ENGINE PINGING

A one second light ping at WOT isn't too bad. That means you are only a couple of degrees too much at the 2000 rpm ping point.

The car will rev faster under heavy throttle once you get your advance curve dialed in for your particular engine.
Once we know how much vacuum advance is built into your MSD distributor you can start to tweek things a little.

I would contact MSD and/or your local speed parts dealer to see if they offer an adjustable vacuum can upgrade for your model of distributor. It will make fine tuning your ignition advance curve much easier. You can also use a shim around the vac can arm that pulls the advance plate to limit travel and the total amount of vac advance. We can get into that more later once we know what we're working with as far as total vac advance is concerned.

BTW: Are you planning to change cams anytime soon? A new cam will change the
    ignition curve requirements again. A new cam might eliminate the
    ping since most performance street cams have more valve overlap than the stock
    cam you say you have now. The overlap effectively reduces the dynamic
    compression ratio a tad by letting some of the low rpm cylinder
    pressure escape thus reducing the tendency to ping at lower rpms.

Are you running stock cast iron cylinder heads?  

thanx
no plans on changing cam
yes stock cast iron heads

timing at 2000 with vacumn disconected is at 16 degree
timing at 2000 with vacumn connected  is at 30 degree

a difference of 14 degrees

total timing with vacumn disconected is at 28-30 degree at 3500-3800 rpm
total timing with vacumn connected  is at 44 degree at 3500- 3800 rpm

a also a difference of 14 degree

thanx alot
brent  

Total timing with vacuum advance connected @ 44 degrees is OK @3500 rpm. Your engine may have too much vac advance timing at 2000 rpm though, which is probably why it pings for a second.
Too be sure, disconnect and plug your vacuum advance line and accelerate like you do when it pings. If the pinging has stopped then the vaccum advance is providing too much advance @ 2000 rpm.
If the vac advance can was adjustable you could adjust it down from 14 to 12 degrees or adjust it so the vacuum advance is delayed coming on strong until maybe 2300 rpm depending on how your distributor is designed.
Most modern vac advance canisters have a small allen wrench nut inside the vac cannister you can access through the vac cannister hose nipple. You might try a few small allen wrench ends and see if your is adjustable. Usually turning the wrench clockwise tightens the spring in the diaphram and reduces the amount of vac advance and the point it starts. Counter clockwise does the opposite. Probably a half turn clockwise would be right for you to start with. Trial and error. Minimum adjustment to make the ping go away.
Make sure you have your vacuum advance can hose connected to PORTED vacuum above the carb throttle plates otherwise the vacuum advance will always be on through manifold vacuum and will come in too soon. Ported vacuum only allows the vac advance to work at partial throttle and not at idle or wot.

Are you getting vauum advance at idle? Check timing @ idle with vac connected and again disconnected and plugged. If you see any vac advance at idle then the vac advance hose is probably hooked up wrong and that is your problem.

Let me know what you find. Once you get set up right and eliminate the ping you can start fine tuning the ignition curve for more power. Need to establish a no ping baseline first. You are very close now.  

thanx
i have acceelerate the car the way  it pings ,,with the vacumn advance disconected.
no ping when cooler temp,,but pings very ,very little when hot

i have no vacumn at idle ( checked with vacumn gauge ) RUNNING PORTED

I WILL CHECK , BUT BELIEVE THE VACUMN CANISTER IS NON ADJUSTABLE
I WILL ALSO SEE IF I CAN MAKE A SHIM TO RESTRICT VACUMN ADVANCE

TAHNX BRENT  

Good you are running ported vacuum source.
Check your timing again at 2000 rpm with vac advance and without vac advance again to be sure 14 degrees of total advance at ping rpm is still contributed by the vacuum advance can. Then you will know how much shim to put in if you can't adjust vac can with an allen wrench throught the vac can hose nipple.

Is your harmonic balancer accurate? If the outer ring of the balancer rotated, as they sometimes do on older units, you may think you are at 6 degrees base timing but it could be a lot more. Check to be sure. Bring number one cylinder to TDC by watching the valves. They should both be closed. Insert and hold a small rod, screwdriver or piece of coat hangar into the #1 spark plug hole to make sure the piston isn't moving up or down @ the top of the compression stroke. That is TDC. Now look at your balancer and see what it says. It should read @ or near 0 degrees/TDC. If not, then the outer ring on your balancer could have shifted. Your distributor rotor should also be touching your number one spark plug wire terminal at this point too.

It just seems like your basically stock 302 with only 6 degrees initial timing and vacuum advance disconnected should not ping under hard acceleration.
Try going to 4 degrees intial timing and no vac advance and see if the ping is eliminated.
Otherwise you might have some carbon build up in the combustion chambers that is increasing the compression ratio or a pair of small chamber heads or thinner than stock head gaskets that is forcing the comp ratio higher to ping point at normal stock timing. Just a theory.

