I already ordered them and they are on their way. In the mean time, can you answer my questions?

"Now, when I get the proper tools to do this non idiotically, with the vac gauge, I would plug that where? Anywhere with vacuum? And adjust the air fuel screws to idle fast, but with as much vacuum as possible? And with the timing light, I have never even held one...how do I set what you call initial timing, etc?"

I assume that the basic idea is, you get timing nailed down first, then go after the fuel/air mixture. With the timing, when you say initial, is that done in the dizzy, via recurve? Turning the dizzy seems to me to be total timing, yes? Anyway, I assume the basic idea behind setting the timing is, you set cylinder 1 to TDC, plug the light into the empty spark plug spot, and then set it for whatever degree you want, mark the belt, and match the light with the marked belt?

Also, REALLY dumb question, but the screw on the front of the passenger side of the carb is for the secondaries, and the screw on the driver side is primary jets? Google simply couldn't seem to answer my question on that one...

 

Initial is the basic setting of the dist with the vacuum disconnected and engine at idle. The dist has a mechanical (centrifugal) advance of around 20*. You want around 36* total, centrifugal and initial (this does not include vacuum advance). set your initial at about 16* so with your mechanical of 20* you should end up with around 36* total, check these settings with your timing light.

There is a little tab usually on the drivers side at around the 1 o'clock area near the crank pulley, you should be able to see if from the alternator area looking down to the crank pulley. Clamp the inductive clamp from the timing light on the number 1 cylinder plug wire and point it at the crank pulley. There should be a line on the ballancer that will show up as the strobe flashes, this is the timing setting at idle (initial).

The screws on the front of the carb are the idle mixture screws not the air valve adjustment that Lars speaks of. The air valve adjustment screw is located on the passenger side of the carb on the air valve pivot shaft. Its not easy to see if you don't know what your looking for.

Lars is the expert here and hopefully will chime in with directions for you.

Neal

 

Timing first, then carb.

I would post in your regional section and get some help from a local Corvette owner with a bit of experience - I'm 100% confident someone will be ready, willing and able to help

Some background reading in your service manual, the link below and by emailing Lars for his timing paper will help you start gaining the knowledge required to tune your C3.

http://forums.corvetteforum.com/c3-t...long-post.html

 

I.....I don't even know where to start here......

OK, go to the consolidated FAQ and read the thread called info on timing, see if that helps you get a handle on things.

The two idle adjustment screws on the front of the carb control each side of the carb. They only affect the primaries, and they are what decides the air fuel ratio at idle and low speed cruise. Once the throttle blades open up a certain amount, the low pressure area under the throttle blades is lost, and airflow through the venturies takes over, and the engine is running on the main jets. They should be set the same number of turns. Use a vacuum guage to get the highest vacuum, then adjust the idle speed screw to get the idle where you want it. Reapeat until you have the highest vacuum at the idle speed you want. Might take a few tries. Here is a video that should help you out:

http://www.youtube.com/watch?v=XRCUi...feature=fvwrel

As for how to use a timing light, it should come with directions. You will probably LOL when you see how far off your idea of using a timing light is! Don't worry, it's pretty easy, and you have the general idea down. You don't screw it into the spark plug hole, you just clip it onto the #1 plug wire, and you use an already existing mark on the harmonic dampener, not a mark on a belt. And you don't have to get the engine at TDC, so don't worry about that. If you have never used a timing light before, (and it sounds like that is the case) it's actually a pretty clever little gadget. When it was invented years and years ago, it was probably considered super-duper high tech.

Your intuition is correct on at least one thing, though, the rule of thumb is: Set timing first, then monkey around with the carb. Changing carb settings won't really affect what your engine wants for timing, but changing timing can affect what your engine wants for carb settings.

Edit: You might give some thought to dialing back the attitude a little bit. We are just trying to help you out. At your level of knowledge, you are not bringing a whole lot to the table here, and it can be difficult to instruct someone who doesn't even yet have the vocabulary to speak intelligently about a subject, so please be patient with us, OK?


Keep the shiny side up!
Scott

 

I actually read that a LOOONG time ago, but now that I am at the point of trying to do some of this, the thread makes a LOT more since to me, lol. I don't have a service manual, though I have the AIM for my car...but I don't think that matters, as the motor is no longer stock.

The reason why I am all of a sudden trying to learn this is, the guy who WAS helping me along with this, has left the state, and I have no idea when he is coming back...and I just wanna drive my vette again without torching any more spark plug wires due to overly hot exhaust gasses. My light and vac gauge don't come in till thurs, so I have until then to learn how to do this stuff...and as it is, I gotta sneak those packages in so my wife don't see, as I've already exceeded my vette budget for this year!

