Theory: Venting the doghouse and cold air port / intake

Since all I can do currently is dream about my future a108 I have spent a lot of time researching and planning.  Please excuse any naivety and feel free to share your experiences.  I have a few other theories coming.


So obviously people have been running these vans stock just fine for decades so if in good order there is likely no need to mod but....inherently the doghouse is not a great design to flow hot air out to drop temps and provide cool air for the intake.





My theory part 1

If you expanded the DH towards the back it would give more space for air to escape out the back after the fan has blown hot rad air back at the engine.  My guess is you could start half way down the back of the DH for ease and lack of curve and just slant out a few inches creating a much bigger area for air to escape.  I am guessing header wraps would also help a ton as heat from the headers rises.


Cold air intake

I found this pic which uses an insulated tube which looks pretty sweet.  Obviously this means you are using an electric fan.  The other possible option would be to port the driver side of the DH and run a tube out the side and use a tube to go down through the floor behind the driver seat.



Now many wont want to go this route since you are cutting the floor and the DH even though you could easily make port covers but the one advantage could be that if you had a situation where the inside of the cabin was cool (maybe with ac) and the outside was hot (traffic in the Lincoln tunnel choked my Mustang) you could have the cold air box pull cold air from the cabin temporarily without exposing the cabin to the DH temps.  Also could work if you had to driver through water where you might be concern about pulling air from so low.  Regardless....if you are going low one would likely want to shield from puddles.




Thoughts?  Experiences?

I like the cold air induction, that is the rout that I have planned. Shouldn't be to complicated to figure out how to make it fit under the dog house (I hope).

It is always good to feed the carburetor with cool(er) air than what is under the dog house. Plus at freeway speeds you may pickup a couple of HP due to the "ram air" effect.

Keith D wrote:I like the cold air induction, that is the rout that I have planned.  Shouldn't be to complicated to figure out how to make it fit under the dog house (I hope).

It is always  good to feed the carburetor with cool(er) air than what is under the dog house. Plus at freeway speeds you may pickup a couple of HP due to the "ram air" effect.

Yeah only problem is the fan up front and headers to the side. Anything small enough to squeak by is probably choking it of air.

I honestly think extending the doghouse BOTH in front and back a few inches would do wonders for a few issues and would require minimal and basic level metal work.

Also a scoop on the underside on the frame rails to prevent air from skipping by the rad wouldn't hurt

https://photos.app.goo.gl/86QsujZXDoGKBJy99

Just finished an involved cold air induction setup on my drag van. Two piece aluminum sheetstock assemblies and insulated. Draws excellent ambient air from above the radiator.

Also a scoop on the underside on the frame rails to prevent air from skipping by the rad wouldn't hurt

From the factory there is a piece that goes there , it goes from the front back to the radiator.  Extremely important to have that piece in place.

[quote="lws67"]Just finished an involved cold air induction setup on my drag van. Two piece aluminum sheetstock assemblies and insulated. Draws excellent ambient air from above the radiator.


Is the idea it will grab air that skip past the to of the radiator or will there be a tunnel to somewhere in front?

                                                                                                                                      I ran mine over the top of rad and made a plate to seal the air from coming around the rad. I have a fan on the belly pan forcing air up so its being forced threw the rad and into the carbs. I doubt there is any forced air effect but it is cool air and slightly pressurized.  biggest thing on getting air into rad is not allowing anywhere for it to escape. many argue of removing air from the doghouse but it is wide open underneath. force air in and it will force the air out of engine bay.

I have thought about a CAI like that, looks like a nice simple solution. I also am thinking about an after run fan below the dog house. I have a rear defroster fan/plenum assemble from a 60's something, thinking about mounting it to dog house and piping it out of floor. My only concern is that it is not an "explosion" proof motor. Never know what could happen with all the gas fumes in there on a hot day if it vapor locks.

