Distributor/Timing question?
Thread Starter
Intermediate
Joined: Oct 2006
Posts: 27
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From: Upstate South Carolina
Distributor/Timing question?
I'm replacing the intake and carburetor on my 78 350 with new edelbrock parts. I've also decided to change the distributor (going with a mallory). Before removing the distributor I attempted to set the engine to top dead center #1. The marks on the damper line up, but the distributor is 180 degrees out. The rotor should be pointing to the #1 spark plug wire, but it's not. The engine ran before I started to tear it apart. Should it have ran? Am I missing something?
Race Director
Joined: Jun 2000
Posts: 10,043
Likes: 674
From: FL
OK, you are at TDC for #6. Remember, the camshaft and distributor turn at 1/2 the speed of the crankshaft. So, the crank turns twice for every rotation of the distributor.
You can do two things:
1) If the old distributor is still in the car, make a mark on the firewall where the rotor lines up. DO NOT MOVE THE CRANK. Drop the new distributor in so its rotor lines up with the same mark. That should get you close enough to start the engine and set the timing.
2) If you have already pulled the dist and no longer have a reference mark, put a wrench on the balancer and rotate the crank ONCE. You will know be at TDC on #1. (You can confirm this by pulling the valve covers and seeing that the valves on #1 are closed and those on #6 are partially open). Then, turn the crank back a little so the timimg mark is at about 8-10 degrees before TDC. Now, this is where you want #1 to fire. So, drop the distributor in and rotate it so the the rotor is pointing at the #1 terminal on the cap. You may need to take the cap on and off a few times to get it close. It should be close enough to start and you set the timing from there.
Hope this helps.
You can do two things:
1) If the old distributor is still in the car, make a mark on the firewall where the rotor lines up. DO NOT MOVE THE CRANK. Drop the new distributor in so its rotor lines up with the same mark. That should get you close enough to start the engine and set the timing.
2) If you have already pulled the dist and no longer have a reference mark, put a wrench on the balancer and rotate the crank ONCE. You will know be at TDC on #1. (You can confirm this by pulling the valve covers and seeing that the valves on #1 are closed and those on #6 are partially open). Then, turn the crank back a little so the timimg mark is at about 8-10 degrees before TDC. Now, this is where you want #1 to fire. So, drop the distributor in and rotate it so the the rotor is pointing at the #1 terminal on the cap. You may need to take the cap on and off a few times to get it close. It should be close enough to start and you set the timing from there.
Hope this helps.
Last edited by SteveG75; Oct 17, 2006 at 01:15 PM.
Tech Contributor
Joined: Aug 1999
Posts: 14,377
Likes: 6,377
From: At my Bar drinking and wrenching in Lafayette Colorado
Originally Posted by 78vettespender
The marks on the damper line up, but the distributor is 180 degrees out. The rotor should be pointing to the #1 spark plug wire, but it's not. The engine ran before I started to tear it apart. Should it have ran? Am I missing something?
Racer
Joined: Aug 2006
Posts: 330
Likes: 3
From: Wellington, New Zealand
Valve timing TDC and ignition timing TDC are as you have found out 180 degrees apart. Spin the crank 1 full turn and bring to TDC again and you will find the rotor will be pointing to number 1 cylinder pin on the distributor cap, you are now good to go on the removal. Mark rotor position to distributor body before and after you pluck it, as it rotates as you pull it up.
