Timing advance help needed.

[reckerd]

I am trying to time my 383 stroker but am having an issue with the timing advance maxing as soon as it is connected to my Holley 80508SA carb. I am attaching a picture to help me show what I have. With the vacuum disconnected and plugged I can time the low end to 10 degrees TDC but as soon as I connect the vacuum it shoots up to @32 degrees. This doesn't seem right to me. I connected the vacuum line to the port the manual shows as the timed spark (to distributor). Is there something wrong or am I just not educated enough on how it all works and it is actually correct?

107796

[NAZ]

Wrong metering block gasket? Idle screw open too far?

Sounds like your vacuum can will add 22-deg which for some engines may be too much so just listen closely for any ping at rapid throttle tip in under load. If no ping -- no problem. Also, many set-ups run better off manifold vacuum rather than the timed port and unless you have to pass a Poeple's Republik of Kalifornia style smog check you may find the engine will run better when the vacuum advance is attached to manifold vacuum.

Note: to obtain your engine builder's recommended timing curve you may have to tweak the mechanical advance.

[FF33rod]

I found this article helpful on why vacuum advance is desirable on street driven cars https://www.hotrod.com/articles/quick-tech-still-need-vacuum-advance/

[GoDadGo]

Reckerd,

My carb is an Edelbrock so I can't give you any information there, but FF33rod's article pretty much sums up it up well.

For what it is worth, I've disconnected my Vacuum Advance because of the lack of load on the engine and the fact that my engine produces a pretty low vacuum signal.

Also, NAZ knows tons and tons of stuff and is a fellow Chevy Guy who has helped me with some issues and knows way more than me when it comes to these engines.

Shown below is my set up:
1. 383 Small Block Dart 10-1 Somewhat Pump Gas Friendly Compression Ratio!
2. Eagle Internally Balanced Rotating Assembly With 6" H-Beam Rods With Floating Forged Flat Tops.
3. Dart Iron Eagle 215 CC Heads with 2.05 Intake & 1.60 Exhaust Valves.
4. Harland Sharp Roller Rockers.
5. Comp Cam Extreme Energy 288 Hydraulic Roller Tappet Cam
6. Edelbrock AVS 800 Feeding A Weiand 7530 Team G Single Plane Manifold.
7. Schoenfeld IMCA Modified Headers.

Steve

[reckerd]

Thank You everyone who replied. Since this is a long weekend I will have time to play with it. Naz, I am in Arkansas so no worries about the smog stuff.