Timing survey

[aptruncata]

I would like to know how many member on this forum have their timing set at 5 deg btdc as service manual says vs how many have advanced or retarded them and to how many deg.

I understand this topic has been discussed in the past however it didn't really say much about how many of us are content with 5 deg vs various degrees of advance. I ask because i have a 84 22r carb. that at the time of purchase had 13 deg. advance. it felt great and satisfactory at the time but ever since i've put it back to 5 deg. to pass smog....it really feels noticeably weaker climbing even the slightest hills. it sometimes slows down (down to 35-40mph) at times on the fwys.

[zero]

I would like to know how many member on this forum have their timing set at 5 deg btdc as service manual says vs how many have advanced or retarded them and to how many deg.

You're referring to the static timing or "initial" timing specs. You cannot fairly compare those initial settings between users without knowing what the timing actually is when the Toyota is being driven down the road.

One person's Toyota might be set at 5 degrees BTDC (at engine idle) and be properly advancing to 18 degrees at highway speeds. Another person with the same year Truck might have the initial timing also set at 5 degrees (BTDC) and have a stuck non-working advance and only be running with 5 degrees total advance at highway speeds.

Those tune specs for initial timing are pretty useless unless you can verify that the vacuum advance and the centrifugal advance are both working. Same for diesels, more-or-less.

Most any truck or engine maker will give "compromise" tune up specs since they do not know what altitude you're running at, what load you're hauling, and what the octane (gas) or cetane) diesel is.

I've seen a lot of ratty trucks (gas and diesel) that people tried bumping up the initial timing to get them to run better. Sometimes it works if it was compensating for a faulty vacuum and/or centrifugal advance.

A typical 4 cylinder engine with non-computer controls has an engine set at 5 degrees BTDC at engine idle if lower then 4000 feet altitude. By 1350 RPM, the timing is supposed to be 14 degrees, By 2500 RPM it climbs to 17 degrees. By 3000 RPM it runs at 18 degrees BTDC. Besides RPM, there is the vacuum advance that can change timing by 11 degrees.

One added issue it if someone has an aftermarket camshaft installed. Then all bets are off.

[MontanaChinook]

The timing on my 83 22R is slightly advanced. Can't remember where I put it, but it's not at 5.

[WME]

I set mine for 10 deg and used midgrade gas

[zero]

i have a 84 22r carb. that at the time of purchase had 13 deg. advance. it felt great and satisfactory at the time but ever since i've put it back to 5 deg. to pass smog....it really feels noticeably weaker climbing even the slightest hills. it sometimes slows down (down to 35-40mph) at times on the fwys.

If you notice that much of a difference I suspect your automatic RPM advance and/or vacuum advance is not working and your static (initial) timing got bumped up in an effort to work around the problem. Your automatic advance is something totally separate from your initial setting you make by loosening and moving the distributor.

Your engine is supposed to have a preset "best" timing for engine starting. That's what you are adjusting when loosening and rotating the distributor.

When the engine is actually running at driving speeds - there are two automatic systems that advance the timing as needed.

On older trucks with mechanical timing controls (like these Toyotas) there are two things that go wrong over time.

#1 is the RPM advance. When you take the distributor cap and rotor off - there is a spot that is supposed to get oiled during routine tune-ups. If not, it gets stuck and the advance stops working.

#2 is the vacuum advance. It senses engine vacuum and changes the timing whenever a load is put on engine and you hit the gas pedal (open carb lowers vacuum). It works with a rubber diaphram. The diaphram breaks and wears out. Its another item that is supposed to be checked during a tune-up. Very easy to check with a vacuum -tool (hand-held suction gun).

If these systems are not working - and your engine is set for an initial timing of 5 degrees - at high speeds your engine will be retarded by 13 degrees. If you try to work around the problem and bump up the static timing to let's say 10 degrees BTDC - the engine will still be retarded at high speeds by 8 degrees. If you say the heck with the auto-advance and just bump up the initial timing to 18 degrees (by moving the distributor) - the engine will be properly timed when the engine is revving at 3000 RPM - only. At lower speeds it will be way off and likely to burn holes in pistons, start hard, etc.

The only way to properly check the timing is with a timing light and revving the engine up to 3000 RPM and check the advance.

Note also that timing is different if driven in high altitudes.

[MontanaChinook]

One thing I will stress, beyond all that info from jdemaris, is that you must state whether you set the timing with your advance connected, or disconnected. The proper way is disconnected and that's where my number comes from, but you never know...some people just stick a gun under their hood and read what it says and say "my timing is set at xx".

[MontanaChinook]

Oh, and my town is at 5,000ft.

[zero]

Oh, and my town is at 5,000ft.

With Toyota and the 20R, 5 degrees extra advance is supposed to be dialed in for trucks driven over 4000 feet above sea level. 13 BTDC instead of 5 BTDC for many engines. You also wind up with less power since a non-turbo engine loses 3% of it's power and efficiency for every 1000 feet above the ocean. In your case, you've got an engine making only 88% as intended. Some companies put special high-altitude pistons in engines that ran at high levels. Problem was - if driven in low altitudes they could self-destruct.

"Altitude compensators" also used to be common. Now they're called "turbochargers" and used more for power enhancement instead of power restorers.

My son took my 1987 diesel Chevy Suburban from central NY to where he lives at over 6000 feet in Colorado. It barely ran and smoked so much they wouldn't let him drive it. Ran fine here in NY. He finally found a complete turbo setup at a local junkyard and installed it. Problem was fixed.

[Maineah]

If it late enough to have a diagnostic connector (little box that has a lid saying "diagnostic") be sure to jumper Te1 and E1 other wise all of your timing adjustments will be for naught.

[5Toyota]

that hand vacum pump is nice to check the vacum advance vac diafram rupture is a known problem it will cut your power a lot you can check it with the old suck on a piece of rubber tube wit h the dist cap off if the plate does not turn or stick toung on tube and hold vacum no hold replace vac unit