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Old 07-19-2008, 06:48 PM   #1
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Need help with Loss of power (New Motor)

Hi (first time to post)
I have been lurking for a while and I find a lot of great info on this board.
My question is: I just replace the engine in my 2000 TJ 4.0 Litre inline 6. I spent a good amount of money having an engine built to be a torque monster. I had a RV cam installed, ported and polished head, etcc. and since I installed it it seems it has less power now than the old tired motor. It runs great, idles smooth, gas miolage is normal, but I thought it would have Guts now, and it is a gutless wonder. It pulled my boat better with the old motor.

I am wondering if the cam sensor is not spot on will this cause it? It is the only thing on the motor that I had to time? Also could the valve springs need adjustment after a while to bring them in to a fine tune. I am totally confused.

It has about 3000 miles on it now and it runs a bit better but it just doesn't have any pulling power that the six is known for.

I have driven jeeps most of my life so I am no Jeep newbie , but this is puzzling me.

Thanks in advance
Larry

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Old 07-19-2008, 07:59 PM   #2
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Based on what you have stated, there are too many possibilities and variables to try and troubleshoot this on a message forum.

Was the engine taken out of the Jeep, or was the top end just replaced with the block in? Did you change a torque converter? Was it ran on a dyno?

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Old 07-19-2008, 08:05 PM   #3
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ya i agree, i'd check the timing, i'd research the cam thats in there. a performance cam, without the right set up could do more harm than good. there are no valve adjsutments on jeeps.

we need more info.
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Old 07-19-2008, 08:25 PM   #4
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make sure they dialed in the cam. Alot of rebuilders just stuff them in and go. It makes a big difference.
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Old 07-19-2008, 08:48 PM   #5
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Quote:
Originally Posted by BretStep View Post
Based on what you have stated, there are too many possibilities and variables to try and troubleshoot this on a message forum.

Was the engine taken out of the Jeep, or was the top end just replaced with the block in? Did you change a torque converter? Was it ran on a dyno?
The Engine was removed and I had a complete longblock built special for this jeep from a very reputable engine builder. I removed and installed the enigine myself. I have been a mech all my life and currently work on 737's. That being said I have no clue as to what could be the problem. I know that the 4.0 has hydraulic lifters but if the springs are not adjusted correctly it could cause valve ineficiency. Also as I stated the Jeep runs great Just no real Torque.
I had to install the cam position sensor and time it according to the manual. If this was off just a bit would this cause a problem? Is there a way to dial it in on a machine?

Larry
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Old 07-20-2008, 08:57 AM   #6
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if that cam sensor is off it could cause it. i'm not sure on the proper procedure for dialing it in, but i'd guess you'd need a scan tool.

and i repeat, there's no adjustments on the valve train on jeeps.
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Old 07-20-2008, 03:23 PM   #7
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[QUOTE=physhstyx;247567]The Engine was removed and I had a complete longblock built special for this jeep from a very reputable engine builder. I removed and installed the enigine myself. I have been a mech all my life and currently work on 737's. That being said I have no clue as to what could be the problem. I know that the 4.0 has hydraulic lifters but if the springs are not adjusted correctly it could cause valve ineficiency. Also as I stated the Jeep runs great Just no real Torque.
I had to install the cam position sensor and time it according to the manual. If this was off just a bit would this cause a problem? Is there a way to dial it in on a machine?

Larry[/

With the buildup that they completed, did they give you a computer generated horsepower / torque graph of stock vs. modified? Did they give you a guarantee with it?
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Old 07-20-2008, 03:37 PM   #8
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I'm betting they just gave you the usual high HP at high rpms cam which will cause a serious loss of low-end torque and make the 4.0L feel gutless at the low end.
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Old 07-21-2008, 10:52 AM   #9
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Specs...what are the engine/cam specs?

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