Jump to content
Sign in to follow this  
luke240ZED

TDC - Is this Top Dead Centre

Recommended Posts

With the timing markings here and on the compression stroke and my dizzy rotor here.

 

005-3.jpg

 

Is this where I need to be for TDC?

 

Cheers

Luke

Share this post


Link to post
Share on other sites

They swap the leads around to suit. To get it back where it should be you remove the oil pump, remove oil pump drive and turn around 180. It's been documented on here in another thread.

Share this post


Link to post
Share on other sites

LOL.

I always laugh when someone says "the dizzy is 180* out."

 

While it may be common to have the #1 spark plug lead in a certain location, you can in essence have it placed anywhere around the circle of the dizzy cap, as long as the rotor also starts the firing order from the same point.

 

Something else to think about, is that the crank turns twice for every rotation of the cam, AND the dizzy, so you may actually be at TDC of the exhaust stroke (just as the exhaust valve closes and the intake valve opens). The best way to verify this is to remove the cam cover and make sure both valves are closed. Alternatively, you can remove the spark plug, and bump the engine over with your thumb over the hole feeling for compression, as it does build compression, this would be TDC of the compression stroke, and you can then finish turning it to TDC, of the compression stroke by hand.

Share this post


Link to post
Share on other sites

 

 

            For what its worth, if the dissy has been pulled apart & the upper section has been put back 180 dgrs out you will also have this problem.

           

            Stands to reason that  if the bottom of the motor hasn't been touched then it  has to be the dissy.

     

            Might also mention that if you fit a 280z elctrnc dissy you also have to use the 280 base plate otherwise timing will be out.

 

            Am easier way to find TDC without to much hassle is to remove the #1 spark plug then rotate motor so that timing mark lines up & relevant   

            piston is at the top of stroke you can use a torch to visualize or a  long screw driver  thru the plug hole.                         

                           

                                                                        Regards: Alan.

Share this post


Link to post
Share on other sites

An easier way to find TDC without to much hassle is to remove the #1 spark plug then rotate motor so that timing mark lines up & relevant   

piston is at the top of stroke you can use a torch to visualize or a  long screw driver  thru the plug hole.                         

                           

                                                                        Regards: Alan.

 

 

Something else to think about, is that the crank turns twice for every rotation of the cam, AND the dizzy, so you may actually be at TDC of the exhaust stroke (just as the exhaust valve closes and the intake valve opens). The best way to verify this is to remove the cam cover and make sure both valves are closed. Alternatively, you can remove the spark plug, and bump the engine over with your thumb over the hole feeling for compression, as it does build compression, this would be TDC of the compression stroke, and you can then finish turning it to TDC, of the compression stroke by hand.

 

As six shooter just pointed out, the crankshaft rotates twice for every single rotation of the cam AND the dizzy.

While you can remove the plug and see the piston reaching the top (or use a soft probe to feel it)

It'll only tell you that the crank is at top dead centre, not whether its TDC compression, or TDC exhaust, which are 180 degrees apart from one another on the cam and dizzy.

Share this post


Link to post
Share on other sites

Best to get a small torch and check both cam lobes for #1 cylinder are making a "V". both pointy ends pointing up. There is also a small mark on the distributor body showing number 1 position. Between the cap and body.

Share this post


Link to post
Share on other sites
LOL. I always laugh when someone says "the dizzy is 180* out."

 

While it may be common to have the #1 spark plug lead in a certain location, you can in essence have it placed anywhere around the circle of the dizzy cap, as long as the rotor also starts the firing order from the same point.

This man speaks the truth. The leads do not have to in the exact position (for example, #1 doesnt have to be at 3oclock), you just have to have the leads on the correct post for the particular position of the crank. So dont bother disassembling anything, just put the leads on to suit.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×