360 knocking after new advance springs

[J20DAN]

Well here is one for "if its not broke don't fix it" I read the TFI upgrade section in the tech library and said I can do that. So the first thing I did was replace the advance springs in the distributor. I then set everything back to where it was and now with the proper timing 8 degrees (with a timing light at the proper rpm), I have significant knocking/pinging at 35mph and up that was not there before. So I double checked everything and put in one heavy spring and one light, same result. I now have the timing set at 4 degrees and the pinging is reduced but still noticeable. What the heck have I done wrong?

Thanks
Dan White

[Bob Barry]

How much slack is there for that heavy spring? If there's a lot of slack, you may be running too long on that light spring before the heavy spring steps in to slow it down. Try switching the posts that the springs are mounted on; a little distance can make a big difference.

[Kris]

Are you checking the timing with the vacuum advance disconnected and pluged ?
If so...
Have you tried re-installing the old springs and checking for ping?
Also, check the vacuum line to the EGR, it might have come off.

kris.

[J20DAN]

vacuum line is plugged and no EGR.

Dan

Only tried one of the old springs with one new one. One flipped off when I changed them and I have yet to find it.

[turtle jim]

If it were me at this point,I'd try different spark plugs,one or two ranges colder.Worked for me once before when I got pinging after a tune-up.

[J Series Trucks]

It could also mean that you might benefit from an adjustable vac advance. There are two kinds of pinging on that occurs from too much total timing (at WOT), and pinging at partial throttle. Your advance curve may be good for total timing, but the vac might want to be less agressive on partial throttle where the vac advance is working. Somehwere your advance curve is too aggressive. One stpe colder is usually good for a stick-ish motor. You'll know when you've gone too cold by the plugs fouling-then go back one step up.

BTW, a hotter or colder plug isn't actually hotter or colder, it refers to the plugs ability to remove heat from the combustion chamber. If your plug is too hot (not taking away enough heat) it can stay hot enough to cause detonation in the cylinder much like a deisel igniting unburned fuel without the plug actually sparking.

Brad Feick

[Bob Barry]

Luckily, the stock vacuum canister on a Motorcraft distributor IS an adjustable unit! smile.gif

Stick a 1/8" allen-wrench into the vacuum nipple and turn counter-clockwise a 1/4-turn at a time until the ping goes away.