Argh this is getting old... more ping problems...

[SadbutTrue]

OKay, well I took everyone's advice and did the following: The car now has 91 octane in it (and has for the last three fills), I added a pertronix ignitor, put in cooler plugs, and backed the timing back down (its 8 degrees BTDC without vacuum advance, 14 with)... and it still pings.

Any ideas?

 

[SadbutTrue]

Anyone? Is there any other thing that could be causing this pinging? I also have heard it might be carbon build up... whats the best way to get that out?

Also, whats an easy way to tell if my engines been missing? I hear a beeping-like soun?d that happens on a regular interval and my engines been stumbling... what could it be?

Thanks

 

[68GEETEE]

What is your total advance at 3500 rpm with the vacuum advance? IF you are over 40btdc, you are most likely gonna detonate, even with 91 octane. You may need to get the timing under 40 total advance to get rid of the ping.

 

[SadbutTrue]

how do i measure/change total ignition timing without changing initial (if its possible)... and my timing wheel only has marks to 25 or 30 I believe, so its sorta hit and miss. Any reasons my timing would be advancing more than it should be?

 

[WRXracer]

oh

maybe your not getting enough gas has you cleaned the fuel filter and check the pressure.. maybe your carb isnt working..

 

[pabear89]

how do i measure/change total ignition timing without changing initial (if its possible)... and my timing wheel only has marks to 25 or 30 I believe, so its sorta hit and miss. Any reasons my timing would be advancing more than it should be?

Change your total advance by resetting the screw in the vac advance on the dist or shimming it outward.
Depending on type that you are using.
To find total advance run eng to 2500 rpm and use adjustable timing light to bring your mark back to 0. then read where the dial is set.

PB

 

[10secgoal]

Change your total advance by resetting the screw in the vac advance on the dist or shimming it outward.
Depending on type that you are using.
To find total advance run eng to 2500 rpm and use adjustable timing light to bring your mark back to 0. then read where the dial is set.

PB

You HAVE TO get a advance timing light if you don't have marks that go all the way to 40 or so. Initial doesn't really matter as much as total timing when you get detonation. I had the same problem after rebuilding my motor with the stock dist. It had 65 degrees total timing !!!! The advance will more than likely need an allen screw.

 

[SadbutTrue]

would just backing off on that allen screw inside the distributor gradually until it stops pinging and then maybe a little bit more work? Which way do I turn it to reduce the timing advance, and can you give me a better idea of what I'm looking for? I've been in the distributor many a time and never seen any allen screws or other small screws. Or is it on the vacuum advance... which would xplain why I've never seen it.

 

[ratio411]

You are running lean.
That covers both your ping and the 'miss' like noise you hear (stumbling).
I call it 'lean pop' out of lack of knowing the correct term.
Jet up your carb, put some timing back in, use the hottest plug you can without either running rich or bringing back ping.
If you do not intend to keep running premium fuel, keep the cold plugs.
Good luck
Dave

 

[SadbutTrue]

well, the only thing about that is I actually think my carb is running rich. I've richened the mixture several times, and I can basically smell the gas while driving. in any case, whats the best way to tune an idle mixture? The edelbrock guide requires you to be able to see 20 rpm decreases and such... and I have no tach capable of that, and with a carbed car thats pretty tough anyway...

 

[Ronstang]

The best way to set idle mixture is with a vacuum guage (probably $20 or less at Sears). Start at 1.5 turns out from a light bottomed out position (or the starting position Edelbrock recommends) and try adjusting it each way and watch the reaction of the vacuum guage. Find the point where the vacuum reading is the highest. You want it set at the leanest point that the vaccuum is highest so lean it out again and sneak right back up to the highest vacuum again.

 

[SadbutTrue]

yeah, thats pretty much what I had been doing, but I had been richening it to compensate for pinging. Can anyone elaborate on that part that pabear and 10secgoal said? I really think my problem has to do with total advance.

 

[Ronstang]

Get a timing tape that is for the diameter of your balancer and install it. Then using a timing light rev the engine up and see where the engine stops advancing....it will bounce around a bit when it tops off so just take the average. If it is above 40 degrees you have a total advance problem, most Ford egnine builders shoot for 36-38 degress total advance. It should also stop advancing by 3000RPM. If you have too much advance try adjusting the allen screw in the vacuum advance to bring it down. You might have to take some of the mechanical advance out too....but that is rather complicated.

 

[10secgoal]

The allen screw is actually ine the diaphram. It's in the little hole where the hose connects. Another quick way is just to disconnect the dist. completely so you only have a few deg. advance. It won't be enough for peak performance, but it may give you an idea with your total timing so low, if it is the timing that is actually causing the detonation.

 

[ratio411]

well, the only thing about that is I actually think my carb is running rich. I've richened the mixture several times, and I can basically smell the gas while driving. in any case, whats the best way to tune an idle mixture? The edelbrock guide requires you to be able to see 20 rpm decreases and such... and I have no tach capable of that, and with a carbed car thats pretty tough anyway...

No.
The idle mixture has nothing to do with lean stumble.
You can run rich at idle and lean on jetting.
I took it that your stumble and noises were while driving...
What you describe as stumble, ping, and exhaust noise are all signs of lean jetting. If you just had one symptom, it would be a different story, but together it fits.
Dave

 

[SadbutTrue]

ok, well, does anyone offhand know what I should use as a starting point on an edelbrock carb when tuning it? Also, if I have to rejet the carb, what is the jet size that is one or two steps richer than stock on a 600 cfm Edlebrock? Finally, as far as the advance timing idea goes, what size harmonic balancer comes stock on a 69 351w? This allen screw, assuming I find it... which way do I turn it to retard the timing (I suppose I could find this out through trial and error rather quickly, but... I'd rather know what I'm doing first).

 

[pabear89]

Turn the Adv screw counterclockwise to loosen the spring.
It will take more vac to advance.
By turning it clockwise it draws the spring in and takes less vac to move the breaker plate.


PB