P2123 in the wet

[Jack Houpe]

Sorry for the thread drift, but this part of the topic has me interested. I was working int eh front compartment and noticed the fresh air inlet is located on the driver's side. It seems that pulling warm air form the front compartment is not a great idea. My fresh air NACA ducts are not connected. I think Steve C 2125 has his connected. This has to have some affect on warm air getting into the cabin I would imagine. Here is a thread that relates:

http://www.gt40s.com/forum/superformance-gt40s/28698-air-ventilation-opening.html

If you look at Steve Cs mods you will see the NACA ducting.

Mike

Mike you are correct, they should have the connections from the naca duct to the fresh air inlet on the tub. My car came with both (air tubes) installed but only one goes to the tub, the other has a plug in it. The MKIIs radiator venting system is much better than the MKI's, the MKI's will allow you to bake bread in the foot well area.

 

[Mike Christian]

same here - my passenger side is plugged. I am thinking of connecting the driver's side NACA to the open one so that I can get outside air.

However, I see that both front brake ducts are not connected and just dump air into the front compartment too. I am thinking this might be easier to plumb to...I think I just need to reduce the size of the tubing down a little....hmmmm.

 

[Jack Houpe]

same here - my passenger side is plugged. I am thinking of connecting the driver's side NACA to the open one so that I can get outside air.

However, I see that both front brake ducts are not connected and just dump air into the front compartment too. I am thinking this might be easier to plumb to...I think I just need to reduce the size of the tubing down a little....hmmmm.

Mike put your hand in the hole where the front brake ducts are located. You will find they are blocked off. You will have to mark them with a scribe then remove the front bonnet and cut the openings out.

 

[Rick Muck- Mark IV]

Mike put your hand in the hole where the front brake ducts are located. You will find they are blocked off. You will have to mark them with a scribe then remove the front bonnet and cut the openings out.

As I related some time ago, you will flood the front of the tub with ambient air....perhaps warm air, but certainly lower temp than radiator outlet air!

 

[Ian Clark]

Interesting thread, even with the drift. There is a relationship between the water leaks and the NASA ducts however.

I think SPF has it right with only one side connected to the tub to supply make up-air to the A/C unit.

On CAV GTs we build the right hand NASA duct is plumbed to the tub where it meets with a seal and integral dust screen. The interior side is directly plumbed to the Heater/AC unit via flex hose and a custom end cap molding. The goal being to ensure the make-up air is fed into the fans rather than simply dumped in the area and hope for the best. This provides 25% make-up air with the interior fans running. It also creates positive cockpit pressure, the benifit being no exhaust smells clinging around the cabin and less opportunity for rain to get in. Works great.

It's important to feed the make-up air in a way that the fans pick it up instead of doing the lazy thing of recirculating ambient air, otherwise you're not getting full benifit. The Heater/AC unit in the CAV is in the open cabin area under the dash so we had to do it this way.

Somewhere it was mentioned that the NASA ducts on the hood beside the headlights are in a neutral area pressure wise, unlike the duct infont of the winsdshield like all passenger vehicles. So fan assist is essential when pulling air from area with no positive pressure to begin with.

The race cars were another matter all together. All the lightening holes in the cowl bridge, panel gaps and token weatherstrips weren't intended to keep anything out (or in) the car. I mentioned leaks to Craig Fisher, ex Comstock team driver, he said in the rain at Sebring there was an inch of water inside the GT40, that's race cars for you.

There's probably a speed at which air bleed from the cockpit overwhelmes the fans on the Heater/AC unit and cabin pressure goes negative, futhermore adding the second NASA duct could reduce the efficiency of the AC system, eluding to Ricks' point.

I surmise that's if your going fast enough the exhaust can't swirl forward and the rain is blowing by you have other things on your mind. In town or at posted highway speeds the coupled make-up air works.

 

[Mike Christian]

Mike put your hand in the hole where the front brake ducts are located. You will find they are blocked off. You will have to mark them with a scribe then remove the front bonnet and cut the openings out.

Yup, just as you described. Thanks for making me look in there Jack. I put a flashlight in there and found a dead bird...must have got sucked into my brake intake at speed.

Yuck.

 

[Steve C]

Somewhere above "windshield weatherseal pucker" is discussed.

Easy to fix:

Cut out pucker with razor knife (don't overcut, just enough to have both cut ends mate) and glue down with gel superglue.

Lynn and I did and now have perfect no pucker gasket (mine 18 months and looks great.

