No boost? Can't figure it out...

**68mustang** · 04-13-2011, 05:23 PM

So I have a 79 with a sn89 all hooked up..my problem is I'm not seeing any boost... My guage is hooked up below the carb on intake manifold.... It shows vacuum on the guage... N at wide open drops to zero but doesn't go up to 5 or even passed zero... So what's wrong? I hear the charger working n it's sucking in air... So what's wrong? I looked at car idleing with a rev held at 3000 n no boost.... I then drove it n at 4500 still no boost..

**Michael** · 04-13-2011, 06:47 PM

Can you hook up the boost gauge to the blower's outlet? There's a threaded hole on the outlet side that (I believe) is meant to take a boost gauge.

Since you've driven the car, does it feel quicker? I'm just trying to determine if you are indeed getting boost, which might mean the issue is with the gauge itself.

**68mustang** · 04-13-2011, 07:24 PM

Yes it does but I have my mechanical pump hooked up there for boost reference... And also..no it feels like a bolt on foxbody.

**Michael** · 04-13-2011, 07:28 PM

I should probably already know the answer to this question, but did you recently rebuild the blower?

**68mustang** · 04-13-2011, 08:24 PM

Yes. It has been rebuilt n oil is all good... Nice and cherry

**Michael** · 04-13-2011, 08:51 PM

Who rebuilt it? Did you do it, or did you get a shop to rebuild it? If you did it, did you check the torque needed to turn the blower with and without the oil seals in place?

I'm trying to determine if the turning torque (which relates to the ball pressure inside the blower) is within spec.

**68mustang** · 04-13-2011, 09:01 PM

I did... And I can't remember the spec off. Hand... Can I use a torque wrench on the pully now and check it?

**Michael** · 04-13-2011, 09:27 PM

Yes, I think you can.

According to another post here on the forum, Craig @ Paradise Wheels suggests 20-22 in-lbs with no seals and add 5-8 more with seals installed (25-30 in-lbs). The latter is what you should be looking to see.

**zray** · 04-14-2011, 07:57 AM

Originally Posted by 68mustang

Yes it does but I have my mechanical pump hooked up there for boost reference... And also..no it feels like a bolt on foxbody.

you should intall a T fitting in the line to the boost reference so you can run the gauge line off the same signal as the boost reference line.

Z.

**68mustang** · 04-16-2011, 04:31 PM

Before the carb? I heard u take boost below the carb? N it torque outs fine... All good there...

**zray** · 04-16-2011, 11:02 PM

Originally Posted by 68mustang

Before the carb? ........"

yes. take it from the exit port of the supercharger right where you are getting the boost reference for the fuel pump, just as I described above.

Z.

**68mustang** · 04-17-2011, 07:22 AM

I had my turbo set up on my 68 and I have it on the intake tube but they told me to always take boost reading under the carb to make sure your not losing boost through the carb hat etc.. This isn't the case?

**zray** · 04-17-2011, 07:47 AM

just do it however you want.

apparently you aren't going to satisfied with a procedure that has worked for me for 10 years and was recommended to me by SN authority Conley of Paradise Wheels

Z.