Indexing my Distributor, #1, #2 or 180 swap?

[Patrick N.]

My distributor is back in the motor-(thanks again to everyone that helped me get the last items sorted), I have a non stock cam in my 68 L68 and before I 180 the dimpled gear on the dist shaft I want to check that I am clocking the dist correctly. Motor is set TDC correctly for #1 (not on exhaust stroke). Looking in the AIM, the L71 and L68 show rotor contact for the #1 cylinder pointing to #2 cylinder. Is that correct, Should it be pointing to the #2 cylinder for this motor?

My understanding is that the rotor contact should point in the general direction of the #1 cylinder. The issue is with my vac canister, when my rotor points to the #1 cylinder and I rotate the dist body to match the cap with the rotor, the vac canister will hit either the carb or the bracket for the shield.

Thanks again,
Pat

[Michael W.]

Re: Indexing my Distributor, #1, #2 or 180 swap?

The OEM position for the rotor tip is pointing towards cyl. #2. The distributor vacuum advance housing should sit (ideally) midway between making contact with the intake manifold or the shielding support when the points open. If this cannot be achieved, then the flipping the driven gear 180* should help.

[Patrick N.]

Re: Indexing my Distributor, #1, #2 or 180 swap?

Thanks Michael, seems obvious to me this morning but last night I realized the #1 was not working out.

Best,
Pat

[Duke W.]

Re: Indexing my Distributor, #1, #2 or 180 swap?

You should set the crankshaft at the proper initial timing point, not TDC. I don't see how big blocks could be any different, but on small blocks if the dist. in installed properly, the rotor tip should be pointing in the general direction of the #1 terminal on the cap with the housing about halfway between the interference points.

Once installed, eyeball or using an ohmmeter, rotate the dist. housing until the points just open, and at this point the VAC should be about midpoint between the two interference points. If not, the dist is either off a tooth, or the gear should be rotated 180 deg.

Once the above is squared away, start the engine, and set the final timing. If you did the above correctly, it should be within a degree or two of your target.

Duke

[Patrick N.]

Re: Indexing my Distributor, #1, #2 or 180 swap?

You should set the crankshaft at the proper initial timing point, not TDC. I don't see how big blocks could be any different, but on small blocks if the dist. in installed properly, the rotor tip should be pointing in the general direction of the #1 terminal on the cap with the housing about halfway between the interference points.

Once installed, eyeball or using an ohmmeter, rotate the dist. housing until the points just open, and at this point the VAC should be about midpoint between the two interference points. If not, the dist is either off a tooth, or the gear should be rotated 180 deg.

Once the above is squared away, start the engine, and set the final timing. If you did the above correctly, it should be within a degree or two of your target.

Duke

Thanks Duke,
I will double check initial timing point. I clearly have something that is not set up correctly and will chase that down, I will get to remedy this tonight once I am home.

Regarding rotor tip pointing towards #1 terminal, I thought the same thing that SB or BB would be the same but the AIM is showing #2 as the position. Would that really make a difference?

Pat

[Gene M.]

Re: Indexing my Distributor, #1, #2 or 180 swap?

Patrick,
Check out the AIM as I think there is a wire clocking position shown for the distributor cap. But as the guys pointed out it is based on the #1 being in the correct spot to all "align" right.

[Patrick N.]

Re: Indexing my Distributor, #1, #2 or 180 swap?

Patrick,
Check out the AIM as I think there is a wire clocking position shown for the distributor cap. But as the guys pointed out it is based on the #1 being in the correct spot to all "align" right.

Will do, I will take a step back tonight to check things out.


Thanks,
Pat

[Michael D.]

Re: Indexing my Distributor, #1, #2 or 180 swap?

Distributor and intake manifold should have stake marks. Lower the distributor and line up the stake marks.

[Duke W.]

Re: Indexing my Distributor, #1, #2 or 180 swap?

Thanks Duke,
I will double check initial timing point. I clearly have something that is not set up correctly and will chase that down, I will get to remedy this tonight once I am home.

Regarding rotor tip pointing towards #1 terminal, I thought the same thing that SB or BB would be the same but the AIM is showing #2 as the position. Would that really make a difference?

Pat

With the dist. housing set at the proper #1 initial timing position, the spark is going to jump from the rotor tip to the nearest cap terminal, and you want it to fire the #1 plug, not #2, right?

Keep in mind that the AIM illustrations are just that - illustrations. They are not accurate engieering drawings.

You should also refer to your CSM. It should have a specfic procedure to R&I the distributor.

Something else to consider. When you "exercise" the centrifugal advance by turning the rotor, the tip moves off the relaxed postion, but this is not how it works when the engine is running. With the engine running, as revs are increased the cam assembly advances, but the rotor tip remains pointed at the same position as when the centrifugal mechanism is relaxed. You can see this if your remove the rotor and manually move the weights out as they would move with the effects of centrifugal force.

Duke

[William C.]

Re: Indexing my Distributor, #1, #2 or 180 swap?

if worst comes to worst, pull the distributor, pull the in on the lower gear and rotate the gear 180 degrees. There is an odd number of teeth on the gear. which allows for "fine tuning" of the vacuum advance orientation.

[Patrick N.]

Re: Indexing my Distributor, #1, #2 or 180 swap?

if worst comes to worst, pull the distributor, pull the in on the lower gear and rotate the gear 180 degrees. There is an odd number of teeth on the gear. which allows for "fine tuning" of the vacuum advance orientation.

Yup, I'm in the garage now- that was my original fall back if I set this up right and it still is not oriented right, I'd rotate that gear- I do have an after market cam installed and could very well be the issue. I have the rotor tip aimed toward #2 cylinder and the shop manual as my guide- its almost right.

Turns out that was the ticket- after all else failed, knocked the pin out and rotated the lower gear on the dist shaft and it aligned nicely.

Best,
Pat