BlueGerbil
NAXJA Forum User
- Location
- Germany
Looks very clean!
my home brew Cowl induction hood
- Thread starter Simon 88YJ94XJ
- Start date
Simon 88YJ94XJ
NAXJA Forum User
- Location
- Virginia
flexjay87 said:
Sure it was Sherwin Williams (most people think of them for their house paint but they are a huge auto paint company) brand called 2nd Dimension, it's single stage; no clear needed to keep it glossy (but it wont stay glossy for as many years of course) in 3 parts, (base, mid temp reducer and wet look hardener). It was EXTREMELY forgiving paint, it self leveled unbelievably well... it's the best single stage paint I've used, out of 3 or 4 brands.
I used several rattle cans of primer filler for rough sanding and final sanded with 320 grit and then 3 coats of 2nd Dimension primer sealer (gloss primer which promotes better gloss in the color coat. And 3 coats of color the 3rd closely followed by a misting to even out the metal flake. The total for the auto paint (not counting the cans) was 74 bucks for a quart each of color and sealer, hardener and reducer.
A Harbor frieght HVLP gun (cheap but it got the job done, several jobs in fact) was used at about 15 PSI using a generic 4 gal compressor with a 100PSI max which flows supposedly 4.6 CFM at 90 PSI (good for a small electric it'll run air tools but with frequent short pauses to let pressure peak up).
Didn't quite use all of the paint but I also misted the second coat to even the metal flake, and shot a pair of KC lights with body color. If I had done a better job misting the second coat I would have had a third of a quart left.
It was soft for a couple days, I mean finger nails could have torn it off, because I put 3 sealer coats on and 3 coats of color all in the space of about two hours. I would have liked to let it flash off for longer with that many coats. But a side benefit of that is the paint/primer REALLY self leveled, as long as there is no sagging or outright drips which would have gotten worse.
Simon 88YJ94XJ
NAXJA Forum User
- Location
- Virginia
aparke4 said:
Too many, the sanding was the real time sink, I had it ready for mud in one day off (maybe 6 hours of actual work with 1 or 2 acumulated hours of imagining how it would look, measuring, changing my mind etc.) and then spent many after work evenings between the time I clock out and the time my Wife gets unhappy (aproximately an hour or so) sanding with a bondo rasp, and a long 18" strip of sandpaper which helps level things smooth and avoid waves you get with a small block. If I'd bought an air file before I started I would have cut many hours out of it. I also got pretty anal with the primer filler stage of priming and sanding...
I really appreciate all the positive comments.
aparke4
NAXJA Forum User
- Location
- Atlanta, Ga
you could start a biz with that work i mean thinking about it the ones on quadratec sell for 450 plus! though i guess shipping is a biatch with hoods...anyways looks good
Simon 88YJ94XJ
NAXJA Forum User
- Location
- Virginia
aparke4 said:
Yeah and I think those are unpainted, it would cost roughly 3 bills to get the thing painted by a decent autobody shop. There's definitely money to be saved by doing this yourself.
lighthouse jim
NAXJA Forum User
- Location
- san mateo coast, CA
... and you were concerned about getting flack for being a newbie! Great job. you've inspired a lot of us just before the daylight savings time switch sends us into our garages for the winter. Thanks
Thumpersdriver
NAXJA Forum User
- Location
- california
Yes its true. You need to shut the hell up about the Noob thing and make me one of those.
( I suck at painting)
( I suck at painting)
mojojojo
NAXJA Forum User
- Location
- Gresham, Oregon
speechless! thats fffffffreekin awesome work man!
falcon1235
NAXJA Forum User
- Location
- oak harbor Washington
very nice work
hmm i got a 93 parts xj looks like i know were the hood is going now...... attempt one... hehe sheet metal still evades me i like the thick stuff hehe
hmm i got a 93 parts xj looks like i know were the hood is going now...... attempt one... hehe sheet metal still evades me i like the thick stuff hehe
Simon 88YJ94XJ
NAXJA Forum User
- Location
- Virginia
well I warped things pretty bad at first but using 18 or 16 guage and tacking back and forth (as far as possible from the last tack) until you have it all stitched up worked fine... remember with hundreds of spot welds it's no big deal if you have a couple cold welds.... they will be way less of a big deal then the holes you'll put in it if you try to make each stitch perfect. and even a few holes are no big deal (mine has at least 5 or 6) the Bondo will hide them. As long as the whole thing is sturdy and not flexible when you're done.
XJCRAWLER
NAXJA Forum User
- Location
- Flowery Branch,Ga.
You must be a bodyman for a trade. AWESOME WORK!
