cj-7 4.2 upgrade
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cj-7 4.2 upgrade
- Thread starter cj77
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Torxhead
Always Off-Roading Jeeper
What year Jeep do you have and with what engine. Ignitions are a good upgrade to make.
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- 84 cj7, 91 cherokee, 78 chevy 3500 pu, 78 CJ7
You know if you would fill out your profile like you were supposed to it would make it easier to answer your questions.
hatersaurusrex
Jeeper
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- Nashville, TN
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- CJ-7
258/MC2150/Nuttered/Rush'd
T-4 (bleh)
D300 (woot)
AMC20 (meh)
Dana30
I'm gonna go out on a limb and guess... a '77?
Sent from my Latitude 10 - ST2 using Tapatalk
Sent from my Latitude 10 - ST2 using Tapatalk
- Posts
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- 57
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- 11
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- Frederick colorado
- Vehicle(s)
- 84 cj7, 91 cherokee, 78 chevy 3500 pu, 78 CJ7
Thats the point we shoundn't have to guess filling out your profile is required.
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- Springfield, Missouri-U.S.A. Earth
- Vehicle(s)
- '85 CJ-7, 258/4.2L 6cyl. Bought new in 1985. Full cage, Warn 8274 winch, Ford 9" rear, front/rear Detroit Lockers w/4:88 R&P. T-5 tranny and 4:1 t'case. 33X12.50-15 BFG/AT, MSD ign, on board air---
It's a tough engine as is.
What are you looking for for?
X2 on fill'n out your profile-
LG
What are you looking for for?
X2 on fill'n out your profile-
LG
hole
Crazy Sr. Respected Jeeper
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- 83 CJ 8, 258 I6, T19, 4-1 Dana 300,4.0 Head, Mopar MPI, 10k winch, OME YJ springs w/3" lift,CS 144 Alt upgrade,Locked 20 & 30, Border Collie co-pilots are stock.
4.0 head with MPI will bring it to life. How much you want to spend?
ThisGuyUKnow
Full Time Jeeper
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- 1986 CJ7 Laredo 4.0,Nv3550,D300 Twin Stick,AMC20 3.31, 31 BFG
Honda vtx1800c
x2 4.0 MPI and Head.
CJim7
Crazy Sr. Respected Jeeper
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- '84 CJ7 - 430hp 401 on propane - T18a/D300 twinsticked, Superior axles, Lockers, full boatsides, Warn 8274, OBA, 36" TSL's.
You are only Limited on how much you want to spend.
But the first thing I would do is get rid of the Prestolite ignition and replace the dizzy with a Motorcraft. from there you can upgrade the ignition system to either an HEI or a TFI very easily.
Depending on your emission laws, you can de-smog it to the point you are running nothing but PCV, CCV, vacuum advance, and ICM.
If you do this, upgrading the carburetion is recommended. Actually, it is recommended even if you don't.
Everything I mentioned above are the "cheap" things relatively.
Once you've decided to drop more money, one of the best upgrades for the AMC 258 i6 / 4.2l is a 4.0L head swap....with or without the injection. You can keep it carbureted and gain significant power and performance. It also keeps it simple if you have de-smogged the engine.....otherwise you can use the 4.0L injection system and adapt your emission's system to accommodate it.
Adding a better cam, high compression pistons, p&p the head.....these upgrades compliment a head swap nicely.
One other word of advice. The AMC 258 i6 / 4.2l in it's stock form does not possess what I would call a very free-flowing head (thus the advantage of a 4.0 headswap). Therefore, adding an expensive exhaust system to a stock AMC 258 i6 / 4.2l is meaningless. The stock exhaust system is more than adequate for this engine.
But the first thing I would do is get rid of the Prestolite ignition and replace the dizzy with a Motorcraft. from there you can upgrade the ignition system to either an HEI or a TFI very easily.
Depending on your emission laws, you can de-smog it to the point you are running nothing but PCV, CCV, vacuum advance, and ICM.
If you do this, upgrading the carburetion is recommended. Actually, it is recommended even if you don't.
Everything I mentioned above are the "cheap" things relatively.
Once you've decided to drop more money, one of the best upgrades for the AMC 258 i6 / 4.2l is a 4.0L head swap....with or without the injection. You can keep it carbureted and gain significant power and performance. It also keeps it simple if you have de-smogged the engine.....otherwise you can use the 4.0L injection system and adapt your emission's system to accommodate it.
Adding a better cam, high compression pistons, p&p the head.....these upgrades compliment a head swap nicely.
One other word of advice. The AMC 258 i6 / 4.2l in it's stock form does not possess what I would call a very free-flowing head (thus the advantage of a 4.0 headswap). Therefore, adding an expensive exhaust system to a stock AMC 258 i6 / 4.2l is meaningless. The stock exhaust system is more than adequate for this engine.
zzzhopperzzz
Jeeper
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- South
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- 1981 CJ7 Renegade, Have other street/trail cars/trucks
/bikes..
The distributor mod is VERY worthwhile and cheap to do.. I'll bet I gained 15 horsepower easily. Find an old inline six Chevy Truck/Car that has the vacuum advance HEI distributor. You will have to peck the old drive gear off and replace with a Jeep type gear, but it will slide right in and requires only one hot wire from the ignition to work! I also noticed an increase in MPG with this mod, and much easier starts...
hole
Crazy Sr. Respected Jeeper
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- St George Utah
- Vehicle(s)
- 83 CJ 8, 258 I6, T19, 4-1 Dana 300,4.0 Head, Mopar MPI, 10k winch, OME YJ springs w/3" lift,CS 144 Alt upgrade,Locked 20 & 30, Border Collie co-pilots are stock.
A lot of info in this thread http://www.jeep-cj.com/forums/f2/258-4-0-head-swap-results-8500/?highlight=head+upgrade