Timing Advancement; How Far?

[kevinmrowland]

There seems to be two schools of thought on this, factory spec, set it and forget it.
Or...........For those of us who like to tinker, push it as far as you can until the engine pings under load.

My question;
Does optimum engine performance result from advancing the timing as far as possible? Or are there negative effects?(other than pre ignition and the pinging)

 

[overhanger]

Good question, Kevin, and I look forward to the informed answers you are sure to receive. My experience, mostly with high revving small block V8s, is that the farther the timing advance the better when it comes to making useable horsepower. Still, that is in the realm of sports car racing and high rpm horsepower rather than low rpm tractor power torque. As long as you aren't having to use 102 octane leaded pump gas like we had in the guddle days and aren't melting spark plug electrodes, the sky is/was the limit regarding ignition advance reaping rewards. As I said however, more informed answers should be forthcoming and I look forward to reading them.

 

[kevinmrowland]

Hey Steve! Good to hear from you, been awhile.

I'm looking forward to peoples thoughts on this as well. This is something I have been thinking about for awhile, so, figured I would see what the tractor gurus think.

 

[Texx]

I've always advance the timing, "horsepower in a can"...especially on Fj62. Obviously, you want to be careful, but it only takes a couple loaded runs up a hill or towing to know where the limit is. I wouldn't accept any spark knock under load, other than that, the more the better. First thing I do when I buy a wagon.

 

[MoCoNative]

I'm running bone stock 1984 60, 207,000 miles. Bought it with 175,000.

It was sluggish and hesitant when I got it, guy had just driven it, done minimal maintainence. I have driven a 40 for years, had it kind of souped up at first, Holley carb, headers and Mallory distributor. So I tinkered with it quite a bit.

I run the 40 at about 11 degress of advancement. Even though I have gone back to stock carb and exhaust. This gives me good power and very smooth idle and running. I also live at 6200 feet elevation.

Now back to the 60. It was running badly. So I thought what the heck, lets check the timing. There is a specific process to do this, I think the emmisions sticker on the passenger fender describes it, a couple of vac lines need to be undone. It was running at the stock 7 degrees. So I kicked her up a notch, to around 10.5, 11 or so. What a difference that made, no knock or anything bad, smoothed it right out at the time and I had far better power while accelerating.

Coupled with a carb rebuild the vehicle ran great afterwards.

I highly recommend advancing timing. Talk to some old hotrodders, they know how far to go. Bottom line is that Toyota's spec were for new vehicles at the port at sea level. Not old ones at elevation. Probably a degree or two at sea level will help. I've never lived or driven at low elevation, so don't know for sure. Lowest I have gone is about 3000 foot in Arizona in the 60 and still had excellent performance. But I tune for where I live, timing wise and jet wise in the carb if you can. I know there is a formula kind of, that is where I got the 11 for the 40 years ago and I have used it, works good for me.

 

[FJ40Jim]

My question:
Does optimum engine performance result from advancing the timing as far as possible? Or are there negative effects?(other than pre ignition and the pinging)

Optimum engine performance occurs at the optimum ignition timing point. There are no negative effects to achieving optimum efficiency.
Pinging & low efficiency is a negative consequence of timing that is too soon.
High EGT and low efficiency is a consequence of timing that is too late.

 

[TheJackRabbit]

Is fuel octane a secondary consideration? If you intend to use 93 octane or Trick 107 octane fuel, can't you advance that timing to a point that would have resulted in pinging if regular 86/87 octane fuel is burnt? Or, is the compression ratio so low on the F2 that fuel is not a factor?

This is a theoretical question as I doubt anyone but a racer wants to spend $ on high test fuel.

 

[kevinmrowland]

Just a balance like everything else it seems.

So do you guys think that "optimum" spot is right before the pinging starts (under heavy load) ?

I have a desmogged cruiser, properly I hope, and I have the timing set at about 12-13 versus the specked 7

I can also turn on my HAC manually. If I turn it on under load the timing advances another 6 degrees total, still no pinging, and perhaps the truck pulls a bit stronger, but that is probably just in my head;p

With the timing fully advanced by the diaphragm, the HAC advancing it further and the idle tickover at 5 degrees over spec the engine must be running somewhere around 30-40 degrees of advance.
It runs good now, but would it run better if I push it further?
No real ill-affects from trying, right?

 

[kevinmrowland]

Is fuel octane a secondary consideration? If you intend to use 93 octane or Trick 107 octane fuel, can't you advance that timing to a point that would have resulted in pinging if regular 86/87 octane fuel is burnt? Or, is the compression ratio so low on the F2 that fuel is not a factor?

This is a theoretical question as I doubt anyone but a racer wants to spend $ on high test fuel.

I think the compression is so low that our tractor motors would not be able to take advantage of higher octane fuel, timing advanced or not.

 

[MoCoNative]

As I recall 40 degrees total advance at speed is as far as you want to go. Sound like you have your system working just right.

I figured with my 11 degrees advance on my 40 with the 22 degree advance in the mallory distributor I was getting near optimal advnacment for a 1F, I think 35 is great, 40 is the max for F series engines.

Can't recall where I saw that though, saw it long ago.

 

[toyman317]

I have mine set where the BB is just at the edge of the opening, probably around 10 or 11 and it runs great. No pinging.

 

[60wag]

The spec of 7 deg is with both advance diaphrams disconnected. When you reconnect the vac lines, and are above 3500ft, the HAC adds 6-7 degrees. So the effective advance at idle is 13-14. The carb and mechanical advance add to that.

