sancho

First off, I know that the oil pump shaft has to be positioned correctly before anything. My engine rebuild book is telling me that it should be positioned so that the shaft points to the #7 intake valve (or roughly 10:00), so I've done that.

The #1 cylinder is also exactly at TDC (hopefully it has stayed there since I lined up the dots on my new timing chain...).

So, here's what I'm wondering: is this exactly (or very close to)the point where #1 will fire?

I'm wondering because, if that's the case, then I can theoretically choose wherever I want the rotor to be, as long as I have a terminal on the dissy cap that will be across from it.

Thanks

SMasterson

If the dots on the timing chain are still lined up (cam at 6, crank at 12) then cylinder #6 will be the terminal the rotor should point to.

This is why some people get 180° off on the distributor when installing a new chain, cam, etc.

When both dots are at 12 o'clock then the camshaft is in position for #1 to fire (compression stroke).

Rotate the crank 360° and align it to fire #1 or set it to fire #6. You can have your wires anywhere you want on the distributor as long as they go to the correct spark plug, in the correct sequence, and the rotor is in time with the camshaft/cylinder compression stoke.

Vader

Sancho,

As long as both of the valves are closed in the #1 cylinder, you're at the firing position for #1.

As for the pump drive shaft position, you'll have to check that. Aftermarket distributor drive gears usually pin to the distributor shaft in the correct position, but it would be a good idea to verify that. Set the rotor position to wherever you want, then check the oil pump drive pin position. It should be pointed out that the stock position for the distributor is calculated to place the rotor contact near the center of the pole piece in the cap at the correct timing position. Setting the rotor at other positions can create problems, since it can alter the relationship between the signal point of the pickup coil and the rotor position.

To elaborate, many drive gears have 13 teeth. This means that each tooth is spaced at about 27.7° of rotation. Each breaker point or pickup coil firing interval is spaced at 45° apart.

Because of this, installing the distributor one tooth off the design position will skew the relationship between the distributor contacts and the pickup/points by 17° - or partway between the correct pole in the distributor cap and the wrong one. Installing it two teeth off the specified position would be closer, but still off by about 10.4°. It gets worse as you go around the circle. At 180° out, the rotor contacts are still over 13° off the intended position.

Other than the stock position, the closest you'll get to the correct phasing between the rotor and the pick coil/point set is at 8 teeth off, which will phase the cap and rotor within 3.5° of the correct position, or close enough. That would have the rotor facing almost rearward (straight toward the firewall). If you have clearance problems with the stock position because of an aftermarket intake, special carb(s), or other obstruction, this may be your best alternative.

sancho

Okay, mabye I didn't do this correctly then...

SMasterson: I know for sure that #1 is at TDC (I've done enough leakdown tests to know that by now). I also know that the timing chain gears are in the "dot-to-dot" position necessitated for proper chain installation. This is how I've left it.

I would love to do what Vader is saying and just see if the valves are closed or not, but since I have hydraulic lifters that have bled off and the intake manifold is on, I have no other way to tell which valves are open and which are closed.

So, just to confirm: Given the above, I am *not* in the compression stroke, and I need to rotate the crank exactly one full rotation?

Vader: Assuming that I am at #1-TDC in the compression stroke, in what direction does the rotor need to be pointing (*after* the dissy has been properly seated)? I have things setup right now so that it is pointing direcly towards the front of the car (it just makes the geometry easier than "pointing towards the #1 intake" or something like that). Is this acceptable, just so long as I have the #1 pole on the cap aligned with the rotor in this position (directly towards the front)? In other words, can I still achieve the "design position" dropping the distributor in with the rotor facing directly towards the front?

I want to make sure that I get this right--after reading these replies, I'm starting to think that I was never timed correctly the first time I dropped the distributor in (which would explain a lot).

Thanks again

Vader

Sancho,

Did I throw you off with that one?

O.K. It really doesn't matter which way the distributior goes in, since the cap is keyed to the housing and the cap rotates with the pickup assembly. The only ones that really matter are the CPI engines with a cam position sensor in the distributor (like Vortec engines).

I'm a little surprised no one called me on that one yet. Maybe you're all still thinking about it?

Incidentally, the stock position has the rotor pointing directly at the physical location of the #1 cylinder.

Kingtal0n

So wait now you've got ME confused...

When i put my new cam in, and aligned the 2 dots to each other, thats NOT Piston #1 Top Dead Center COMPRESSION Stroke???


then how come its running? I put the rotor pointing towards #1 and it fired right up...

Will it RUN 180* off like that?

radiateu2

The dots on the gears can place you 180 out if you are not careful. This is from experience. The only sure way to make sure your ATDC is to pull the driver side valve cover, on the #1 cylinder rotate the crank until the both valve close on the #1 cylinderbring the piston to the top of the cylinder while both valves are closed. Then you will be ATDC for #1 cylinder. Place the distributor cap on the distributor. Place a pen mark where you want the #1 cylinder wire to be. This where your rotor should be pointing when you install the distributor. It really doesnt matter where #1 is on the cap just as long as the rest of the firing order is correct after it.

ede

installing the crank and cam gear dot to dot will put you at #6 fireing. i have no idea why all the books say to do this (except that it's easier to line up) and not tell you that it isn't fireing on #1. you can tell if the valves are closed by pulling a valve cover, the lifters won't or won't matter if they're full of oil or not to check. thing is the valves are closed twice per cycle, #1 and #6 will both have closed valves.

