Vacuum Question

Skoobie

Skoobie

Damn...Tyler65's hot!
May 25, 2003
655
0
17
Vancouver, WA
#1
I know I saw this on here somewhere but my searches arnt comming up with anything. I was wondering how many Hg vacuum an 89 5.0 should be pulling at the PCV line. I hooked up a guage and it read 10-11 PSI. Is this normal? Here is a list of my mods:

GT40 Heads (Ported)
GT40 Lower intake (Ported)
Explorer Upper intake (Ported)
1.6 Roller rockers
E303 cam
3G Alternator
83mm Mass Air
C&L Power pipe
CAI
Ford racing wires
3.73 Gears
Pro 5.0 Shifter
Nitto 555 DR's
Eibach Sportline springs
Monroe GP Shocks/struts
SSM lift bars
Sub-frame connectors
BBK shorty Headers
MAC O/R h-pipe
Magnaflow catback
 
#2
a stockish motor should pull 15-20" hg at idle. i dont know what a PCV line would read, as i have never read it. the check-valve, blowby and bi-directional nature of it would make it so i would not know how or when to check it, in order to be consistant.

the number above is for manifold vac (i.e. read off a fitting on the vac tree).

good luck.
 
#3
Ok so I tried a reading off the tree and its hovering between 11-12. I dont know if it make a difference what part of the tree you use? I used the S/C fitting (dont know what that stands for?). So does this indicate a vacuum leak then? :shrug:
 
#4
the way you did it should be fine. sounds like you have 11-12". (if you removed a hose (rather than a cap), did you plug the tree or line (whatever was not attached to your gauge)? otherwise you likely created a vac leak right there and then.

much of the vac one sees depends on the cam. i dont know the characteristics of that cam to know. it does not sound horrible to me - and it may be normal. ill bump you for the E cam guys. :)

good luck.
 
#5
Just to be sure I re-checked it at the same fitting and blocked off the tube that I unplugged with the same result (11-12hg). The guage is color coded (red-green red being 0-12hg, yellow being 10-15hg, green 15-22hg) so according to the guage there seems to be a leak :shrug: Unless like you said its a characteristic of the e-cam. Any other opinions?
 
#8
what exactly is the problem? if you thought it was a vac leak, i take it the idle hangs when coming down from revs? perhaps hunts a little?
 
#9
DING DING DING! Couldnt have described it better myself. I've had the car since April and it idled fine then. It was quick to calm down, no hanging or searching, and had a nice smooth lope to it. Now it does as you say and even when it does get down to 600-700rpm it feels like its a shakey shuddery idle not smooth like it use to be. I posted this in another thread but long story short when I pulled the upper intake the gasket had a break between two of its ports and there was also a broken bolt at the rear of the intake. I fixed both of these problems and it doesnt seem to have made a difference. I wish I could remember when things went soulth but I cant :( I just remember it getting to the point where the idle wouldnt settle below 1100-1200rpm. I took it to a Mustang shop and they found a frozen PCV which I replaced and adjusted the timing that seemed to help but never totally cleared things up. The only odd thing that I discovered was a few weeks later I was taking the stang on a long road trip so I gave the bay a once over. I heard a sucking sound comming from the under side of the upper intake near the front. There were three vac connections, of which two (the right and left connections) were blocked off but the center was open and sucking quite a bit of air. First I tried looking for a vac line that may have popped off but I didnt see anything so I ended up just capping it off (which helped things even more but still didnt fix the problem). It always bugged me though because Im 99% sure that leak was not there when I first got the car, like I said it ran perfectly. I guess a cap could have just popped off but I dont know :shrug: I didnt do most of the modifications to the car. :( I hate playing catchup, especially with my car. Goes to show you, get a stock car and do the mods yourself, its easier to fix that way :nice:
 
#10
ok cool. we are getting somewhere. :)

the line under the front of the plenum (upper) concerns me. that line is quite prone to cracking - mine broke when i took the upper off too. i had to fab something up as it was a weird size or tapered (or something funky - i dont recall). i dont recall where it went (somewhere to the front of the upper).

i would go over it again (arrgghh) and check for leaks with your favorite method. i would not be surprised if you find a cracked line (maybe not even visible). hard to find, cheap to fix.

good luck, bud. :)
 
