Timing issue

[zdude1967]

I hooked a timing light and with with the dist lined with the timing mark at the adjustment nut the crank pulley timing mark is not even close to the timing degree tab. If I remove the dist nut and crank it as far as it will go towards the drivers side the timing mark gets closer to the crank pulley and timing tab but still a good 1/2 inch away from the entire degree measurement tab. Whats the deal. It also seems to idle way too high. All the carb idle throttle speed screws, balance screws etc are backed out to the point they are not even touching anything but the rpms are 1200 to 1300. It does lower when the dist adjustment screw is removed and the dist turned all the way towards the drivers side as far as it will go. At this point it also backfires through the carbs. My poor sick Z and my less then needed Mr Goodwrench skills are not seeing eye to eye. Any thoughts

Thanks

[Zed Head]

Do you have the vacuum advance hooked up to full manifold vacuum instead of ported? That would give you an extra 10 - 18 degrees of advance at idle and increase your idle speed.

[JLPurcell]

History? Has this developed over time? Has engine been worked on recently? JLP

[lmcguffin]

I had a similar issue with timing when I got my 74 and found that the distributor drive shaft was not oriented with #1TDC. The PO had rigged the distributor adjustment clamp to compensate (also had to do with fitting a 240 dist on an F54 block). This can happen if the oil pump is removed and the shaft falls down and is not replaced in the correct orientation. Some other thoughts:

A digital timing light can determine the exact degree of timing when the pulley mark is off of the scale. This is good for checking total advance.

If they are SU carbs make sure that the chokes are off - could cause the high idle. I had some that were binding and the linkage would not pull them down.