V6 TKS next cylinder TDC 60 or 120 rotation

[berlinbai]

Hi everyone,


I’m doing a leak-down test on a GM V6 Vortec (4.3L) and need some help understanding the manual’s instructions. The firing order is 1-6-5-4-3-2, and I’ve already found TDC on cylinder 1 during the compression stroke.


The manual says to rotate the crankshaft 60° per step in the firing order to bring each subsequent cylinder to TDC for testing. But isn't a V6 needs 120° of crank rotation for the net


Can someone clarify?
I can definately find TDC of each cylinder with a whistle but i want to learn the why.

 

[nola mike]

You've got 6 cylinders, not 3. The 4.3 has an offset crank to allow it to fire evenly over the 2 banks, so each is firing every 60'.

 

[berlinbai]

You've got 6 cylinders, not 3. The 4.3 has an offset crank to allow it to fire evenly over the 2 banks, so each is firing every 60'.

thank you!
but being a 4 stroke, 2Rev will give 1 spark per cylinder, 6cylinder thats 6 sparks, 720degree device by 6 isn't it 120 degree?
I'm so lost

 

[alldodge]

The manual has a misprint, it should be 120*

 

[nola mike]

thank you!
but being a 4 stroke, 2Rev will give 1 spark per cylinder, 6cylinder thats 6 sparks, 720degree device by 6 isn't it 120 degree?
I'm so lost

Yup, you're right. Coming to TDC every 60, firing every 120.