67mustang302

You need to learn what an ignition system does and how altering it affects engine performance, same thing with a carb. Trying to tune a carb'd engine yourself without knowing what's going on is asking for trouble. And don't shim the spring on the pump linkage, you can make it a bit tighter or looser by turning the adjusting nut on it, but you change fuel delivery with cams and squirters. You need to get your timing right first, a carb'd engine will always have throttle response issues if timing is not right, they're notoriously sensitive to ignition timing. The rule of thumb is that about 90% of carburetor problems are really ignition problems.

You need to surf the net and read and learn, that's really the only way you can do it. We can only help you so much over the internet, but if you don't understand what we're telling you it's not doing anyone any good.

First, set your timing at 14 at idle with vacuum advance unhooked. Hook up the vac advance to ported vacuum on the carb. The vacuum advance won't operate at WOT since you'll have less vacuum than it needs to function(they typically pull out all the vacuum advance by 6" hg manifold vacuum, and at WOT you're less than 2"). The total advance without vacuum should be around 34-36, and it should occur by or slightly before 3,000rpm, but that might need to be played with, what timing curve an engine tolerates depends on the specific engine.

Slo5oh

Quoted for emphasis

Azriel_Strife

Allright guys, thanks for that, I can't advance my timing at idle to 14deg, it will ping garenteed. The best I could do for manual advance is 12 degrees without ping. I would go about testing my mechanical vac advance max by running with and without it, and then measuring the difference?

from there once I know how much my vac adds, I can tune my max mechanical to get a total advance of 34-36 deg?

Slo5oh

What are you using for gas that is making you detonate? This is a stock car, with stock ignition timing. There really should be no issue. Are you sure you are detonating?

Azriel_Strife

yeah, i'm 100% sure it's detonating. from inside the car it sounds like marbles bouncing around in my block. only happens when i advance the timing.

thats why i'm unsure about doing all this work, if my total advance is too high then it will still detonate. with this distributor, i should just have to set it to 10 deg btdc, and it should run happily. so why do i need to unlolck a dizzy for my daily drver?

Slo5oh

is your car running?
A. Take a video, because I refuse to believe your car is detonating.
B. go find a hill, put your car in the highest gear (5th or 4th) and accellerate slowly. If you have any detonation youll know it then lol.

67mustang302

If the advance curve is too steep it might ping from too much timing right off idle. But yeah, with the right curve on a stock engine it shouldn't ping with 14 initial. Are you sure the timing marks are right? Try disabling the vac advance, and check the timing in neutral while you rev the engine, get someone to look at the tach and have them tell you what rpm you're at when the engine is fully advanced.

Azriel_Strife

I don't know what you mean by asking if it's running, it is driven daily though. I'm totally sure it's detonating, I may not know much about timing on a v8, but I know how detonation sounds. The only thing I can think of is that my balancer turned on the crank. That could explain most of my problems. Including my timing being out a bit.

Right now it's set to 10 deg, and I know I can completely resolve my hesitation problem by advancing only my timing, but it detonates when I advance past 12-13 deg. I suppose thats neither here nor there though, because it begins detonating before the hesitation dissapears from advancing the timing. I use regular 87 octane, usually from chevron. Perhaps I should check my TDC against my balancer.

How do I know when my #1 cylinder is at TDC on the compression stroke?

Slo5oh

If your car is having a hard time starting as it sits, your ballencer may have slipped. That would be a good indicator that your timing isnt truely at what its reading.

hard starting or backfire while trying to start.

Azriel_Strife

Hmm, it starts nicely, 2 pumps and crank with a tiny bit of throttle, starts right up. no choke has ever been needed.

I'm going to see my v8 friend tomorrow, so hes going to help me dial in my dizzy, we'll see where to go from there, I'll post back with results.