Steve P2125

 

[Steve C]

Mike,

SPF design is similar to Ian's CAV description.

SPF MK11 has the 2 NACA fender cut outs ducted under the fenders to the tub front. L or R drivers side is functional other side tub opening is plugged. Functional duct feeds air to the servo valve that either brings in outside air or cabin recirc controlled by the door switch.
As Ian points out this is the best way as the air is able to be moved by the cabin fan.

To prevent water ingestion I have opened a drain hole in the bottom lowest point in the under fender duct AND partially closed off about 20% of the lower part of the tub opening.

See pic of tub opening screened to prevent junk from entering the A/C evaporator or clogging up the fans in pic below. Pic before adding 1/2 moon shaped flat rubber stock to bottom of opening to eliminate water intrusion (any water injested in the NACA duct is stopped and with drain hole at lowest point in the duct doesn't get into the A/C or fan lines.

Steve P2125

 

[Richard]

Jack thanks for posting some pictures. Video in the car seems to never be easy unless you spend big money. I keep thinking I can fix that but haven't so far. Fortunately they fixed the window gasket issue in later cars.

 

[Mike Christian]

Mike,

SPF design is similar to Ian's CAV description.

SPF MK11 has the 2 NACA fender cut outs ducted under the fenders to the tub front. L or R drivers side is functional other side tub opening is plugged. Functional duct feeds air to the servo valve that either brings in outside air or cabin recirc controlled by the door switch.
As Ian points out this is the best way as the air is able to be moved by the cabin fan.

To prevent water ingestion I have opened a drain hole in the bottom lowest point in the under fender duct AND partially closed off about 20% of the lower part of the tub opening.

See pic of tub opening screened to prevent junk from entering the A/C evaporator or clogging up the fans in pic below. Pic before adding 1/2 moon shaped flat rubber stock to bottom of opening to eliminate water intrusion (any water injested in the NACA duct is stopped and with drain hole at lowest point in the duct doesn't get into the A/C or fan lines.

Steve P2125

Thanks Steve! And that piece that goes from the NACA duct to the inside of the tub is an Olthoff special? The sheetmetal side panel in the tub must be cut to allow air through this piece?

Regards,
Mike

 

[Mike Christian]

Jack thanks for posting some pictures. Video in the car seems to never be easy unless you spend big money. I keep thinking I can fix that but haven't so far. Fortunately they fixed the window gasket issue in later cars.

With a rubber/foam gasket?

 

[Steve C]

Mike,

" And that piece that goes from the NACA duct to the inside of the tub is an Olthoff special?"
No it's factory and the new cars come with them, one each side. Olthoff or Lance may be able to get for you. You would need to glass them into the front clip (that's what was done to mine and it looks "factory".

"The sheetmetal side panel in the tub must be cut to allow air through this piece?"

Realize that although there are 2 NACA slots, one in ea fender and on the new cars and my retrofit two moulded ducts that are glassed into the underside of the fenders. There is only ONE opening through the tub (see my pic above) used (drivers side only), the other side has provisions for use if built with opposite side steering. So bottom line is: I'm sure you have the tub opening on your left side otherwise your AC or fan only would only operate in "recirc" mode. Without the NACA ducting you are pulling warm/hot front compartment air into the AC or or fan only when the door recirc sw is NOT illuminated.

OK?

Steve P2125

 

[Mike Christian]

Realize that although there are 2 NACA slots, one in ea fender and on the new cars and my retrofit two moulded ducts that are glassed into the underside of the fenders. There is only ONE opening through the tub (see my pic above) used (drivers side only), the other side has provisions for use if built with opposite side steering. So bottom line is: I'm sure you have the tub opening on your left side otherwise your AC or fan only would only operate in "recirc" mode. Without the NACA ducting you are pulling warm/hot front compartment air into the AC or or fan only when the door recirc sw is NOT illuminated.

OK?

Steve P2125

Yes, this I understand - I have the opening in the tub on the driver's side. I am trying to get fresh air there instead of pulling from the front compartment. Looks like my brake ducts are blocked and my NACA ducts are not connected. Either way I am modifying the clip at this point. I will contact SPF to see about getting the NACA duct bits.

Thanks Steve.

Mike

 

[Kirby Schrader]

Dennis Olthoff sent me two of the fresh air fixtures for my car after I had it home for a couple of months. I've installed one on the left/driver's side and it works well.

