Ok, I have been trying for months to get this fixed, only problem is no one around here knows how to adjust the vacuum adv timing. I have a 71 ford 429 with dove-c heads, holley 770 truck avenger, edlebrock perf rpm intake, lunati cam etc... I have my base timing at 10 btc and I am getting constant pinging when it gets hot. And it does get hot now over 200. Sometimes it even runs on after I shut it off. The engine is about 10,000 miles just rebuilt about 1 year ago. I use premium fuel every other tank I even use octane booster. I used some sea foam and changed the plugs today also. It is no better. I need to know how do I adjust the vacuum advance timing? I set my base with the vacuum disconnected and plugged. Do I use an allen key and which way do I turn it? How do I vheck the advance timing?

 

I forgot to mention that the truck has no bottom end power and also has some hesitation. The truck use to hover around 160 all the time before I screwed with the timing,new pulleys and such. The Vacuum advance was disconnected and plugged before I bought the truck. I have since reconnected it.

 

You need to check total advance without the vacuum connected. If it is higher than 38 degrees (34 is better), you need to back off on you initial timing. Vacuum advance can be checked several ways. The easiest is to run the engine with vacuum connected at 3000 rpms and check the timing and the engine vacuum. Record those numbers. Now disconnect the vacuum and run again at 3000 rpm and check timing again and vacuum. The difference between the timing numbers tells you how much the vacuum is rolling in. But you need to be aware that it can be as much as 10 to 15 degrees over mechanical advance. Prefer using vacuum pump instead of the engine vacuum, but if you don't have one the engine method works. Vacuum advance drops out very fast when you go down on the throttle when the engine is under load as it is a function of engine vacuum..

 

OK, anybody know of a shop near Oceanside CA. I am lost and need to get this fixed.

 

How do I check total advance without it being connected? Is that possibe?

 

You have to check the mechanical advance first as it is a function of engine RPM and isn't effected by engine load (vacuum). The total advance is normally concidered to be the mechanical only. Vacuum varies to much.

 

Ok, I am confused. How do I check the mechanical advance? To check base I just remove the vac line and use my timing light correct? But how about mech adv?

 

my truck is a little sluggish down low which way on the mech advance do I need to go in order to liven up the bottom?

 

I also have a 460 with DOVE-C heads, and have had pinging problems, and also the engine was lazy. What I did was remove the vacuum advance and just ran the timing up till the engine pinged when in hard acceleration and then backed off some. The engine runs cool and has lots of power. My ignition system is a MSD box and distributor, but this method will work for a factory ignition setup as well. To check mech. advance, run the engine at 4500 rpm's and check timing.

 

Yes, and to check total timing you hook up the timing light like normal. Disconnect the vacuum line from the carb and plug it (I don't but the experts claim you should). Now rev the engine until the timing marks stop advancing. That will be your total advance. If you have a light with an adjustable timing, set it to 30 degrees. Then you won't move past the end of the numbers on the damper. Then add whatever the pointer stops at to 30 and you have your total advance.

 

Yeap, you can run without vacuum advance and the engine will run fine. However, your gas mileage will suffer. Back in the dark ages when gas was 25 cents a gallon I use to run a dual point dist without vacuum advance in my 428CJs. But in this day and age with $2.40 a gallon gas no one can afford to run without vacuum advance unless they are rich.

 

Well I definately have a problem then because mine will not run w/out the vac advance. It studders and hesitates real bad with it disconnected and plugged.

 

Where is the vacuum advance hose hooked up too, the carb or the manifold?

 

The carb. I used the one that stated it was for vac advance. it is a holley ta 770 and the port is on the pass side front.

 

Is the port on the carb on the metering block or on the carb base plate? You need to check to see if there is vacuum on that port at idle. If there is and it a a base plate port that is normal, if it is a metering block port then the throttle valves are too far open.