1997 4.0 and older 4.2

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griftymcgrift
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Joined: January 6th, 2010, 11:53 am
Vehicle Year: 1997
Vehicle Make: jeep
Vehicle Model: wrangler

1997 4.0 and older 4.2

Post by griftymcgrift »

ok, i have searched a bit and cant find my exact request. i have a 1997 jeep with a 4.0 and i am getting a 4.2 for cheap. im not sure of the year on the 4.2. a bit ago i overheated my 4.0 and a tiny bit of aluminum was stuck on my cylinder wall. i picked the aluminum off and put the head back on. i know thats not the greatest choice of action, but i was very short on cash. with tax season coming up ill have a bit of cash and plan on buying a beater so i can work on the jeep.

what, exactly, can i do with the parts i have in the two motors, and what do i need to do to build something good. i was thinking of just using the 4.2 block and rotating assembly under my 4.0 head, but i know the crank and rods will fit in my block..

im just looking to get the most out of a hybrid of the two, and i am not afraid to buy a few things to make it awesome. my main question is what machine work needs to be done to the block/ crank/ etc...

thank you

wes
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SilverXJ
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Re: 1997 4.0 and older 4.2

Post by SilverXJ »

What you want to do is use the 258 crank rods in your 4.0L block with 4.0L pistons and the 4.0L head. That is the basis of a stroker. There are options to go from there like using 4.0L rods with Keith Black 944 pistons or completely custom. You have a lot of research to do.
YJason
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Re: 1997 4.0 and older 4.2

Post by YJason »

griftymcgrift
Posts: 6
Joined: January 6th, 2010, 11:53 am
Vehicle Year: 1997
Vehicle Make: jeep
Vehicle Model: wrangler

Re: 1997 4.0 and older 4.2

Post by griftymcgrift »

ok, the rotating assy is from a 1983 4.2. do i need to machine the front of the crank to match my balancer or should that work? i know i have a bit of machining to do and i want to go .020over, that should give me 4.6L. i really just need to know if there are any crazy snags like my fuel injection not working after this or something. ive built harley engines that cannot be beat before and am familiar with car engines, i just dont want to get WAY over my head with machining.

thanks,
wes
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Plechtan
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Re: 1997 4.0 and older 4.2

Post by Plechtan »

as far as the crank goes, just buy the spacer for $35.00 from Hesco and you are good to go.

The EFI will work, but you will probably need larger ( Mustang 24lb) injectors. An adustable fuel pressure regulator would also help you tune it.
Peter Lechtanski
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griftymcgrift
Posts: 6
Joined: January 6th, 2010, 11:53 am
Vehicle Year: 1997
Vehicle Make: jeep
Vehicle Model: wrangler

Re: 1997 4.0 and older 4.2

Post by griftymcgrift »

ok, i found on ebay, but didnt buy yet

.030 over teflon coated im guessing stock 4.0 pistons for 130.
rings should be 55
24# ford injectors 65

i have the crank and rods from the 83
need a gasket set, and im estimating machine shop work at 300
clean block and bore to +.030

my heads in good shape....probably do valve job and new seals


so, is 600 plus the gaskets a reasonable amount? or am i missing anything big? and should this bolt together and run, or do i need to dish the pistons or something? premiums not a problem...id rather have the extra power than have to drop the CR.

thanks for the info everybody
dwg86
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Re: 1997 4.0 and older 4.2

Post by dwg86 »

I would dish the pistons. The little bit extra HP you gain is not worth the damage that can be caused by detonation(my opinion). Contact oletshot on this board. He does a great job, with fast turn times and a good price. I would also deck the block to get a tighter quench. This will help stop detonation. You can run a higher compression without detonation with a tighter quench. I am running a zero deck .043 quench and 9.25:1 static compression, and I can run 87 octane with no detonation. The bigger factor is the dynamic compression. Your camshaft selection will have an effect on this(intake valve closing). My dynamic compression is 7.75:1. I don't know what the max dynamic compression ratio would be for pump gas. I would think you would be ok with a quench of .040-.060,9.5:1 static compression with 8.0 dynamic compression. I would do some more research on it.
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