440 initial timing and spark knock

[PurpleBeeper]

Well, I have a slightly different perspective on this. Unless the engine is running really hot, if you hear any "ping" you need to reduce your total timing. Your total timing = initial timing + mechanical advance (inside distributor) since you're not running any vacuum advance. You "could" get away with this amount of total timing with race gas, but 93-octane is just about the highest you can find for "pump gas"

So, my suggestion is to reduce the initial timing a little bit more & see how it runs (maybe another 2-degrees, but AT LEAST 1-degree). If that works, run it.

If the engine becomes very "lazy" and doesn't seem like it runs as well, then you'll have to increase your initial timing back to where it was & limit your mechanical advance (inside the distributor). Depending upon the type of distributor you have, you can either adjust the limiting screws, install a limiting plate or "weld & file" the advance slots. Again, your goal is to eliminate "ping".

After ALL that is done, THEN you can start to play around with different springs/weights inside the distributor if you like.

HOPE THIS HELPS!

 

[Crackedback]

Take timing out of the distributor. That's the right way to fix the issue. It's not likely done with springs.

 

[furryfrog]

My newly rebuilt 440 is running great but getting a little spark knock under load. My initial timing is about 18 adv and all in around 38. My total timing is pre set in my Summit electronic dizzy. What do you guys run (initial and total)?
Specs:
1970 Belvedere
-440 30 over
-Keith Black raised pistons
-Comp cam (mild) 110 and .48 lift
-Quick Fuel 650 brawler carb
-Spread bore to square 3/4” spacer
-Stock intake and 452 heads
-Long tube headers
-will add ported vac advance after tuning

Lots of good info here, but of all the specs you listed, comp ratio would help, along with the exact cam your running. Lobe seperation angle and lift don't tell the story.
Just going to add that keep track of the rpms it pings at, and keep track of what rpm all your timing comes in at, I.E.does it ping in your timing curve or after it, or both.

 

[BSB67]

Lots of good info here, but of all the specs you listed, comp ratio would help, along with the exact cam your running. Lobe seperation angle and lift don't tell the story.
Just going to add that keep track of the rpms it pings at, and keep track of what rpm all your timing comes in at, I.E.does it ping in your timing curve or after it, or both.

Right. But I would suggest giving us cylinder pressure at this point.

The reason the springs might matter is because of what the OP said, "......slight spark knock under load......" without knowing more specifics about the motor, car and conditions, it is possible that his audiable ping is occurring because he has full timing to early. If he is cruising at 2200 rpm and tries to accelerate and it pings, slow the curve down. This can help or maybe fix the problem if this is the condition.

If he has audible ping at WOT above 3500 rpm, he has a compression ratio/cylinder pressure issue, assuming everything else is correct. And correct includes at least 36° total timing in his case, in my experience. Reducing timing is a solution to the ping, if you don't mind giving up horsepower. I will always pick reducing total timing as a last resort. There are several items that you can do before that, and I mentioned some of them.

It sounds like the OP is on the edge with his ping, and sounds to me to be a good candidate to try some simple measures to keep his max power without ping. That said, there are times where there is simply too much CR/cylinder pressure, and nothing will help other than pulling timing, or going back into the motor, or changing fuel.

 

[Sonny]

Lots of good info here, but of all the specs you listed, comp ratio would help, along with the exact cam your running. Lobe seperation angle and lift don't tell the story.
Just going to add that keep track of the rpms it pings at, and keep track of what rpm all your timing comes in at, I.E.does it ping in your timing curve or after it, or both.

 

[furryfrog]

Cool, good street cam. Like others have mentioned you should be able to get it under control with timing, and more simpler mods.