scootchu

I was searching for how to use a vacuum guage to adjust a carb and timing and read this:
"Test drive your car and listen for any ping under light acceleration as well as under heavy acceleration. Additional retarding of the timing may be necessary if excessive pinging occurs. You should hear a very slight ping under light acceleration, and none under heavy acceleration. Your engine is now optimally timed to run on today's lower octane, no lead fuels."

It was part of an article found here:
http://automotivemileposts.com/garage/v2n8.html

I have always thought pinging was bad anytimeit happened. I was running my car last night and indeed found that under light throttle I got some slight pinging and that's why I was searching for tuning my 302.
According to what was written, a light ping is acceptable under light acceleration. Can anyone clarify???

pass1over

ive never heard of any kind of pinging being go0d. Thats not how I would tune my car at least.

blue66mustang

Nope…PING = DETONATION. Detonation = explosion. You don’t want to blow up your motor do you ?
If you want to use a vaccum gauge to set timing go here...
http://www.mustangproject.com/links/...g%20timing.pdf

scootchu

I know I don't want to. I just found this curious.
Eliminating Ping totally, while achieving the "sweet spot" is my goal.
Today I am going to retard the timing a bit, back to 8, install a set of Mr Gasket curve springs, and make sure total advance is 36-38. I have a feeling my vacuum advance is too strong, so after I get the intial and total dialed in, I will dial in the vacuum advance.

67mustang302

You need to stop reading that site. Pinging even under a light load will still get things very hot and eventually ruin your engine. Try and get it around 12 initial at 34-36 total, with all the timing in by around 3,000rpm, and see how it works. And if you can tweak your vacuum, set it to add only about another 10-12.

Starfury

Blue, you don't set timing with a vacuum gauge. Not at idle, anyway. You'll end up with a ridiculous amount of advance at idle. Under no-load conditions, the engine will want a LOT of advance, but as soon as you stick it in gear it will either fall on its face or detonate.

67mustang302's method is the proper way to do it, although I think 12* at idle is a little too much for a stock motor.

67mustang302

I'm just ballparking.

I usually set timing based on the ballpark of what I know is ok for a combination, but then tune based on how it drives and what gives the best performance. Total timing is best set at the track where you can get clean plug readings and see mph.

jlg2002

Try looking at Mustang Monthly, April 2009 pp 66-67. it has a very good article on rebuilding dist's and how to tune one.jlg

scootchu

You guys are right. If you do set your initial with a vacuum guage it's gonna be way up there. That's not the first time I have heard doing it that way though. I settled for 8 initial and the light set of curve springs, which gives it about 36-38 at about 2800 rpm. My problem comes with the pinging on light throttle and I am beginning to think my Holly 600cfm is leaning out from idle and causing that. That being said I am now running the idle mix at a little over 3.5 turns out. I tried to set that up using a vacuum guage and it caused nothing but problems. This 302 makes my head spin. It most likely will be either rebuilt or replaced sometime in the near future, but for now I just want it to run the best it can.

Starfury

The mixture screws on the carb are only for idle mix. Once you get above 1500rpm, they don't really do much. There are other things you need to do to richen the mixture up under load, but I'll let the Holley guys help you there.

That 36-38* @ 2800 may be a hair much on a stock cam, which builds more pressure at lower rpm's than a performance cam would. You might try to drop the total timing back to 34* and/or widen the curve a bit so that total doesn't come in until 3k or so.

Or it could just be crappy/low octane gas. What octane are you running? What's the 302 out of?