78TA HEI Distributor - Which way around?

[Steve B]

Hi all

To make a long story short, does anyone know which way around the HEI distributor should go on a 78TA L78 400?

The 78 service manual shows the vacuum advance pointing passenger side, yet the 78 parts catalog has it pointing driver side (see attached images).

Problem with it pointing passenger side is that it now fouls the heater hose connection on the cylinder head, but because my heads are earlier heads I'm not sure if this is why. But seems odd that two official Pontiac documents differ, which still leaves the question open.

Difficult to find any reliable images on the internet or YouTube, as usually obscured by other parts.

Hoping to find a consensus from a few owners just to be sure either way, all help will be very much appreciated.

Thanks
Steve

[bhm1712]

It has a nasty habit of fouling the heater hose, mine used to be the same.

It doesn’t actually matter where it points as long as the actual ignition timing is set correctly. I removed my distributor and set everything so that the vac advance was pointing towards the firewall or straight back at the 12 o’clock position if you like.

As long as the rotor arm is over the number 1 spark lead post when it should be, all will be well with it. You can fine tune afterwards with a strobe lamp.

[Steve B]

Thanks Ian, yes, I think I'll switch it back around.

My feeling now is that the service manual illustration where it's pointing the other way is intended more for the 301, where the cylinder head would be in a different position.

[bhm1712]

I had a 301 too, and it was the same situation with that. The blocks are the same, just a shorter deck height, but not short enough to stop that issue.