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 Post subject: Engine rebuilding
 Post Posted: Thu Dec 25, 2008 10:39 pm 
Looking into rebuilding my engine, so im gonna use this thread for my questions. The closest ive come to rebuilding a engine has been tearing one down and putting it back together at school. In that instance, there wasnt any part ordering or measuring, or machine work involved. So im pretty much at a loss to all that. I know i have the ability to do the work, just not the experience.

Heres whats most likely gonna happen, however i am still tossing around a stroker build but prolly wont follow through.

Rebuild the 4.2. Have it bored out 30 over most likely. Get the 4.0 head checked out and water jackets welded shut. Deck the head and block. Reuse the crank and rods. New pistons and rings, obviously due to the overbore. Completely re-seal engine.

So my first set of questions are

1. What machine work do i need done. I know for the head i need it to be hot tanked and then magnafluxed(?) to check for cracks and such. Then i need to have it decked to be sure its flat and seals good. If determined by C and P i may also need to replace some valves. For the block, i also need it hot tanked. Then checked for cracks as well. Overbored, and decked. And from what ive read its better to have them install the new cam bearings. Anything else, or anything i dont need that ive listed?

2. All the rebuild kits ive looked at have had different sizes of bearings for the crank and rods. How do i determine what size i need? I know once i have them i check the clearance by using plastigauge (already know how to use that), but how do i know what size to order? I may not order a kit, but instead order the parts individually (read that sometimes you can piece it all together cheaper than a kit), but ill still need to know what bearings to order.

Thanks in advance, and any input helps!


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 Post subject: Re: Engine rebuilding
 Post Posted: Fri Dec 26, 2008 1:52 am 
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Tang Soo
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Location: NE Indiana
The bearings are sized based on if the crank has been ground. I would have the crank magnafluxed and ground if your doing that to the rest of the motor. C & P would let you know what size bearings you would need then.

mac 'modern marvels of the internal combustion engine' gyvr

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 Post subject: Re: Engine rebuilding
 Post Posted: Fri Dec 26, 2008 10:44 am 
macgyvr wrote:
The bearings are sized based on if the crank has been ground. I would have the crank magnafluxed and ground if your doing that to the rest of the motor. C & P would let you know what size bearings you would need then.

mac 'modern marvels of the internal combustion engine' gyvr


Sweet. Thanks! Ill have to talk to them sometime once i figure out whats going on to get an estimate on all the work.


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 Post subject: Re: Engine rebuilding
 Post Posted: Fri Dec 26, 2008 11:29 am 
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Thread Necromancer
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You may look into getting a mild cam also, it will really waken the engine up. Then possibly a valve job if you have the extra money. You could also get differently dished pistons to change compression and add power. Something that you can do on your own in the mean time is port, polish, and gasket match the head.

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 Post subject: Re: Engine rebuilding
 Post Posted: Fri Dec 26, 2008 3:39 pm 
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Tang Soo
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Location: NE Indiana
i'd becareful with a cam in a 4.0 or 4.2...

it seems to lessen the reliability off road...

mac 'at least it did for rosco...twice' gyvr

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 Post subject: Re: Engine rebuilding
 Post Posted: Fri Dec 26, 2008 4:14 pm 
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Giggling Little Schoolgirl
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have heard bad things about cams in 4.0's

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 Post subject: Re: Engine rebuilding
 Post Posted: Fri Dec 26, 2008 9:08 pm 
Ya, i have been reading that cams in the 4.2s and 4.0s cause some headaches. Most people are saying that the stock cam is a good cam for the motor. So ill prolly just stay with the same cam (may buy a new one depending on wear) and valve train setup. I know with the 4.0 head i need to use different pushrods, but i think its just that you are supposed to use the 4.0 pushrods instead of the 4.2s. I also think that some brackets have to be either modified or changed, but im not for sure. its been a while since ive read the material, but ive been slowly going through all my bookmarks and checkin up on stuff.


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 Post subject: Re: Engine rebuilding
 Post Posted: Sun Dec 28, 2008 5:31 pm 
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Giggling Little Schoolgirl
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another idea like mentioned earlier is a valve job...
you could do a multiple angle valve job (2 of 3angle) it will help it flow alot better

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 Post subject: Re: Engine rebuilding
 Post Posted: Sun Dec 28, 2008 7:59 pm 
Ok, i wanna call C and P sometime this week and get an estimate on the machine costs. So I wanna be sure that i have everything ready to ask about

Head:
Hot tanked
magnafluxed
Decked
Valve Job (3 angle, might as well)

Block:
Hot Tanked
Magnafluxed
Decked
Overbore (.030 or .040)
New cam bearings installed

Crank (if needed, or if money permits):
Magnafluxed
Grind
If the crank checks out i probably wont do anything to it to save some money.

Sound good? Anything else?


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 Post subject: Re: Engine rebuilding
 Post Posted: Mon Dec 29, 2008 5:46 am 
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Tang Soo
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you list is good, only thing i would add is for sure have the crank magnafluxed for cracks and checked for wear. if they dont have to grind on it they should tell you you don't need it and theres no advantage to grinding on it...

and unless there is wear on the block you don't have to have it bored out, and boring it out isn't going to add any noticable power...and if it doesn't have to be bored out then you may be able to reuse your old piston's and save money there too...

have them check the pistons too if your going to reuse the old ones...

mac 'fuel injection too' gyvr

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