SMasterson

Yep, I was/am confused. I read it about 12 times. But. . ., it's not the first time I've had to re-read one of your posts before I smacked myself on the head and said, "oh yeah!"

You can get pretty hi-tech sometimes, but it's appreciated!

Vader

Not a problem. The whole issue is a "non-issue" as long as you use what was intended to be the #1 plug wire terminal for the #1 spark plug, no matter which direction it is pointing. If , however, you use the #6 cap terminal for the #1 plug and continue the order from there, you could experience the phasing problem described.


The #1 terminal is keyed to teh distributor base in phase with the pickup coil/point cam. I'll try to get a simple diagram together to help illustrate the theory.

Kingtal0n

Vader does all of that apply to an aftermarket MSD Setup that doesnt use a computer or anything icky like that?

I just lined up the oil pump shaft with the rotor and dropped it in, then i turned the whole thing around till #1 was where i wanted it. was that bad?

Vader

King,

As long as the #1 plug wire is on the terminal that was intended to be for #1, everything is fine, no matter which way you dropeed it in there.

Kingtal0n

<b>As long as the #1 plug wire is on the terminal that was intended to be for #1, </b>

but they dont specify which terminal is for #1!!!
I just picked the closest one!

Vader

You worry too much. the pickup/points are dostributed at 45° intervals, and so are the terminals on the cap. If it's running correctly, you've got it right.

I know that most caps don't identify the intended #1 position, but some do. Regardless, this is the original design, but it doesn't matter if provided you have the order correct:

sancho

Kingtal0n: The terminals are all the same; with regards to the distributor cap alone, it makes no difference which terminal you decide to be #1, provided that the rest of the plugs are in proper sequence after that. To add to what Vader said, the "terminal that was intended to be for #1" is whichever terminal that is <i>directly across from the rotor contact when you dropped the distributor</i>.

Another thing...on the stock distributor, there is a rotating circular plate under the rotor with eight evenly-spaced "bumps" along its circumference. Each one of these bumps is spaced at 45 degrees, radially corresponding to the terminals in the cap. Outside of this circular plate there is another bump in a fixed position points inward towards the center of the axle. As the circular plate rotates with the distributor axle, the bumps on it eventually come directly across this fixed bump. So, to initially align the desired #1 terminal on the cap to the rotor, I like to get two of those "bumps" directly across from each-other and then put the cap on. That way, whatever terminal that appears to be nearest the rotor when you put the cap on should be exactly where #1 will fire.

I'm sure that's probably not the "ideal" timing for engine--that can only be found using a timing light. But it should take some of the guesswork out of getting the engine started up for the first time.

Of course... I could be altogether wrong. Somebody correct me if that happened.

radiateu2

Right, where ever you point the rotor when you install the distributor will be number 1 firing regardless of where it is on the cap ie if the rotor points a 6 o'clock then the terminal at six o'clock is firing #1 so long as the #1 piston is on compression/firing stroke ATDC

Riley's35089rs+

I was watching one of the speed shows this weekend, and it showed how to adjust the rotor position....after install...with a timing light on the rotor itsself...it showed that sometimes even when the firing order is correct the rotor may not be lined up with the terminal on the cap...causing the timing mark on the balancer to move around when under the light...anyone seen this happen?

They cut a hole in the old cap and put the light on the rotor ......

radiateu2

Didnt see and never heard of it. I assume its possible since you did see it. Not sure what the purpose would be to adjust the rotor position when that is achieved when you rotate the body of the distributor. Does sound interesting though. Do you remember what show it was?

Vader

On a car that DOESN'T have a crank position and cam position sensor (as most ThirdGens DON'T), the only way I can understand that occurring is if the distributor was disassembled, and you somehow installed the reluctor and/or the pickup coil pole piece in the wrong orientation. You'de really have to be trying to do that, since they are indexed to both the distributor shaft and base, respectively. Basically, you would have to try to alter the phasing between the rotor position and pickup coil/points. It would be easier to alter with points through th edwell angle/gap adjustment, but we're still only talking a few degrees of rotation.

On a Vortec engine with both of those sensors, it IS possible to affect the rotor phasing, which is why there is an installation procedure to follow when replacing the distributor. That doesn't apply to us unless we have installed an OBD-II PCM and control system. Some of the V-6s have a similar scheme, but since those affected don't have a distributor, the whole thing is moot.

Riley's35089rs+

Yeah it was on espn...cant remember wich show...I watch most of them on Sat and Sun Morning, if I dont have to work....I had never seen such a thing...( not that that means a whole lot)..anyway, thanks for the input Vader.