I currently have my Olds 455 open to change the timing chain. I brought the #1 piston to TDC but the camshaft pin is at the 6 o'clock position. The cam pin hole in my new timing chain gear is at the 12 o' clock position when I align the dot with crank gear dot.


Will it be an issue if I turn the camshaft so the cam dowel pin is aligned with the new timing chain gear hole? Or will I have to change the camshaft as well?

 

Chebby engines are at TDC#1 when the two dots are next to one another.

Olds engines are at TDC#1 when the dots on both the cam and the crank sprockets are at 12:00 (straight up).

- Eric

 

Thanks Eric I will turn the timing gear dot to the 12 o'clock position. I already turned the crank to try and align the dots together will it be a problem if I turn back were it was?

 

No, just make sure that the rotor is in the right position when you try to start it, or coche no va, as they say south of the border.

- Eric

 

Well, technically the gears will both be at 12 o'clock half the time, and the cam gear at 6 o'clock half the time. Whether "TDC" is defined as when the piston is at the top of the compression stroke only, or also when it's at the top of the exhaust stroke as well, is the question here.

 

There's no question - TDC is defined as ANYTIME the piston is at the top of it's stroke. That's why you need to specify TDC on the compression stroke or TDC on the exhaust stroke.

 

Gotcha. Then installing the timing chain either way is fine, just means you might have to realign your distributor.

 

Or rotate the crank one revolution...

 

That too. It's important that people understand the relationship between the different parts, though.