Looking for the best timing advance setup, I found this article here:

https://www.ford-trucks.com/forums/6...g-10-btdc.html

But I thought I should not revive a 10 year dead article. So here is my question:

Sticker says 6 deg btdc. At this setting this newly rebuilt engine has spark knock at partial throttle under load (such as going up a steep hill). This knocking goes away at wot.

In an unrelated thread, it was suggested that maybe I am making too much vacuum and the distributer is advancing too much, causing the knocking.

I was playing with the timing and the knock was still present (although less) at 3 deg btdc, and had gone away at tdc. This has got to be murder on my mileage. But what choice do I have, I would rather not have to replace this engine again too soon because of excessive engine knock.

With the dizzy loose I found that the engine makes peak vacuum when the timing is advanced a little past the timing marks (this is a method (peak vacuum) of setting timing on fordsix website).

I could just advance it to 10 btdc and disconnect the dizzy...?

What should I do?

300/T-18/2.75/30 inch tires running regular unleaded thru a non feedback carb.

 

Does your distributor have a vacuum advance canister on it? If so, it may be adjustable.

There's your initial advance, mechanical advance, and vacuum advance. Setting the initial is only one part of the equation.

The mechanical advance is set by weights and springs inside the distributor (all adjustable), but if your engine is stock, it shouldn't be an issue. However, you can try adjusting the vacuum advance to back it off a little. That way you can run more initial without hurting your engine.

The vacuum advance canister is usually adjusted by inserting a hex wrench in where the vacuum line connects on the distributor and rotating left or right. I can't remember the exact size, but it's pretty easy to tell because if it's too big, it won't go in, and if it's too small, it'll feel like there's nothing inside. Be careful though because it won't "bottom out". The only thing in there on the other side of the adjustment is the diaphragm. If you get one that's too small and insert it too far, you could puncture it.


Check out: Distributor advance

 

I agree with AB that a vac advance adjustment is where to start. If you have one of those Mityvac hand vacuum pumps with the gauge on it (they are made for vacuum bleeding brakes. They are useless for that, but they are handy for a lot of other things) you could try this:

Pull the vac line of the vac advance and plug it at the carb. Then loosen the dizzy, start the motor and twist the dizzy with your timing light until the initial advance is 0 degrees. Tighten the dizzy and connect your mityvac pump to the vacuum advance. Start pumping it to put vacuum on the vac advance. Everything 3 inches of vac or so see how advanced the timing is. Go clear up to 22 inches (this is where my own 4.9L idles at). This will give you a sort of map of what your vac advance is doing. Then find the right allen wrench like AB mentioned and figure out which way you need turn the diaphragm adjuster to increase sensitivity up or down. Once you do that I would adjust it all down, or at least really far down. Then set your initial advance back to 6 degrees BTDC, plug the vac line back into the vac advance and go for a drive. Then start slowly adjusting the sensitivity of the vacuum advance back up and going for a test drive each time. Repeat that until you find part throttle detonation again then back off a small bit and call it good.

If you're feeling intrepid then once you've got all that done then move your initial timing forward to 10 degrees BTDC and go through the vac advance adjustment process again. It's possible your engine might like that even more. Worth a try if you have the time anyway.

 

I'm going to likely raise a few eyebrows here, but what heat range plugs are you running?
If you have a higher heat range plug, it will hold more heat, which could lead to detonation under light throttle.
Correct me if I'm wrong, but aren't we discussing the engine you just rebuilt and installed? If so, piston to bore clearance, nor excessive carbon buildup should be a concern. However, if the clearances are still a bit tight, there could be a little extra heat inside the cyl, due to added friction.
Have you tried running a higher grade of fuel?

I will add to the above info regarding the dist advance by saying that the mechanical advance springs may be a bit weak, allowing the timing to advance too fast.

 

Yep, same motor. I started it in a more proper forum, I didn't want to keep going through the 87-96 forum (at least in that thread).

I have autolite copper plugs in, not sure what heat range, I just went with coppers because of what a lot of people on here were saying about how they work best...

The dizzy is a new reman from Napa, should be relatively tight right?

It is just regular gas, after I dumped this much dough in it I didn't have a whole lot to put a higher grade in those two big tanks.

I am just asking about this because I want this to last me a good long time, and the knocking has me worried. Also today I noticed going home from work that my temp was higher than usual (it doesn't get hot in Whidbey Island...) it was at the high end of the gauge, where it is usually middle of the road. I am looking at setting it back to 6 deg, and trying what that article said above, (which was a great deal of info I didn't know).

I can't thank all of you enough for your help. I have been using a plain timing light borrowed, but today I got one that has the advance adjusting ****. Hopefully I can use it correctly... Will keep you posted on what results I get.