I have my impeller house apart for cleaning and it appears there were alignment pins for the front and back halves . How many are there? I have 2 pins around the impeller itself. There seems to be holes in the perimeter for pins too? Please review and advise so I can dig up some more as needed

Best

Robert

Diagram does not show the housing in 2 pieces

Click to view attachment

I pulled another housing apart and it looks to have the original screw, and only 2 alignment pins...

So all good here

Best
-Robert

My fuzzy memory agrees with 2 pins.

AWESOME..>That matches what I have too

Thanks for sharing

What are people in the "914 Word" doing with cars with no heat and headers?
(NOT the Thermostat Flaps) But I do have to relocate my stat away from the headers.
NO lower tins?
What about the flaps on the impeller housing? The little pins will fall out
Anyone block this off for more flow around the heads and cylinders ?

Or just let them BLOW

I blocked them off. I made small wood plugs to fit, used Vulkem calking to keep them in place. Not all calking will handle the heat and exposure. I'd probably just make an aluminum block off plate if I did it over again.

I have heard arguments that the cooling setup was designed to have air coming out of those, and blocking them will mess with the rest of the air flow. I have not done any research on this, but I do know that air flow is some of the trickiest and least-sensible mechanical engineering out there.

--DD

I only found two. They are the key to splitting the housing. I used a punch.

I've been told that Jake Raby does not block off the little heater outlets. His testing showed that it caused turbulent air in the fan housing decreasing cooling ability.

I've not seen the original thread where he says that so take it second or third hand but I am running with no block off.

I was considering blocking off the small rectangular outlets, but have not due to a concern it may impede cooling air flow. Germans!!

I would like to see the data supporting that. The discussion reminds me of people with water cooled engines putting flow restrictors in so that the water has “more time to cool off in the radiator. Thermodynamics says it ain’t so, and in my life the laws of physics aren’t just opinions. Opening the flaps will certainly reduce the air pressure driving cooling air past the nice cooling fins. I could certainly believe in some weird standing wave or other turbulent idea though.
When I installed the 3.2 with headers I certainly made a block off plate rather than simply leaving the plastic heater feeder sitting there open. But that isn’t a four.

Looking at the snail shaped fan or fractal. The air flow must be changed on the snail shape, not at ends. Leaving the air space makes turbulent air fighting free flow.
Thanks,
Matt

If you think about it in the stock heat exchanger system when the air reaches the distribution valve the air has one of two paths, into the cabin or it just bleeds out the mushroom cap. I do realize there's a bit of back pressure in the stock heating system, but it's still wide open for the most part.

So how is that much different than running the openings unblocked when using headers?

The heating system does offer a fair amount of restriction to airflow, so just leaving the ports open would allow more air to escape. It does seem a shame to waste cooling air. Also, if you look at the design, the two scrolls are designed differently. The bottom scroll is much larger (note the position of the pins: for equal scrolls the pins would be opposed across the fan); but the lower scroll feeds both heater ducts, the alternator, and the oil cooler in addition to the cylinders. If the heater ports were blocked off internally as in this diagram, then internal turbulence would be minimized.

As I said earlier, fluid dynamics is the least-intuitive and most empirical of all of the engineering disciplines. There's a lot of "well, we have fiddled the equations to fit the observations" because a lot of it just doesn't make intuitive sense from underlying principles.

--DD