Ive been driving my fresh 428 and I get detonation at low rpm 3rd gear if I hit throttle hard. When I'm at a good cruise speed In 3rd it has lots of snap and power when throttled hard.
Motor is 10:5:1 and I try to run 94 but at least 91 octane gas.
Next my ignition is a stock points with a petronix lll ignitor upgrade with the proper matched coil. The vacuum advance might be the issue. I have it disconnected but doesn't seem to help even when connected. I seem to get some engine run on as well.
I'm debating on going with new msd ready to run distributor or the billet pro without vacuum advance.
Does this seem like a ignition problem? I feel this motor should have more to give and the detonation needs to go away so I can mash the pedal at all times with no issues!!

 

What cam?

Any other details on the engine might help.

 

What is your total mechanical ignition timing. I will bet it is higher than 38° which is your problem. Oh and the vacuum advance connected will just make it worse.

 

Here's the cam
33-248-4 - Xtreme Energy

More info
670 Holley
Performer rpm intake
D2teaa heads with 1.65/2.09 cj valves
Headers

 

Would I have to limit the total with little stops on the pins or I heard of putting tack welds on the weights..??
What should I run for initial and total?

 

I have the stock dizzy with the Pertronix III as well. I couldn't get my timing correct, it was way too advanced. I replaced the old worn dizzy with a rebuilt, reinstalled the Pertronix, and I was able to get the timing correct with 38 deg total and 12 deg initial. I believe 8 deg is the stock setting, but mine ran better at 12. My weights are 13x2=26+12 initial=38 total. There are some good posts here, Bear has one in particualr, which explain the procedure for timing. Good luck.

Kurt

 

KO1960, and I will bet his dist. is in the 18° advance curve slot. 18X2= 36+6= 42° for a conservative initial timing. Or more likely, 18X2=36 + 12=48°. Either of which is way to much advance.

 

When you guys say "dizzy" do you mean distributor??
I think of the bottom gear. That's the first question
Second is do I just check the weights to check my total timing with stamped #s?
Should I buy a new rebuilt distributor and then replace with my petronix? Or is an msd much better and if so how much?
If I buy a new rebuilt unit can I get an ideal total timing I should be looking for?
And how does a guy recurve a distributor? Read that shops can do it with a machine to driving style and motor type?
Willing to do that if needed.

 

I brought in a distributor for Monday. It's a cardone 302807. $85
Told the guy it's a 73 f250 with a 390 and with vacuum
Advance.
I'll admit mine is original and a oldie freshened up. Do I need to change weights and if so where do I get them and what should I install that would be more ideal. Your help is very much appreciated!!

 

You never believe stamped numbers. You check total advance by running the motor sans the vacuum advance connected and with a timing light (with retard **** preferred) on the engine. Rev the motor until timing quits advancing. If no retard ****, then you have to add some timing marks using paint or chalk. Use 10° increments, that will be close enough. FYI the weights and springs only control how fast the timing comes in, not the total. The stops control that.

 

It may be apple to oranges but I have the same distributor and similar cam (a little smaller Crane cam). I sent the distributor out with the cam specifications, to be set up. The shop set it up with total advance @34-35 degrees/3500RPM and initial advance 14-15 degrees, vacuum advance 11 degrees @18" vacuum. I haven't got this motor in the truck yet so I can't comment on whether or not it's dialed in. Just FYI.

 

Without knowing the total specs of the engine; compression, heads and porting, intake, carb, exhaust; the cam specs are a waste of timing for dist. setup.

tater_51, the dist advance curve belong in a Mustang and not a truck unless you are running a minimum of 4.10 gears. Otherwise it is gonna ping the hell out of the motor.

 

73 ford guy, go to the tech folder in this forum and read Bear's post on recurving a dizzy, complete with pictures and info. It is comprehensive and will explain better than I can. By the way, my old dizzy had 10L and 13L weights. The rebuilt one came with 13L and 15L weights. Good luck.

Kurt

 

I sent all the information I had at the time, 410 FE, 10.1, cam spec's, 4.10 gears, stock heads, intake, 4 speed, etc. They advised that I will need to run premium, also stated that I could have went with a little more cam to avoid any pre-ignition. I was looking for some low end grunt so I guess I'm stuck with what I have.

 

AGAIN, The advance in the dist. has nothing to do with the weights. The weights and springs control how quickly the timing comes in. The maximum amount is controlled by the stops, of which there are two in the dist., and they will be different from each other. Both settings will use the same weights and spring.