Thanks. That was next on my list. Right now I have it at 14° initial. Going to try 18°. Also a valve lash adjustment. The cam manufacturer recommend. 022 hot so that may be off also.

Durham Missouri

62, 
If all is good as you say, try advancing the timing a bit. The richness you describe may be unburned fuel in the exhaust.

Thanks. I appreciate your guys being so patient with me.

Durham Missouri

The restrictors are probably the same thing as air bleeds, which affect the fuel curve.

There should be loads of tachs that will work.  It is not a one wire tach.  It is simply the output for a tach.  The tach will still use 2 or 3 wires.



Lawrenceville, GA

The Summit carbs also have a accelerator restrictor kit available. I looked for a cheap tach that would hook up to the 1 wire hook up that is on my MSD dizzy. No dice yet. What exactly does the idle feed restrictor restrict? The jets are in the booster but no fuel is coming out at idle.

Durham Missouri

If you want to get serious about tuning, you need to have a tach of some kind.  No guessing allowed.
If you don't want to have one permanently in the car, there are tachs designed specifically for tuning, which attach, temporarily, to the coil using alligator clips.

I didn't realize that summit carbs had that tuning ability.  That is pretty sweet.  Might cure your problem.



Lawrenceville, GA

Forgot to add that I don't have a tach but I would say it is idling around 900 rpm.

Durham Missouri

Ok,my engine is a stock bore 292,has mild head porting 1.85 and 1.6 valves,1.43 rockers,cam is 280°duration 110 LSA 236@.050,9.1 comp,valve springs are 70lbs seat 190 open, ported Blue Thunder intake with a Summit 600 carb.
I checked the carb as Charlie suggested and all is good there. No fuel from either booster. I put the vacuum gauge back on and played with the idle mixture and got it up to 12 hg. It is still a tad rich though. I did notice the vacuum gauge would bounce about 2-3 hg at idle. I checked for vacuum leaks and didn't find any. Summit has a idle feed restrictor kit that is supposed to cure a rich idle. How does it do this if no fuel comes from the booster at idle? I was planning on going down one jet size on the booster and see if that helps.

Durham Missouri

You don’t mention what your cubic inches are but the camshaft being 236° @ 0.050” isn’t that big a camshaft in the grand scheme of things.  The 312 engine I use as a dyno mule for testing has a Crower 238° @ 0.050” cam in it and actually idles quite well at 850 rpms with a 750 Holley on it.  Your manifold vacuum is on the low side but I failed to see where you mentioned the actual rpms the engine idles at.   The dyno mule I use for testing has 12-13” Hg vacuum at 850 rpms.  Changing out the carb to a smaller size does not affect the manifold vacuum at idle on this engine.  Changing the ignition timing and valve lash does have an effect though.
  
Where your camshaft is installed in regards to intake lobe centerline and TDC will have an effect on the manifold vacuum at idle.  If the camshaft was not degreed in upon installation, then you may have a camshaft that’s not installed at the optimum position and based on the manifold vacuum at idle, then it could be in a retarded position.  The valve lash being set on the ‘tight’ side will also have a negative effect on manifold vacuum at idle.
 
Assuming that the distributor vacuum advance chamber is hooked up to the staged signal port on the carb, then there should be no vacuum signal to the distributor at idle.  As soon as the throttle is cracked open, then the vacuum advance portion of the distributor will throw some extra advance into the ignition curve; this occurs due to the staged vacuum port hole within the carburetor throttle bore now being below the throttle blades instead of above them.  By its original design, the vacuum advance works specifically during cruise situations to add additional ignition advance for a leaner fuel mixture during low load conditions (cruising).  At idle and any primary throttle position past 1/3 open, there is no staged port vacuum signal available.  This is due to the lack of air velocity going across the hole located within the throttle bore when the throttles are either at idle (closed) or open to the point that air velocity drops in speed enough that the vacuum signal cannot be generated.
 
If the vacuum is hooked up to a direct vacuum source, then the tuning parameters must be altered to compensate for a full vacuum advance when the throttle blades are in the idle (closed) position.  This is a different set of tuning parameters that will not be found in the factory service manual for your Y-Block.

Lorena, Texas (South of Waco)

Chassis dynos are expensive. If you are capable of doing the work yourself, that's the direction I would go.
I would buy and install a threaded bung for one or both of the exhaust head pipes and get an AF meter.
I would check for vacuum leaks using a propane torch (unlit, of course).
Your cam is NOT too big . Mine is 246 @ .050. (Not a Y block).
My idle is 900 rpm with 10" vacuum.
Your carb is just fine. There should be NO reason to have to mess with the secondarys for idle stability.
This may only come up when using (2) 4 bbls.
First, check for vacuum leaks