I have been running my distributor off the driver side, manifold vacuum port (always has vacuum), since install instructions say "for non-emission controlled engines". Today, I tried the other one Timed Vacuum Port "for emission-controlled engines" with vacuum at idle. It runs better with the vacuum at idle, and advances to 20 degrees or so at idle with the hose hooked up. On the non-vacuumed one, it continues to idle at about 12, where I have it set initially. No pinging, knocking, etc. Either way. Full out timing is about the same, I am guessing 40 degrees or so. But idles higher and seems to accelerate better on "timed vacuum port". Which should I use? Edelbrock 600cfm, stock 302, moderate cam, Performer 289 intake. PS-I have been running it on the "always vacuumed" port for about 3 years, and have done no permanent damage yet. Just wanted to know what is right.
Well ... here is what Edelbrock has to say ... It should be timed vacuum as far as I know ... To select the proper distributor vacuum port on your Edelbrock carburetor, we suggest the following procedure to locate the correct outlet. Before removing your old carburetor (with the engine warmed up to operating temperature and idling), pull the hose off the port that routes to the distributor vacuum advance canister. After the hose has been removed from the carb, place your finger over the vacuum outlet. If, (at idle), you feel your finger being sucked in toward the carburetor, you have full-time vacuum advance. If you don't feel any vacuum pulling at your finger with the engine at an idle, you have timed/ported vacuum advance.
yeah, I read that...today. I took the old intake and carb off 3 years ago, along with all the EGR, vacuum lines, A/C, anything else that did not make the engine run. I am assuming that it should be the timed vacuum port, since it has no vacuum at idle. But since I have the low compression, and it accellerates better on the vacuumed port, I was wondering if it would hurt to run it advanced (at idle). It still runs about the same at cruise and full WOT.
every motor i've worked on used full-vacuum port. my old L6 and my new 302. And i cant get mine (302+cam+heads+edl carb/intake) to run worth squat on timed port. (pop, belch, backfire, NOT HAPPY) maybe i'm just messed up??????????
I read a good article on this a while back and saved it but I can't seem to be able to paste it here. It describes how to set up an engine to run full vacuum saying the engine will run cooler and better. I tried it on my 351 in my F100 but could'nt get the idle to smooth out on it. Every Ford I've ever worked on was set up on ported vacuum so that's the way I keep mine. I think if you set it up correctly it will work either way. Which way is better? Don't know but I would guess the one that runs the best with your combination. I think it's like carb spacers. No one spacer works good on every combo. Just have to try a couple and see what works best with what your combo is. clint
I think I may run it at the track friday night, and without changing anything except initial timing and idle, swap the port. Run again, then decide which to use. It really idles better and has quicker response running full vacuum. I guess if it is advanced 20 or 25 degrees at idle, is is already half-way accellerating at idle (does that make sense?) and responds more quickly when I punch it. The advancing part of the acceleration is already started before I hit the pedal. The plugs have looked nice, no pinging/knocking, good gas mileage, etc. so I guess full vacuum just might work better for me.
When running on full vacuum you just add timing to it constantly. Just bump up the timing manually and plug the vacuum advance.
