Help me estimate my timing setting - and where it should be. (1 Viewer)

[SiestaTom]

Here is the background. 6/74 FJ40. Engine was de-smoged and it has headers. I was told the original owner milled down the heads for better compression but compression now is just OK. Everything else is pretty original. Oh and I’m at 9000 ft elevation.
I set timing with a light and it idles faster and I get greater vacuum when I advance the BB below the pointer. In fact I can advance it so the BB is out of sight, below the edge of the inspection opening, and it seems to run best there. But of course I loose any visual reference once the BB goes out of sight, though I can try and judge how far by how much I’m turning the distributor. Despite running in this range of advancement, I’ve never detected pinging.
I’m confident the distributor is installed correctly. The rotor is pointed right at #5 when it’s at TDC.
I think the BB represents 8 degrees BTDC. I’ve read there is a mark for TDC but I haven’t found that. If I’m running it with the BB right at the lower edge of the opening, what would my timing be? And how can I time this rig to the optimal setting? Thanks for any suggestions or insight.

 

[tls3601]

I am guessing you would be at about 10 degrees before TDC, stock setting is 7. For reference I am at 5300 ft and run slightly advanced at 10 degrees, no issues runs excellent. I believe you can advance more at higher elevations. Hope that helps.

 

[NMC_EXP]

Thanks for any suggestions or insight.

My Dad taught me to use a timing light. Later an old school mechanic told me of another option. (1) Fill it with the octane you normally use. (2) Set the timing to the book or your best guess. (3) Drive it under heavy load, say on a hill or with the hardest acceleration you would use. Listen for ping/spark knock. (4) If it does not ping, advance the timing slightly. (5) Incrementally repeat the load / acceleration test until it does ping. (6) When pinging occurs slightly retard the timing in stages until the pinging stops.

At that point the timing of your specific engine set-up (say shaved head) and elevation ought to be where it should be.

I still have Dad's timing light but have used this trial and error method on early technology engines with success.

 

[cbmontgo]

I live at 9,100’ down the road from you. I’ve set timing very advanced so that the BB is all the way to the far edge...12 degrees or more. My 2Fs run very well this way.

 

[1969FJ]

Try looking at this.

 

[Shark56]

From what I remember reading the desmogged engine likes about 12 or 13. I think Jim C or Mark A said the bottom of the window was about 13 degrees. You might need a touch more with the reworked head.

 

[SiestaTom]

A huge thanks to all of you. This is really excellent information and confirms my actual experience so far.
However, I want to make sure I don’t have things completely backwards, based on what I read in the article attached to 1969FJ’s post.
That article says you turn the distributor clockwise to advance, but I’m pretty sure it’s the opposite on our engines. Can someone confirm that? Also, I believe that as you advance the timing, the position of the BB drops lower in relationship to the pointer.

 

[1911]

My Dad taught me to use a timing light. Later an old school mechanic told me of another option. (1) Fill it with the octane you normally use. (2) Set the timing to the book or your best guess. (3) Drive it under heavy load, say on a hill or with the hardest acceleration you would use. Listen for ping/spark knock. (4) If it does not ping, advance the timing slightly. (5) Incrementally repeat the load / acceleration test until it does ping. (6) When pinging occurs slightly retard the timing in stages until the pinging stops.

At that point the timing of your specific engine set-up (say shaved head) and elevation ought to be where it should be.

I still have Dad's timing light but have used this trial and error method on early technology engines with success.

This is the way I do all my older engines in everything.

The factory timing of 7 degrees BTDC has to work all over the world, in every market at every elevation and with every quality of gasoline, so it is quite conservative. As has been noted, higher elevation requires more advance, as does de-smogging.

My de-smogged 2F at only ~1,000' elevation likes 10-11 degrees advance, so at 9,000' I would expect yours to take more.

 

[ToyotaMatt]

this is NOT a skill set for any estimating ?

its needs to be exact and spot on

you need a print media FSM engine

please post year make modle and note any MODS

i WILL post the necessary factory step by step instructions from FSM form you ............

do i right the Toyota fsm way

do it only once , .........

 

[tls3601]

A huge thanks to all of you. This is really excellent information and confirms my actual experience so far.
However, I want to make sure I don’t have things completely backwards, based on what I read in the article attached to 1969FJ’s post.
That article says you turn the distributor clockwise to advance, but I’m pretty sure it’s the opposite on our engines. Can someone confirm that? Also, I believe that as you advance the timing, the position of the BB drops lower in relationship to the pointer.

Yes as advanced it drops lower in the window.