[jimbo68]

Happy Holidays,

I have a quick question is regards to the correct location to place the two marks on the harmonic balancer when performing the TDC test. I bought TDC tool from summit have all the plugs pulled, valve cover off and on the #1 compression stroke (up). Even pulled the dist cap to ensure rotor is pointing at #1.

I read bring the piston up until it stops then mark the balancer? Where does this mark get placed? Is this where the (0) mark on the timing tab stops on the balancer? Then rotate the motor backwards 180 until it stops again and mark where the (0) shows on the balancer mark again. Then divide the distance between both marks and assume this is TDC?

The car is 68 Camaro with a 6 3/4 balancer has the straight keyway to TDC line on the outer ring at the 2:30 o’clock position- or 2º before. Thanks as always!:thumbsup:

 

[jimbo68]

Thanks Mike!

When it stops I assume the original TDC cut in the balancer will stop somewhere between the tabs ends. But I need to use the tab as the marking point correct.

 

[jimbo68]

Mike,

Sorry for the late response. I was out in the garage and wife is upset not in the house with the company! I will mark the balancer with dots of white paint as mentioned, but where on the balancer do reference to place the marks on the balancer. I was thinking it would be the timing tab location since it has 14 degrees before and after TDC. I guess this only makes sense when I think about it?

Makes no sense to place anywhere else!

 

[jimbo68]

Thanks Steps!

I will do this first thing in the morning. Thanks for the step by step info. By the way what time is it in New Zealand now?

 

[jimbo68]

Thanks Fred!
I actually purchased the piston stop from Summit a while back and will try your recommendation. I have the distributor cap off to verify #1 in use and the battery is disconnected. I will ensure the first mark is made on the compression stroke up (mark balancer) and tab if applicable (possible).

Then click the the rachet and reverse direction until the piston cycles again and stops (mark balancer) and measure for exact center between lines.

It's an original unit (40+) years and the way I drive it I am not expecting perfection. It a pre-69 unit with a straight key way to TBD mark (-02) degrees offset at a 2:30 setup as best I can tell. I have looked all over Summit and Jegs and cannot locate a decent replacement except for the damper doctor site, but it looks to be OE and wanted something a little more stout? Any idea's?

 

[jimbo68]

Steps,
Actually tried your suggestion sent last night with a thin blade screw driver as suggested holding the blade level and when the piston engaged the blade felt it climbing up until the screw driver was at a 45 degree angle (handle) aiming down and blade aiming up into the cyclinder.

I have in old school terms (pop up) pistons that had to be fly cut for the larger valves I used and I am just not 100% sure since the driver went past the level mark to 45 degree angle that the blade was just to far in it may hit the pop up and give me a false reading.

I need to just have the stop go in about 3/4 inch into avoid touching the pop ups? I would assume if the stop was in there and hit the piston incorrectly and stops to soon it could give a me a false reading? This is why I will test both ways and compare data.

 

[jimbo68]

Thanks all for all the different suggestions. Both solutions were valid approaches based on skill level and repeated attempts. I first got a good idea on where TDC was based on Steps method and determined the existing TDC line on the harmonic was off. I guess at 42 years old we all would be a little off!

Too fine tune the exact location I next used the piston stop and marked the balancer as noted. After measuring the mid point between both marks the original TDC mark was approx 10 to 12 degrees off!

I have since remarked the new TDC and have a new MSD timing tape on order as an interim fix and plan to order a new balancer soon.

Again thanks to all who provided input! :thumbsup: