Ok so I couldn’t find an exact forum this should be in so excuse me if it’s in the wrong spot.
I have a 355 running 9.5:1 compression, a Holley Brawler 750, Flotek 200cc aluminum heads a Comp Cam XE268H and a Holley single plane intake. I know the intake and carb are mismatched for their rpm ranges that’s a future item to address.

Currently I’m running a Summit Racing billet distributor with a MDS Street Fire ignition box and MDS ignition coil. Base timing is at 13degrees and mechanical advance of 21degrees for 34 all in around 3,100rpm no vacuum advance connected. I hooked up the vacuum advance in the timed spark of the carb to try and get some mpg back on the highway, after I did this if I punched it from a stop or from off throttle it pops and just about dies before it comes back, easing onto the throttle even all the way to wot and no issues.
Do I have too much base timing to try and run vacuum too?

 

Base timing is adjusted to best suit the camshaft that is installed. Total timing needs to be programmed electrically or mechanically depending on the distributor since increasing the base timing will also increase the total timing which the engine may not want.

10- to 12-degrees of initial timing when the duration of the camshaft is less than 220-degrees @ 0.050” of valve lift
14- to 16-degrees of initial timing with a camshaft duration of less than 240-degrees @ 0.050”
18- to 20-degrees of initial timing when the camshaft duration is less than 260-degrees @ 0.050” of valve lift.
More than 260 degrees @ 0.050" is normally a full race cam and a locked out ignition set to full advance with a start retard is generally used but you can still use a timing curve if you want.

Where your engine wants the total timing is best figured out on a dyno or dragstrip. 32-34* total timing is most common but higher or lower numbers can be used depending on how the engine is built and used. Power adder engines usually want less total timing while NA engines usually want a little more but there are a lot of other factors in there also.

Once your base timing is set based on your camshaft, it never needs to be changed. You adjust the advance to increase performance depending on when components used in the engine. Since not all engines are the same, nobody can tell you how much total timing your engine needs.

Put some steel braid on that fuel line

Sounds more like you have a carb tuning problem than an ignition problem. Vacuum advance is only for part throttle operation and is not used at WOT.

 

Ok cool, the duration on my cam at 0.050” is 224/230 so I’m in the right neighborhood. I’m thinking about just letting a place that was gonna dyno tune my carb do the ignition as well so I know someone with more knowledge is handling it.

 

Like I said, once the ignition timing is figured out, any other tuning will not affect where the engine likes the timing. Timing is always done first.