My understanding was most of the time the plenum with air horns is for cold air. The plenum is plumbed to a fresh air source instead of drawing air from under the hood. The adjustable length is a bonus.

Unless of course you don't mind a little hood alteration....

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Nitrous cars are like old men on Viagra. Once the bottle is empty they are useless.
FJD

CNC-Dude
that is why in my post I mentioned
but however you choose to do it,, a very nice project,,

Tom Drake,, the photo of the two piece manifold is right on,,as the slant is a non cross flow, the cast tubes on the section that bolt to the head need to be long enough to get the silicone hoses clear of the header heat...

I think if you could make the plenum box large enough, you could lengthen the runners on the inside of the box, leaving the external length that bolts to the head a fixed length. That way you could just remove the lid to the plenum and put longer/shorter ram tubes on the stubs sticking out on the inside of the box to get the desired results. Provided you don't increase the length internally to the point they begin to shroud the airflow against the plenum walls. You end up with smaller parts to interchange, and removing the runners externally would require having to deal with swapping the injectors and fuel rail onto the new section of runners and dealing with all that.

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There's no such thing as too much cam....only not enough engine!

Air flow thru a hose coupled system won't be as smooth as 1 piece or bolted together manifold.....

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

yes a clean transition is prefered, air flow at the wall surface is low anyway,, that is why it is nice to have the trumpets in the plenum raised up off the floor.

Found this article in Hot Rod involving the testing and theory of ram tuning with the consulting of Bill Shope of the legendary Ramchargers fame. This test showed that a 2% spread of HP and 10 % spread of torque was observed when altering the ram tube length between 9" to 19-1/2" inches. The 9" test was actually with no ram tube on the injector, just the bare injector base(but only lost 10HP over the peak HP reading).
http://www.hotrod.com/techarticles/engi ... ewall.html

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There's no such thing as too much cam....only not enough engine!

http://forum.e46fanatics.com/showthread.php?t=735897

Check this thread out.

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Nitrous cars are like old men on Viagra. Once the bottle is empty they are useless.
FJD

Same intake.

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Nitrous cars are like old men on Viagra. Once the bottle is empty they are useless.
FJD

Tom, that is slantsix porn!

Olaf

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Aspenized

Yes! Nice to see your posts showing up. You are a legend in the slant six community. Thanks for contributing.

Sam

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I thought it was better to inject directly onto the valve for best atomization?

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1970 Barracuda 225 /6, 3spd on the floor, Blue/Blue

Depends on the size of the injector and the amount of power you are trying to make...

For OEM small #/hr injectors closer to the valve is fine. Helps with emissions and fuel mileage.

Start making more power and increasing the injector size you need to start moving the injector farther away from the valve. A bigger injector does not have very good spray pattern at idle and low rpms. The lower the inlet airspeed at idle, the more important it becomes to maintain the ideal intercept angle. The "intercept angle" should not be more than 45 degrees, although it can be less. Maintaining the proper intercept angle generally helps low-speed driveability.

As Kenny Duttweiler put it "A decent compromise for a hot-rod engine is to locate the nozzle about 1-2 inches upstream from the manifold flange to give atomization a chance, positioning the fuel rail at the best angle you can get away with and still package the harness and fuel rails."

Directly on the valve could lead to a lot of problems especially as rpms increase.

I had a link to a study Ben Strader had done on a dyno.(can not find it anymore) After he had optimized injector location on an engine he then turned the injector to face upstream. He saw an increase in both low end torque and hp by doing this. The assumption was fuel atomization was increased by spraying into the air flow.

Most people interested in a custom intake are not putting it on stock engine. Would cost very little to have two injector bung built in....even if you only ever used one.

_________________
Nitrous cars are like old men on Viagra. Once the bottle is empty they are useless.
FJD

I made this intake for a turbocharged 225. I made it with 1 3/4 EMT (1.5 optional, both weld up to flange), 1/4 cold rolled plate steel, some Ebay intake flanges and an old cast V8 valve cover. I used the ramcharger formula to determine the 5th wave of a stock 225 camshaft (240 degrees intake?) and it turned out to be about 9.25 inches runner length, plus the 3/8 flange and port length. I believe it was closer to 14" total. I decided to use teh head to support the injectors as I could aim them at the valves, impossible mounted to the runners as the port is almost blind to the valves. this is really for emissions as many have had good results with a less than direct injection path. The intake plenum measured 225 cid (ironic!) and all tubes were tack welded/epoxy sealed in their holes. The throttle body is off a Ford Windstar 3.7L V6, close enough for my size and it had the correct PW idle servo for my Megasquirt 2 ECU. total cost minus old valve cover was about $50 with lots of fab time but I wast in a hurry. It uses the exhaust heat riser as a support only, with a support plate sealed to the riser. no heat needed. The ram tube was cut to fit, not tuned as space requirements were getting tight. Stacks are about 1/4 inch off floor and centered off walls as walls stall airflow. ideally they should be raised off floor and radiused or tapered but that was beyond this build. Cast base would be great with a bolt on plenum to keep cost and tooling down as well as custom tops for different intake configrations.

Some interesting pics of intake manifold designs very similar to the one on Tom Drake's photos: http://turbobanditen.se/shop/. Their pages are texted in both swedish and english.
Oh, and take a look at their turbo headers, but place a bucket under your chin first to collect drool...

Olaf

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Aspenized

I personally think the front mount is the better position for the TB as you have shown Olafla. I see it on many high HP competitive inlines of both 4, 5 and 6 cylinders, and thats why I chose to begin with that style. I also like the thought of an internally adjustable ram tube inside the plenum. The good thing about having the first one off of anything is that there is nothing to compare it too to know if its good or bad....

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There's no such thing as too much cam....only not enough engine!