Okay, so heres the deal I thought I knew a great deal about timing turns out after weeks messing with this I need more help than I wanted to admit.

I rebuild the motor last year, bunch of stuff in my sig, pistons, rods, cam, valve-train, head work, intake ect...My motor is running a 9.58:1 compression ratio, with a cam that has a heavy lope with a 108LSA I dont have the cam card but its something like 230duration .480lift. I have a mighty demon on top with the idle eaze and annular boosters for better signal.

Now the problem I am having I am almost 100% sure is attached to me having an shitty MSD street fire distributor. No timing curves other than the stock curve, and you can only mess with the springs which bring the adv in sooner or later.

At 18* initial and 38* final the car sucks off the line, it bogs, and stalls out all the time when I come to a stop especially when cold. I have to keep blipping the throttle to keep it running no matter what I do the the idle adjustment.

I used to have my vac advance hooked up to ported and It runs great when I crank up the initial timing to 30* but my full timing comes in way to high not sure of the number ATM but high. The other problem I have when I have it hooked up to ported is the best vacuum I can get to read at idle is about 12"-14" and the gauge doesn't really react how it should through out the rpm range.

I now hooked my vacuum advance up to my manifold vacuum like someone on another forum suggested that has a street fire dist. The car runs great it cranks up my initial way high when running, yet my real initial is still around 16* or so when starting ect. My full timing comes in around 36-38* which is perfect. my vacuum reads 16-17" at idle 22" cruising and when I blip the throttle it yanks to 0 and back up to 16" like it should.

The giant problem I am having is I guess what you would call hesitation or surging at part throttle/cruising operation if I go to get on it again from a cruising speed it bucks and hesitates. until the rpms come up a bit then I can get on it again.

I am pretty sure I can get rid of this issue by getting a real distributor, coil, and cd box this way I can control my initial to 28* and only add 10* bushing to bring me up to where i want to be on final. Or just lock it out completely at 38*.

Anybody know a way to remedy this situation without going out and spending 600$+ on an ignition setup?

 

You haven't mentioned what you've done with the adjustable vacuum advance. And you haven't mentioned any carburetor adjustments. I can't help until I have the whole picture. Congrats on trying diagnosos before throwing money at the problem. And on finally asking for help.

 

Okay, thanks I will do my best to inform you about how I setup the carb. Its got the stock 75/83 jetting so far I haven't gone that far into the jetting yet. I am running the stock squirters #31 with a less aggressive blue/gray pump cam than what it had in it stock. I am not getting any black smoke when I hit the throttle but it does seem to bog when mashing the throttle fast at a stand still even with lots of initial on the vacuum advance on manifold vacuum. It seems to bog much less when I run ~28* initial and no vacuum but like I originally said full advance is way to high.

Idle adjustment screws are a hair less than 1.5 turns out. Like I said I dont notice any black smoke out of the exhaust but my plugs are darker than they should be. Idle ez is also opened up to help with vacuum.

The power valve is the stock 6.5..not sure if I need a lower PV.

I have not adjusted the vacuum advance at all, only reason being is I honestly am used to running no vacuum advance let alone an adjustable one. I have not a clue on how to adjust it, or what it does. The instructions are very vague.

 

Is there a lot of slop in the accelerator pump linkage? If there is that will give some lean hesitation.

 

No slop in the pump arm. Begins compressing as soon as the throttle is touched and its setup to have at least .020 remaining travel with my feeler gauge.

 

Sounds like you need more pump shot. Put the blue cam in position #2 on the primaries. That should help. If it still bogs with no black smoke keep upping the squirters till it stops bogging.

As far as the power valve, don't go any lower. Actually with the vacuum you have you can go up to a 10.5 if you wanted. That could be the problem you are having with going from a cruise to part throttle acceleration. The power valve opens at such a low vacuum that its not opening on part throttle acceleration causing a lean condition. Try the 10.5 and see how it feels.

 

Tuning Holley-style carbs isn't my gig, mostly I just wanted to be sure you weren't blaming the MSD stuff and assuming the carb was perfect. So, back to the timing: You really do need to start tweaking that. It's a common sense thing. If it's bad now, turn the Allen key a half turn either way. Take notes, see if it helps or hurts. All tuning must be one change at a time, and once you get one aspect right, you have to go through everything else again. It gets old, but eventually everything's good, and you can just enjoy driving. The only way out of this hassle is to run a stock EFI setup on a stock EFI engine, or combine known mods with a known matching EFI tune.