#11
OK lets back up a bit. That 'line' under the upper intake never existed...at least I think it didnt?? I found that leak LONG (July I think?) before I ever pulled the upper intake (Pulled it two or three weeks ago). When I found the leak, since I didnt see any vac lines around it I just put a cap on it. The only line around it that wasent connected to anything lead down twards the old charcoal canister which isnt being used I've been told (smog/AC delete). My buddy said that the line was used to vent the carbon into the canster...not knowing a thing about stangs I took his word for it, although it does look suspiciouly like a vac line...hmm. BTW thanks for all the help man, I hope Im not bugging you too much :hail2: :flag:
 
#12
Skoobie said:
OK lets back up a bit. That 'line' under the upper intake never existed...at least I think it didnt?? I found that leak LONG (July I think?) before I ever pulled the upper intake (Pulled it two or three weeks ago). When I found the leak, since I didnt see any vac lines around it I just put a cap on it. The only line around it that wasent connected to anything lead down twards the old charcoal canister which isnt being used I've been told (smog/AC delete). My buddy said that the line was used to vent the carbon into the canster...not knowing a thing about stangs I took his word for it, although it does look suspiciouly like a vac line...hmm. BTW thanks for all the help man, I hope Im not bugging you too much :hail2: :flag:
Click to expand...
ok, i gotcha. i cant remember where that line went on my ride (i have all the smog stuff). we might be onto something, but ill have to look tomorrow or get some of the nice stangers in here to help out. i just cant remember what the stuff looked like/where it went (i was trying to figure something else out when i noticed the line so i went on autopilot).

PS, this is not bugging me. i tend to hang out in here a lot anyhow and it is slow at night. i just cant remember anything right now. LOL.

good luck with it. ill try to remember to check tomorrow while workin on the camaro.
 
#13
Skoobie - for what it's worth, when I had the ecam in mine, I had to idle it up to about 1050 rpm to get 11" hg at idle. That was as high as I could get it. And it was extremely rough running down there, idle fairly unstable. I tried every idle setting/stabilizing thing I could - including the air bypass plate. 3 months worth of 'tuning' - nothing worked until we used a chip to reset the idle speed. That stabilized the idle, but did nothing to help the low vacuum or rough running/lack of power down low. Finally realized I'd made a bad cam choice (for me/my set up). Got Buddy Rawls to do a custom for me and got rid of the E. That solved the situation completely. Of course I asked for more vacuum at idle and more bottom end torque.
 
#14
The reason Im being so picky is that is use to run fine. I havent done any mods that would have changed my idle or vac (other than a CAI but I doubt that had anything to do with it). I just want to get her back to the way she was :nice:
 
#16
No I dont have a code reader and cant afford one at the point :( I looked under the hood again this morning to double check where the mysterious vac line went to and it does in fact lead to the charcoal canister. I also pulled the plug on that vac connection that I found back in july just to see how much hg it was pulling. 11-12hg just like the vac tree. What was odd though was there was little or no change in how the engine ran when I pulled the plug. :shrug: Would the car run different if there was more than one vacuum leak? If not would this indicate that there is in fact a leak somewhere else? Man vacuum issues suck donkey balls :bang:

:EDIT: Im trying to figure out the vac diagram in the chiltons, while it makes little sense to me it looks like MAYBE the vac connection in question might be for the FPR? I wasent aware the FPR had a vac connection?
 
#17
You don't need a code reader to pull them down, although I got mine at WalMart for only $22. Autozone/PepBoys/Advance Auto will usually pull them for you for free - seems they've figured out you might buy a part from them. PM to ' jrichker ' on this site or the Corral - he'll tell you how to pull them with a paper clip and a simple 12V test light or voltmeter. Good luck with it.
 
#18
ExplodingGopher said:
that cam is going to produce less vaccuum at idle than stock beacuse of its characteristics. I have the B cam and i have barely any vaccuum at idle, its hard to hold my brakes when creeping along, and i know i have no leaks, its just my cam. and the B cam is only 4* more duration than yours.
Click to expand...


I have the "B" cam in a carbed Capri and I pull 14" hg at idle of around 950 rpm.
 
#20
Skoobie - You'd think so, but here's how it actually works. There were only 10 E303 cams ever built. The original 10 purchasers used them for a month or two, and then they pull it out to replace it with something else. They sold the cam used to someone else who does the same thing. To date, thousands of people have been E cam users. And that's the true story of the E cam. :) Oh - there were only 10 original Crane PowerMax 2040 cam users too (same cam).
 
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