Confirmation that I'm Adjusting Timing Correctly

[Cal2121]

I have a rebuilt 390 (about 400 miles on the rebuild). Initial timing is set at 10 btdc and total timing is at 35. When I first was running the engine, the vacuum advance wasn't working because I had a bad vacuum advance canister. I did not notice any pinging at that time at all. I have a new vacuum advance canister hooked up that works. I noticed that now when I pull a hill, I get a small amount of pinging. Based on the vacuum advance instructions, I started (only one adjustment so far) removing advance from the vacuum advance canister. I just want confirmation that this is the correct approach, as I'm still learning the details of timing and its various components. I apologize in advance if I left out any details.



Craig

[Ranchero50]

Something does not compute. Which dizzy? Did you verify the TDC vs. balancer marks during the rebuild? Stock Ford dizzy should be able to run 15 btdc without issue.

[Cal2121]

Thanks for the reply. Dizzy is the PerTronix Flame-Thrower (D133700). Engine builder confirmed TDC when we set initial timing at 10 btdc (with total timing at 35). It did not ping when running without vacuum advance. When I hooked that up, I started getting a small amount of ping under load when going up a hill. I assumed this was from the vacuum advance being hooked up given that the instructions read "Test the vacuum advance setting by load testing the engine. If pinging is detected than turn the vacuum advance setting counter clockwise until the pinging stops."

So, few questions now based on your comment and my original post:

1) Should I increase the initial timing from 10?
2) Should removing advance from the vacuum advance canister (per the instructions) address the minor pinging?

Thanks again.

[Ranchero50]

Yes, more initial and do the adjust on the vacuum can. The ones I've seen had a preload adjuster screw in the vacuum port. Follow their instructions.

I try to limit the max advance to 34 or so. Once you think it's close, do a WOT run for reference and then back the timing off a couple degrees and see if it pulls harder or weaker. You can be over advanced and not into audible pinging. If it pulls harder backed off then you are overly advanced.

[Cal2121]

Thanks, Ranchero. I will do what you said and see how she does.

[farmallmta]

After adjusting your timing and vacuum advance curve to minimize pre-detonation, you may still have load ping on a new engine with higher compression. Low grade fuels of 86 octane will cause pinging under load. Higher octane can help, but so can plugging the vacuum line to the distributor vacuum advance.