Simon 88YJ94XJ
NAXJA Forum User
- Location
- Virginia
Bit of an update; don't do this mod if you have gasoline smells/leaks or oil getting on your headers... The opening flows air really well! right into the heater vents on the cowl... if you have a leaky injector or lots of oil burn off from your leaky valve cover ... ( don't lie you know it's leaky). You will get a Cabin full. Especially when you warm it up or leave it idling. Fortunately this prompted me to look for and find a gas leak... RIGHT NEAR THE HEADER!:flame: Which promted me to change out the plastic fuel lines. It was leaking right where it mates to the hard lines under the intake (boy are these things a bitch to slide onto the metal lines, I replaced them with rubber FI hose).
I intalled an AEM Dryflow 9"X6" cone filter and some home brew cold air tubing temporary (not sealed to the opening yet), as expected the exhaust note changed with the OEM box and that constriction they put in there to reduce intake NVH. Even without sealing I'm confident it's getting cool air being on the cool side of the engine bay away from the header and close to the cowl opening, I'm also sure that it's pulling hot air occasionally.
Threw in some 87 Octane.. It's MUCH easier to tell when it's pinging (this is a 4.6 stroker) it doesn't ping on the higher octane's.
It also runs distinctly cooler, for weeks before I finished this I paid close attention to my coolant temp guage and where it usually sits right smack between the 210 line and the lower line, it's a good 16th of an inch closer to the lower unmarked temp line. The Valve cover is now cool enough to touch without pain, it was burning hot before, which is one of the things that got me thinking about a cowl induction hood. I'm a little worried that it might run too cool especially this winter.
I don't do this professionall just for fun actually, I've done several auto paint jobs but not for a living. The paint has it's warts as I mentioned theirs a distinct razor blade imprint. Several bugs met their demise in my paint and other blemishes. Nothing I can't live with, nothing visible from 5 feet away unless you look really hard.
As far as the underside... well it's flat black, I did not finish it only ground the sharp edges and cleaned it up a bit. All of the factory cross framing is still intact, just no longer glued to the metal of the hump.
I intalled an AEM Dryflow 9"X6" cone filter and some home brew cold air tubing temporary (not sealed to the opening yet), as expected the exhaust note changed with the OEM box and that constriction they put in there to reduce intake NVH. Even without sealing I'm confident it's getting cool air being on the cool side of the engine bay away from the header and close to the cowl opening, I'm also sure that it's pulling hot air occasionally.
Threw in some 87 Octane.. It's MUCH easier to tell when it's pinging (this is a 4.6 stroker) it doesn't ping on the higher octane's.
It also runs distinctly cooler, for weeks before I finished this I paid close attention to my coolant temp guage and where it usually sits right smack between the 210 line and the lower line, it's a good 16th of an inch closer to the lower unmarked temp line. The Valve cover is now cool enough to touch without pain, it was burning hot before, which is one of the things that got me thinking about a cowl induction hood. I'm a little worried that it might run too cool especially this winter.
I don't do this professionall just for fun actually, I've done several auto paint jobs but not for a living. The paint has it's warts as I mentioned theirs a distinct razor blade imprint. Several bugs met their demise in my paint and other blemishes. Nothing I can't live with, nothing visible from 5 feet away unless you look really hard.
As far as the underside... well it's flat black, I did not finish it only ground the sharp edges and cleaned it up a bit. All of the factory cross framing is still intact, just no longer glued to the metal of the hump.
okay minor update but I felt I had to (BTW I've changed my username) if you are doing this mod use more bracing than I did! gusset the inside where the hump profile and original hood lines meet. Because I warped the sheet metal I had to use more extensive bondo than I wanted to, and while it is still all there and the hood still looks cool, there is a crack where I flexed the hood while waxing it (hey you have to wax it at least once to seal the paint), I leaned on it too much which bent the sheet metal downward which produced a hairline crack right on the edge of the hump running up the profile.
With a few gussets underneath and a few more pieces bracing the hump to the cross members (the frame of the hood) it shouldn't flex so easily and even heavier bondo will survive. I've had a few PM's requesting more pics or details of the underside so here's what I have. Warning for those who hate to be left hanging, it still has no grille or screen to cover the opening, and the airbox is still undone.
