North American Turbocoupe Organization



Only 10-11" of vaccum,but car runs good
Ralph H. Offline
Member
#1
I mentioned this in another topic,my car only shows about 10-11" of vaccum on my digital boost guage,less when cruising. Car runs and idles great.I moved the guage sender to dedicated vaccum by itself and was same.I checked for any leaks or loss vac hoses and found nothing.Would a worn cam give low vaccum?When car is hot you hear like a harmonics noise from under valve cover,only when hot.Let me know what you guys think.Ralph
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Ryan H Offline
Posting Freak
#2
A worn cam & followers can give you low vacuum, as can worn lifters, timing changes, leaks, etc etc etc. Have you tried doing a pressure test on your intake? Chances are you have lots of unfound leaks! I've yet to hear of anybody pressure testing and not finding at least 5-6 leaks somewhere. I would go ahead and pop the valve cover off and see what you find. Also check your PCV valve and check to make sure any valve guide seals haven't popped off while the cover is off.

The PCV can be checked in about 5 minutes without pulling the valve cover btw. If its not a Ford part, I'd bet $50 its leaking.
'88 TC Smile Walbro 255HP, Stinger FMIC, PIT BOV, Pro 5.0, Kirban, RR cam, FRPP strut tower brace, T3
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Ralph H. Offline
Member
#3
The pcv I can do tomorrow,how do you go about pressure test intake?I don't want to open up a can of worms right now,I am going to race car at track on 17th,Have line loc and 2 step ignition to finish first,after that I can go ahead with the vac issue.
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Ryan H Offline
Posting Freak
#4
If you have access to compressed air, you just use a rubber coupling from the hardware store and hook it somewhere after the VAM. Then install a tire valve stem or something similar to feed compressed air into it.

You have to put on a pressure gauge of some sort. I just use an automotive tire filler that has a built in gauge. Every hose on my vacuum tree was leaking at ~5 PSI. My EGR was leaking so bad it couldn't hold any amount of pressure for more than ~2 seconds. Almost all of my vac lines needed to be zip tied or clamped!

There is another option I thought of and tried about a week ago and it does work, I just forgot to make a post. What you can do is get the rubber coupling from the hardware store like normal & install the tire valve stem (NAPA for $2.99). Now take a good chunk of dry ice ($1.99/lb at your local grocery store) and stick it in there and clamp it onto your intake. You still need to use a pressure gauge. Don't add water to make it expand faster, you don't want to hydrolock your motor or mess up any sensors.

Once the pressure gets up real high and you have fixed all the leaks, take the core out of the valve stem so you don't blow any gaskets out. This method is also good for leaving the intercooler in place Smile
'88 TC Smile Walbro 255HP, Stinger FMIC, PIT BOV, Pro 5.0, Kirban, RR cam, FRPP strut tower brace, T3
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Pete D Offline
Administrator
#5
Easy to make. I just used a 2" to 2" rubber ture for connecting pcv pipe and a 2" end cap, drilled to accept a male compressed air fitting. Hook it to a regulated air supply, about 10 psi
http://natomessageboard.com/uploads/0000...ody003.jpg

http://natomessageboard.com/uploads/0000...ody007.jpg
Pete Dunham


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Ralph H. Offline
Member
#6
I just got an e-mail back from dynotune where I got the digital gauge from.He said it is a boost only guage accurate to .1 psi,but it will read negative numbers,it is not made to read vaccum.I couldn't find my mech vac guage,I will get another one.
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Matt S Offline
Posting Freak
#7
Is it an electric sender digital gauge? I'd verify with a mechanical one to be sure it's not your gauge.
Sold it Sad*
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Dingus00 Offline
Junior Member
#8
If you have an adjustable cam pulley make sure you have the cam zero'd properly(should line up about 2 teeth the the right of the keyway, double check with stock pulley). I had the same issue, car ran fine felt strong but couldn't get more than 10 for vacuum. Found out that the 0 mark on my adjustable WAS NOT the actual zero mark I was off by 2 teeth!!!
2.3 or bust!
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