Vacuum advance not hooked up!

[1986Silverado]

Noticed today while I had the air cleaner off installing new wires and plugs that my vacuum advance canister on the distributor does not have a hose running to it, it's wide open. What will that do/cause and where does the rubber line run to? Theres not even a rubber hose there?

[pedrofixlater]

rubber line runs to the carb. If it is not hooked up your timing will be retarted robbing you of power. probably running rough also. Once you hook it up you will also need to lower your idle.

[1986Silverado]

Next question would be is to which port? I have and edelbrock carb with 3 ports on the front and the only one being used is the big one for the pcv. Maybe thats why my truck has been running like crap!

[ocbaud]

hook it up to full manifold vacuum, which is the port to the right of the pcv port

[1986Silverado]

Thanks guys!!!!!!!!1

[1986Silverado]

Well, went and bought some hose and hooked it up, didn't seem to make a difference to me but I will not have time to check the timing today. It did seem to idle a little higher after hooking the hose up.

[Destructo]

I don't like vacuum advance hooked up to full manfold, whats the point on vacuum advance if its always advanced? it really should be hooked up to ported vacuum, thats the way it was designed to work.

It really won't help the motor run much better, the motor might actually make more HP without vacuum advance when the dizzy is setup to work without it, its mainly to improve driveability and fuel mileage.

[1986Silverado]

Originally Posted by Destructo

I don't like vacuum advance hooked up to full manfold, whats the point on vacuum advance if its always advanced? it really should be hooked up to ported vacuum, thats the way it was designed to work.

It really won't help the motor run much better, the motor might actually make more HP without vacuum advance when the dizzy is setup to work without it, its mainly to improve driveability and fuel mileage.

What would be your suggestion then? Where would be a source for ported vacuum on a edelbrock carb? How could the dizzy be set up to run without it?

[1986Silverado]

Bringing this back up because I was fooling around with the timing yesterday. Had the timing light on the timing marks and disconnected the vaccum advance hose and it made no difference Also the timing was set at like 12-14(was off timing marks completely) BTDC, so I adjusted down to 10 degrees and shut it off and cranked it up. Seemed to make a difference with my hard/slow starting, but went to drive it and the shifts were not as firm as before, barely felt it shift to 2nd at wot. Before at wot it would shift real firm from 1st to second. Got back and timed it back up to 11 btdc and the firm shifts are back, but the hard/slow starting is also back

[screwballl]

ok i have a new edelbrock 600cfm on my 76GMC with 350....
the hose goes to the front LEFT port, PCV to front center and plug on the front right... this is looking at it standing at the front of your truck looking towards the back...

[1986Silverado]

Tried both ports and did not make any difference, its as if the vaccum can is plugged up or non functional

[screwballl]

could be non-functional... especially if it is a little rusty and the original... might try buying a new one and seeing if that makes any difference... it is supposed to help with starting and running properly...

[truckinbean]

If you have the edelbrock 1400 carb, both the left and right ports on the front are ported/timed sources. It is the only 600 cfm performer that is this way. All the others (1405, 1406 etc.) are the pass. ported/driver's manifold configuration. I thought the 1400 on my blazer was screwed up until I found this out. Two techs from Edelbrock didn't know about this either, and the third one I talked to finally told me what the deal was.

I just hooked my vac advance to manifold vacuum the other day (off the port on the manifold, behind the carb) and it made a world of difference in my idle, smoothing it out a LOT.

As far as which one to hook it to, it seems like the only time it is going to make a big difference is at idle. On the timed port it pulls the same amount of vacuum as manifold vac by 1500-2000 rpm. At wot, there won't be enough vacuum to pull any advance in whether it's on ported or manifold.

I've heard that the engine will also run cooler at idle with man. vac., but it will have higher emissions.

Oh yeah, since I hooked it up to man. vac. the truck doesn't do this weird sputter that only happened when I made a left turn without stopping.

[1986Silverado]

So is a ported source different from a manifold source? If so I may try the manifold port that is behind the carb as you did and see if that makes a difference and try to time it back down to 10 btdc. It'll be this weekend before I can do that though. BTW it is the edelbrock 1405. Thanks

[Brad_Olson]

Originally Posted by 1986Silverado

Tried both ports and did not make any difference, its as if the vaccum can is plugged up or non functional

Easy enough to check, especially if you have a vacuum pump. Just remove the cap and apply vacuum to the canister; if the rod retracts into the body it's working. You don't *have* to replace it if it's not working, but if you do I like to use Accel's adjustable canister.

Brad

[truckinbean]

If you have a 1405 it should be pass. side ported/drivers side manifold. The difference is that ported vacuum is "timed" so that it doesn't let vacuum pull until you hit the gas (the slot that lets vacuum through is above the throttle blades). Manifold vacuum is pulling full vacuum all the time regardless of throttle position. Of course, with your foot to the floor there is not going to be enough vacuum to pull in the vac. adv. on ported or manifold.

If you don't have a vacuum pump you can always just suck on the vacuum hose. Put the timing light on and if the mark on the balancer jumps way past the timing tab when you suck on the hose then you know the vac. can is working.

[1986Silverado]

I had it hooked to driver side port, and when I removed the hose from the carb you could hear the vacuum and also put your finger over the port and feel it, so I am guessing the canister is bad. Only thing that is bothering me is the starting issue, it turns over slowly like the battery is dead then starts and it is not my battery. Also has a new alternator.

[screwballl]

the last comment:
might be your starter or the wires from battery to starter, or possibly the ignition module. another thing to look at is the cold cranking amps of the battery. if it is under 700 might want to get at least a 700 CCA. on my 91 burb w/ a 454 that i just bought, it did the same thing even though the battery is fine and the alternator puts out great, the battery only had 535 CCA and it wasnt enough. Once i put in the 750 it has started like a champ since.
it is possible that you got a bad canister too...

[1986Silverado]

Originally Posted by screwballl

the last comment:
might be your starter or the wires from battery to starter, or possibly the ignition module. another thing to look at is the cold cranking amps of the battery. if it is under 700 might want to get at least a 700 CCA. on my 91 burb w/ a 454 that i just bought, it did the same thing even though the battery is fine and the alternator puts out great, the battery only had 535 CCA and it wasnt enough. Once i put in the 750 it has started like a champ since.
it is possible that you got a bad canister too...

Mine is a 500 CCA.............would that be a problem?