This is the main middle brace at the opening, I mentioned that it is serving as a divider to let the passenger side be "induction" while the driver side acts as a big air vent to flow down (it does flow down, the air at the cowl is lower pressure) in additon to this I had one piece of 1" angle with 3/4" cut off one angle as a wedge shape at the front in the nose I couldn't get a pic of it but it's self explanitory it humps to nose of the hood up where the very front most cross frames all meet together it's about 1/2 high. As well I had two small braces on either side of the middle that landed on the frame cross member at the opening and about two foot further in (which I have no pic of)
right above the filter which is mocked into place
this is an overall shot of the underside, I take it back you can JUST SEE the mid brace passenger side (rust red oxide primer colored square) that I just said I had no pic of. THere's another on the drivers side you can see where welding as melted the nromally straight edge of the cross frame.
my temporary home brew cold air tube made from a mandrel bend 180 2.5" mild steel exhaust tubing.
Just before welding, this is 2.5 which is JUST about the same size as the TB, and for that reason alone it's overly restrictive, As I mentioned it's temporary I'll re do it in SS using a 3.5 inch (which matches my filter and lets me Re-use the silicone 2.5" to 3.5" adaptor that's at the filter now, as the trottle body to tube adaptor. Which in turn means I didn't waste the 14 bucks that damn silicone piece costs on a temporary prototype! I got the 180 degree mandrel bend off ebay from a place in MD that seems to have the best prices on mandrel bends hands down.
to make room for the heat shield box that will seal to the cowl I moved the washer reservoir. This was stupidly easy and cleans things up a lot , I also moved the heater lines and removed my OBA (going to go electric) restored my AC with compressor and bits from a 91 (R12 shhhh :shhh
Note if you haven't figured it out the black PVC tube stuck in the fire wall is a snorkle which will be boxed in with the filter and already leads into the glove box (a PVC elbow will quickly bridge the gap when off roading eliminating the airaid filter and cowl opening and completely closing the system off to water ).
Here I've moved the transmission dip stick by brute force bending it downward I had to do this or it would have been unreachable without unmounting the air box I will be putting in:
With AC and heater lines routed to the fenders (using a bunch of factory prebent hose bends reversed and reused from my 91 parts heep) I've made all sorts of room for the air box, opened up the side of the engine for easy spark plug access and even put the trans dip stick in a more logical and easier to reach location.
"to be continued" unfortunately (for my XJ) life has intervened sucking up all my project time, with a baby on the way it might be summer before I get back to the air box. so for the time being this is where she is:
I do plan on re-doing the cowl hood later to make a more aggressive, higher clearance version to help make room for a little something special that will get attached to the exhaust and the intake.
BTW pm me if you're interested in my OBA parts w/ compressor
With a few gussets underneath and a few more pieces bracing the hump to the cross members (the frame of the hood) it shouldn't flex so easily and even heavier bondo will survive. I've had a few PM's requesting more pics or details of the underside so here's what I have. Warning for those who hate to be left hanging, it still has no grille or screen to cover the opening, and the airbox is still undone.
This is the main middle brace at the opening, I mentioned that it is serving as a divider to let the passenger side be "induction" while the driver side acts as a big air vent to flow down (it does flow down, the air at the cowl is lower pressure) in additon to this I had one piece of 1" angle with 3/4" cut off one angle as a wedge shape at the front in the nose I couldn't get a pic of it but it's self explanitory it humps to nose of the hood up where the very front most cross frames all meet together it's about 1/2 high. As well I had two small braces on either side of the middle that landed on the frame cross member at the opening and about two foot further in (which I have no pic of)
right above the filter which is mocked into place
this is an overall shot of the underside, I take it back you can JUST SEE the mid brace passenger side (rust red oxide primer colored square) that I just said I had no pic of. THere's another on the drivers side you can see where welding as melted the nromally straight edge of the cross frame.
my temporary home brew cold air tube made from a mandrel bend 180 2.5" mild steel exhaust tubing.
Just before welding, this is 2.5 which is JUST about the same size as the TB, and for that reason alone it's overly restrictive, As I mentioned it's temporary I'll re do it in SS using a 3.5 inch (which matches my filter and lets me Re-use the silicone 2.5" to 3.5" adaptor that's at the filter now, as the trottle body to tube adaptor. Which in turn means I didn't waste the 14 bucks that damn silicone piece costs on a temporary prototype! I got the 180 degree mandrel bend off ebay from a place in MD that seems to have the best prices on mandrel bends hands down.
to make room for the heat shield box that will seal to the cowl I moved the washer reservoir. This was stupidly easy and cleans things up a lot , I also moved the heater lines and removed my OBA (going to go electric) restored my AC with compressor and bits from a 91 (R12 shhhh :shhh
Note if you haven't figured it out the black PVC tube stuck in the fire wall is a snorkle which will be boxed in with the filter and already leads into the glove box (a PVC elbow will quickly bridge the gap when off roading eliminating the airaid filter and cowl opening and completely closing the system off to water ).
