Kind of a dumb heater back date question
 

Hi guys - given that it is 100+ outside I was wondering about doing a heater back date in phases. If I want to get going on my heater back date on my '74 with a 3.2 in her by removing the fan ducting etc, but don't have the replacement elbow that supplies air to the heat exchangers, am I creating any running issues?

I know I won't have heat, not really necessary right now, but am I going to be venting excessive hot air into the engine bay?

Like I said, kind of a dumb question.

You need to have air moving through the heat exchangers which is why you want the hoses in place.

OK - got it. Thanks Kurt.

Well, no, you don't have to have air moving through the heat exchangers. However, the holes in the fan shroud should be covered if you don't have them connected to the H/Es. That's the engine cooling air, and if they're open the air just rushes out in an uncontrolled manner, and not over the heads and cylinders like it normally would. You can get block off plates to cover those. See here: Porsche 911 & Carrera Heating & Ventilation - Page 2

Having air flowing through your exchanges will help cool them and your headers to a certain degree, and thus reduce some radiant heat to the bottom of the engine, but the biggest thing is the cooling air loss in the shroud.

The cylinder heads and pistons on a 911 have all those fins so that there is a lot of surface area for the heat to dissipate, the air moving over them from the fan helps remove the heat. The air will take the easiest path - out the big hole. you want the air to go over the fins. Plus all that hot air in the engine compartment gets sucked back in the intake increasing the intake charge and heating up the engine...like a death spiral (well its not that bad, I have seen lots of people drive with a big hole for some time). I would keep the shroud sealed up tight when ever possible.

You can easily make the pieces you need. This is the elbow I think you are talking about.

http://i1228.photobucket.com/albums/...c/8cca365d.jpg
http://i1228.photobucket.com/albums/...c/41309fee.jpg
http://i1228.photobucket.com/albums/...c/1651fb86.jpg

The PVC is a 90* street elbow, 2in in diameter. It is held in place with a generous ring of JB Weld on both sides.
Good luck!

Thanks guys. Roasting the engine is a bad thing.

Are the reproduction ones from Pelican - 930-106-321-01-PH - easy to rework do they fit properly around the distributor? I know John Walker was fabricating some very nice ones at some point.

OR - is a block off plate - PEL-SM-LEFT - on the left but the right side connected still another option?

OR - worth popping for the Turbo one - 930-106-321-02-OEM?