NEWS PARTS JEEP & 4x4 ATV & UTV

replacing a 258 with 304 and tranny Q

1798 Views 14 Replies 5 Participants Last post by ozarkjeep, Feb 11, 2000

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Discussion Starter · Feb 10, 2000

after countless thoughts of building another jeep with a smaller lift than what i already have, I will want a strong drivetrain but have not exactly figure out what i wanted yet untill i stubbled across a 304 amc motor, will a stock tranny out of the 80s (tourque flite 904 or 999) out of cj7 handle the power? not only do i want it to handle the power but i dont want the tranny to be a weak link? the reason why i wanted to leave the tranny in the jeep and just swamp a motor! is a 304 going to make a huge diffrence over the 258 and how close is it to the 360 amc motors? is the 304 a bolt up swap to a auto tranny? from the 80s cj i know that a motor mount has to be changed anything else?
thanks in advance!
84cj7

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G

Discussion Starter · #2 · Feb 10, 2000

If you are going to swap in an AMC V8, IMO a 304 is not an upgrade over a 258. the 258 actually makes more USEABLE power for wheeling, that is a lower torque curve. A 360 is a whole different story, that, or a 401 is a worthwhile upgrade. Just as an example, a Jeeper I know swapped a 304 in place of his 258 because he was tired of breaking things with the 258s bottom end torque! (BTW, I have his 258 in my garage waiting to be rebuilt to get swapped into my CJ-7 to replace the getting tired 258 that is in there now.)

Brad
Get active or get locked out, the choice is yours.

G

Discussion Starter · #3 · Feb 10, 2000

I prefer a v-8 to the I-6. I have a 304 and in stock form it isn't trmendously stronger than the I-6. I still prefer it though. If I do it again it will be a 401. As far as I know, one of the motor mounts needs to be replaced. The 904 or 999 tranny's arn't terribly strong but they would hold up to moderate v-8 usage. I wouldn't use it though. I prefer the th-400 which came on quadratrac equiped cj's or wagoneers,it has the amc belhousing but requires the tailshaft be changed to bolt to a transfer case other than the quadratrack. Another good choice is a tf 727 which bolts up to a dana 300 t case but be sure to get the kick down cable with the 727 since they are getting hard to come by. FSJeeper is selling an amc 360/tf 727 combo on the for sale board which would be a great setup.

Al
My web page

WILL

· #4 · Feb 10, 2000

you could also get a th400 out of a 70's full size jeep. those used the dana 20 behind them as well as the quadratrac.

79/CJ-7/AMC360/TH400/Q-TRAC/d30/d44/33's/RS9000s/Herculiner

Scott_CJ8

· #5 · Feb 10, 2000

I'm going to have to dissagree with the others. I replaced my 258 with a 304 and there is no comparison. The 304 is by far a better engine - not that the 258 is bad (for it's size, it's the best out there IMO), just that the 304 delivers more. It's an easy swap and you can use a lot of the I-6's components on the V-8.

Keep on Jeepin'
Scott

130

· #6 · Feb 10, 2000

I think that the 304 would make a great swap, and with the camshaft from a 401 and a carb that flows 400fps or more, it would make one heck of a torque monster as well as making big HP

G

Discussion Starter · #7 · Feb 10, 2000

hey brad
how about on the street? to move big tires (35 inch tires) would u say that the 304 has more hp, I understand that rock crawlers do not need gobs of hp to be a well built rig but I need the hp for the street and the mud! The terrain that I wheel on now is a variety of terrains,

G

Discussion Starter · #8 · Feb 10, 2000

As I normally say.. I am not a machinic, so I warn you.

However, I just swapped out my 258 for an amc 304. As said above. Its a big difference in my opinion.