Thanks for the help!

 

I don't mean to have an attitude, and I'm sorry that it comes off that way, I'm just upset, because the help I was SUPPOSED to have with this, is not around. Ever undertake a project, with the promise of help, only to have the help get REAL scarce once it got time to get going?

For carb tuning...what I was able to google was, one side was for secondaries, and the other, primary...this is why I gotta come to you guys. That vid helped A LOT, thank you. I'm not stupid, but I AM almost primarily a visual learner, which makes all of this pretty hard for me.

So, at no point am I trying to fiddle around with anything that affects the secondaries? My main issue with the carb is, I don't want to run too rich...if I lean it out too much, it'll ping under load, like if I drove it in 4th at a low speed, or up a hill, or whatever...pretty easy to see and diagnose. But if I run too rich...no real signs, other than, apparently, cylinder wash, overly hot headers torching spark plug boots, fuel igniting in the headers, fuel making it into the mufflers and igniting, etc etc etc. All of THOSE symptoms, I would like to avoid BEFORE they happen. Having brown spark plugs seems to be the least of my problems...

 

So, first I want to set my base timing, however, I'm pretty sure that was done...when I first got the car, 5 years ago now (!), I paid a guy to recurve the dist, which really improved the way she ran. However, since I have a new cam, does that mean I need to do so again?

Dumb question, something was said about putting a rubber band on the dist, does that mean over the little thing the spring is attached to, under the top of the cap? I wish I had a picture book...

Another dumb question...does the cam affect vacuum, as in, will my vacuum advance change based on the amount of, likely, less vacuum I have due to the cam? I can post the specs of the cam if needed...

Also, since the compression is now around 9 to 9.2-1, or so, I am using premium gas...does this also affect how far advanced I want my timing?

 

Oh, and last but not least, I just wanna thank you guys. You're all the secret of my success. 5 years ago or so, I got this car, and with the help hear, I have taken a pretty sad, beat up, neglected 76', replaced the brakes, lines, MC, everything, replaced all of the suspension, and finally finished a top end rebuild. She really is a different car, now...and I owe it to you guys...and a bit of sweat, and, a bit of blood (literally), on my part. So, thanks!

 

Ahhh, I might have been a little grumpy when I posted that, sorry. I know it's tough when you are first learning something, and you don't even know the basics yet.
I don't know where you got the secondaries and primaries thing, but I think something may have gotten a little mixed up somewhere along the line. There is a set sscrew at the back of the carb which you can use to adjust how quickly the secondaries open, but it is for fine tuning, after you get the major things squared away. Don't worry, when the time comes, someone will help you out with the secondaries, it's really just a matter of adusting them to open a little sooner, and keep doing it until it falls on it's face when you punch it, then go back a little bit. But, the rest of the carb has to be tuned up first. Adjusting the secondaries is the final touch, so to speak.

Your engine can sustain much more damage from a lean condition than a rich one. Fuel wash on the cylinders is a very real concern, but if you are running rich enough for it to really cause any short term damage, it will be very obvious. Your exhaust will stink like gas so bad it'll make your eyes water! Black smoke from the tailpipes is another sign of a rich air-fuel mixture. A rich air-fuel mixture will not do any of the other things that you mention, in fact, most people like to have the carb setup so that the air-fuel mixture is slightly rich at full throttle, for the cooling effect that this produces, to avoid detonation. Unburned fuel in the headers, headers running super hot, etc. have much more to do with retarded ignition timing than anything else. If the ignition timing is sufficiently advanced, the fuel is done burning when the exhaust valve opens. One of the reasons people say timing first, then carb. The idle adustment screws really only affect the air-fuel mixture when the engine is under no load, or very little load, the rest of the time, you are running on the main jets, and adusting them requires partial carb disasembly, so that is probably not something that you will be taking a crack at very soon. (someday, though!) You are best off trying to tune the idle adjustment screws to optimize the air-fuel ratio at idle using one of the methods that has been discussed. (I like to use a vacuum guage and tune for highest vacuum, and then maybe make a little tweak from there using the idle drop method.)

If you are a visual learner, the video that I posted a link to is just one of about a gazillion out there on the internet. Google search, and you tube are your buddies here.


Keep the shiny side up!
Scott

 

Help gone? Try this

http://www.longislandvettesclub.com/clubs/CLUBCT.HTM

or

http://www.corvettelegends.com/clubs/ny.htm

Live & in person, they have to have 1 person that likes to wrench & help new guys. A polite offer of lunch & favorite beverage & agreed compensation would go along way.

Good luck.

Jedi