The Stovebolt Site Forums The Shop Area The Electrical Bay Distributor Orientation

Working on getting my rebuilt engine and new distributor set up.

Curious about two things:

#1) What is the proper orientation or alignment of the distributor? (is the #1 cylinder position roughly 3 o'clock, where 12 o'clock is the fornt of the engine... or more like 2:30 or 3:30?)

#2) How will I know if I've got the distributor installed 180 degrees off?

Thanks!

If you mean, is the position of the number one cylinder roughly at 3:00 O'clock as your facing the engine bay from the front of the truck, then that is approximately where it is at on my 235. But really, what I would do is crank the engine to where it is at top dead center (TDC) on cylinder one, (maybe back it off a few degrees), scribe the position of the number one plug wire on the outside of the distributor, remove the cap, and adjust the distributor so that the rotor lines up with that scribe mark. The result should be that the rotor provides power to the number one plug when the number one cylinder is at TDC (or a few degrees advanced). This should be close enough to get the engine running. From there, you can adjust the timing using a timing light. I believe this should work, but you might want ot wait to hear from others as I am a relative newbie and self taught when it comes to auto repair.

I do I determine top dead center?

Can I do it with valve cover on?

Lumbergh your close except that it a 4 cycle motor. You need to be at TDC on the compression stroke. It's usually easier to do it with the valve cover off and watch the valves. After the exhaust has closed (not considering overlap) you are then on intake stroke, then compression stroke. You can pull the sparkplug and put your finger over the sparkplug hole and wait for it be blown off. Turn to the timing mark and put rotor on #1.
Larry

Did a search for TDC and found some good posts with enough information to get me going (or in more trouble)

Thanks for the help!

ok here we go,,,tdc is found turning engine over by hand or starter bring #1 to comp with plug out turn by hand until timing mark is in time as per book,,install dist with rotor at position you want for #1 or very close to it,,note vacum advance as rotor will turn into the advance,,if engine is installed and wiring installed retard dist by hand then advance until #1 plug fires do this with ing on you will be timed...doc

LGriffin,

Sorry, my post was incomplete. You address question #2, or how to avoid the problem of being 180 degrees off on the distributor. I found the second method you noted easier, myself. With the #1 spark plug out it is obvious when the #1 cylinder is in compression. I've never done it by pulling the valve cover and watching the valve positions. I've been told that it is easy to confuse which valve is open and which is closed (exhaust or intake). It also seems a lot easier to just remove the #1 spark plug and replace it than to remove the valve cover and reinstall it.

Be sure that the distributor shaft engages the oil pump. There are a couple of ways that the oil pump can be aligned with the distributor shaft after you have determined that number one is at TDC on compression stroke and where you want the number one plug wire to come out of the distributor. The first is to line up the rotor on the plug wire for number one and take a screwdriver and align the oil pump so the distributor shaft will drop in. The other is the same except you crank the engine over until the distributor drops in place.

Lumbergh, I've done worse. I neglected to say that you needed to watch the valves on #1. I've never been able to hold one finger on the sparkplug hole and crank the engine over with the other hand. I don't really watch for both valves to closed. I'm more concerned with the sequence. When the exhaust valve is closed, it's done with the exhaust cycle. The next stroke is intake. When the intake valve starts to close, I start looking for the timing mark on the crank pulley. If I have any question about how close the timing mark is I've got and old sparkplug that I've knocked the insulator out of and replaced with threaded rod. It's really what ever works for you, as long as you know the basics, then you arn't going to get hurt too bad. btw I just picked up a shop manual for 58 Chevy trucks. There is a real interesting section on how to check your motors power balance. All very logical just never thought about it. It's late I'd better quit before I screw up.
Larry

The normal position for number one is pointing away from the block, at near a ninety degree angle. To find the power stroke you should have the valve cover off. With the timing marks lined up, both valves on number one will have some clearance or slack and one of the valves on number six will have no clearance at all. With hydraulic lifters, you may have to watch them move as you rock the crankshaft back and forth. There will be movement on one of the number six valves but both valves on number one will be closed.

Pretty easy to do. Did you pull the distributor and lose (or never marked) your original orientation? If so, take the valve cover off. Using the crankshaft pulley, turn the engine clockwise and watch the intake and exhaust valves on #1 (front of engine) and #6 (rear of engine). Once you observe #6 intake and exhaust valves moving up and down in sequence with each other as you rotate the pulley clockwise AND you see that #1 valves are not moving at all, you are close to TDC. There will be about 5 or so degrees CW and CCW where the #6 valves are slightly moving. Move the pulley back and forth until you get more or less in between the point where the valves are showing to be closed. Then #1 is at TDC and you are not 180 degrees out. Regarding the distributor, you can start by observing the slot in the oil pump shaft and see where is is positioned. Rotate it with a long screwdriver to about the 1 and 7 o'clock position to start. Take the distributor in hand and with the rotor pointing at about the 8 o'clock position, insert the distributor into the block. As the distributor gear engages the camshaft drive gear, it will rotate slightly CCW towards the 6 o'clock position. If the pump slot is in the proper position, the tang of the distributor shaft will drop in and the distributor will seat fully into the block. If the slot is not in the correct position, move it slightly from the 1 and 7 o'clock position CCW or CW as required until the distributor fully seats. Always start insertion with the rotor at about the 8 o'clock position. You may have to do this several times. Be patient. As truckernix stated, the normal rotor position for #1 is at a 90 degree angle to the block facing the right fender. Hope this helps. Just did it to my rebuild after much searching.

49 geezer - This may be a stupid question, but why does it matter what direction the distributor is facing just so long as the plugs all fire in the right sequence and at the right time for each cylinder? When I pulled my distributor a month or so ago, I just put it back in (making sure that the oil pump was engaged) and set it up so that the #1 plug fires a few degrees before TDC on the #1 cylinder. The #1 position for the rotor is not facing the right fender, as a matter of fact I don't think that it was facing the fender when I pulled the disributor in the first place.

LGriffin - I also have a shop manual for the 58 Chevy Truck and read that section, but I don't think that I will be checking the balance of my engine any time soon.

Lumbergh, You're correct. The distributor doesn't give a crap where the rotor points as long as the #1 cylinder is at TDC (given the BTCD you are speaking of). It can point anywhere as long as you know that the rotor is indeed pointing at a terminal (any one) under the cap and that you install the plug wires in the correct firing order. I think that the only reason people care where the rotor point is that it give them some security during the reinstall. In addition, with the rotor pointing basically towards the fender, the vacuum advance port is towards the front of the engine and can be tubed correctly to the intake manifold.

The factory position for #1 is between 8 and 9 oclock. Other then looking like an amateur put it together, the position doesn't matter. I am not trying to be derogatory here, just honest.