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Discussion Starter #1
i have a '86 bronco with the 351W in it that i bought about a month ago and been messing with. well it idles rough but smooths out a higher RPM so i changed the plugs, wires, cap, rotor, ran some seafoam through it, and did some oil flushes and it still ran rough. it has a edelbrock 1406 carb on it so i got the instructions and adjusted the carb properly and still ran rough. today i ran propane over all the vac. hoses and no change in idle but when i hooked up the vac gauge to some vacuum lines with it running it still reads 0. the only place i hooked up to that had vacuum was where the brake booster goes into the manifold and has that tee off that was capped, and the gauge only read 15. so i know i have a vac leak and what i really need to do is replace all the lines but i'm intimidated with the cluster of hoses. Do i really have a vac leak, or intake leaking? why wouldn't the propane test work if i had that bad of a leak?

Travis
 

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Not if someone unhooked the lines and capped them off. There should be two vacuum trees on that engine, one in back and one infront near the temperature sender. The vacuum lines are defined on the emissions sticker located on the left side of the radiator mount. Each function is color coded. A thought just crossed my mind, do you have a stock intake? If so what I said about the vacuum trees is correct, if not you may not have the one in front and may also have a problem recreating the vacuum functions but it is doable.
 

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Not all of the vacuum lines have vacuum all the time. Without knowing WHICH lines you got 0 in & under exactly what conditions you checked, it's meaningless. You probably have no vacuum leaks. Read these 2 pages and repeat the test with the gauge connected DIRECTLY to a port on the intake manifold. You can disconnect the brake booster & use that port if you want.
 

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By the way 15 might only be an indication that you need a little fine tuning. This vacuum diagram will be pretty close to what you can most likely hook up on that engine. If you have a Edelbroc 1406, I don't think you have the bowl vents so that bit of mess won't be hooked up. The diagram I am attaching is of my system.

Red is Main vac
Orange is heat control valve (heat riser)
Yellow is spark
Gray is canister purge control
Black is canister vapors
Also shown in black is the PCV valve connection
 

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Discussion Starter #5
ok i'll check it maybe tonight. when i did the first test it was fully warmed up and ran for 10 min before i tested it. i plugged the vac gauge into about 10 different hoses that all read 0 then i tries where the brake booster gets vac out of the manifold and got 15. so i don't know but i'll try to check it again

Travis
 

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Discussion Starter #6
hey guys well i played with it again tonight and this is what i found. i hooked the gauge up to a hose that came from the back of the motor "rear vac tree???) that had a few lines coming off of it. at warm idleing at 850-900RPM it flickered between 16-17, rev it up and goes to 0 then shoots up to 21-22 then back down the 16-17. i held it reving up and needle was steady. according to that page i have poor rings?? that sucks i really don't want to rebuild this motor. also the vac line out of the EGRin the back is not hooked to anything, where the brake booster line goes to the mainifold it tee's off twice but both of those lines are plugged. under the carb on the manifold there are 2 outlets one goes to PCV valve one is plugged. also i noticed after i shut the motor off and i still have my foot on the brake it bleeds off the pressure in about 5 secs is that normal? any help is great.

Travis
 

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BIGT2317 said:
at warm idleing at 850-900RPM it flickered between 16-17, rev it up and goes to 0 then shoots up to 21-22 then back down the 16-17. i held it reving up and needle was steady.
May be and maybe not. It could be timing also.

BIGT2317 said:
where the brake booster line goes to the mainifold it tee's off twice but both of those lines are plugged.
This is the reason you don't get vacuum at other locations. They are unhooked.

BIGT2317 said:
under the carb on the manifold there are 2 outlets one goes to PCV valve one is plugged.
That is normal. The EGR spacer has more ports than it actually uses.


BIGT2317 said:
Also i noticed after i shut the motor off and i still have my foot on the brake it bleeds off the pressure in about 5 secs is that normal?
That is normal

My question is what do you want to do? Do you want to rehook up the disconnected functions? If so which ones? Does your truck have the emissions sticker on the right side of the radiator support? Do you have the stock intake manafold on it (for the second time)?

