should i time it right, or worry about vaccum

[cutlassguy]

i got this gauge from an ol timer i know and when i did my timing, i hooked it up to manifold vaccum, (or the line that comes off the branch thing that goes to my vaccum advance and comes from the carb), and whenever i changed the timing so it would say "normal", it ran like a bag of cats, and when i would adjust for good idle and power, the gauge would say "late IGN timing"...anyone care to shed a little light on this? i thought you wanted as much vaccum as possible, but going by this gauge, i should be timing my engine to run like sh*t... my timing light doesnt have degrees or anything but i found timing it to 8degrees on the tab made it run fantastic. i think its somewhere are 2degrees when the gauge says normal but it could be the other way too, cant remember...

 

[jmt455]

Does your car still have the CCC system on it? Can't set timing with the CCC system active.

 

[Phoenyx]

I've used those gauges for setting mixture screws on a carb. Never heard of using them for timing.

 

[cutlassguy]

yah everythings original, ccc carb an all. im assumming its a proper vacumm gauge. just wondering why it would run so shitty when it says it has good or normal vacumm and visa versa? personally i dont care what anyone says im gonna run it so the timings right and i have good performance, but why would this gauge be telling me otherwise?

 

[chevy2480]

yah everythings original, ccc carb an all. im assumming its a proper vacumm gauge. just wondering why it would run so shitty when it says it has good or normal vacumm and visa versa? personally i dont care what anyone says im gonna run it so the timings right and i have good performance, but why would this gauge be telling me otherwise?

Why ask a question if you dont care what anyone has to say?

 

[cutlassguy]

i care what people have to say but im not going to time my engine like sh*t just cause a gauge says so. im wondering if i should chuck this gauge or actually use it to get better performance. why reply if you dont have something interesting to add??

 

[cutlassguy]

how do i set my timing properly with a ccc carb? i basically plugged the VA, and timed it to about 8 degrees. was there something else i should have done with the carb?

 

[Tank]

General practice of timing a motor, assuming it is a stock 305/307 since I am unsure of what motor you have but you would either dial it in by ear or using a timing light. I do know a SBC is runs best between 6 to 10 degrees advanced. If yours runs fantastic at 8 degrees then that is what I would leave it at. The vacuum gauge would works well for adjusting the idle screws on a carb to get the air/fuel mixture dialed in.

Just my 2 pennies worth.

 

[azmalibuwagon]

Tank is right, 6-10 degrees usually works good. Mine (305, ccc engine) likes 8 degrees.

But you can set your initial timing with a vacuum guage. I was taught to set it for max vacuum and then back it down a pound or so.

Other than reading the vacuum numbers, ignore what the guage says. How would it know what the best vacuum setting would be for your motor? For instance, a big cam will give you less vacuum and vice versa. The guage has no way to know that.

 

[jmt455]

The vacuum gauge is a great tool for engine diagnosis, setting timing and setting idle mixture, but if your CCC system functioning, you cannot set the base timing with the vacuum gauge. You would be "setting" the timing while the computer is changing it!

The CCC system controls both ignition timing and mixture. Cutlassguy; if your car was originally sold in Canada and it is a 305 Chevrolet engine, it may NOT have the CCC system. If your distributor has a vacuum advance mechanism, you do NOT have CCC.

Does your carb have two electrical connectors at the front/top of the air horn? If not, it is not a CCC carb. You can see the two connectors in this image. One is a 2-wire dark gray/black connector, at the very top left corner of the air horn and the second is a 4-wire connector, "natural" color, pointing down and forward at the right, front corner of the throttle body.

If your carb does not have these electrical connections, it is not a CCC unit and you CAN use a vacuum gauge to set the base timing.

Here is a good description of what a vacuum gauge can tell you about your engine, including how to use it to set timing:
http://classicinlines.com/Vacuum.asp

Though the article refers to inline 6 cylinders, all of the instructions are common to V6 and V8 engines.
Typical vacuum readings for a "street" cammed engine will be in the 13" Hg to 20" Hg range. Performance cams with a lot of overlap will have lower vacuum readings, sometimes as low a 2" to 6".