timing with vacuum gauge...where to stop?

[wimberosa]

Details: 1979 2F with OEM everything and smog
Elevation: 7000'
Timing WITH HAC advance connected but with ported vacuum disconnected
Vacuum gauge tee'd off brake booster manifold port

I've gotten my idle problem somewhat squared away (would not idle without choke previously). It idles nicely around 750 rpm with choke in now. I do not believe I have any vacuum leaks (pee tube tested, smoke tested) other than what smog introduces (e.g. HAC vacuum has a designed leak).

Timing data that is confusing me.... I started out at around 9 degrees advanced and a steady 15 in Hg on the gauge. The best vacuum I can accomplish is around 16 in. Hg and it starts around 13 to 14 degrees advanced. The 16 in. Hg HOLDs steady all the way up to 30 degrees advanced. The thing that changes when I advance beyond 14 degrees is the RPMs go UP....normal? Where should I be stopping or what should I be listening for? Take it to the first point I get 16 in. Hg and then road test it for pinging or other suggestion? Likely advance range for 7000' feet?

 

[charliemeyer007]

I'm only at 4000' and I have a new chinesium Delco straight mechanical advance dizzy (that replace a real Delco that was on my rig when I got it in 82) plus a Rochester 2BBl carb that also came with the rig. Also have a Man-a-fre header from when the cast iron manifold cracked in half about 1893 I haven't really adjusted the carb since I got the rig. I don't run the vacuum booster, because it leaks and I can't feel the brake pedal pressure due to right below the knee amputation about 15 years ago. When its warm out I can set the timing up to just going out the window, in the winter I set it back a whole lot so it doesn't kick back and take out the starter, way closer to the BB, but still advanced more that the book says. I drive with a big vacuum gauge Back in the 90's I got like 25 mpg driving freeway and back country roads with like 50 to 100 miles on each leg. Now I get about 15 mpg. I bought a heated ultrasonic cleaner and a gallon of carb juice for it, but winter came before I could really clean the carb. The rig sat for like ten+ years, and I just got it back on the road last spring. Health issues suck. Replaced drums, shoes, master and slaves for both the brakes and clutch.

+1 for road testing. Hopefully people with OEM stuff will chime in and offer more advice. I always try and remember its a tractor not a 917 S Porsche.

 

[Pighead]

The thing that changes when I advance beyond 14 degrees is the RPMs go UP....normal?

I think that's normal. I have to turn down my idle speed screw when I advance my timing. Running 22* BTDC at 3k feet right now.

 

[middlecalf]

15 in Hg @ 7000ft is over 19 in Hg @ sea level. And increasing timing will increase idle speed. Set your timing on the ball, idle at 750 then check compression. If 15 in Hg, then drive it and see what you think. Yeah, these motors can take more timing, but if it drives ok why use more than what Toyota recommends?

 

[pb4ugo]

As others said, Yes idle goes up as timing is advanced. You can adjust it down. Drive it and attempt to put it under load to see if it pings. If it does ping retard timing a couple of degrees. Drive it again.

 

[wimberosa]

I think its just not really clear why and how people arrive at these higher advances. Yes the FSM says 9 degrees at idle....but clearly people are running much higher. I'm not sure if perhaps their ported vacuum advance on the dizzy may be kaput and some advance off 9 makes up for it...or whether they are listening for some responsiveness or highest vacuum. Doing some silly looking around makes me wonder if using vacuum is really even the best course of action.

e.g. don't use vacuum on timing

At this point given I'm at a high altitude I think minimally I should be at 9 degrees (toyota FSM) plus the ~3 degrees the HAC gives me (i.e. the toyota designed altitude advance) = 12 degrees. Thats not very far off my highest vacuum which started around 13 degrees. I think 13 is where I set it at initially and then do as @pb4ugo says and start driving it under load.

 

[pb4ugo]

Driving it and adjusting it, you will get it to your liking. Your plan sounds good. Pinging is bad. Once you are happy with it, record where it's set for the future.

 

[rlong]

Yes, advance till start of pinging, back off. When one’s starter or battery are weak, a less advance timing will help starting easier. If you race the baja, run it a little higher.