Do you have A/C or did it have A/C?

Does your intake sort of look like this?
 

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Discussion Starter #8
yes i think i have the stock intake. all i want do do is have this motor idle properly instead of real rough and pass inpection.. it did have a/c but the guy said it had a leak and they never fixed it. yes i have the sticker on the support but like i said i no nothing of carbs and vac hoses, on the sticker it has a bunch of abbreviated items that i have no idea what they are of what they look like. i would like to just redo the whole mess but since i don't know what goes where and what things look like, i'm unsure about it.

Travis
 

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Seabronc said:
May be and maybe not. It could be timing also.



This is the reason you don't get vacuum at other locations. They are unhooked.



That is normal. The EGR spacer has more ports than it actually uses.




That is normal

My question is what do you want to do? Do you want to rehook up the disconnected functions? If so which ones? Does your truck have the emissions sticker on the right side of the radiator support? Do you have the stock intake manafold on it (for the second time)?

Do you have A/C or did it have A/C?

Does your intake sort of look like this?

oh god flashback to my 85 before my edelbrock carb and edelbrock intake. ah why you post that. :twak Just make life easy and get a edelbrock intake since you have the carb already. not like its hard to change your intake when you have carb. plus youle beable to see your rods and lifters. thats when i found out i had a bent rod. cyl 7 for me. oh lucky me. plus youll be able top eleminate tht hose mess. i think i have 2 vacuum lines on my engine. one for distributor and one for the tranny. :chili:
 

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Discussion Starter #10
so if i get a aftermarket edelbrock intake, i will not have as many vacuum lines? what about getting it inspected, if i loose all the vac lines will all the emissions go away? here in texas they are getting a little stricker so i want to be able to get it inspected. also what intake would you suggest i want one will power on the low end. thanks

Travis
 

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BIGT2317 said:
yes i think i have the stock intake. all i want do do is have this motor idle properly instead of real rough and pass inpection.. it did have a/c but the guy said it had a leak and they never fixed it. yes i have the sticker on the support but like i said i no nothing of carbs and vac hoses, on the sticker it has a bunch of abbreviated items that i have no idea what they are of what they look like. i would like to just redo the whole mess but since i don't know what goes where and what things look like, i'm unsure about it.

Travis
Ok, here is what I would suggest:

1. first restore the vacuum support for the A/C controls. No matter if you have A/C now or not, you need the vacuum part so the controll will properly operate the vacuum motors.

That connector on the fire wall should have aline to the rear vacuum tree. It should also have one line connecting to the vacuum line to the transmission. The third line should go to a check valve and then from the check valve one line to a vacuum reservoir and the other to your A/C control.

If you don't have this arrangement you will probably find the heat switching from vents to defrost any time the engine is under a load.

Picture attached of the vacuum check valve.

Take a picture of the emissions sticker or let me know if it looks like the one attached.
 

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OOPS!!!!!
 

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BIGT2317 said:
so if i get a aftermarket edelbrock intake, i will not have as many vacuum lines? what about getting it inspected, if i loose all the vac lines will all the emissions go away? here in texas they are getting a little stricker so i want to be able to get it inspected. also what intake would you suggest i want one will power on the low end. thanks

Travis
If you change intakes and want to keep the emissions controls you need to get one that has a place for the Heat Control Valve and EGR function. I'm not sure you can get that. I do remember that Edelbrock allowed for atleast one of those functions on one of the Performer series intakes.

Edelbrock does make one that looks like it has both functions, it is number 3783. http://www.edelbrock.com/automotive_new/mc/manifolds/ford_sb_perf.shtml

The inspection process and your sensitivity to the air quality determines what you need to hook up. If you want the emissions and cold start and run functions the way they should be, I am willing to advise you on how to hook it up. Other wise, have at it. :scratchhe
 
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