Vacuum advance plugged?

[biggsie]

So my 351w has a duraspark system installed. Replaced the module and coil this spring due to no spark. Ran great with the exception of a stinky black exhaust at idle. Tuned the carb and set timing to 10deg and black stink at idle is gone. Now it runs well just seems to lack the "punch" it had before. I'm thinking about "tuning" the timing next. The vacuum pot on my dist is plugged..... What should I do? Hook it to full vacuum and try it? Take apart the distributor and check anything?


Sent from my iPad using Tapatalk (http://tapatalk.com/m?id=1)

[92SupraComp]

It should be a mechanical advance that advances up to 36* or so around 3600 rpm I believe..

[cadunkle]

Do not want vacuum advance on a boat. It'll either do very little if adjusted right or will advance too much and detonate. Leave it capped and check your total advance. I'd shoot for 34*-38* by 3000 RPM, starting at 10*-12* initial. Listen for detonation along the way, it'll kill an engine quick. Never seen a Duraspark on a boat but I can vouch they work well underwater if the distributor is sealed and plugs greased. Only had one failure and been running Duraspark for 10 years or so in wet muddy high vibration conditions.

[biggsie]

Perfect! Thanks, that's exactly what I wanted. Now I have something to shoot for.

By the way... I have about 14" of manifold vacuum at idle with an edelbrock performer intake and a 1" spacer block. Is that good? Seems high from the research I've done.


Sent from my brain using Tapatalk.

[CJD]

Higher vacuum is not bad. You may have a slightly higher idle speed. Or, if your timing is too far advanced, it could raise the vacuum a bit. The sign of too far advanced is hard starting (sounds like the engine is firing against the starter), or detonation (which is bad).

Be sure to take your distributor cap off and twist the rotor to make sure it moves and feels springy. If not, the advance mechanism is corroded. If that is good, though, adjust your timing and if the vacuum stays up there you are good.