TeamRush or other experts 258 - Off-Road Forums & Discussion Groups
Jeep-Short Wheelbase All discussion of short wheelbase Jeeps: CJ, TJ, YJ and JK

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post #1 of (permalink) Old 08-20-2000, 08:13 PM
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TeamRush or other experts 258

'77 CJ-7, 258 I6, Carter BBd, 4.10s' driving 33" BFGs', this is a recent OH on the engine ane everthing is new except head, block, crank and rods. Bored 0.040 over...problem...this combination will not take much of a load -- period. I do not wined it up past 3200 turns, I do not think it will go much further anyway. I have read your posts on upgrading the ignition, 78 up, any help for this poor '77? I don't mind buying everything new aftermarket - I am about to pull this gutless 258 and put in a 350 Chevy.. Also figured out that I have a T18A and about to trade that out to a NV4500 to go with the 350. Stupid I know, but shifting to 3rd to climb 3 degree hills or bucking a strong wind doesn't seem right or am I expecting too much out of the 258?

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post #2 of (permalink) Old 08-20-2000, 08:55 PM
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Re: TeamRush or other experts 258

with the playing I have done with the 258,its pretty tough to get any power out of them,dont get me wrong I love the legendary 258,but even with the mopar mpi kit,headers etc with 33"s or 35"'s they are still hard pressed to make freeway speed let alone pass anyone .the bottom line is what will you use it for?
if you want it for slow speed rock crawling the 258/t-18 is a deadly combo,but if you want any power at all on the top,put in a V8.If I were you in your situation,with already having a bullet proof tranny,I would drop in a AMC 360,because it will bolt directly to your t-18,you only need to modify your rad,drivers side engine mount and exhaust,and some smaller details.
I put a bone stock (except .030 bore)AMC 360 2bbl from a wagoneer in my 83 cj7,with 35"tires 4.56 gears,and a total weight of 4500 lb's,my 0-60 is 14.5 sec's,I'm not sure what my max speed is (I've never tried)but I've had it to 80mph a few times,and it was ready for more.
plus you can find the 360 and parts fairly easily,and if you want more power,the entire "performer"kit is available from edelbrock,as well if you want to inject it,Howell makes a great kit using GM TBI as well Holly prejection is available,for ignition upgrades TeamRush has a recipe that uses ford over-the counter parts that is very affective,also Cape Conversions has a true GM HEI that bolts right in.

my two cents.

post #3 of (permalink) Old 08-20-2000, 09:45 PM
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Re: TeamRush or other experts 258

The upgraded Motorcraft/ DuraSpark ignition upgrade will make your 258 much more drivable.
It's easy to do, and all the parts are over the shelf at any auto parts store.
The distributor was built for your engine for over 12 years, and the rest of it is just a little wiring.
Upgrade cost will be under $200 if you use the economy store brand lifetime warranty parts.

Going to the Motorcraft distributor and a MSD 6 series module will make the little I-6 even more drivable.
The MSD 6 series modules start about $130 and go up to about $250. The $130 module is just fine for most applications.

The GM HEI is a conversion. You simply convert your inadequate Prestolite ignition for an inadequate GM HEI ignition.
The Motorcraft/ DuraSpark ignition is a true upgrade, and will give you the most bang for your buck.

The MSD 6 series module is just as suited for V-8 use and I-6 use, in case you decide to upgrade the engine later.

I've never used them (I don't do I-6 engines), but the reports from users, and the numbers from Clifford are impressive.
I'm sure they could recommend intake/ cam/ header combinations...

I will post the ignition upgrade again if you want to use it. It has some part numbers, and what to ask for at the parts stores.

Think carefully about application before you decide to "Upgrade" your Jeep again.
That NV-4500 is really wasted behind your I-6.
If you decide to go V-8, think carefully about that, especially if you live in an emissions state...

The Ford 302 or 351W is probably the best engine for a V-8 upgrade for a Short Wheel Base Jeep.
It's a little lighter, and a little narrower than the Small Block Chevy, and just as powerful, comparing CID...
They are everywhere, cheap, have factory fuel injection systems available, and have factory transmissions and T-cases that will bolt up without adaptors....

On the down side, they won't bolt straight up to your AMC bolt pattern bell housing, you will have to fabricate or buy aftermarket engine mounts & transmission mounts.

Stay with as much off the shelf stuff as you can, so parts can be found everywhere.

If you decide to drop in a direct bolt in, Go with the AMC 360.
Minor changes only needed, bolts to your current bell housing, and there are parts available from the factory sources.
There are tons of 360's in full size jeeps, and they are everywhere.
They make good torque and reasonable horsepower with very little modification.

On the down side, The AMC 360 isn't the strongest engine in the CID class.
The 304 and 360 both have weak bottom ends, with the weak link being cast iron rods.
They will not take high RPM, or lots of shock loading.

If you decide on the small block chevy, the 350 is a really good choice.
They grow on trees, are available everywhere, and everybody makes something for them.
Very effective fuel injection systems are available from the factory.
Transmission and T-cases are made to bolt straight up to them, so adaptors aren't a problem.
There are parts everywhere, and everybody knows how to work on them.
I think every production part ever made for any small block is still available through the factory or aftermarket sources...
Jeep even used GM automatic transmissions for a while.

Draw backs,
They are heavier than the little Ford, and about the same weight as the AMC V-8. They are wide, so you are going to have trouble finding efficient exhaust manifolds that fit inside the frame.
All of your engine mounts, transmission cross member, and linkages will have to be fabricated or bought aftermarket.

If I were looking it changing the engine to a non AMC....
I believe I would do the big V-6 engine today.
Great horsepower and torque for the weight and CID, factory fuel injection systems, ready and available transmissions and T-cases....

Don't over look them when making up your mind.
Look up CJ-8/5.2Mag, and ask him what he thinks about the little V-6 engines...

CJ Dave, Dave, TEX and a few others would be good sources of information on this thread also.

You should also get with TEX or somebody that can help you figure your true final drive ratio, it sounds like you may have a problem there also...

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post #4 of (permalink) Old 08-21-2000, 12:10 PM
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Re: TeamRush or other experts 258

Just moving this to the top,
It got lost in all the flatulence on the BBS this morning...

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