I have the same 302 motor you do but with a slightly bigger cam. I run 10 degrees inital base timing with 24 degrees centifugal advance on a stock rebuilt Ford distributor with a Pertronix module. I adjusted the vacuum can to provide another 10 degrees of timing advance for a total of 44 degrees - all in by 3300 rpm. My engine has 9.25:1 compression and will run all day long in hot or cold weather on 87 octane gas without ever pinging. I can't make the engine ping if I wanted to at this setting. I have 64cc cast iron heads using 0.040 thick head gaskets.  

THANX
I HAVE BUILD A ADJUSTABLE SHIM .WHICH I WILL TRY TONIGHT , BECAUSE I CAN NOT ADJUST THE VACUMN CAN
I HAVE CHECKED TDC WITH THE VALVE COVER OFF, WATCHING THE VALVE TO MAKE SURE THE ARE CLOSED ON COMPRESSION STROKE ,AND THE POINTER IS AT  # 1 CYL, I BELIEVE THE BALLENCER IS COORECT.

WILL TRY TO REDUCE THE AMOUNT OF VACUMN ADVANCE WITH MY NEW SHIM
GETTING COLDER IN CANADA DONT KNOW HOW MANY MORE TIME I CAN GET THE CAR OUT( LOL )
I WILL LET YOU KNOW

THNAX BRENT  

OK Brent. Good luck. Hope that shim works to cut down some of the vacuum adcance for you before you get snowed in.  

thanx
i think i just about got it now
i shimmed to allow only 7 degree on the vacumn advance
i am running only 20 degree with vacumn coneected at 2000 rpm
without shimming i was running 30 degree with vacumn connected at 2000 rpm
i have to really listen to hear if it is pinging now,, it is extremly light ping

should i continue to shim to limit advance a little more?

thanx brent  

I don't think more shimming is necessary. If you can barely hear a faint ping for less than a second at WOT on hard acceleration it probably won't hurt anything. Besides, if you take away too much vacuum advance you'll make less power and have worse gas mileage. The trade off isn't worth it at this point. I think you are as good as you can get for now.
BTW: What altitude are you at?
Have you done a static compression check? Take number one spark plug out.Put in a compression tester. Disconnect main coil wire so engine won't start. Have someone put throttle all the way to the floor and keep it there to hold carb throttle plates wide open. Turn engine over with starter for a few seconds and read your compression guage. That will give you an idea of what your compression really is.
Mine came out to 160 on all eight cylinders. Yours should be somewhere near there. If it is a lot higher then you could have more than the 9:1 compression you think have and that could be part of the answer to your ping question.  

thanx
reddeer alberta is 2805 ft above sea level

i have done a compresion test as described my ranged from 149-151
thanx brent  

Brent,
Compression seems right on for your compression ratio. So that part is OK.
Altitude may play a partial factor in early pinging since atmosheric pressure
is less at that altitude and even less on a hot day. Fuel/air ratio is impacted and could impact cylinder charge density transitioning from idle to primary fuel delivery circuit and on to secondarary circuit on hard acceleration.

What primary carb and primary jet size are you running?

Might want to call your carb manufacturers tech line and explain what happens and see if they have any info about higher altitude operation that would be helpful to know.  

holley 0-80570 , 570 cfm double pump
primary meter jet = 54
sec meter jet = 65
pump discharge nozzle =0.031

prim power nozzle =85
sec power valve n/a

i am on holley tech line i will let them know
thanx brent

do i need to time/ adjust curve this car differently now that the ping is gone
if so do you think your cars timing might be a good place to start
thanx brent  

Suggest checking with Holley on what primary jet and primary power valve size they recommend for your stock motor at your altitude.

Now that ping is gone I would leave the base timing at stock setting of 6 degrees BTDC since you have a stock motor with a stock cam operating at 3K feet above sea level. Your centrifugal advance seems to be pretty good @ 24 degrees with one heavy and one light spring combo so I'd leave it alone too. I'd just try to bump up the vacuum advance as much as possible before it starts to ping again. That is about as good as you can get for now. At most you'll probably have 6 initial + 24 mechanical + 10 vac = 40 total degrees vs the 6 + 24 + 7 = 37 total you have now. Somewhere in between there is where you will wind up with max advance and no ping the way the carb is set up right now. Then you are dialed in.

If Holley recommends some changes to the carb you might experiment with more vac advance to see if the motor likes it without pinging. You might also try seperately or in combo with more vacuum advance going up another degree or two on your initial base timing to 8 degrees and see what happens. You just want max advance without ping.  

thanx alot
i will contact holley
i dont know how fast they are to respond

i will try your advice tonight and let you know

thanx brent  

My 600cfm Holley Model 4160 4 bbl P/N 0-80457S uses a 6.5 power valve and #67 primary jets with a #70 jet equivalent secondary metering block. I live at 350 feet above sea level.
How much manifold vacuum does your engine draw @ idle in NEUTRAL and what is your engine idle speed in nuetral?  

Holley Tech Phone: 270-781-9741
Email: carbs@support.holley.com
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