1987L69

I dont want to start a huge argument here, I have read on several sites what people run on their engines. that being said, I was wondering what people here are running, state what you are running, ported or manifold/full vacuum and your engine mods, and how it acts with both!

Tuned Performance

iTrader: (92)

Ported

midias

Full time, runs way better, idle smother and starts better with no choke. Mods in the sig

sofakingdom

iTrader: (1)

Ported was introduced as an emissions thing in the late 60s. Its purpose is to retard the timing at idle, to reduce NOx. Prior to that it was always full-time.

Most engines will run best with full-time as long as the vacuum can properties are such that idle vacuum is a good bit higher than the can setting. If idle vac is too low compared to the can, the idle will be massively unstable.

Best approach is to try both and see which works better for your situation. Although with a stock LG4 or L69, or any stock EFI setup, it's a totally moot point; the ECM's calibration handles all that.

1987L69

My computer is removed and im running a non CC dizzy and carb. stock everything else, car makes like 24" of vacuum at idle and i have it to a ported vacuum port on the edelbrock carb and 12* initial timing, thinking of taking it down to 8-10* and moving it to a manifold vacuum.

Biledriver

I think you should stay how you are. With vacuum off I would bring the total up to 34 and see where that leaves you initial. The more initial your batt and starter can handle the better. I have 18 initial and 34 total with no vacuum at all. I want to lock it to 34 all the time and see if my starter can take it.

MSgt Luttrell

I'm running a camshaft with 241 deg Intake / 246 deg Exhaust duration @.050" and .558" Intake / .566 Exhaust lift and a 110 degree lobe separation in my carburated 383, with aluminum heads. I have tried running it with ported vacuum, manifold vacuum and no vacuum at all to the distributor and I've found that mine runs much better with the base timing set at 14 degrees, 34 degrees total and vacuum advance connected to manifold vacuum. It idles better, is more responsive, runs 15 degrees cooler and the spark plugs don't try to foul out at idle during cold starts in cold weather.

redneckjoe

i run full manifold vacuum. same thing, runs a noticeable amount cooler and smoother idle.

as stated, it only takes a few minutes to switch it around and experiment.