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Unread 07-25-2007, 06:25 PM   #1
jeep795
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1992 YJ Wrangler 
 
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some crankshaft questions

hey when building a stroker, is it a good idea if using a used crank to balance it. and how much would a machine shop charge to do so. what else should be looked at on the crank besides the bearing surfaces. another question, to get pistons dislodged from the rods should i bring those to a machine shop as well, or is there a way to do it. i'd rather not crack a piston by trying to press it out myself. i read somewhere you can put it in the oven to like 450 to press on and off. any idears? any idea on price for a shop to do this?

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Unread 07-25-2007, 06:35 PM   #2
Cobra Jeep
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The crank: Kinda depends on how mutch your willing to spend. If your on a budget then dont worry about it. But if you have the money and want to do it right, have it balanced. It will even things out and help it run smoother. A correct balance job includes the rods and pistons you intend to use, as they all get weight matched. As for price, it will kinda vary from shop to shop. I had my 401 balanced and although I cant remember, I am thinking it was somewhere around a couple hundred or less. Its been so long ago.

As for the rods: I wouldnt risk it and try doing it yourself. I would take it to the machiene shop and let them do it. Most shops wont charge too mutch for that.
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'93 YJ 4.0L, AX-15, NP-231HD/SYE, 8.8in rear, OME 2.5 lift, WJ knuckle/brake conversion, hydroboost. Warn M10000 winch. Hope to some day build a stroker for it.

'79 Cherokee Chief, 401 MPFI fuel injection, T-18/D-20 and hydroboost. Otherwise stock.
Future mods: NV4500, NP205, high pinion D60 front and smooth bottom D60 rear, e-lockers front & rear. SOA with 35X12.50's
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Unread 07-25-2007, 07:54 PM   #3
jeep795
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that's not all that bad... i'm planning on building 2 stroker motors, one to sell, and one to run. the one i'm gonna sell i was gonna build right, but if i can get a cheap enough price on balancing and weight matching i was gonna build em both up right.
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Unread 07-25-2007, 08:15 PM   #4
4.7stroker
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When I built my stroker I used the 4.2 harmonic balancer so I wouldn't have to machine the snout.
Now to the balancing , I static balanced my rods/pistons and matched them up so they were within 2g.
The motor is smooth untill 3700rpm then there is a vibration, were I to do it again I would dynamicaly balance the rotating assy.
My machine shop only charges $150 to do this and I regret cheaping out.
Don't get me wrong the normal range that I operate in is perfect but if it was dynamicaly balanced it would rev to 5 k with no problem.

Dwayne
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Unread 07-25-2007, 09:22 PM   #5
jeep795
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interesting.... my jeeps gonna mainly be a trail rig. but sometimes, i just like to hear the roar of an engine, i think i'll just get them both balanced accordingly. stroker, what year crank did you use, i was planning on using a 4 weight crank from 87-90, i thought you didn't have to cut the snout down. but incase i do have to cut down, did you run into issues with using that harmonic balancer?
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Unread 07-25-2007, 09:32 PM   #6
4.7stroker
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I used a 86 crank, not worried if it had 12 or 4 counterweights, it was local and cheap.
I used all 4.2 accessories and everything fit without modification.
The 4.0 crank snout is around a 1/2" shorter than the 4.2 snout so I used the 4.2 hb to avoid having the snout machined.
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Unread 07-25-2007, 09:41 PM   #7
jeep795
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sounds mint... out of curiousity, i'm assuming that you bored the motor out unless your name is extremely misleading, what was the charge for boring? did you do any head work as well?
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Unread 07-25-2007, 10:19 PM   #8
4.7stroker
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It should cost you around $12-$15 per hole for the rebore, I left the head stock except for a 3 angle valve job.

Dwayne
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Unread 07-26-2007, 05:26 AM   #9
jeep795
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man, thats cheaper then i thought it was... i think i'll get a bore too.
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Unread 07-29-2007, 11:06 AM   #10
jeep795
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not exacly sure how a stock 4.2 vibration dampener would work, different belt is used. does anyone possibly have a picture of the spacer they've used with the stock 4.0 balancer?
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Unread 07-29-2007, 11:23 AM   #11
4.7stroker
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I used the damper for the 88, it was for a serp setup, I also used all of the accessories for the 88.
The 4.2 and 4.0 blocks have the same bolt holes so the 4.2 stuff will bolt right on with no issues alowing you to use either setup, I used the 4.2 stuff so I didn't have to machine the snout
Otherwise the machine shop can machine the snout down so it is the same length as the 4.0 if you want to go that way.

Dwayne
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Unread 07-29-2007, 12:26 PM   #12
jeep795
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hm, never thought of that, what are 4.2 alternators rated at for amperage? would it be possible to just swap over the pully's from the 4.2 alternator, p.s. pump and idler over to the 4.0 stuff?a little off topic but will 4.2 oil pans work with a 4.0?
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Unread 07-29-2007, 12:57 PM   #13
4.7stroker
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Oil pan will work, dont know about the pullies though.
All of my accessories were already serp from the 4.2 and I just reinstalled everything and it all lined up just fine.

Dwayne
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