Well if ignorance is bliss than I must be in heaven on this. I have been reading different threads both here and out on Chevelles.com about this subject. There is so much knowledge out there and I applaud you all for it ...especially I-man but could someone explain ported vs. non-ported vacuum. My guess is that ported is direct of the manifold and non-ported would be off my carb.
I have a situation on a stock L-34 402 engine that is very similar to the posting over on Engines and Drive Train. I found this out on a car when I went to do a tune up 6 months after I bought the car.
*Vacuum line is plugged all the time. Why the previous owner did this I do not know. It was a surprise to me
*At about 900-1000RPM idle my timing mark is at about 12:00 on damper and when I dial the mark back on my timing light from zero I get about 35-36 degrees of timing which I know can't be good
*At about 2000 RPM it climbs to about 40-41
*I did not increase RPM yet to see where it stopped but my guess would be around 50 like the other posting
I want to get it back to stock preferred settings which I suspect should be
* 8-12 BTDC with vacuum disconnected (like it is now
* About 20 with vacuum connected to "ported" vacuum
* and about 36-38 total at increased RPM
On this motor I have a fitting on the back of the stock cast iron manifold with 3 tubes (2 are currently capped). Should I take the permanent plug out of the distributor vacuum line and connect the line to one of those tubes on the back of the manifold and run like this all the time as a ported vacuum set-up???? The factory used the line off the carb I believe asis how it is currently hooked up even though I am getting no vacuum because of the plug in the line. Is this just an improvement on performance from the factory???
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