Custom airflow with intake manifold. picture.

[CandyCaneXj]

So I drilled 6 holes and tapped them for 3/4 pipe threads. I'm using 3/4 barb fittings and running heater hoses to a homemade throttle body box made up of a pvc cylinder. The cylinder will also have hose barb fittings and a seperate throttle body with a second throttle cable going to gas pedal. I think this will flow more air than the newer small runner intake manifold. Any opinions?

[SilverXJ]

When will the second throttle body open? On WOT?

This is an interesting idea and similar to what some modern intakes have. Some have a valve that ie either vacuum or electronically operated that changes the air flow in the manifold, giving different paths for low RPM and higher RPM.

One concern is how much are the barb fittings protruding into the intake runner?

[CandyCaneXj]

It's pretty nice they only stick out inside about 1/32 to 1/16 of an inch. There really is not much manifold material there(two or three threads) so I might add jb weld around the outside(don't feel like brazing them in). Right now they are pretty tight with teflon tape. My main concern is the gas pedal being harder to keep down with added spring pressure. I was thinking to start the second throttle body at half throttle but i'm really not sure. I'll be experimenting with it for days i'm sure! Each barb fitting really only provides .25 square inches of air flow. So thats equal to adding a 35mm throttle body roughly. It's pretty much just to allow some of the air to not have to go around those sharp corners entering the runners and to allow me to keep the 62mm throttle body at the stock location without upgrading that. Also rigging up the new plenum will be fun. Got a square air tight conduit box at Lowes. It might work! Might need to add some metal brackets to it. This will be going in a 4.8L with a ported 2.00/1.57 valve head and lunati 63502 cam.

[SilverXJ]

This is definitely an interesting experiment. I had toyed around with adding a second throttle body, but nothing ever came of it. The longer runners help with low end torque, while shorter runners help with upper end power. If you google "variable manifold" you will get a better idea of the modern designs.

One other thought. Don't connect the secondary throttle body to the pedal. Use a vacuum servo that will open the throttle body when the manifold vacuum drops.

[CandyCaneXj]

I wonder if the heater hoses are going to act like runners though and make them even longer sort of say. I decided I will break the engine in without this hooked up atm. Just plug the hoses for first week or so. Really want this engine in soon before winter ha. Maybe this weekend. I know nothing about using vacuum to open/close a throttle body. Is this somewhat simple to calibrate? Do I need a special type of throttle body or carb? Does not seem to be much info online about it. It soiunds like it could be worth while to look into if it's dependable.

[SilverXJ]

Its a vacuum servo with a rod sticking out of it. Look at supercharger bypass valves and heater box valves and you will get the idea. Just fab a bracket to hold the servo and a linkage.

[krom]

for this to work like a dual runner intake, you would need put a throttle plate in each hose barb, and hook the barb directly to a large plenum, or individual air filter. In a perfect world the cross sectional area would be the same as that of the runner, and the opening would have a bell mouth.

using a little math, you can adjust the lenght, to get a tuning advantage at a desired RPM

https://en.wikipedia.org/wiki/Helmholtz_resonance

[CandyCaneXj]

I understand the vacuum idea now. That is an interesting idea I may try that. I'm confused why each barb fitting needs it's own throttle body. Why can't I run all six hoses into a common plenum then have the second throttle body? I am not too concerned about it not flowing as much air as the primary one I just want a little extra air without spending $400 on a 70mm throttle body haha. Well if anything does not work well with it at least it's the dirt cheap intake manifold no one wants Well got the engine in this weekend. Still need to run true dual exhaust but at least I have the routing figured out. Two barb fittings barely cleared!! Cylinder #1 just touches a fuel line, and cylinder #4 was hitting the tab on the idle(name??) sensor wire connector so I had to cut the tab off. Cylinder #3 fits pretty nice in between the cable linkage. The fittings are plugged for now till I break the engine in. Maybe I can use the wrangler style air intake for the primary throttle body to give me tons of room to work with at the stock location for the secondary setup. But then I might to add a hood scoop for clearance. So not sure about that atm either. Some pics.

[CandyCaneXj]

This is not my picture but it appears I would not need a hoop scoop in a cherokee to do this. That would be great to have all that room to work with on the driver side for the secondary setup.

[krom]

long runners are for low rpm torque.