I run my rebuilt 2F (with 0.05" head shave) at the stock 7 advance. I had a persistant problem with random pinging. It mostly occured with 85 octane, sometimes w/ 87 and even occasionally w/ 89. I verified that all the smog hardware was working, especially the EGR. I played with retarding the timing with some limited success. I was really close to having the dizzy recurved when I tried eliminating the check valve in the carb advance circuit. My thinking was, if the manifold vac is low at wide open throttle, and that's when it pings, why not lose a bit of the advance at that point. Without the check valve it runs great, even on 85 octane. No knock, no ping, and the power feels about the same. What's wrong with my logic?

 

[cruiser88]

i set mine just a slight ping under load going uphill.i mean you really have to listen to hear it

 

[FJ40Jim]

So do you guys think that "optimum" spot is right before the pinging starts (under heavy load) ?

I have a desmogged cruiser, properly I hope, and I have the timing set at about 12-13 versus the specked 7

I can also turn on my HAC manually. If I turn it on under load the timing advances another 6 degrees total, still no pinging, and perhaps the truck pulls a bit stronger, but that is probably just in my head;p

With the timing fully advanced by the diaphragm, the HAC advancing it further and the idle tickover at 5 degrees over spec the engine must be running somewhere around 30-40 degrees of advance.
It runs good now, but would it run better if I push it further?
No real ill-affects from trying, right?

Yes, the optimum timing point is usually several degrees retarded from the point where pinging is audible.

Be aware that pinging happens too fast at high RPM to be audible.

Fiddling w/ the timing on a 2F is not likely to blow it up in a day.

Story: A recent engine rebuilt was due to having both vac advancers hooked to the ported vac fitting, and a worn stop pin. Result was ~58* total timing. A couple thousand miles of highway operation resulted in exploded engine in Ohio. W/ a properly curved dissy and a fresh bottom end, truck is driving fine now.

 

[beaufort-fj60]

jim,

what effect on the engine does a stock 60 dizzy have with no vac lines connected (no vac advance)

 

[kevinmrowland]

Um, you get no vacuum advance

Couldn't resist. Why would you do that? You would not have much power to spare (like we do anyway)

 

[kevinmrowland]

Yes, the optimum timing point is usually several degrees retarded from the point where pinging is audible.

All right, I'm gona keep pushing it and see what happens.

If the pinging is inaudible at high RPMs, how can you tell it is there? Feel for the loss of power?

There is a stop pin inside the dizzy body? is there a separate one for the secondary diaphragm?
I would like to make it so my HAC advances more like 12 degrees than the current 6. Is that possible? I should just go look at it before I ask you.

 

[kevinmrowland]

The spec of 7 deg is with both advance diaphrams disconnected. When you reconnect the vac lines, and are above 3500ft, the HAC adds 6-7 degrees. So the effective advance at idle is 13-14. The carb and mechanical advance add to that.

I run my rebuilt 2F (with 0.05" head shave) at the stock 7 advance. I had a persistant problem with random pinging. It mostly occured with 85 octane, sometimes w/ 87 and even occasionally w/ 89. I verified that all the smog hardware was working, especially the EGR. I played with retarding the timing with some limited success. I was really close to having the dizzy recurved when I tried eliminating the check valve in the carb advance circuit. My thinking was, if the manifold vac is low at wide open throttle, and that's when it pings, why not lose a bit of the advance at that point. Without the check valve it runs great, even on 85 octane. No knock, no ping, and the power feels about the same. What's wrong with my logic?

Random? Not under load? I think the higher octane should fix that under all circumstances.

I thought the check valve was actually just a one way valve, in case of back pressure the dizzy would not retard, or get pushed back. I do not have the FSM here in front of me, so I am just guessing.
I would think that under normal circumstance removing or replacing the check valve would do nothing.

 

[kevinmrowland]

As I recall 40 degrees total advance at speed is as far as you want to go. Sound like you have your system working just right.

Nice to hear, but it could always be just that liiiiiiiiiiiiittle bit better;p

 

[60wag]

Random? Not under load? I think the higher octane should fix that under all circumstances.

I thought the check valve was actually just a one way valve, in case of back pressure the dizzy would not retard, or get pushed back. I do not have the FSM here in front of me, so I am just guessing.
I would think that under normal circumstance removing or replacing the check valve would do nothing.

Ok, it wasn't really random, it was when the engine was "under load." The odd thing was it would be ok on 87, then not, it would be ok on 89 for a while and then I could get just a slight ping sometimes. I could even get no ping on 85 sometimes. It sort of seemed related to drive time. There is a hill climb about 7 miles south of me. I could consistently get the ping going up the hill. The temp gauge is usually up to normal within about 3 miles from home. Four miles later I go up the hill and it knocks. I would have thought everything would be sufficiently up to temp in less than 7 miles. I head up into the mountains, put another 50 miles on the truck, then try the same hill again and no knock. The next morning, I go up the hill again and it knocks. I don't think its related to carbon buildup since it'll change overnight.

Anyhow, I pulled the check valve and no knock. What the check valve does is maintain the vac on the dizzy side of the valve when the manifold vac drops.

Another thing I tried was to add a sleeve to the limit pin for the mechanical advance. I think it was Jim C who mentioned that he had seen damaged or loose limit pins. I checked the mech advance system and the pin seemed ok. A slice of 5/32 air hose is a perfect fit over the pin. I effectively makes the pin bigger and reduces the max mech advance. Unfortunately it didn't solve my problem. One of these days I want to get another distributor and have it properly recurved. This would give me a good comparison to my current setup.