adjustable cam gear + timing

[rustlude87]

I recently adjusted my cam to -2 degrees and runs great. But when I go to time the motor the timing marks do not line up all the way. Whats the best way to time the motor?

[cygnus x-1]

I recently adjusted my cam to -2 degrees and runs great. But when I go to time the motor the timing marks do not line up all the way. Whats the best way to time the motor?


When you change the cam timing the ignition timing will also change. So if you advance the cam by 2 degrees you would need to retard the distributor by 2 degrees. Probably the easiest way to do it would be to unplug the vac advance and set the timing to 0deg BTDC.


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[87roach]

Good info.

What if you're obd1?

[cygnus x-1]

Good info.

What if you're obd1?


It would still apply since the timing is referenced off the cam, although you can't disconnect the vac advance, 'cause there ain't none. I guess you would have to just set it for whatever the idle advance is programmed for. Or if you have the tuning software you could program the idle timing to 0* and set it that way.


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[87roach]

So you mean, if I were to advance or retard the cam gear. I wouldn't move the distributor, I would tell the tuning software that it's 0*?

If no tuning software, then change the distributor as needed. Makes sense to me.

[89T]

To keep it simple. If you retard the cam timing 2 degrees you will have to add 2 degrees to the dizzy. so the crank will say 12 degrees and then you retard the cam 2 degres now it will read 10 degrees ...add 2.

[cygnus x-1]

So you mean, if I were to advance or retard the cam gear. I wouldn't move the distributor, I would tell the tuning software that it's 0*?

If no tuning software, then change the distributor as needed. Makes sense to me.


What I meant by reprogramming the software to 0*, was to basically mimic the idea of disconnecting the vac advance. The idea is to get the ECU to fire at what it thinks is TDC, so that you can use the TDC mark on the flywheel to set the distributor. The problem with the flywheels on these engines is that they aren't fully marked in degrees from zero to whatever the timing is supposed to be. There is a TDC mark and then another mark whrere the stock timing is supposed to be set. But with OBD1 or any other tunable ECU you might have the idle timing at say 16* but the mark on the flywheel is at 12*. So unless you have a dial back timing light, the only way to set the timing is to program the ECU to fire at either 16* or 0* where you have a flywheel mark.

OR, if your tuning software has a programmable offset you could also adjust that. I'm not familiar with the any of the OBD1 software so I don't know what they have for ignition settings.


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[87roach]

To keep it simple. If you retard the cam timing 2 degrees you will have to add 2 degrees to the dizzy. so the crank will say 12 degrees and then you retard the cam 2 degres now it will read 10 degrees ...add 2.

I'm not sure that simplified things..

After doing your math it seems me that all you'd have to do is move the distributior instead of the cam gear. Unless I just totally misunderstood.

So basically if for whatever amount of degrees you advance or retard the cam gear you do the exact opposite to the distributior?

Cygnus, I think I understand what you're getting at. I cannot also comment on the tuning software as I haven't interacted with any. So how do obd1 hondas usually set tdc then?

[cygnus x-1]

So basically if for whatever amount of degrees you advance or retard the cam gear you do the exact opposite to the distributior?


Exactly.



Cygnus, I think I understand what you're getting at. I cannot also comment on the tuning software as I haven't interacted with any. So how do obd1 hondas usually set tdc then?


Umm, I would guess they don't. Most likely they just have a specified idle timing (say 12*) with a corresponding mark on the flywheel, and you just move the distributor until it lines up. On said OBD1 engine, if you then used a cam gear to advance the cam timing 2 degrees, the ignition timing would now be at 14* and you would need to reset it to 12* via the distributor again.

This is all fine if you have the right marks on the flywheel. I suppose you could also paint/scratch some more marks on there.


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[87roach]

Ok, glad I figured that out. Thank's for helping me understand :)

I just have a basic timing light so I don't think I can get too fancy. I'm not even sure how you'd go about adding new accurate mark's on the flywheel...

[rustlude87]

Thanks for all the help cygnus :)

[cygnus x-1]

Thanks for all the help cygnus :)


Anytime! :wave:

Hey, did you do ITR Expo this year?


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[rustlude87]

ITR Expo was held in N. Carolina, which was a little too far for me. I will be attending WMHM meet instead :)

[Strugglebucket]

Remember you need to ground pin D4 when you set the base timing with an obd1 ecu.

[cygnus x-1]

ITR Expo was held in N. Carolina, which was a little too far for me. I will be attending WMHM meet instead :)

Cool. Might try to make it out there if I'm not still totally broke. And if I have the time. July is turning into a busy month.




Remember you need to ground pin D4 when you set the base timing with an obd1 ecu.

Ahh, so that's it. Is the base timing 0 then or something else?


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[Strugglebucket]

15btdc usually

[stat1K]

yeah you jump the service connector and unplug the iacv according to my manual.