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Unread 09-04-2009, 11:47 AM   #1
honda250ex
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Engine modifications "more horsepower"

Hey I have a 1987 jeep wrangler with the 258ci 4.2 I6, I'm looking to getting some engine modifications. I don't know what to do I was wondering if you guys had any thoughts, feel free to put your input. I want something that's gonna give it more horse power.

Thanks
-MIKE

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Unread 09-04-2009, 12:33 PM   #2
4.7stroker
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The best path to HP/TQ is to get a 4.0 and build a stroker, failing that installing a 4.0 head and an uprated cam is a good start.

Dwayne
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Unread 09-04-2009, 12:52 PM   #3
PASKS
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Quote:
Originally Posted by 4.7stroker View Post
The best path to HP/TQ is to get a 4.0 and build a stroker, failing that installing a 4.0 head and an uprated cam is a good start.

Dwayne
stroker questions.....

what chamber size on the 4.2 head VS. the 4.0 head ?
what does the stroker kit make the final CI number ?
how much does it boost CR ?
is the cam you mention a custom grind or just a 4.0 cam ?
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Unread 09-04-2009, 12:55 PM   #4
tobias94yj
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if you want the keep your 4.2 then do some searches on doing a 4.0L HO head conversion and look into doing a fuel injection conversion. that will put at the power of doing a 4.0L stroker
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Unread 09-04-2009, 02:29 PM   #5
1998zj
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Up the power much and that crappy BA10 transmission will bite the dust.
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Unread 09-04-2009, 02:31 PM   #6
honda250ex
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yea Clifford performance makes a conversion for the 4.2 to the 4.0 motor same horse power and all that.
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Unread 09-04-2009, 03:09 PM   #7
4.7stroker
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Quote:
Originally Posted by PASKS View Post
stroker questions.....

what chamber size on the 4.2 head VS. the 4.0 head ?
what does the stroker kit make the final CI number ?
how much does it boost CR ?
is the cam you mention a custom grind or just a 4.0 cam ?
I do not know the chamber size, the head flows much better making it a worthy swap.
The CR depends on the pistons used and weather you zero deck height the block/pistons.
The cam was from Comp cams for the 4.0.
Be sure to have the rotating assy spin balanced.
This may help http://www.jeepstrokers.com/forum/vi...a6ebbdac130ee8

Dwayne
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Unread 09-04-2009, 03:28 PM   #8
Pitbullcustoms
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What about porting and polishing the stock 4.2L head and a cam?
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Unread 09-04-2009, 03:34 PM   #9
tobias94yj
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Originally Posted by Pitbullcustoms View Post
What about porting and polishing the stock 4.2L head and a cam?
I would say not worth the money when 4.0 HO can be readily had. and I know I read on bc4x4 about the 4.0 stroker that when they researched the head work that the power gains were not significant.
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Unread 09-04-2009, 04:03 PM   #10
PASKS
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Quote:
Originally Posted by 4.7stroker View Post
I do not know the chamber size, the head flows much better making it a worthy swap.
The CR depends on the pistons used and weather you zero deck height the block/pistons.
The cam was from Comp cams for the 4.0.
Be sure to have the rotating assy spin balanced.
This may help Jeep Strokers • Stroker Basics

Dwayne
thanks. that looks fun.
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Unread 09-04-2009, 04:46 PM   #11
wheresthebfh
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So I am doing the same thing. I was thinking stroker originally but as i got into the project more I settled on just doing the 4.0 swap. The main reason I settled with just the swap was the 4.0 was attainable and it was easy to find a good 4.0 with the ax-15 already mated. I do not know if cost is an issue but I just went ahead and bought an XJ and stole the 4.0/ax-15 and got a spare np231. The swap is moderately easy and I can use my 4.2 parts to build a stroker down the road. I also parted out the rest of the xj to offset the cost. Got the XJ for 700. This option also allows you to deal with the ba-10 issue. The wiring harness is a pain however but you will have to do it no matter what you do if you lose the 4.2
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Unread 09-04-2009, 04:54 PM   #12
vmann7
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^^^X2, my 87 has borla headers, weber carb, hei dist and other little odds and ends, it still generates just enough power at speed to barely get out of its own way.

Don't be incremental like me, save and go with a 4.0/AX-15 already attached. Just my .02 pennies.
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Unread 09-07-2009, 11:13 PM   #13
honda250ex
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Thanks for all you inputs, I appreciate it
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Unread 09-08-2009, 12:30 AM   #14
lclark2074
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i thought a stroker was 4.2 crank in a 4.0 block making it 4.7 ?
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Unread 09-08-2009, 03:49 AM   #15
tobias94yj
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Quote:
Originally Posted by lclark2074 View Post
i thought a stroker was 4.2 crank in a 4.0 block making it 4.7 ?
there are quite a few different combos but yes it usually is a 4.2 crank and connecting rods with 4.0 pistons which turn the 4.0 into a 4.5 due to the longer stroke. you can also use the 4.0 connecting rods but then you have to have custom pistons so that they do not slap the valves because 4.0 rods are longer than 4.2 rods
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