bore, just enough to stop the piston from reaching TDC.

When the stopper is in place turn the engine one way until it stops and mark where the balancer TDC mark is on the on the casing. Turn the engine the other way and mark where it stops. TDC is halfway between the 2 marks.

This is by far the most accurate way to find TDC. I learnt this from my Crane Cams installation procedure.

This is for determining crank TDC and is totally independant of inlet or outlet stroke.

 

2nd Mustang

Founding Member

Feb 24, 2002

2,488

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46

Southern California

Jul 4, 2006

#9

• Jul 4, 2006

• #9

I also use a stick down the spark plub hole. Call me anal, but I go one step further and pull the valve covers just to make sure both rocker arms are level on the compression stroke.

 

Max Power

Active Member

Jul 31, 2003

1,774

1

36

St Paul

Jul 4, 2006

#10

• Jul 4, 2006

• #10

ozstang65 said:

The stopper doesn't have to go far down into the bore, just enough to stop the piston from reaching TDC.

When the stopper is in place turn the engine one way until it stops and mark where the balancer TDC mark is on the on the casing. Turn the engine the other way and mark where it stops. TDC is halfway between the 2 marks.

This is by far the most accurate way to find TDC. I learnt this from my Crane Cams installation procedure.

Click to expand...

If you doubt the markings on your harmonic, this is the only accurate way to determine exact TDC with the heads on.

If you are trusting your harmonic, you can just put your thumb over the #1 spark plug hole and feel for compression, then rotate by hand to get to the TDC mark on the harmonic. You can bump the motor over yourself using a screwdriver over the starter solonoid to the I terminal, or if you plan on keeping a vintage Ford for the long haul, get a remote starter switch from Summit or Jegs for about $11. You will use it often over the years.

With the head off, use a dial indicator.

 

K

kEITH m.bARROW

New Member

Jul 5, 2006

3

0

0

Jul 5, 2006

#11

• Jul 5, 2006

• #11

PENCIL TRICK

tAKE THE PLUG OUT OF THE #1 CYC.
pUT A PENCIL IN UNTIL IT TOUCHES THE PISTON, TURN THE CRANK AND WHEN THE PENCIL IS AT THE SHORTEST YOU ARE THERE.