hey,
Took my 69 camaro to the track for the first time. First run was a horrible 17.2, after an entire night of racing my best quarter mile time came out to be a 15.9! The entire night my car was having problems getting down the track at a good time. The engine would boug down on me every once in a while. I adjusted the idle up and down, that didnt help out much. It would boug down a little bit of the line, then it would get back in the game and run good, then half way down the track it would boug down once more. Would this have anything to do with the timing? Some help would be nice, I am shooting for the 13.'s, is this going to work?

 

Adjusting the idle speed isn't gonig to improve your launch.

The transfer slots in the venturis should only be exposed about
0.040" over the throttle blades.

The hesitation or "bog" of the line is most likely the accelerator
pump cam/fuel ratio. Too much fuel, not enough, or timing of
the fuel "shot" can cause a hesitation.

There are a few key items in the accelerator pump circuit that will
adjust the "Off line performance" and that is:

- the pump cam
- the squirter nozzle
- the accelerator pump over-ride spring

If you're not sure how to tune/adjust these points, let us know.
I am somewhat familiar with setting these properties.

The bog down the track may also be fuel related. How much
fuel is your pump able to supply? Is it the stock mechanical pump?

If so, that's probably not enough fuel and you are leaning out.
It would be a good start to list the carburetor model, transmission
and any modificatoin made to the engine (along with the type
of engine).

 

I am not so sure how to adjust that stuff. It is an edelbrock performer series 600 cfm carb, part # 1406. I dont know what kind of fuel pressure I have. The engine is a 350, with the turbo 350 tranny, and factory 3.08's in the rear. I will be installing a set of 3.73's on thursday night. Yesterday I checked the fuel filter and it was pretty dirty so I replaced it and it seems to do a lot better, I havent seen any bogging down.

 

It could be timing but it sounds more like fuel delivery or carb tuning. The timing should be set at about 38 degrees total and run as much initial advabnce as you can and still have 38 total. If you are able to adjust the amount of travel in the distributor, set it at 24 degrees or so at idle (or as fast as you can and not have starting problems) and still have 38 degrees total. This should get you "close".

If the fuel pump is not keeping up, that would cause this. A dirty filter or a float level out of adjustment could as well.

Assuming the timing is correct and the carb is the problem, I would adjust on the carb, and make sure that fuel delivery is not the problem.

When you have the timing "close" and assuming the valves are adjusted correct, good plugs, cap, wires, etc. have the car idle and use a vacuum guage and adjust the idle mixture screw to get the highest vacuum.
The accelerator pump rod is the little rod that has 3 holes to fit in and it is on the front of the carb and goes up to the top of the carb on the drivers side. The acceletator pump is the little plasctic 1/4 inch round stem that stick up. Move the rod to the hole in the lever that is closest to the carb. This will give the "most" pump shot and more than likely help the situation.

This is kind of a "crash coarse" and if the problem still persists, I would get help from someone that has worked on these carbs before to help with jetting, vacuum springs, squirter sizes, etc. They sell a KIT for tuning this carb and if the above mentioned paragraph doesn't help or fix it, you will need the parts in that kit and someone that has experience with it or use trial and error and keep reading spark plugs for jetting, vacuum guage for the springs and "seat of the pants" for the squirter size.

good luck

NightTrain66

 

With the car idling and the timing light it shows my timing around 12. This seems to be the best timing possible for my car. This must not be the same as initial timing becouse it is not anywhere close to 38.

 

That is probably about right for a stock distributer curve. It some times works better to disconnect the spark advance and run more initial advance with the same total. You would need a timing light with the dial or timing tape to find total.

As I mentioned, either unplug the spark advance and raise the "initial" timing or get an HEI curve kit for about $15 thru Jegs. (assuming you have an HEI). Running more initial and /or a quicker curve will make the car run better when uned correct. If there is a fuel delivery problem, carb too lean, not enough accerorator pump shot, etc, the car might not run as well. If the carb is even "close" to being right, this will help though.

As far as bogging down while you are going down the track, that sounds like fuel delivery (dirty filter, pump, low float level, etc) but all of these things mentioned will help you.

NightTrain66

 

12 would be your initial timing, 38 would be your "total" timing. I find 36 works best, but thats all down to tuning the car and seeing what works best for you. Buy a timing light that lets u set an off-set, set the off set to 38 degrees and rev the engine up to around 3000-3500rpm with your hand or get someone to sit in the car n do it, then move the distributor till the timing light flashes on 0 TDC on the balancer mark, that'll be 36 degrees (because you set the timing light to 36 degrees)... now check your initial timing and see what that's at, make sure the engine has no pinging, take it for a test drive, see how it runs.

But a bog is usually an accellarator pump problem, squirter size, pump cam color etc.