Total Ignition Timing


#1

1987 Ford F150, 302 5.0, automatic, 120k miles.

I just relocated the TFI module and had to pull out the distributor to insert the new plugs into the module’s ports. This led me to research total timing. I know how to use the timing light and set it to 12 btdc, but I never really understood total timing. I watched a few videos that mentioned it, but I don’t want to screw anything up.

How I understand it to work:
Unplug the spout, let it get to operating temperature. Then, set it to 8-12 degrees before top dead center. Don’t tighten the distributor lockdown bolt. Then, accelerate to about 2500-3000 rpm and turn the Distributor so it is at 30-36 degrees before TDC. Now, tighten the distributor lockdown bolt.

Again, I’m not sure if I’m correct in this assessment, but I’m not finding exact (and dumbed down) directions anywhere. I would greatly appreciate some pointers on this.


#2

Warm it up remove the spout set timing to 12 BTDC tighten bolt connect spout and you are done. The spout connects timing to ECM and allows it to advance the timing by 20 degrees at higher RPMs

If you have a code scanner read the section in the manual that tells you how to check total timing advance. A very simple test.


#3

Or plan B check ignition timing with spout connected at 3,000 RPM and if it’s approx 32 BTDC you’re good to go


#4

Okay, awesome. Thank you for the replies. The 30-some degree mark was new to me when I read about it, so I hoped to find more out about it. You’ve been a big help, thanks again


#5

Glad i could help


#6

Do not under any circumstances try to adjust your timing with the PCM connected to the distributor. Never, never, never do that. Set it with the spout disconnected at idle, plug it back in and then only check that the PCM is advancing the timing at higher RPM. The exact timing once the PCM is connected is set by the PCM, if you attempt to adjust the timing with the PCM plugged in, you are fighting the PCM.

Edit: check your service manual for instructions and follow those instructions explicitly. It may want you to set the timing for a higher advance with the PCM disconnected so that the PCM uses that timing signal and then retards the timing to the calculated spec for the conditions you are driving under.


#7

Here’s the blow by blow for setting the base timing to the factory spec. of 12 BTDC:
Warm up engine
remove spout connector
loosen hold down bolt
Set timing to 15 BTDC
tighten hold down bolt
reinstall spout connector
check timing at 3,000 RPM & if it’s approx 32 BTDC the PCM is properly controlling the timing and all is good


#8

Thank you all for the helpful input, I’ve got it running again.


#9

Nice job remote mounting the TFI module, if I had done that 20 years ago on my 87 2.9 liter Ranger i wouldn’t have had to replace the module 3 times
Thanks for the update, glad to hear you’re up & running