vac advance

[garettjaxx]

My truck had the emissions gutted before I got it. Where should I put the vac hose for the distributor? Straight to the intake manifold?

1983 k10 chevy 4x4 v6 700r4

 

[Irishman999]

Ported vacuum, what carb are you running?

 

[garettjaxx]

carb

Its a Rochester Verajet 2. Can anybody recommend a good replacement with a manual choke? I'm not a big fan of electric chokes.

 

[HotRodPC]

Definatly not to the manifold. Many will argue the point, ported vac or full vac. I've explained why ported vac should be used many times in length. FInd the ported vacuum port on your carb and hook it up there.
Ported vac port is NO VACUUM at idle. The second you come off idle then the port has vacuum.

 

[garettjaxx]

right on. thx for the help.

 

[sschevystepside]

Carb

If your still lookin for a carb cant go wrong with the Edlbrock Performer series carbs with electric or manual choke check ebay lots on there

 

[Dr. Paradox]

port vacuum is for racing applications or when you don't have centrifugal advance. for a street application where you also have centrifugal advance you need to use manifold vacuum. you'll get much better performance and fuel mileage.

this is totally an opinion thing so don't everyone go bashing on me.
all I can say is that somebody had my truck hooked up to port vacuum when I got it and it didn't run worth a crap and got 12 mpg. I hooked it to manifold vacuum and it runs much much nicer and now I get about 17 mpg

 

[Dieselshine]

I'm gonna give the ported vac a try my trucks on manifold vac as is but when I gut the emissions gonna try ported

 

[Jims86]

Usually the passenger side front port on the carb base plate.
Avoid Edelbrock and carter afb's at all costs. There is nothing wrong with electric chokes, they just need to be set up correctly. The carburetor you have is the best carburetor you can possibly get for your truck. Contact Sean Murphy at www.smicarburetor.com, and see about having him rebuild yours.

 

[Jims86]

If your still lookin for a carb cant go wrong with the Edlbrock Performer series carbs with electric or manual choke check ebay lots on there

4 barrel is usually too much for a stock 4.3, and he would have to change his manifold.
The only place i have seen a 4 hole 4.3 is in boats.

 

[HotRodPC]

port vacuum is for racing applications or when you don't have centrifugal advance. for a street application where you also have centrifugal advance you need to use manifold vacuum. you'll get much better performance and fuel mileage.

this is totally an opinion thing so don't everyone go bashing on me.
all I can say is that somebody had my truck hooked up to port vacuum when I got it and it didn't run worth a crap and got 12 mpg. I hooked it to manifold vacuum and it runs much much nicer and now I get about 17 mpg

You are absolutley right about one thing and IMO, one thing only. That it is an opinion thing. I've argued this point on several forums, and I find it's about a 50/50 on which way to do it. My way is opposite of yours as I'm sure somewhere in this thread I"ve explained already. Vac Advance is to be hooked to ported vacuum period. Racing app, Street App, Centrifical advance or not. I know I'll never change anyone's opinion who strongly beleive the way they do, but I do explain, if your going to hook to manifold vacuum and not ported, then why not just set your initial timing to what it would be hooked to manifold vacuum and be done, cuz that is essentially all you are doing, is increasing or advancing the timing, then you romp on the motor and lose vacuum, then you are RETARDING the timing while romping on the motor when you should actually want to be ADVANCING timing to romp on the motor and expect performace gain. It's just backwards to hook to manifold.

SO, I've had to stop and give thought to WHY in the hell do some people think hooking it up wrong works??? It has to make sense one way or another or 50% of the people wouldn't think it's right, when clearly ALL auto manufacturers clearly explain to use ported vac, and disconnect it while setting initial timing and for a reason. So I figure what is happening, those who do it this way are setting initial timing. Hook to manifold vac and get advanced timing with a FALSE POSITIVE or performance gain, and when they nail the pedal and romp on it, they actuallly LOSE or RETARD timing which keeps the motor from pinging. So I do see why they think it helps in performance, but who needs more performance at idle, or light throttle??? That is the only scenario I can think of. But, I"ll always use ported vacuum and those who see different and more than welcome to hook to manifold vac. I'm not going to knock anyone for hooking it how they wish. It just makes a good topic argument for gearheads.

EDIT : BTW, For racing applicaitons, there is no sense in hooking vac advance up at all. Usually with a big cam, lots of valve ovelap, you don't have engine vacuum to advance it anway. Best to rely on Centrifical advance only with racing counterweights and springs so you can get more advance, and lighter springs to bring on the advance much quicker.

 

[HotRodPC]

I'm gonna give the ported vac a try my trucks on manifold vac as is but when I gut the emissions gonna try ported

FOR DAMN SURE, use ported vacuum while emmisions testing. 2 reasons, ONE is because that is how vac label sticker shows it to be done RIGHT and they can FAIL you if your vac line routing is wrong. TWO, advanced timing will make dirtier tailpipe emmsions in NOX (Oxides of Nitrogen), so you actually want the more retarded timing at idle for cleaner tailpiple emmisions. After that, then you go playing around and hooking it up different and playing with results.

