Specifications

Poor idle with big cam (Less than 112 degrees on Lobe Separation)

If you install a larger cam that has a Lobe Separation of less than 112 degrees, you will notice a very poor

idle (sometimes dies at the light) and running too rich at idle as well. This is caused by the MAP signal

being too low due to the cam. The MAP vacuum at idle (with a stock cam) is 12-13" at the MAP port on

the throttle body. With a larger cam, that has a 108-110 degree Lobe Separation, the vacuum at the MAP

port is 6-8". This is too low and will cause poor idle qualities. Also...make sure you set the distributor in

properly as there is only ONE WAY that is correct. Set the distributor index (fuel sync) at 4 (+/ -1) after the

initial break-in (fire up).

Plug the MAP port on the throttle body and relocate the MAP line to manifold vacuum (should be about

12-13" at idle). This will simulate the factory signal and your idle quality will be back to normal. There is

no adverse affect on the cruise or WOT performance with this modification.

Recommendation: Select a Cam with 112-114 degrees Lobe Separation. They are MAP friendly.

4.7L Throttle Body Swap

For those who don't know, the 4.7L comes with two flavors of throttle bodies. The '99-'00 models use a

65mm and the '01 models use a 68mm throttle body. You can easily swap out the later model 68mm

throttle body for your performance-limiting 65mm without any problems. You can tell which one you have

by looking at the stamped number on the throttle plate. "65" = 65mm / "68" = 68mm

Throttle Body Spacers (Primarily the "Helix" style)

These spacers do not provide any gains in HP at all. They claim to increase TQ and MPG but we tested

one and it gained nothing. The Dyno showed no gains in HP or TQ. We also had contacted one of the

manufacturers for their comments on them and here's the direct quote (from email):

--------------------------------------------

From: AirAid Info

Subject: Re: AIRAID.COM Contact Form

Date: Fri, 09 Mar 2001 09:20:36 -0700

Dear Sir, thank you for your inquiry in our products. The spacer makes no HP on the Dyno. It makes all of

it's power in torque in the low end. If you haven't noticed any power on the Dyno or the track then it's doing

what it's supposed to. You would not see any gains down the 1/4 mile or increases on the Dyno. The idea of

the spacer is to improve overall drivability and fuel mileage. In most cases when people install a bolt on

part they expect better mileage and power, what happens is they are into the throttle a lot more than before

trying to test performance and that's when the decrease in mileage happens.

Sincerely,

-------------------------------------------