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  #1  
Old May 15th, 2006, 22:25
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scorpio_vette scorpio_vette is offline
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4.0L "stock" bored throttle body

i have an extra throttle body laying in the garage, and i was wondering if any of you guys have just bored out the bottom end of it???

if i remember right, the bottom of them tapers down a little, so if i had it bored perfectly straight through, would that make any difference???
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Old May 15th, 2006, 22:30
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nhrocker nhrocker is offline
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Re: 4.0L "stock" bored throttle body

Oh yeah. I've got a stock one that was opened up so it's a straight shot through and it definitely made a difference. Sorry, no hard stats to back this up, but the seat-of-my-pants meter says it was a significant gain.
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Old May 15th, 2006, 22:39
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cassio cassio is offline
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Re: 4.0L "stock" bored throttle body

im thinking about doing this too....so i'm gonna listen in too!

cas
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Old May 15th, 2006, 23:43
ju$tice720 ju$tice720 is offline
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Re: 4.0L "stock" bored throttle body

been done & here it is.. stpe by step.. http://go.jeep-xj.info/HowtoTBboring.htm
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  #5  
Old May 16th, 2006, 06:54
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Re: 4.0L "stock" bored throttle body

well since it's cheap enough to do, i'm not so much worried about actuall numbers. now if it was $300 on the other hand..................LOL

well i guess i'll have to give it a try. Thanks,
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Old May 16th, 2006, 08:01
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mikeyl mikeyl is offline
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Re: 4.0L "stock" bored throttle body

i bored my stocker out. based on my observations these are my opinions , and being such are always open to refute and correction. my bored tb certainly made lots more power up high. it would pull up into the rpm range way further than before. it will whistle, a lot. with an air tube it is way noisey around 1200 rpm. i'm used to it but everyone asks "what is the noise"? i belive turbo city does an extra under cut and some grooves to mitigate the noise.what i did notice is that it is abrupt off the bottom. i think the actual taper is more of a slight "d" shape than a true taper. this would give it less air at low openings due to partial obstruction and smooth out the first response. this was one of the few times a tb spacer helped a bit (so it seemed anyway). it tamed the abruptness a bit. the newer l2000 large intake manifold helped a lot more. but it still hits a little hard off the bottom. i have considered finding a stock used tb and comparing both on the trail to validate my findings, but so far i'm just too lazy.
your results may vary!
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Old May 16th, 2006, 09:04
steveareno steveareno is offline
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Wink Re: 4.0L "stock" bored throttle body

http://www.thefastman.com/Throttlebodies40.asp
That's the way to do it. Coupled with high air intake/filter and enlarged exhaust. Suck it in and then push it out.
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Old May 16th, 2006, 09:41
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Re: 4.0L "stock" bored throttle body

Quote:
what i did notice is that it is abrupt off the bottom
do any of you have experience with this offroad???

what i'm wondering now that you mentioned that, is..........................does it act so abrupt that you couldn't "gently start to crawl" when you're on the trail???
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Old May 16th, 2006, 13:23
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Re: 4.0L "stock" bored throttle body

I've had mine done for about 6 months now. I would agree with the abruptness of the larger bore. I do drive a manual tho, so i changed the way I drop the clutch, but that is about all I had to deal with. I didn't notice any ill side effects on the low end, nothing but positive results. If anything just stronger and more responsive thru the power curve. Doesn't hesitate like it used to around 2200 rpm.

On a side note, I dremel-ed around the slot in the side of the tb and rounded the corners off of the opening slightly, say 2-3 mm's, didn't stop the whistle, but it definitely cut down the pitch of the whistle and lowered the volume so to speak. It doesn't have to be exact, and i actually egged mine out a little toward that wall leading to the intake, gut feeling after listening to my engine whistling for about a week before i was annoyed enough to take it off and do something about it.

I have the old 90 d bend intake manifold, so I don't know about about the newer horseshoe style, but i do have a tbs and even with that it definitely is noticable as far a increase power and response. I was also surprised my mileage hasn't changed noticably, although i really don't gun it @ town anyway.

my .05...... definitely worth the time, i used a wheel similar to gojeep's writeup, I hand turned the tb with the wheel locked down into the tb so i could use two hands to hold the tb and just eyeballed the opening to the butterfly, (i was really careful not to go too far). I actually tapered both sides to the butterfly, so i has an hourglass shape from top to bottom now.
btw I do have an open air homemade intake with a 6" k&n which i did clean at the same time i did this upgrade, so i know that affected my power also.

do it.
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  #10  
Old May 16th, 2006, 17:46
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mikeyl mikeyl is offline
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Re: 4.0L "stock" bored throttle body

yes, mine has been wheeled resonably well, clawhammer (the hammers area), rubicon, moab. i'd like to say it jumps a bit hard when starting an approach. but in all fairness, it's probly my lack of finesse! i'm running an auto so i can ride the brake a bit, though i often forget that. also i run an air tube, the 2000 big plenum intake, the mustang injectors,banks header,hi flo cat, and flowmaster 40, so i'm sure all that makes the hit harder ,so come to think of it,my oppinion is kinda skewed. and acrid is right, it pulls strong right thru 2200rpm. i also used gojeeps layout but machined an inside chuck and lathed it out at work. as far as milage is, it might have increased slightly, but i find i like the power and put my foot into it, lol. it's a nice cheap mod, but you have to get the fuel in and out to feel the most gains.
go for it!
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