Timing issue (pinging) solved!

[TrybalRage]

Just wanted to share what I've been dealing with to hopefully help someone else out who ever runs into the same problem.

I've been dealing with a pinging issue for a while, one that I've ignored by dialing my timing back to 2-4° BTDC. I was starting to think that everyone was nuts, talking about setting 10-14° as their base timing. Around town my truck was fine, but I moved recently to an area with a lot more hills, and I've had to do quite a lot more highway driving. Up those hills I'd start to ping, and have to back out of the throttle further and further to avoid it to the point I was barely crawling up the hill. On the highway I could cruise along all day, but if I had to pass someone, forget it.

I've been running with a Skip White distributor I bought after the ESC went bad on my factory one and I just wanted to go to a "normal" HEI. Initially I had my vacuum advance run to a 'ported' line but after much reading, I started running it off of manifold vacuum. For a long time I thought my pinging problem was the adjustable can that the distributor came with.

I've been playing with timing, swapping out vacuum cans to the original, and doing a lot of reading on here and other sites. Finally I decided it was time to get this fixed.

Bought a piston stop and verified TDC. The marker on my balancer was within a degree or two. Stuck a timing tape on there to better track my numbers. Disconnected my vacuum can and increased the idle to make it drivable and started testing. At 10° initial, I was still getting horrible pinging at medium-heavy throttle under load. WOT was fine, no pinging. Ok - maybe the springs are too light, advancing too early. Had picked up a Mr Gasket recurve kit so I started putting in heavier springs. Started with the medium - no go. Still pinging. Put in the heavy - nope, still pinging. WTF. Everything I've read says if I verified TDC, set to ~10°, heavy springs should be too slow of an advance, but here I am, still backing out of the throttle on hills.

So I started looking at my factory distributor. The springs. The weights. How it all came together. Looked back at the dizzy in the truck and realized that the Weights seemed to be very "loose". Checked timing again and realized that with the heaviest springs, the first tap of the throttle was still advancing the timing by 7-8°, at least. Took the cap off again and saw that the weights were able to move outwards quite a bit before the springs ever even limited their travel (this is with the weights it came with).

So even though they looked different, smaller, I took the weights and bushings from the recurve kit and put them in the distributor. Almost no play. Kept the heavy springs, and took it out for a spin. No more pinging! Reconnected the vacuum advance (the adjustable one the Skip White came with), still no pinging!

So it turns out the weights it came with were pretty sloppy, allowing advance to happen before it was supposed to, causing a lot of under load/middle throttle problems. I still have some tuning to do, I think I can drop the heavier springs for some lighter ones, and adjust the vacuum can a bit, but I finally feel like I'm on the right path.

Hopefully this helps someone out there, and thanks for everyone else who posts their advice and tips (Rich's distributor insight is invaluable, BTW).

[lilpoindexter]

Congrats.

[StarDust]

If you want to further fine tune your timing I highly suggest a timing light. Now I'm no expert but I don't think just setting your timing until it idles and runs decent will cut it. What I do is rev it up to 2400rpm or until the timing stops increasing and set it to 36° btdc and let the initial timing fall where it wants. If the initial is too high or too low then swap springs until the initial is where you like it.

[Gregski]

Originally Posted by StarDust

If you want to further fine tune your timing I highly suggest a timing light. Now I'm no expert but I don't think just setting your timing until it idles and runs decent will cut it. What I do is rev it up to 2400rpm or until the timing stops increasing and set it to 36° btdc and let the initial timing fall where it wants. If the initial is too high or too low then swap springs until the initial is where you like it.

I second this one, yesterday I got off the phone with Rick from Specialty Auto Parts U.S.A, Inc. the guys who make the Proform distributors. He is such a nice guy, does not try to impress you, does not talk down to you. And he recommended the exact same thing with the exception of reving it up high to like 3500 RPM to ensure you are all in, but pretty much the same deal, and with the distributor vacuum canister disconnected setting the timing to 36 degrees, than checking your initial timing just to see what it is

[TrybalRage]

Originally Posted by StarDust

If you want to further fine tune your timing I highly suggest a timing light. Now I'm no expert but I don't think just setting your timing until it idles and runs decent will cut it. What I do is rev it up to 2400rpm or until the timing stops increasing and set it to 36° btdc and let the initial timing fall where it wants. If the initial is too high or too low then swap springs until the initial is where you like it.

Oh, I've had a timing light this whole time. But I had to set my initial way, way lower than everything I read to avoid any pinging, and I still had it happen when on the highway or up hills. I got the tape so I could better see where it was falling at higher RPM's (tab only goes to 12°).

I was at 35° or so with the engine speed up, but couldn't explain the mid-throttle pinging.

Now I'm at about 32° at 2500, so I could increase it more. I just quit fiddling with it after replacing the weights and fixing the problem.

[Firebirdjones]

Originally Posted by StarDust

If you want to further fine tune your timing I highly suggest a timing light. Now I'm no expert but I don't think just setting your timing until it idles and runs decent will cut it. What I do is rev it up to 2400rpm or until the timing stops increasing and set it to 36° btdc and let the initial timing fall where it wants. If the initial is too high or too low then swap springs until the initial is where you like it.

In that instance you want to modify the stop bushing (first make sure it's still there, they commonly fall out causing over advance conditions) Most are cheap plastic. Swapping springs will only slow or increase the rate of advance curve but doesn't fix the issue at hand.

Once total is set (at 36 for instance) if your initial isn't where you want it you either need to increase or decrease the diameter of the bushing or file the bushing slot to make it longer, or fill it to make it shorter.

I like to solder in a brass bushing so it will never fall out. Then file and modify that to limit travel about 18-20 degrees. Then set my initial timing to 16-18 which give me 34-38 total with room to adjust total up or down depending on where the engine makes best power on the dyno.

Only after all that will I start to dial in some adjustable vacuum advance. Usually 10-12 degrees is enough. Different combos vary but these are good ballpark numbers to start with.