3FE timing, maxed out distributor rotation! (1 Viewer)

Spook50

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So today I set the timing on my 3FE. First time in years and figured now that I exclusively burn ethanol free 91 octane and had recently done a top end cleanup it'd be a good time to do it. I did it with the engine hot. Connected the vacuum gauge to the brake booster nipple on the intake manifold. Idling at 700 RPM I showed 18 inches of vacuum. When I went to adjust the distributor, it was already almost at its maximum rotation. I was able to take it up to 19.5 inches vacuum at its max rotation, so rather than max it out I set it to 19 inches vacuum and then readjusted the idle back down to 700RPM. Took it for a test drive and was shifting early to load the engine pretty good, and no pinging. Driving it normally, there was a noticeable improvement in power. Not a massive improvement, but enough to tell it wasn't just placebo effect. A rule of thumb I've used is to max out the idle vacuum by adjusting the timing, but then back it off two inches from max vacuum. With my distributor being close to maxed on rotation, I couldn't find where it would reach maximum vacuum at idle. This has me wondering if there's more I can get out of it. Obviously the most efficiency I can get from it the better, and it's been going well so far!

To anyone else's experience, would I be able to remove the distributor, advance it a tooth, and then replace it at the lowest point on the adjustment tab; or would that result in too many degrees of advance adjustment?
 

red66toy

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So today I set the timing on my 3FE. First time in years and figured now that I exclusively burn ethanol free 91 octane and had recently done a top end cleanup it'd be a good time to do it. I did it with the engine hot. Connected the vacuum gauge to the brake booster nipple on the intake manifold. Idling at 700 RPM I showed 18 inches of vacuum. When I went to adjust the distributor, it was already almost at its maximum rotation. I was able to take it up to 19.5 inches vacuum at its max rotation, so rather than max it out I set it to 19 inches vacuum and then readjusted the idle back down to 700RPM. Took it for a test drive and was shifting early to load the engine pretty good, and no pinging. Driving it normally, there was a noticeable improvement in power. Not a massive improvement, but enough to tell it wasn't just placebo effect. A rule of thumb I've used is to max out the idle vacuum by adjusting the timing, but then back it off two inches from max vacuum. With my distributor being close to maxed on rotation, I couldn't find where it would reach maximum vacuum at idle. This has me wondering if there's more I can get out of it. Obviously the most efficiency I can get from it the better, and it's been going well so far!

To anyone else's experience, would I be able to remove the distributor, advance it a tooth, and then replace it at the lowest point on the adjustment tab; or would that result in too many degrees of advance adjustment?
Did you adjust it per the FSM with the jumper in the “service port” (I don’t remember the exact ones)? Having a dizzy maxed out seems weird. Maybe the ECU is able to correct for that extreme setting still?
 

Spook50

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Did you adjust it per the FSM with the jumper in the “service port” (I don’t remember the exact ones)? Having a dizzy maxed out seems weird. Maybe the ECU is able to correct for that extreme setting still?
I don't expect the ECU was compensating for the adjustment, since the vacuum changed (and stayed) as I adjusted the distributor. I did not bother putting the jumper in, since I was going off vacuum rather than the timing marks on the flywheel. I could definitely tell a difference as I drove it afterwards too, so the adjustment did stick. I suppose I could pull the bolt completely and see how far it turns before it reaches maximum vacuum and when I set it 2 inches back. Very curious to see if I'm right where I should be or if I can go farther.
 

4Cruisers

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Based on some calculations I did during the R&D for the FJ60 points distributor I recently built, the length of the slot in an FJ60 distributor body is about equal to one tooth's worth of rotation, without measuring it I believe the FJ62 distributor is the same. So if you were to move the distributor one tooth you'd be back to the other end of the adjustment range and could continue to increase the advance.
 

FJ40Jim

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Adjusting timing for highest idle vacuum results in over advanced timing with any kind of normal advance curve.

Adjust the timing for highest torque at max torque RPM.
 

Spook50

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Based on some calculations I did during the R&D for the FJ60 points distributor I recently built, the length of the slot in an FJ60 distributor body is about equal to one tooth's worth of rotation, without measuring it I believe the FJ62 distributor is the same. So if you were to move the distributor one tooth you'd be back to the other end of the adjustment range and could continue to increase the advance.
That's what I was wondering. I suppose it's worth a shot to see what it'll do.

@FJ40Jim Completely agree. A rule of thumb I've used is to find the highest point of vacuum at idle, then back the timing off 1.5-2 inches of vacuum. That usually ends up pretty close to max efficiency. Obviously what you said, finding the highest torque at max torque RPM is the most sure fire way to dial in the best initial and vacuum curve, but I don't have easy access to a dyno and with a 3FE don't expect I would gain enough by toying with the curve of a 3FE (haven't even looked into it but IIRC it's controlled solely by the ECU) to make it worth the effort. Maybe if I get too curious for my own good, again, in the future. Meantime the vacuum method is what I've stuck to.
 

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