I sawed it in half, made a hole in the clip and then fiberglassed the two pieces on. This way, I got both pieces to line up with their respective holes (the naca duct and the hole in the firewall) as best as I could get them. The fresh air definitely is cooler than what was coming in before.

I have not installed the other side yet. It's low on my priority.

FWIW,
Kirby

Yes, this I understand - I have the opening in the tub on the driver's side. I am trying to get fresh air there instead of pulling from the front compartment. Looks like my brake ducts are blocked and my NACA ducts are not connected. Either way I am modifying the clip at this point. I will contact SPF to see about getting the NACA duct bits.

Thanks Steve.

Mike

 

[Richard]

I think pictures would help here. Asuming your car is LHD the NACA duct on the right should be blocked off at the tub. If you open it up it just opens out under the dash. In the picture the yellow circle is the opening that should be blocked and as you see there is nothing to direct the air after it arrives and there is not way to shut it off.

Also if you look directly above the circle and to its left you'll see two holes (red circle). On my car these holes were covered up by the cover that sits there. The problem is the gasket that's part of the cover that should cover up those holes don't. It misses by a mile. The same holds true for the other side. I think those may drip directly onto your legs and feet.

In the center of the bright spot to the left of the picture is one of two drains (green) I'm adding to each side of the cowl. You can see the drain tube just sticking out of the rectangular before it was hooked up. I taped into the drain tube that's under each gas cap.

There is one more hole in the picture (blue). Not sure what that was for but the factory plugs it but I would check to make sure they did a good job.

 

[Mike Christian]

Dennis Olthoff sent me two of the fresh air fixtures for my car after I had it home for a couple of months. I've installed one on the left/driver's side and it works well.

I sawed it in half, made a hole in the clip and then fiberglassed the two pieces on. This way, I got both pieces to line up with their respective holes (the naca duct and the hole in the firewall) as best as I could get them. The fresh air definitely is cooler than what was coming in before.

I have not installed the other side yet. It's low on my priority.

FWIW,
Kirby

This tells me I need to swing by SPF HQ and see about getting these parts. Thanks Kirby.

 

[Mike Christian]

the picture helps a great deal Richard.

 

[Richard]

Mike, this is the picture that surprised me. The inlet from the NACA duct to the tub does a 180 and goes directly into the A/C unit. Since the A/C unit has its own water drain it may not be as big a source of water during a rain storm as we think. It could also just be that the flex ducting isn’t sealed well just as it enters the tub, and the water dumps in at that point. At any rate eliminating the water before it gets a chance to go anywhere is always a good idea.

The problem as I see it that a standard SPF GT40 has so many places for water to come in it will not always be easy to tell which one the culprit is. If you take a good look at every one of the front suspension connection points you will see that they all allow some water infiltration, some only allow water to seep between layers of metal that will eventually rust but others have rather large holes that disappear into the tub. I had to remove the entire front suspension to do a good job of pluging all the holes.

I’m currently working on a few “How To” articles on how I solved some of my specific problems in this area, starting with the roof vent. In the mean time while on the subject of the cowl area I have one more problem to report. If you follow the A pillar down to where it meets the flat part of the cowl just above the door hinge, it appears they trimmed a bit too much which left a gap about 2” long in the bottom of the window frame (see picture, yellow rectangle). I filled mine with seem sealer.

 

[Jack Houpe]

I’m currently working on a few “How To” articles on how I solved some of my specific problems in this area, starting with the roof vent. In the mean time while on the subject of the cowl area I have one more problem to report. If you follow the A pillar down to where it meets the flat part of the cowl just above the door hinge, it appears they trimmed a bit too much which left a gap about 2” long in the bottom of the window frame (see picture, yellow rectangle). I filled mine with seem sealer.

Richard when do you think your going to get to drive your car? You have really taken it apart! Will be waiting for your "HOW TO".

Jack

 

[Richard]

Jack, funny or not so funny that you should ask. Went to put coolant in it last night so I could start it for the first time. Of all things the radiator has a leak. Not sure yet but I think one of the screws that hold the fan assy on nicked one of the bottom tubes. Called SPF but only got to leave a voice mail. Might try to fix it myself, what's the worst that could happen.

I'm much closer than it looks. I only have the A/C set aside to do the final on the pedal assy and set the throttle cable length. Of course close to me might mean insanity to others. There is the thing about the dash being torn apart and I still have to make the mold for the drivers side firewall carpet and mold one. And that other thing.... Yap, just about done, week maybe two tops.