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Motor is a 5.7l tpi 350 chevy motor swapped from a 1990 Firebird. My vehicle is a 75 chevy truck.
Heres the story:
-Mixed up order of spark plugs. All except 1.
-Rewired them based off that one wire using a diagram of my firing order i found online.Concerns:
Motor runs fine just skeptical about
1) the accuracy of the online diagram I found.
2) how the last owner installed the distributor.
(since i rewired them based off what he did and I dont want to rely on his work)
Im concerned about 2) for one because he numbered the wires with some weird cross hatched order (by that I mean number 1 wire was diagonal from 2 and 3 and etc.) and two to be honest most of the work he done on the truck was pretty sketchy.I dont even know what brand it is but anyways the first clue I have so far is there is a little line molded into the distributor cap pointing towards the driver side fender.
My question is how do I determine the TRUE orientation of the distributor.
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Replies
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#1 on the distributor, if it is properly installed on the engine, should be at ~ 5 O’clock position.
You need to find Top Dead Center (TDC) of the #1 piston when both valves are closed (Not TDC overlap).
Usually easiest way is just remove #1 spark plug and place a finger over the spark plug hole while bumping the starter.
When the piston is moving to TDC after intake closing, the pressure will blow past your finger.
Check the harmonic balancer and move the engine crank position to be about 10-degrees before TDC.
Remove the distributor cap, and the spark plug tower that the rotor is pointing to is the #1 spark plug wire position.
If you want to reorient the distributor so the rotor is pointing at a different cap tower, you need to remove the distributor, and re-position where the dist gear meshes with the cam gear. Then you may have to rotate the engine to get the distributor to engage the oil pump drive.
Anyhow, once you have the rotor pointing at the tower you want, and you are at around 10 degrees before TDC, slightly rotate the distributor to align the magnetic pickup with the point of the reluctor, this will get the timing close so the engine will start.
Route the remainder of the spark plug wires using the established #1 position.
Remember to put the #1 spark plug back in the engine.
Most domestic V-8 firing orders are 1-8-4-3-6-5-7-2. For some reason FORD numbered their cylinders front to back on each bank, but if you layout the cylinder numbering like above (side to side) then you end up with the same firing order. There are exceptions like the GM LS that has 4/7 firing order swap, and the Buick Nailhead, and a few others.[quote=”451Mopar” post=179591]You need to find Top Dead Center (TDC) of the #1 piston when both valves are closed (Not TDC overlap).
Usually easiest way is just remove #1 spark plug and place a finger over the spark plug hole while bumping the starter.
When the piston is moving to TDC after intake closing, the pressure will blow past your finger.
Check the harmonic balancer and move the engine crank position to be about 10-degrees before TDC.
Remove the distributor cap, and the spark plug tower that the rotor is pointing to is the #1 spark plug wire position.
If you want to reorient the distributor so the rotor is pointing at a different cap tower, you need to remove the distributor, and re-position where the dist gear meshes with the cam gear. Then you may have to rotate the engine to get the distributor to engage the oil pump drive.
Anyhow, once you have the rotor pointing at the tower you want, and you are at around 10 degrees before TDC, slightly rotate the distributor to align the magnetic pickup with the point of the reluctor, this will get the timing close so the engine will start.
Route the remainder of the spark plug wires using the established #1 position.
Remember to put the #1 spark plug back in the engine.
Most domestic V-8 firing orders are 1-8-4-3-6-5-7-2. For some reason FORD numbered their cylinders front to back on each bank, but if you layout the cylinder numbering like above (side to side) then you end up with the same firing order. There are exceptions like the GM LS that has 4/7 firing order swap, and the Buick Nailhead, and a few others.[/quote]thanks so let me see if im understanding you correctly.
Crank the engine till 10deg pass tdc . At this position the rotor in the distributor will be pointing at 1?
what does the rotor look like? will it be obvious what its pointing at?Thats 10-degrees BEFORE TDC, and the only importance is so you can rough set the ignition timing so the engine starts easely after moving the distributor.
The disrtibutor rotor is under the cap, and has a brass tang that directs the ignition energy from the center (coil) terminal to each spark plug terminal.
At #1 TDC is will be pointing at a terminal which should be connected to the #1 spark plug wire.
Side note: Because of rotor to cap phasing, with the spark normally occuring 10-40 degrees before TDC, you would want to check the rotor pointing to the terminal somewhere in this area, not after TDC.
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