It is really hot here today and drove the van to work about 40 miles. It never overheats, but can run a bit rough after a short shutdown. Smooths out pretty quick so I have not really worried about it..

I like your dual Weber set up. Is that a Datsun Z air cleaner?

nyc108hopeful wrote:

lws67 wrote:Just finished an involved cold air induction setup on my drag van. Two piece aluminum sheetstock assemblies and insulated. Draws excellent ambient air from above the radiator.


Is the idea it will grab air that skip past the to of the radiator or will there be a tunnel to somewhere in front?

There is more than enough airflow into the grill opening. Air flows through the radiator, and upwards over the top of the radiator. Not really ideas or theory, just in use actuality. I have no cooling issues at idle or any speed, just capturing ambient temperature air above the radiator. Ambient air will show results vs. ram air. There's ample info across the web. Ram air only comes into play at much higher speeds. Read David Vizard articles on both subjects to get additional insight.

I also wouldn't waste time with header wraps unless on cheap headers or budget builds. Stick with ceramic coated headers, they are well worth the investment and do exactly as they are designed to do., And they won't rust out like wrapped headers will.

yes, mid '70's z 240 or 260. I really didn't notice much difference with the cold air intake on the van but did a similar mod on my car and was amazed at the difference it made. my theory/guess is that the cars ecm corrected the air fuel mixture while my vans carbs remained at the same jetting. having your electric fan run after shut down would have the same effect as the second fan venting the dog house. if the cool air goes in, either the hot air is forced out our your dog house swells like a balloon and bursts! as I have yet to see one expand from air pressure, I am assuming the air is escaping out the wide open bottom.

I ran that dryer hose cold air intake for a bit, didn't notice any difference. My overall temps in the doghouse are ok, the problem I had was with boiling the carb bowl (percolating) if the ambient temp in there got too hot.

I re-reouted the fuel lines to come up the firewall (oem runs it right by the passenger side exhaust manifold), added an electric fuel pump and put a heat spacer under the carb to fix that problem.

When I put my mild-street 318 build in I plan on running a throttle body injection setup to disappear the fuel/heat issue altogether.

Ive thought for some time about how to lower temps in the engine box and it all comes down to airflow, not through the radiator but air exchange in the box itself. I've seen some pictures where they extended to front of the doghouse into the floor to make a tunnel of sorts.

One thing Ive played with from an idea perspective is to add some pipe/ductwork and have 1 or 2 fans either blowing air into the box or pulling air from the box as needed (in traffic etc.) Maybe marine bilge fans would work to pull. Maybe duct the original air tunnel and add 1 or 2 high volume fans behind the grill to push air through the radiator and into the box regardless of speed.

slowflapper wrote:I ran that dryer hose cold air intake for a bit, didn't notice any difference. My overall temps in the doghouse are ok, the problem I had was with boiling the carb bowl (percolating) if the ambient temp in there got too hot.

I re-reouted the fuel lines to come up the firewall (oem runs it right by the passenger side exhaust manifold), added an electric fuel pump and put a heat spacer under the carb to fix that problem.

When I put my mild-street 318 build in I plan on running a throttle body injection setup to disappear the fuel/heat issue altogether.

Ive thought for some time about how to lower temps in the engine box and it all comes down to airflow, not through the radiator but air exchange in the box itself. I've seen some pictures where they extended to front of the doghouse into the floor to make a tunnel of sorts.

One thing Ive played with from an idea perspective is to add some pipe/ductwork and have 1 or 2 fans either blowing air into the box or pulling air from the box as needed (in traffic etc.) Maybe marine bilge fans would work to pull. Maybe duct the original air tunnel and add 1 or 2 high volume fans behind the grill to push air through the radiator and into the box regardless of speed.

Yeah I bet even two PC. Style fans venting out hoses in the back by the trans would help. That and exhaust wraps or shields would be helpful on hot days. There just doesn't seem to be a lot of space in the back of the dh.