Distributor curve

[Fox80]

Normal idle, don't mess with a car that is in gear. Set-up correctly it will return to 10 degrees at 1,000 rpms and reach full advance before 2,500. Just make sure you calculate the total advance in the dist. or it may retard to far and not start or advance to much. I described a few ways in the other post to do it

 

[CamaroAdam73]

How is your idle? Any off idle stumbles? I would try for full advance as soon as possible.

It's hard to tell because the motor shakes around from the cam but YES I've been paying close attention and noticed what i think is a stumble AT IDLE. Shouldn't the 'shake" from the big cam be consistent?
There are no off idle stumbles, i also noticed the engine runs smooth, no shaking, when i rev it up alittle and hold. This was all observed In park though.
When in gear, yes the engine will stumble and try to stall only sometimes if i jump on it quick when its in 2nd or 3rd. In 1st gear it just spins tire. Confusing.

I still haven't calculated the total advance in the dist, i was busy working on other cars the last couple days. I'm also waiting to get a better timing light, i don't have a dial back type just a hook up and flash style.

Fox, you said Set-up correctly it will return to 10 degrees at 1,100 rpms. I'm confused, i was told my initial timing should be between 16-20.

I'm having some other problems right now and it's getting alittle overwhelming. To get the secondaries to open i had to disconnect the primary pull off because it won't let go. I checked it's release and it releases in under 2 seconds, however with the car running it absolutely will not let go no matter what RPM i rev it too, and therefor the secondaries were not opening. When i disconnected the primary pull off the nipple for the vacuum line fell out of the carb... I'm guessing this was causing a vacuum leak.

One more thing i need to note, I have the engine idling at 1100 RPM, when i put it in gear it drops to 600 RPM, sometimes as low as 500 RPM.

Sorry for the jumble of info, its just whats going on. I'm starting to wish i had just gone with a crate engine......

 

[pontiacgp]

according to olds gurus a 403 is 20º at 1100 rpm

 

[CamaroAdam73]

according to olds gurus a 403 is 20º at 1100 rpm

There would be my first issue, i have it set at 16 right now. I won't be able to work on the car tomorrow but Thursday my plan of attack so far is to set initial timing to 20 and switch to the light set of springs, then check total advance as long as i get ahold of a good timing light.

 

[Fox80]

The 10 degree at idle is a number I use to find the total advance in the dist. This is where most guys have trouble you need to know how much vacuum the motor makes how much total mech advance the dist has and how quick the motor wants the advance to come in. You are getting close, if I have to guess I say the mechanical advance is not returning enough at idle that might be what makes for the unstable idle. Having the carb want to open is not helping you either, again need to know the vacuum the motor makes to set the secondary spring as well. For sure get your hands on a dial type light nearly impossible to do this without one. The biggest thing is to get the car to run and idle off the mechanical advance first vacuum will only make your problems worse. Just be patient your getting there, make sure all your vacuum lines are plugged as well that will make a bad shake at idle. The initial timing numbers most guys throw around us for stock springs can't really use them with a curve kit

 

[Fox80]

This label shows you how different OEM motors need different initial timing, the factory sets up the dist. for the motor its going in. That is what you need to do as well. Once you change the cam, intake, heads, comp. ratio I nor anyone else in the world can tell you what to set the initial timing at or what to set the curve to do. Without a chassis dyno its down to the tune and drive method. This is not easy or fast, that is why most guys just put in a mechanical advance only dist. in it and just live with the fuel mileage and poor part throttle performance.




http://www.justanswer.com/uploads/Hamme ... _Carlo.gif

 

[olds307 and 403]

16 at idle is passable. Anything less 15 base won't idle as nice, at least on the low compression ratio Olds V8's I have owned and tuned. The Moroso weights are supposed to be decent but have 24 mechanical like the points set up. Find where your total timing is at.

 

[Fox80]

I would agree with that as passable , like I said I just use ten as a number because the car will still run and its an easy number to figure out the total advance

 

[CamaroAdam73]

Gotcha, i'll drop initial back to 10 when i check for total. My C/R should sit somewhere between 9:1 - 10:1 is that still considered low?

 

[Fox80]

Lol the difference between 9-1 and 10-1 is pretty big, every .1 will make a difference. 10-1 is considered average for mild performance motors today, 11.3-1 is about the max on pump gas. Most motor guys building a motor for someone they aren't real sure can tune it correctly will set it at 8.6-1 to 9.2-1 that way the guy cant get himself in trouble or hurt a brand new motor with the wrong timing or lean carb.