ENGINE PINGING

MY 302 , 4  BARRELL,  MSD IGNTION , IN A 66 MUSTANG PINGS UNDER WOT THRODDLE FROM A STOP LIGHT,,  ALWAYS AT 2000 RPM

WHEN COOLDER OUTSIDE IT IS BETTER ,,IT SEEM TO MAKE NO DIFFERENCE WHERE MY TIMING IS SET   4,6, 12 15 , 17 INITIAL,,,, MECH ALWAYS TO 34 TOTAL AT ABOUT 3500 TO 4000 RPM..

WHAT ABOUT VACUMN LEAK CAUSING THIS ??
PORTED OR MAINFOLD VAC ?

PLEASE HELP  

While it is true that cooler inlet temperature will reduce pinging, its hard to believe that your timing has nothing to do with it. Vacuum leaks do lean out your mixture especially at lower rpm. You should in most cases be using ported vac for your vacuum advance(was that your question).  

What is your compression ratio and what grade gas do you use?
Disconnect and plug your vac advance and see what happens. The vac advance should be almost zero @ WOT but you won't know for sure until you disconnect it.
If you have 12 degrees initial plus 34 degrees mechanical then that might be too much at 46 degrees total (plus vac advance its even higher).
Sounds like your advance curve comes in too high at 2000 rpm. If it still pings at 2000 rpm with the vac advance plugged and disconnected then you might want to put a heavier counter weight spring in the distributer mechanical advance mechanism to slow down the rate of advance a little. Do that only if knocking back the total mechanical advance to about 24 mechanical (for a total of 36 with intial timing @ 12) doesn't do the trick. Then make sure (using a timing light) that your vac advance doesn't get you to more than another 15 degrees on top of that for a total of 51. More than that and you could get some ping.
Let us know what happens.  

my total advance comes in at 34 @ 3500 rpm
if i set my base timing at 6 then i increase my mech advance to 28 which give me 34 total ,,if i increase my base to say 12 then i decrease my mech to about 21  for a total of 34

always total at about 34

the car seems to ping  at 2000 rpm under wot from stop light
no matter what i do

thanx brent  

sorry i use premium fuel
new plugs ( ccoler ones )
new t stat
9 to 1 compresion
newer rad

thnxs  

Compression and fuel grade good. Total initial + mechanical timing of 34 is good.

What kind of cam do you have? You won't need more than 10 or 12 degrees initial advance for most mild performance stree cams.

What kind of plugs & what do your plugs look like after running the engine?

You carb could be leaning out the air/fuel mixture at 2000 rpm when the carb transitions from the primary to secondary circuit at WOT if you have the secondaries come in too soon or if the power valve or jet sizes aren't right.
Tell us about your carb.

Now, disconnect vac advance line and plug it. Run the car and see if it makes a difference without vac advance hooked up.

Put a timing light on your motor and rev it to 2000 rpm and tell us what you see on the balancer in degrees with the vac advance still disconnected. At WOT the vac advance should not operate much if at all.

Now connect the vac advance and check again at 2000 rpm to see if there is a difference.

If your timing is really advanced beyond about 18-20 degrees at 2000 rpm with the vac advance disconnected then the mechanical advance is too loose and and advancing too soon. Need one stiffer centrifugal advance counter weight spring in that case.

Also be sure the timing marks on your balancer are accurate and haven't shifted over time on the outer ring of the balancer if it is an original or old unit.
When the number one cylinder is physically at true TDC the balancer should read the same. If not, it shifted. Then buy a new balancer or a timing tape and remark your old balancer (beware: it could shift again if it already did once).  

thanx for responding
not 100 per cent sure but believe cam is  stock
champion rj 17  GAPED TO 35
light tan in color ( new )
carb is holley 570 cfm double pumper vacumn secondarys , sec have mid sized spring in pump..
22 DEG AT 2050 WITHOUT VACUMN ADVANCE
runs good at idle,, thanx brent  

Use brown spring in Holley vac sec. Plug color sounds OK. Why not Autolite plugs with .034 gap? You might try to knock back the advance at 2000 rpm a few degrees with stock cam by using stock 6 degree initial timing setting. 22 might be too much at 2000.  

thanx alot

i changed the sec pump spring to black ( mine is black )( the heavy one  )
i will try this out tonight
i will also back off my initial timing ,,till i have maby 16-17 degree at 2000 rpm
i will let you know  

Sounds good. The black spring opens the secondaries even later than the brown spring so you are OK with that and a stock cam. The brown opens just a little sooner. Don't go with anything other than the black or brown with the stock cam. For ping reduction stick with the black until you get the ping problem solved.
Was trying to make sure you didn't have too weak a spring in there that could be part of the ping problem. You don't. It's OK.

16-17 degrees @ 2000 sounds good too.  

thanx for replying
putting heavery springs in the distributor to delay total timing ,to lower degree at 2000 rpm .. this will increase rpm that total come all in at..
( say 5000 )
lower base timing to allow for less timing at 2000rpm ,,,reduces total timing at the same rpm  that the total comes in at ( say 4000 )

which way do you think is better

thanx brent  

Total timing should be all in by about 3500 rpm.
You only want to reduce the number of degrees at 2000 rpm since that is where you get the pinging. Everything else is OK except there.
I would try just reducing the base timing to 6 to 8 degrees and see if that works first.
If not, then just put in ONE heavier spring to delay the advance a little. Two springs might be too much and shift the delay too far which could cause other problems. Only go with two heavier springs if base timing and/or one spring doesn't do the trick. Bottom line : make the minimum change(s) necessary to get rid of the ping problem @ 2000 rpm.  

thanx
tying to reduce timing at 2000 seems to affect total  at 3500-3850 rpm
i reduced base timing to 6 deg
now i have 16 deg at 2000 ,,
28 deg total  at 3850 with 1 heavy spring and 1 light spring ,, pings less,,,,less low end power
will i need to get this back up to 34 deg total ( if i increase stop bushing to get to 32-34 total at 3500-3850 will this affect tiiming at 2000 rpm )
thanx brent  

Is the new timing of 28 degrees total advance with the vacuum advance connected or not?
Check your total timing with the vacuum advance connected and see what that reads compared to the the same test with the vacuum advance hose disconnected and plugged. The difference is your max vacuum advance.
Also do the same test at 2000 rpm where it pings to see how much vacuum advance you get at that point.
Then you can dial the timing curve in by moving the vacuum advance amount and start point around.
Leave your initial timing and total timing where it is for now so there is a base line for further info. This is a good place for now since you say the pinging is reduced. Describe the pinging you get now. Is it very light and only for a second heavy and longer in duration? More info helpful.  

thanx
the total timing of 28 degrees is with vacumn disconnected
did not check it with vacumn connected ( will do tonight )
the pinging is light and mabey 1 second
car seems to take longer to rev up  when under haevy troddle.
vacumn advance is not adjucstable on this msd distributor
thanx alot

brent