intake/throttle body hole

[dmwelljr]

Can someone tell me what the 3/8" threaded hole is for on the flange of the intake manifold that the throttle body bolts to? Its a tubular gt40, Thanks!

 

[Ourobos]

The cover / plate for the top of it?

 

[dmwelljr]

no, its on the side of the throttle body flange, the side facing the front of the rig when the tb is facing the pass side

 

[dmwelljr]

I got my maf, and throttle body, getting it all out together and just noticed it, I have no idea!

 

[dmwelljr]

 

[trentturner27]

I think the act sensor is 3/8 and that could be where they had it

 

[Tonka7777]

My tubular upper does not have that hole.

 

[Broncobowsher]

That is not a factory hole. Lots of things it could have been used for, ACT to NOS. Put a plug in it for now.

At first I thought you were referring to the hole on the MAF side of the throttle body. That is the breather line for the crankcase vent. Goes to the oil filler neck. It allows air into the engine to make up for what is sucked through the PCV. Since it is after the MAF, it is metered, thus the clean air that the PCV sucks through is part of that metered air. This way the computer still knows how much air is going through the engine. Cap it and put a breather oil filler cap on and you mess with the MAF calibration as you are letting unmetered air into the engine (via the PCV). So it is best to follow the original design and not add random breathers to the EFI. But that is for a different hole then the threaded hole you posted a picture of.

 

[dmwelljr]

That is not a factory hole. Lots of things it could have been used for, ACT to NOS. Put a plug in it for now.

At first I thought you were referring to the hole on the MAF side of the throttle body. That is the breather line for the crankcase vent. Goes to the oil filler neck. It allows air into the engine to make up for what is sucked through the PCV. Since it is after the MAF, it is metered, thus the clean air that the PCV sucks through is part of that metered air. This way the computer still knows how much air is going through the engine. Cap it and put a breather oil filler cap on and you mess with the MAF calibration as you are letting unmetered air into the engine (via the PCV). So it is best to follow the original design and not add random breathers to the EFI. But that is for a different hole then the threaded hole you posted a picture of.

I don't have the factory valve covers, so I don't have the oil fill neck with that port, what would be another place I could hook that to?

 

[Ourobos]

Not stock. I'd plug it. Probably an ACT at 3/8". Could have been a vacuum tree also.

 

[garberz]

I don't have the factory valve covers, so I don't have the oil fill neck with that port, what would be another place I could hook that to?

If your not running stock valve covers, make sure the ones you have are sealed. As in, non vented oil fill cap and no vent on the other (PCV) side.


Mark

 

[dmwelljr]

If your not running stock valve covers, make sure the ones you have are sealed. As in, non vented oil fill cap and no vent on the other (PCV) side.


Mark

Ok, will do, thanks! So can I just plug the vacuum port on the throttle body?

 

[garberz]

No, you can't just plug that one. You'll need to run that port to the valve cover somehow. I'll assume you're running a PVC. All the air that the PCV sucks in from the crank case comes in from the valve covers. The air that the valve covers lets in, needs to be measured by the MAF. That port on the throttle body is measured air going to the valve cover. That's why every other opening on the valve covers need to be sealed. This is what Broncobowsher was explaining in post #8.

Mark

 

[Broncobowsher]

While we are on the PCV confusion, don't forget that the EFI PCV is located at the back of the intake sucking out of the lifter valley. Goes into some of the lower plenum ports, if present.

For the drilled and tapped hole that originally started all this, yes that can be plugged. If you need a vacuum source (power brakes, PCV, transmission modulator) you can use that as a full vacuum source.

Now I do have a theory to what happened. If this intake was used with a set of taller aftermarket valve covers the fittings normally used for the PCV at the bottom of the longitudinal plenum may have interfered and were plugged. To make the PCV functional the hole was drilled and tapped for PCV. Again, only a theory. Used parts are often filled with mystery.

 

[dmwelljr]

Ok, thanks guys, this is my first ford build, and my first efi build. The valve covers I have now are the fabricated ones, with no hole whatsoever, so I have to drill them myself, I have grommets and breathers to install, apparently I done need! I'll have to look for an oil fill plu with a port on it to hook that line into, thanks agin, drilling those covers was my next step!

 

[mattt]

That is not a factory hole. Lots of things it could have been used for, ACT to NOS. Put a plug in it for now.

At first I thought you were referring to the hole on the MAF side of the throttle body. That is the breather line for the crankcase vent. Goes to the oil filler neck. It allows air into the engine to make up for what is sucked through the PCV. Since it is after the MAF, it is metered, thus the clean air that the PCV sucks through is part of that metered air. This way the computer still knows how much air is going through the engine. Cap it and put a breather oil filler cap on and you mess with the MAF calibration as you are letting unmetered air into the engine (via the PCV). So it is best to follow the original design and not add random breathers to the EFI. But that is for a different hole then the threaded hole you posted a picture of.

Not stock. I'd plug it. Probably an ACT at 3/8". Could have been a vacuum tree also.

If that was a factory Lightning intake, which it probably was, it is a factory hole. There was a vacuum tree in that hole that provided vacuum for power brake booster and various other small colored vacuum lines that went to the engine components. I'll get you a picture later. I used it on my setup for brake booster and fuel rail regulator. I swapped the vacuum tree from the factory Lightning 7 port fitting down to a 2 port fitting from a Thunderchicken 5.0. ACT at that time period was in #5 intake runner in the lower.

 

[Dannyboy71]

If that was a factory Lightning intake, which it probably was, it is a factory hole. There was a vacuum tree in that hole that provided vacuum for power brake booster and various other small colored vacuum lines that went to the engine components. I'll get you a picture later. I used it on my setup for brake booster and fuel rail regulator. I swapped the vacuum tree from the factory Lightning ~8 port fitting down to a 2 port fitting from a Thunderchicken 5.0. ACT at that time period was in #5 intake runner in the lower.

I would like to see that picture as well Matt. If you have the time.

 

[dmwelljr]

If that was a factory Lightning intake, which it probably was, it is a factory hole. There was a vacuum tree in that hole that provided vacuum for power brake booster and various other small colored vacuum lines that went to the engine components. I'll get you a picture later. I used it on my setup for brake booster and fuel rail regulator. I swapped the vacuum tree from the factory Lightning ~8 port fitting down to a 2 port fitting from a Thunderchicken 5.0. ACT at that time period was in #5 intake runner in the lower.

Awesome, pics would be great, I'm going into this build pretty blind! Thanks again

 

[mattt]

pic 1 is factory.
pic 2 is how mine is now.