Here is some discussion that came up when looking at original GT headers over on Marty’s #40 thread.

Thought it was worthy of further discussion in a separate thread


QUOTE(gereed75 @ Aug 19 2021, 06:16 AM) *

Pete, That is a really interesting thought. I have always thought about the application of an aviation style heat muff for our cars as a more simple alternative to the stock heat shrouds. The problem with that is they need an un-obstructed section of straight pipe to fit onto, and that does just not exist on the stock headers or on most other headers. See this

http://www.velocedge.com/Starduster/Projec...ter/Default.asp

But this configuration does provide that straight section. The issue would be getting the blown air routed back to this section and then returning it to the heat pipes.



I think maybe this deserves some further thought and its own thread so as not to detract from #40 worship.

Gotta say that #40 is the holy grail and Marty and crew are the perfect custodians. Sometimes life and karma do produce the perfect match!


Agree with all your points—particularly that last one.

Those straight pipes really do provide for some interesting options, and small HEs would be one of the best of them. I would be interested in cats with HEs as I would love to have a cleaner 914—though I'd want to weigh that against the implications for engine oil temps and transaxle oil temps. The heat muffler you linked is very, very interesting—as is the flapper box in the pics, particularly if it seals better than the Porsche flappers. The new ones I bought years ago still bled heat from my SSIs, which was super annoying on hot days. sad.gif

Agree about the question on how to get the heat forward again, to the flapper boxes, but suspect fairly elegant heat return tubes could be made to work. One begins to wonder if the GT headers could also provide an easier way to do valve adjustments, if the straight pipes and muffler could be left in place? How cool would that be? Looking at some of those GT hangars/mounts with increased interest now, as I am wondering if they support the front of the straight pipes? Or if that is even necessary for a valve adjust?

Yes, a separate thread is probably warranted to avoid polluting this one—but this fantastic thread on #40, a 914 that has been inspiring me for more than 30 years and is prominently displayed in the 000 office, prompted the crazy thought. Which gets me back to your last point… beerchug.gif

Click to view attachment

I don’t think the straight section will give you the surface area or heat output you need to make the cabin warm but I’m just guessing. I could ask my son, he did a similar experiment in physics while in college but he’s in Germany drinking beer this week. Ben @MB911 might know through all his experience in the aviation industry and making thousands of exhaust systems.
I’m betting that if there was an easier way to do this, Porsche would have pursued it.

Can't open the link, bur be careful of un-equal lengths due to differential thermal expansion. these tubes will be hot and at the same temperature rise, will expand to different lengths. that's why lots of race headers have slidable joints.

I have a single heat muff in my airplane cabin (a bit bigger and way draftier than a 914) and it provides significant heat.

I think most will agree that the stock shrouds are overkill when the system is working well. I think Smaller would suffice to take the edge off and defrost windows.

Opps, linky no workee, here a pix of a different example

Click to view attachment

Aircraft Spruce used to carry those... thought about doing that years ago.

Smart kid…



^ Very interesting.

I suspect a fair few 914-6 and six conversion owners are really after a way to keep feet warm and defrost the windshield. Anything past that is gravy, at least for me. The stock 914-4 and 914-6 heater systems were impressive, and had to be as many customers lived with serious winters, but very few 914s are used in serious winter conditions these days…

I have this set of 914-6 headers that were
a backup set for 1 of Ralph Meaney's cars
back when he moved out of Massachusetts
years ago..

I used them on my car for a number of years..

They are pretty short..


Click to view attachment

Nice thing is Marty at MSDS has replicated the factory racing headers, and it sounds like in two sizes for small and big sixes?

Love the idea of MSDS headers on my car, made right here in the USA, and love the idea that they came directly from #40 going into his care. Have to think the header design was "pretty decent," too, and if the straight pipes allow for even a reasonably effective heat muffler…

How warm is the air from the fan? Can one use backdated heat straight from the shroud to the heat valves then inside.

I am currently doing a test with that and it Really doesn't work well.

My single heat exchanger setup though does work really well. I have used it now for 650 miles and really happy with the heat Qty

Do you offer a bolt together exchanger box

^ Interesting idea on the fan/shroud, but my guess is the customer racing/racing department at Porsche would have used that all day long had it worked. More likely, they just let drivers freeze (it was the Piëch era, after all).

Very cool to hear the single HE works well! A little less weight/cost/complexity, and if it's enough to take the edge off, keep toes warm, and keep the windshield clear, that's a good option.

I'd be fascinated to see a comparison of the factory GT headers/exhaust vs "traditional" HEs and headers for the 914-6, as I remember Bruce Anderson and Jerry Woods found their best results when they added pipe length x3 to move the collectors all the way back to the muffler flange. Then again, that was 20-30 years ago, and we've learned a lot about air-cooled 911 engines in the meantime…I am amazed at the power some have pulled from even the smaller displacements, all the way down to 2.0 and 2.2.