Here I've moved the transmission dip stick by brute force bending it downward I had to do this or it would have been unreachable without unmounting the air box I will be putting in:
With AC and heater lines routed to the fenders (using a bunch of factory prebent hose bends reversed and reused from my 91 parts heep) I've made all sorts of room for the air box, opened up the side of the engine for easy spark plug access and even put the trans dip stick in a more logical and easier to reach location.
"to be continued" unfortunately (for my XJ) life has intervened sucking up all my project time, with a baby on the way it might be summer before I get back to the air box. so for the time being this is where she is:
I do plan on re-doing the cowl hood later to make a more aggressive, higher clearance version to help make room for a little something special that will get attached to the exhaust and the intake.
BTW pm me if you're interested in my OBA parts w/ compressor
Last edited:
New update, I recently sealed the Air filter to the cowl opening and also measured the temps in three different test runs. Duct taped closed, open like I've been running it for the last year, and the new sealed cold air box. First the air box build:
The best way I could figure out to prototype the air box that seals to the cowl opening was a cardboard box... I'm geek enough to have done this before, the last one was for a Mustang. So I have learned a trick or two. I found the right size box, made a hole for the filter to connect to the cold air tube, and slit it so the top would crush down progressively as the hood closed.
Here it is cut down after many trail and error fittings.
Used the box as a template to cut out 16g sheet panels and it worked like a charm... I couldn't believe it but this pic is the first test fitting of the mostly assembled box (tack welds) And yes I'm going to need to get the sharp bends out of my heater manifold hoses before winter I moved that stuff as shown in the previous post.
My sheet welding has improved since the hood, These welds I am proud to say were created with a $119 dollar Harbor freight Flux core welder running on household 110 current. And a generous amount of Lincoln Anti-spatter spray. I am getting good with my TIG but still tend to burn through sheet.
Final fitting, I used the weather strip from the hatch of a parts XJ as the rubber seal, it works very well, due to wire reinforcement which keeps it shaped right and snug. I then closed the hood and checked the seal:
I was expecting to spend hours trying to get it this tight. I Lucked out. Here it is coated:
For the temperature testing I got a cheap intake temp gauge used off ebay and stuck the sender right above the TB in the cold air tube. I also used a laser infrared thermometer.
I started by duct taping the cowl closed and driving a 30 mile loop measuring average intake temp, with a short stop in the middle with engine off (where I recorded peake engine off temp), and a return trip after which point I measured the under hood temps with a laser thermometer. I repeated this with the duct tape removed after several hours of cool off, and then once more with my newly fab'ed air box tightly sealed to the cowl opening on the passenger side which leaves the driver side of the cowl opening still open for engine heat dissipation. All three runs where at roughly the same ambient temp, 90 to 92 degrees. And yes I know I am a huge geek!
For those of you who's eye's are rolling into the backs of your heads from attention deficit disorder: My sealed cold air cowl induction got me as much a SIXTY DEGREES cooler intake charge and that's average not peak.. For those of you who like numbers read on.
Duct taped closed:
The average intake temp @ 55-60 MPH was: 150 degrees (varied between 46 to 155)
peak intake temp with engine off was 165 after 5 Minutes.
Average under hood temp after trip (taken at 6 locations with laser
Thermo then averaged) was 168.5
Open cowl cone filter routed to passenger side very close to cowl:
Average intake temp @ 55-60mph was: 112 (109 to 115)
peak intake temp engine off for 5 mins: 146
Averaged underhood temp: 159
Air intake sealed to cowl opening:
Average @ 55-60mph averaged 95 degrees varied between 92 and 98 (yes
that's 2 to 6 degrees from ambient air temp, nice!)
Averaged under hood temp 152.5
The under hood temps "average" is a little misleading... the hood was nearly 30 degrees cooler in the last test than the first, but I threw out the high and the low for each average.
The cowl "venting" is effective especially above 30 MPH when it rapidly cools things... Sealing the intake made the cowl openings useful even at a crawl, just leaving the driveway at a crawl had the intake temp dropping steady.
One big difference is the sound... the metal air box resonates, and instead of the filter blasting the sound all around the engine compartment with only a little escaping; the air box forces all the sound out the cowl opening... I can honestly say that my XJ "howls" now. when I crack the throttle more than a third open it puts a big stupid grin on my face every time.
The best way I could figure out to prototype the air box that seals to the cowl opening was a cardboard box... I'm geek enough to have done this before, the last one was for a Mustang. So I have learned a trick or two. I found the right size box, made a hole for the filter to connect to the cold air tube, and slit it so the top would crush down progressively as the hood closed.
