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I did the cowl hood modification on my project and had an idea at the time but skipped it to get the Jeep on the road. I'm now coming back to the idea because I want to free up the space occupied by the air box.
The idea is that with the cowl I could have the air filter draw air from the cowl. Either by mounting the filter to the hood and mating to the throttle body with hood closed or mounting something on engine/throttle body and having it mate when closed with hood.
The second might have the advantage of having filter still in place when hood is open if done right. I'm sizing it up now and looking to mock something up with cardboard for a prototype. It's tight but I think do-able. There's more space below hood on pass side but would still have to route over engine to throttle body.
put an filter in the intake tube. spectre sells the filter separately i think
Not a fan of those but the way I'll go if I fail.
Here's what I'm planning
Enclose underside of hood with sheet material across the webbing. Cut rectangle the size of the bottom half of a stock air box. This opening will be positioned in cowl area just to the pass side of the valve cover over starter motor and distributor.
Cut top 1 1/2 inches of bottom half of stock air box retaining the clips to hold top half on. Mount this facing down into hole just created. Put stock air filter upside down into the air box and snap on stock top half of air box with intake port facing firewall.
With hood closed this should hang down into mostly empty space only need to re-route heater hoses out of the way slightly. This should in my case leave at least 2 inch space above air filter and top of hood for air flow plus all the space around the filter in the cowl area.
Route intake from air box over rear of valve cover to throttle body using appropriate flex tubing and connect stock PCV likewise. Viola, fresh air from outside through the cowl opening similar to the mod taking air through the firewall but with less noise intrusion to the cabin.
I've sized the air box configuration and it does fit the space described and with hood up the box is mostly out of the way and easily removed. This mod however, would likely be problematic for reaching auto dipstick which I don't have.
I don't think normal driving is bad. It is louder than it was before.
It is loud for about a minute on cold starts and during wide open throttle. I haven't driven it much so I don't know if it's going to be annoying or not.
Over the holidays I spent some time working on this idea and here's an update on what I was proposing.
Bracket and stand off.
Here it is installed. On the opposite side the stand off is screwed into the top of a head bolt.
Kind of a tricky slope and angle to it to follow the hood line.
Here's with air box installed.
With the hood closed I have about 2 inches from top of filter to the bottom of hood. The bump on my cowl is just about 2.25 inches and that's about the clearance. Others who have gone with a bigger bump would obviously get more air space. I think this will be fine with air flow but I'll see. I plan to install sheet aluminum across webs under cowl with knockout for the air cleaner sealing air intake off from engine bay. Also need to connect air box to throttle body. Had hoped to use original rubber elbow but it's too tight a turn now.
It's pretty much done as soon as I figure out how to connect the airbox to the throttle body. It's going to be a couple weeks before I get to test this though as I'm also re-doing all my accessories through a a new PDC using a Bussman 10 relay RTFM. My triple fan dirtbound setup melted my old PDC as I had all three fans on a single 30 amp fuse. I made the mistake of calculating load using running amps instead of starting amps and melted the fuse terminals right out without blowing the fuse. My miscalculation isn't the real cause as obviously the PDC wasn't up to the 30 amp rating per line it claimed but I got much closer to that 30 amps than I initially thought. I'll write that up on another thread.
I see you are doing this with a cowl scoop hood, that is cool.
I was thinking of using the stock hood, and doing the mod to pull from the fresh air intake in the stock cowl, but instead of the inline filter most use like the Spectre, I was going to get the smallest square filter I could find, cut the hole in the firewall to match the filter and rig a box to adapt to tubing going to the carb which would also be used to clamp the filter to the hole in the firewall. That way would just have to open the hood and release a couple catches to change filters, nothing else to disassemble. Since I only have a carbed 2.5L, shouldn't need too large of diameter tubing to connect from filter box to carb.
I see you are doing this with a cowl scoop hood, that is cool.
I was thinking of using the stock hood, and doing the mod to pull from the fresh air intake in the stock cowl, but instead of the inline filter most use like the Spectre, I was going to get the smallest square filter I could find, cut the hole in the firewall to match the filter and rig a box to adapt to tubing going to the carb which would also be used to clamp the filter to the hole in the firewall. That way would just have to open the hood and release a couple catches to change filters, nothing else to disassemble. Since I only have a carbed 2.5L, shouldn't need too large of diameter tubing to connect from filter box to carb.
You'd probably end up starving the engine for air. The filter is the size it is because it has to be. Not having done the math but assuming Spectra and others have, the conical filter ends up having the same surface area or equivalent.
You'd probably end up starving the engine for air. The filter is the size it is because it has to be. Not having done the math but assuming Spectra and others have, the conical filter ends up having the same surface area or equivalent.
Most of the Spectre setups are made for the 4.0, so at half the displacement should need less filter size. The stock filter is about 1.5" high and 10" diameter which is about 45-50 sq inches. That would equate to about a 5x9 filter. I may not be able to even find one that small.
Also I haven't seen a Spectre that was designed to work with the carb.
Most of the Spectre setups are made for the 4.0, so at half the displacement should need less filter size. The stock filter is about 1.5" high and 10" diameter which is about 45-50 sq inches. That would equate to about a 5x9 filter. I may not be able to even find one that small.
Also I haven't seen a Spectre that was designed to work with the carb.
Totally missed the point that yours is not the 4.0
Never seen one of those. What size is the stock filter. Go by that.
Well I finally got around to finishing this up. The angle of the snout coming out of the box just wasn't going to work so I cut it out going thru the airbox wall (i.e. not cut if off). Needed the whole snout. I also cut 2 inches out of the accordion section of the snorkel as it was too long and glued it back together with some rubber cement and covered with some 4 inch shrink tube I found on ebay. I placed the snout I removed into the snorkel and placed on the throttle body with the snout sticking thru the gaping hole I made in the airbox. About 3 packages of JB Weld and it was good to go. Works good and I'm not getting any noise intrusion.
12-01-2016, 11:19 AM
Cowl Hood Air Filter