 

[Skreddy]

Are you adjusting the mixture on the carb as well? It’s a dance with timing, mixture, idle speed to get the best vacuum.

 

[wimberosa]

Are you adjusting the mixture on the carb as well? It’s a dance with timing, mixture, idle speed to get the best vacuum.

Thats up next which is why I really had the vacuum gauge installed.

Was re-adjusting the valve lash as well and have realized that some of my valve oilers are not doing much of anything (cylinder 1, 2, 6). whereas 3, 4, and 5 are spewing like a waterfall. Something must be clogging them up. That's a short term back burner fix as well as why my igniter and spark are so weak. I think I'm going to retrofit an fj60 igniter and coil on it. See my idiocy with the yazaki wire in another thread.

 

[CruiserInProgress]

Thats up next which is why I really had the vacuum gauge installed.

Was re-adjusting the valve lash as well and have realized that some of my valve oilers are not doing much of anything (cylinder 1, 2, 6). whereas 3, 4, and 5 are spewing like a waterfall. Something must be clogging them up. That's a short term back burner fix as well as why my igniter and spark are so weak. I think I'm going to retrofit an fj60 igniter and coil on it. See my idiocy with the yazaki wire in another thread.

I think you'll like the FJ60 ignition upgrade with yazaki delete. Mine also included the big cap distributor and dented pushrod cover. It all worked well for my desmogged 79.

 

[rkymtnflyfisher]

I advance mine to highest vacuum (something like 13.5-14.5ish) then I back it off at bit just to tame it down.

Typical lean drop method, 3,500ft elevation.

I'm not saying it's right, but it ain't wrong.

 

[charliemeyer007]

Tuning by ear works and is a lost black art. Then 50 years later old age and too much rock & roll plus gun fire reduces the ear's effectiveness. I think it was Beethoven that played/composed the piano with a chopstick in mouth and the other resisting on the piano when he went deaf, so he could feel the music - adapt and overcome.

 

[Skreddy]

I advance mine to highest vacuum (something like 13.5-14.5ish) then I back it off at bit just to tame it down.

Typical lean drop method, 3,500ft elevation.

I'm not saying it's right, but it ain't wrong.

My 60 series, 2F, about 300k miles, desmogged, I’m at 12 degrees and 18 vacuum at 2500’. Oil burning F in the 40 is closer to 17 degrees timing, 16 vacuum but also has a sniper efi.

Basically, in the words of Uncle Jack; “the heart wants what the heart wants”. Go until it pings, diesels or kicks back the starter, then back off a little. Advanced timing doesn’t hurt anything, until it does….

 

[B y r o n]

Like @rkymtnflyfisher mentioned, back off your timing by about 2 in Hg to avoid pinging when pushed hard. Another adjustment is adding 1 degree above base setting for every 1,000 ft in elevation. Adjusting idle mixture and idle speed and re-test until you're satisfied with the results.

This is one of the reasons I switched to EFI. Let the computer make adjustments as needed on the fly!

 

[Pighead]

I think its just not really clear why and how people arrive at these higher advances.

Back in the day, our timing lights just blinked. They didn't have knobs or LEDs. Tuning by ear and seat of the pants told me that the engine liked more advance and once the BB disappeared out of the window I had no idea what number I was at. So I timed it by vacuum for many years. Finally got a new-fangled timing light and found I was at 25* BTDC. I fixed the leaky dizzy diaphragm and turned it down to 22*. That's where I get my almost best manifold vacuum at idle and the rig drives the best. It's not a stock engine, got a cam and stuff, and I been fiddling with this engine for 22 years.

 

[77mustard40]

Back in the day, our timing lights just blinked. They didn't have knobs or LEDs. Tuning by ear and seat of the pants told me that the engine liked more advance and once the BB disappeared out of the window I had no idea what number I was at. So I timed it by vacuum for many years. Finally got a new-fangled timing light and found I was at 25* BTDC. I fixed the leaky dizzy diaphragm and turned it down to 22*. That's where I get my almost best manifold vacuum at idle and the rig drives the best. It's not a stock engine, got a cam and stuff, and I been fiddling with this engine for 22 years.

I guess I'm still back in the day, no knobs or led's for me... seems to work fine for the mighty 2F