Timing Question

[jes72mustang]

I checked and adjusted the timing on my 72 today. Wow, I was surprised it was at about 38 degrees advanced when I started, no wonder I thought I was having a miss. Brought it back to about 8-10 degrees advanced, smotthed the idle right out no more stumbling around.

would there have been any advantage to the PO having it that advanced? I would thing that the MPG would be a bit better now as well.

 

[my66coupe]

The Po probably did the timing with a vacumm guage and set it to where he achieved the most vacumm, which can result in a large amount of advance. Setting your timing should always be done with a light for accurate settings.

Mike

 

[grego37]

whats a PO????

 

[Capt Dan]

whats a PO????

Previous Owner.

 

[a.vannoy]

whats a PO????

Previous owner

 

[grego37]

got it!
"pervious owner"

TY
"Thank you"

 

[oz]

Be careful, there is a good chance that either the vacuum advance or the mechanical advance is not working properly. There would be no other reason for the PO to set it this high otherwise. I bet it was nearly impossible to crank over...
If both advances were working properly and initial timing was 38, at higher RPM's you would almost certainly have pinging. You did set your timing with the vacuum advance unhooked and plugged right? You are using a 'timed' vacuum port, correct? (If it's the stock carburetor, disregard this question)? The timed port will have no vacuum at idle...

Put your timing light on the car and start it up. Increase engine speed to about 3500 and hold it steady. What is your total advance? Do the same with the vacuum advance unhooked and unplugged. There should be less total advance with the vacuum advance unhooked. If it is the same, your vacuum advance is not working.
If, while the vacuum advance is unhooked, you don't get advance from your idle setting of 8 - 10 as you increase engine speed then your mechanical advance is not right.

If you have set your idle advance to 8 - 10 (with vac unhooked) and you get about 38 degrees at 3500 (with everything hooked up) then you are good to go.

 

[jes72mustang]

The Carb is an Edelbrock 600CFM, the distributor is an MSD Pro billet, I have Crane Fireball ignition. When My mechanic tuned the carbafter installation he disconnected the vacuum line to the distributor, said it wasn't needed, something about mechanical advance. (not sure what exactly that meant) When we adjusted the timing the engine was fully warmed up, and running at idle. After adjusting we revved it while hitting it with the timing light and it stayed at about 8 degrees. Drove it around that day with no noticable issues.

 

[oz]

hmmm... that would indicate that your mechanical advance is not working... Mechanical advance should come on smoothly with RPM and max out at ~3500 RPM.
I have the same carb and one of the ports on the front is 'timed' advance. It will be the one that does NOT have vacuum at idle. Plug the one that has vacuum at idle and hook the other up to the distributor.
I am not familiar with that distributor and he may be right that you don't need vac advance but I'd question the lack of mechanical advance at higher RPM's. You really need 38 - 40 degrees at 3500. You will lose a ton of power if you are only at 8 degrees advance at higher RPM's.
If you hook up the timed vac advance, does it run any better at higher RPM's?

 

[jes72mustang]

Interesting.

So the timed port on the carb should be hooked to the distributor. I will check that out and go for a ride later this evening.

 

[jes72mustang]

Connected the Timed port on the carb to the distributor, and drove a bit. Still ran smooth, I will have to check it with the light again to really tell if anything changed. Probably this weekend. Plan on driving it more this week though.