Idle Speed Issue

[Zach]

Howdy, everything is bone stock besides a fresh SR rebuild kit from Cliff in the Quadrajet #17057263.

The carburetor is the original one sitting on top of a stock 1977 Pontiac 400 W72 (think it has a better cam and slightly more compression compared to a stock 400). My current issue is that in order to get the target idle RPM of 775 it requires me to almost completely unscrew the curb idle screw which I assume is where my slight hesitation on and off the accelerator comes from since there is almost no transfer slot seen. The initial timing for a Pontiac 400 is 18 degrees, which is high compared to most and this means my idle is gonna be higher as well, I have tried a more tame 8-12 initial with the carburetor transfer slots properly visible, however, there is a lack of power once I get on it, most likely due to total timing being low.

Car is running absolutely flawless besides this very very slight hesitation, just wondering on some solutions to this issue. 19 with very little experience with all this so I am just learning as I go. Should state there shouldn't be any vacuum leaks, went over everything + cliff installed new bushings.

[Cliff Ruggles]

Higher compression might be a player here.  Those engine used a LOT of initial timing because the compression ratio was really low and not squeezing things very hard at idle speed.  If you retard the timing the engine will certainly idle slower, but you'll have to modify the advance curve so it still gets enough total timing to make best power......

[Zach]

Higher compression might be a player here.  Those engine used a LOT of initial timing because the compression ratio was really low and not squeezing things very hard at idle speed.  If you retard the timing the engine will certainly idle slower, but you'll have to modify the advance curve so it still gets enough total timing to make best power......

Ok, figured the solution was to change the curves just wanted to see what you guys had to say, thanks.
Guess I will start researching, got any good resources for proper timing procedures? I assume I will square off the transfer slots and then retard timing till idle is where it should be and consider that where my initial should be. Then I just have to find the right springs and weights for HEI and swap them. Will I need to swap vac can at all? It’s running off emission timed manifold vacuum (mimics ported) or can I get by with just messing with mechanical. Thanks again, wouldn’t survive without these forums, learned a lot from them.

[Cliff Ruggles]

The stock weights, center cam and springs are fine, you just need to modify the advance curve by adding a positive stop to provide the amount of timing needed.  I use a MIG welder here to weld up the slot and round file to open it up.  Timing is measured using a degree wheel.  10 degrees at the distributor is 20 degrees at the crank, etc.....

[novadude]

That pointer and degree wheel is a fantastic idea for setting total centrifugal! 

[Cliff Ruggles]

It saves a LOT of work setting up a distributor and tells me EXACTLY how much it will add in degrees of advance.  Then all I need to do is select the right springs to get the advance to start and all-in where I want it.

I quit using a distributor machine decades ago as it really isn't needed and just adds a bunch of time to the job.  I've set up thousands of distributors of all types over the years and can just smell it and tell you if it's where it needs to be or not!

Just a note on  advance springs.  Everything I've seen in the past 40 years or show showing up in these advance "kits" from Mr Gasket, Moroso, etc are JUNK!  Most of the wire diameters are too small, too many coils, eyes too close together (stretching them out too far) and they go "soft" once placed in service.  That's one thing the offshore companies haven't figured out yet is how to make good spring wire.....

[73ss]

Where is a good source for springs for a good old fashioned delco points distributor?

[Shiny]

If Cliff doesn't have them, you might reach out to Bob Davis in TN (Sun Tuned on PY Forum).  PM me if you want contact info.