1997 TJ w/ 33's & 1984 CJ7 w/35's
http://members.aol.com/a4x4jeeper/

251

· #9 · Feb 10, 2000

This thread started out serious, and now Im laughing my ass off...

the only reason id put in a 304, is be able later easily drop in a 360/401

the 904 wont hold for long, the 999 will, the tf727 of Th400 is a better choice but the 727 is more common with an adapter OTHER than QUADRATRAC, as stated before you can use your dana 300 with tf727 if you have some lift, the 727 uses a MECHANICAL kickdown linkage that youll need unless you have the valve body modified., or you can buy an aftermarket cable type from Lokar I think

You could start from scratch, go to a 4 speed stick, T18 or T176, pretty easy to find, and will hold ot V8 power, unless you really like the automatic.

Dont pay much for a 304 unless its fresh, and under $400, I had a running one last year, I couldnt give the damn thing away...

OzarkJeep
NW Arkansas

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G

Discussion Starter · #10 · Feb 11, 2000

if i do put a 304 in my jeep would there be any alterations that i would have to do from a 304 swap to a 360 is the motor mount in the same spot as the 304, i can pick up a 304 that has a recent rebuild ( i do not know what the person calls a rebuild) with a set of new headers all for 400 and will not budge alot on the price? will the headers of the 304 fit the 360?
another i option i have is I saw in my local paper a 96 cherokee motor 4.0 injected with 22k came out of a rolled xj for 1000 how does that sound?

251

· #11 · Feb 11, 2000

all things bolted to a 304 will bolt onto a 360, and vice versa, either will mount to frame and tranny the same, thats what i meant by later an easy swap!!

the 4.0 is a damn good engine! 96, low miles, VERY tempting, BUT lots of electronics to figure out, special bellhousing for crank sensor required I think
not sure if factory 258 mounts will locate it in your frame or not..

Not worth $1000 in my opinion ( itll take another several hundred if you do all th small stuff)

the 304 will be a very easy swap in comparison, and sound WAY better, and plus its a V8!
and next year when you find that $300 360 youll have it already to drop in!

OzarkJeep
NW Arkansas

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G

Discussion Starter · #12 · Feb 11, 2000

geese i had no idea that a 304 would bing so many mixed feelings! anyways why not just keep the 258 untill i just find a 360? it is only one motor mount diffrent? if the 258 has more tourqe, what exactly does the 258 lack? the hp? I am trying to build a smaller jeep than my jeep with 40s that will be street legal with the new laws in mass (emissions is not a problem because of the year

not yeat anyways!) why do peole not like to run 35s with a 258 my question is what does it lack that the v8 has just not enough anything??

251

· #13 · Feb 11, 2000

258 and 304 have ABOUT the same torque numbers..

304 has like 40 more HP? ( guessing from memory)

the 360 has substantially more torque and HP!

you can do ANYTHING with a 258 with proper gearing

from what I think your asking, Id stick with the 258, gear with the tires and ride that puppy

OzarkJeep
NW Arkansas

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Smokngun

· #14 · Feb 11, 2000

A few of you said a 360/727 would bolt up to the 300. Is the 727 any longer than the tf999? My '83 has 258/999/300, and I would like to upgrade to 401(or 360)/727/300. Would the the transfer case be mounted back further (different drive shafts?) or is it a bolt in affair? What is the best/most plentiful vehicle to get a 360/727 combo out of that will bolt to my Dana 300? Sorry for all the questions, but I'd really like to do this. Thanks in advance!

Mike H.
1983 CJ-7 Laredo
1999 Dakota 4x4
/wwwthreads_images/icons/cool.gifo[[[[o

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251

· #15 · Feb 11, 2000

I THINK the tf727,999 are teh same length, same case, Ive messed with lots 727s, never seen a 999 other than in the rebuild books...

Keep in mind I think youll need some lift to give you proper front driveshaft clearance, and its hard to find headers for an AMCV8,Chryco tranny

Full sized Jeeps after 1980 are the best bets for the tf727/360

Grand wags, you know those old faded blue things all over teh place with peeling woodgrain? yeah those...

OzarkJeep
NW Arkansas

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