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Unread 02-13-2013, 06:17 PM   #1
Lrasser
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1998 TJ Wrangler 
 
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barely goes over 55mph. gearing or fuel issue?

I just finished my build. 87 wrangler 4.2 weber 32/36 3 speed auto 3in lift 33 km2's. The truck runs and drives real nice. My issue is speeds over 55mph. At 55 im running about 2100rpm's. It will get up to the speed decent but once i hit 55mph it looses acceleration. If i floor it i can slowely get up to 68 max and that keeping my foot to the floor. The only two things i can think of is either the 307's arent enough gear to push it at that speed OR i'm just not feeding enough fuel to it. at 68mph im only at 2500rpm's and there is no more pull left. It's at it's max.

Any thoughts?

I'm between regearing to 410's or installing a howell fuel injection system. I can't afford to do both right now. I just want more highway usage from it.

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Unread 02-13-2013, 06:26 PM   #2
Mark05059
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regear is what you need... the 4.2 make torque at much higher rpms (over 3k) and thats why you have no pull left.
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Unread 02-13-2013, 07:16 PM   #3
Lrasser
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will that help increase my top end?
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Unread 02-13-2013, 09:54 PM   #4
dancytron
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Did you do the nutter bypass when you replaced the carb? How did you set the distributor timing? How did you set up the vacuum advance? Have you done the regular tuneup stuff (cap, rotor, spark plug wires etc).
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Unread 02-13-2013, 11:11 PM   #5
Lrasser
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single wire HEI. rebuilt head with all new valves 150lbs compression in every cyclinder. vac and mech advance both working properly through the curve from 4-26 deg with no pinging. All emissions removed. brand new exhaust. new timing chain. and much more
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Unread 02-14-2013, 06:25 AM   #6
CJ51973
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258 with torque over 3000 rpm? The 4.2L is good (it will spin faster but...) for about 2800-2900 max rpm cruising down the road. I have 4:11 with the same tranny and I only run 60 mph at around 2700-2800 rpm. If you are wanting to run 70 I would run 3:55 or so.
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Unread 02-14-2013, 09:31 PM   #7
Lrasser
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Thats what im confused about. ive been told by a shop it will give me my top end back if i go to 410's since it will give me my power. are you running an automatic or manual?
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Unread 02-15-2013, 11:50 AM   #8
CJ51973
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You will gain power but at the expense of speed. Your engine will only turn so many rpm. So it's a balance between how fast you want to go and how fast you want to get to that speed. My 4:11 are great for off the line power (not the reason I have them, that would be rock crawling) with 33s but because it isn't really good to spin a 258 at over 3000 rpm for extended time I run 60 mph or 2700 rpm. The I6 isn't a high rpm motor, at least in stock form. It's more of a low rpm torque motor. So if you are wanting speed you need an overdrive transmission or a gear ratio which will allow you to acheive that speed at a safe rpm with your existing transmission. there are a number of calculators around on the web which would help with that.
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Unread 02-15-2013, 09:19 PM   #9
Lrasser
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I've used some of the calulators but there not that great. If i use my current settings its not to close. It's a wrangler and if i was looking for speed i wouldn't have purchased a brick with wheels. right now 60 is really my max since it would need to floor it to go any higher. I'm not looking to do 90mph just simply keep up with traffic and 65. if i could get to 65 mph wil min effort and hit my max id be happy since it's only my weekend warrior.
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Unread 02-15-2013, 09:47 PM   #10
flcracker
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your gears are killing you, you don't have the torque to pull that high of a gear and 3.73 or 4.10 will give your engine the leverage to go....
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Unread 02-15-2013, 09:58 PM   #11
Michaelgoesrawr
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Quote:
Originally Posted by Mark05059
regear is what you need... the 4.2 make torque at much higher rpms (over 3k) and thats why you have no pull left.
Nope. 112hp @3200 RPM and 210 lbs of torque at 2000 RPM. Its his gears.

Quote:
Originally Posted by CJ51973
258 with torque over 3000 rpm? The 4.2L is good (it will spin faster but...) for about 2800-2900 max rpm cruising down the road. I have 4:11 with the same tranny and I only run 60 mph at around 2700-2800 rpm. If you are wanting to run 70 I would run 3:55 or so.
This.
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Unread 02-16-2013, 10:13 AM   #12
wanabejeeper
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Hey lrasser I'm in the exact same boat. I have the exact same build as you with 3.07 and 31's. I can pull all the way to 55, My tach doesn't work so I'm not sure what rpm I'm at but above that I'm flooring it. I'm going to add an aftermarket tach and start looking at gears. I've been thinking of getting an AW4 for the overdrive. Keep in touch and we can compare whats working. I did look at gears and ratios and 3.55 was what I found. I'm just not into spending that kind of money on the D35 and I'm not ready to put in a new axle yet.
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Unread 02-16-2013, 02:12 PM   #13
pasinbuy
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Unless you re-geared your speedometer you are going faster than you think. I also have 33's and my speedometer is off by 10%.

Speedometers are off by a percentage and not ever mph.

So when you are going 60 mph you are really going 66 mph. At 63 or 64 mph you are hitting 70 mph.

If you can hit 68 mph you are really doing 75 mph which is decent as hell.
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Unread 02-16-2013, 09:07 PM   #14
Lrasser
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I have a local guy willing to supply and install an 8.8 and front d30 with 410's with t=all labor, parts, and hardware fopr $1400. im strongly considering it.
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Unread 02-17-2013, 02:25 AM   #15
140mower
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Is an sye included in the price as well? If so and he's reputable and puts out good work, I think I'd be on that. I might even ask how much to toss a locker in the front while it's out and easy. (I like to torture myself when the budget is tight, as it always is.)
A gear change will wake it up the way you want it,and it will be a night and day difference.
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