 

[Tyger13us]

You are absolutley right about one thing and IMO, one thing only. That it is an opinion thing. I've argued this point on several forums, and I find it's about a 50/50 on which way to do it. My way is opposite of yours as I'm sure somewhere in this thread I"ve explained already. Vac Advance is to be hooked to ported vacuum period. Racing app, Street App, Centrifical advance or not. I know I'll never change anyone's opinion who strongly beleive the way they do, but I do explain, if your going to hook to manifold vacuum and not ported, then why not just set your initial timing to what it would be hooked to manifold vacuum and be done, cuz that is essentially all you are doing, is increasing or advancing the timing, then you romp on the motor and lose vacuum, then you are RETARDING the timing while romping on the motor when you should actually want to be ADVANCING timing to romp on the motor and expect performace gain. It's just backwards to hook to manifold.

SO, I've had to stop and give thought to WHY in the hell do some people think hooking it up wrong works??? It has to make sense one way or another or 50% of the people wouldn't think it's right, when clearly ALL auto manufacturers clearly explain to use ported vac, and disconnect it while setting initial timing and for a reason. So I figure what is happening, those who do it this way are setting initial timing. Hook to manifold vac and get advanced timing with a FALSE POSITIVE or performance gain, and when they nail the pedal and romp on it, they actuallly LOSE or RETARD timing which keeps the motor from pinging. So I do see why they think it helps in performance, but who needs more performance at idle, or light throttle??? That is the only scenario I can think of. But, I"ll always use ported vacuum and those who see different and more than welcome to hook to manifold vac. I'm not going to knock anyone for hooking it how they wish. It just makes a good topic argument for gearheads.

EDIT : BTW, For racing applicaitons, there is no sense in hooking vac advance up at all. Usually with a big cam, lots of valve ovelap, you don't have engine vacuum to advance it anway. Best to rely on Centrifical advance only with racing counterweights and springs so you can get more advance, and lighter springs to bring on the advance much quicker.

I have argued this point with people till im blue in the face,, i agree HR,, PORTED vac..

but i do find that most people are running the garage door spings in there dist mech advance and they never get full mech advance,,(if it works at all),, or its usually froze up,, another reason why it runs like a slug,, but i find chevy did that for smog reasons,, but heres the ticket,, if people kept there rigs tuned up there wouldnt be any need for smog control..

i run 15 deg advance with a total mech advance of 32-34 and with vacuum total advance 54 all in @ 2500 rpm.... with a power dial light..

SBC should never ever have more advance than full 54 deg,, but ive seen it up all the way up to 65+ deg,, and they rattle like a bucket of marbles......

so they retard the timing till it dont rattle anymore,, then its a dog,, so then they hook up the vacuum to manifold so it will go.............

that is not the right way to do it.........

 

[HotRodPC]

You're right Ty. I do also beleive that those who FEEL and BELIEVE that the manifold vac is the way to go, is because they are not getting enough mechanical advance. As I said, all that hooking to manifold vacuum is doing is a False Positive, and they keeping detonation down cuz when they romp it, they are now actually retarding the timing and taking away from mechanical advance they were getting. I honestly thought it was simple to understand but guess not and I will not criticize anyone for what they believe.
But I haven't thought of it like you mention, and I think you're likley on target. It's got to be they are not recurving their dizzy and using heavy springs NOT taking advantage of mechanical advance and compesating with vac advance. Makes perfect sense. I NEVER used vac advance on a race motor. It was all mechanical and came in farily quick as you describe, by 2500 rpm I was all in.
Maybe if I wasn't a CA Emmisions Smog Test Tech at one time, I wouldn't know what I know and feel the way I do about vac advnace. I even remember back in the day before CA did emmisions testing, you had a TVS (Temp Vac Swtich) That would not allow vac advance to come on until the motor was warmed and the purpose, so the big wigs thought, was to reduce NOX emmisions.

 

[Dieselshine]

FOR DAMN SURE, use ported vacuum while emmisions testing. 2 reasons, ONE is because that is how vac label sticker shows it to be done RIGHT and they can FAIL you if your vac line routing is wrong. TWO, advanced timing will make dirtier tailpipe emmsions in NOX (Oxides of Nitrogen), so you actually want the more retarded timing at idle for cleaner tailpiple emmisions. After that, then you go playing around and hooking it up different and playing with results.

Wouldn't matter much Canada or Alberta has no emissions testing that's why I can take the emissions stuff and egr off and get away with it, I could blow all the rings in it burning antifreeze and aslong as I have a peice of paper that says the truck won't fall apart while it rolls down the street signed by your local backyard mechanic I can drive it till the day I sell it or it catches fire and burns to the ground lol never would happen with my truck but I've seen some vehicles on the road up here that look like they coulda been sunk in a salt water lake for the past 20years and revived lol but getting back to the point I agree with you hotrod 100% there's always the right way of doing things and you be a vet I trust you