Here it is cut down after many trail and error fittings.
Used the box as a template to cut out 16g sheet panels and it worked like a charm... I couldn't believe it but this pic is the first test fitting of the mostly assembled box (tack welds) And yes I'm going to need to get the sharp bends out of my heater manifold hoses before winter
I moved that stuff as shown in the previous post.
My sheet welding has improved since the hood, These welds I am proud to say were created with a $119 dollar Harbor freight Flux core welder running on household 110 current. And a generous amount of Lincoln Anti-spatter spray. I am getting good with my TIG but still tend to burn through sheet.
Final fitting, I used the weather strip from the hatch of a parts XJ as the rubber seal, it works very well, due to wire reinforcement which keeps it shaped right and snug. I then closed the hood and checked the seal:
I was expecting to spend hours trying to get it this tight. I Lucked out. Here it is coated:
For the temperature testing I got a cheap intake temp gauge used off ebay and stuck the sender right above the TB in the cold air tube. I also used a laser infrared thermometer.
I started by duct taping the cowl closed and driving a 30 mile loop measuring average intake temp, with a short stop in the middle with engine off (where I recorded peake engine off temp), and a return trip after which point I measured the under hood temps with a laser thermometer. I repeated this with the duct tape removed after several hours of cool off, and then once more with my newly fab'ed air box tightly sealed to the cowl opening on the passenger side which leaves the driver side of the cowl opening still open for engine heat dissipation. All three runs where at roughly the same ambient temp, 90 to 92 degrees. And yes I know I am a huge geek!
For those of you who's eye's are rolling into the backs of your heads from attention deficit disorder: My sealed cold air cowl induction got me as much a SIXTY DEGREES cooler intake charge and that's average not peak.. For those of you who like numbers read on.
Duct taped closed:
The average intake temp @ 55-60 MPH was: 150 degrees (varied between 46 to 155)
peak intake temp with engine off was 165 after 5 Minutes.
Average under hood temp after trip (taken at 6 locations with laser
Thermo then averaged) was 168.5
Open cowl cone filter routed to passenger side very close to cowl:
Average intake temp @ 55-60mph was: 112 (109 to 115)
peak intake temp engine off for 5 mins: 146
Averaged underhood temp: 159
Air intake sealed to cowl opening:
Average @ 55-60mph averaged 95 degrees varied between 92 and 98 (yes
that's 2 to 6 degrees from ambient air temp, nice!)
Averaged under hood temp 152.5
The under hood temps "average" is a little misleading... the hood was nearly 30 degrees cooler in the last test than the first, but I threw out the high and the low for each average.
The cowl "venting" is effective especially above 30 MPH when it rapidly cools things... Sealing the intake made the cowl openings useful even at a crawl, just leaving the driveway at a crawl had the intake temp dropping steady.
One big difference is the sound... the metal air box resonates, and instead of the filter blasting the sound all around the engine compartment with only a little escaping; the air box forces all the sound out the cowl opening... I can honestly say that my XJ "howls" now. when I crack the throttle more than a third open it puts a big stupid grin on my face every time.
Awesome! How did you secure the air box? Looks like you just have it resting there? Have you found that it rattles at all while driving or at an idle? I found that just an air filter would rattle at an idle because of engine vibs against the fender. Any such misfortune?
the snorkle Tube that bisects the firewall and the opening where the filter passes through into the air tube make it hard to move intentionally with my hands. One corner is also resting on the valve cover. When the hood is closed the seal is compressed almost too much which also keeps it from moving.
I might have to replace the seal with a fresh section and grind some clearance because as it stands there's almost no room for torque flex... On the other hand I have MORE bomb proof mounts and they hardly allow the engine to move anyway so maybe not.
I actually have hardware from a MAC cold air and an OEM Cobra mustang
air box (rubber flex mounts and spacers) that I was going to use to mount the box, using a fabricated bracket off the valve cover and the shelf or lip that's on the firewall, but it's just not needed at all.
I might have to replace the seal with a fresh section and grind some clearance because as it stands there's almost no room for torque flex... On the other hand I have MORE bomb proof mounts and they hardly allow the engine to move anyway so maybe not.
I actually have hardware from a MAC cold air and an OEM Cobra mustang
air box (rubber flex mounts and spacers) that I was going to use to mount the box, using a fabricated bracket off the valve cover and the shelf or lip that's on the firewall, but it's just not needed at all.
lancey3
NAXJA Forum User
- Location
- Columbus Ohio
amazing job.
