V8 engines??

[shaunfg]

I'm fairly new to the Jeep world. I have a 79 CJ7 . .AMC 258 i6 / 4.2l with a T-150 . My question is what V8's will work with that Transmission ??

 

[IOPort51]

my question is why?

I'm fairly new to the Jeep world. I have a 79 CJ7. .258 with a T-150. My question is what V8's will work with that transmission??

 

[shaunfg]

It just seems weak. Won't pull hills very well on the highway.

 

[mtnwhlr]

What gears do you have in it and what size tire do you run?

 

[IOPort51]

what carb, what ignition system, stock head??

 

[Saddle Tramp]

I'm fairly new to the Jeep world. I have a 79 CJ7. .258 with a T-150. My question is what V8's will work with that transmission??

1972 to 1986 AMC I6 & V8s all use a common bell housing bolt pattern making them interchangeable with one another. The swap in of an AMC 304, 360, and 401 in lieu of the AMC I6 is as close to a direct bolt in as you can get; only the passenger side motor mount needs to be moved. AMC 360s are easy to find and cheap in the bone yard and Craig’s List; they provided plenty of power for a CJ. With this swap even your existing clutch will bolt right on. One caveat though, the AMC V8s are all externally balanced, and balanced separately from one another requiring the proper flywheel. (Meaning an AMC 304 flywheel will not work on a 360 or 401 and vice versa; only a flywheel balanced for the respective engine will work.) New flywheels are readily available.

 

[raser13]

the flywheels for the 360's and 401's are alot easier to find and cheaper than ones for the AMC 304 . trust me i've been looking for one for a while and the only one that i've found is like 400 bucks. the ones for the 360's and 401's can be gotten at most parts houses. for like 100 bucks.

 

[1986cj7]

my question is why?

How do you like your mods on your AMC 258 i6 / 4.2l with 4.0 head and all. I have a AMC 258 i6 / 4.2l in my jeep now and trying to decide between a AMC 304 build that I have in the barn, or stroking my AMC 258 i6 / 4.2l .

 

[IOPort51]

I will say nothing against a AMC 304 , 390,401, other than it would seem to be a great deal of work with what I would consider minimal return. this , of course, assuming you have a AMC 258 i6 / 4.2l now.

for a very dramatic return, start with the ignition. the JYG distributor upgrade gives remarkable bang for your buck. I noticed a marked increase in performance for not much more than the price of a good tune up.

the 4.0 head upgrade is great and a good valve job is always a good idea. there was someone in this forum that did actually pick up 30 something horses on a dyno. fact, I saw the print out, or at least a picture of it.

The MC 2100/2150 carb up grade is easy, inexpensive and much more dependable that the carter ever was and for the hard core , TBI is a great project.

I believe the AMC 258 i6 / 4.2l will have a longer useful life than a AMC 304 with 2 and 300 K miles being well within reach with no oiling problems.

lastly I think there are a number of things that high power /high RPM motors are good for but the kind of off roading I enjoy most is not it.

I have a AMC 304 with a flywheel on a stand in my shop taking up space, I should be telling everybody what a great swap it would make and maybe I could get my money back out of it.

How do you like your mods on your 4.2 with 4.0 head and all. I have a 258 in my jeep now and trying to decide between a 304 build that I have in the barn, or stroking my 258.

 

[Incommando]

All of the above upgrades applied to a v8 will net you even greater results. Although the AMC 258 i6 / 4.2l is considered "good enough" by it's fans that is not the standard most enthusiasts strive for. There are folks out there who disdain lockers, saying the open diffs have always been "good enough" for them. You could be able to swap a much more powerful 360 in with relatively little work and for about what the recommended upgrades to the I6 may cost. There is no replacement for displacement.

Obviously I am a V8 fan where others are I6 fans. But as hinted at above there may be a better (although probably more expensive) way to get better all-around performance from your jeep: You need to optimize the gear ratios to match your tire size, power band, and intended use. If the gears and tire size are stock then I think you are seeing the draw backs of a (for the time) small displacement engine with 30 years of "experience."

It is true that many people build engines that are not suited for the intended use. Many off-roaders build a high horsepower/high rpm engine when they need an engine that builds torque at a low RPM. That is the builder's fault not the engine's and does not apply to stock engines. If you look at the power band of stock 360 compared to the AMC 258 i6 / 4.2l I think you will find that the belief that the I6 delivers much more torque at a lower rpm does not pan out. Although the peak torque of the V8 comes at a higher RPM the numbers match up as even though a smaller percentage of the peak torque is available at a low low RPM the peak number is so much greater it still exceeds the I6. Stock the '79 AMC 258 i6 / 4.2l was rated at 114 HP at 3200 RPMs ( and you can't get much more rpm's out of them as they fall on their faces at that point) and 210 #'s at 2000 rpm's. A similar stock 360 makes 175 hp and 285 #'s of torque. So even if only 75 % of the V8's torque was available at that same 2000 RPM it would still beat the AMC 258 i6 / 4.2l . As the AMC 258 i6 / 4.2l made less than peak torque at 1000 RPM's the V8's greater power everywhere on the curve also puts it ahead at that same 1000 RPM's. If you modify the V8 and choose a cam to optimize low RPM torque instead of high rpm horsepower you avoid the mistake that started this paragraph. As you would not be Limited to a '79 360 if you swap you could find a stock example rated at 245 hp & 365 #'s compared to the best ever stock AMC 258 i6 / 4.2l 's AMC 150 /240.

There is nothing wrong with the I6 and if yours is in good shape ( compression, wear, etc...) you could do the suggested upgrades a little at a time until you get them all done and that will spread the cost out. But if you do go with a V8 swap I don't think you will be disappointed especially if you then undertake HEI and induction upgrades to the V8 as time/money allow. Most fairly heavily modified AMC 258 i6 / 4.2l 's (head swap, hei, etc...)have trouble equaling even the '79 360's stock numbers and that modified AMC 258 i6 / 4.2l will be much more expensive in time and money than a stock 360 swap. I can't see where modifying the out of AMC 258 i6 / 4.2l to get closer to (but still less than) the power a simple 360 swap would get you makes any sense at all. If the stock AMC 258 i6 / 4.2l is so great why recommend such mods to get it closer to even the lower power versions of the 360 while expending more work and money? And if you put even half the effort and money into a 360 or start with a higher rated year of 360 you will be even further ahead.

 

[poppatello]

If you modify the V8 and choose a cam to optimize low RPM torque instead of high rpm horsepower you avoid the mistake that started this paragraph.

What do you do to your HWY driving if you install a high torque low RPM cam?
What other mods would one need to do besides installing a new cam? Would you have to change the lifters and rockers?

I'm thinking and I am sure I'm wrong that if you install a high torque low RPM cam your engine will top out @ about 65 mph. I know that should be fast enough but sometimes I want to push my jeep up to 70-72...

 

[Incommando]

Installing the classic "rv" cams generally requires no valvetrain mods. Obviously upgrading stock components to aftermarket may optimize performance but that is true with the stock cam, too. The higher lift coupled with the extended duration of the higher rpm cams are generally what leads to the binding an misalignment issues in the valvetrain.

Modifying jeeps, like any vehicle, is a series of compromises. Being realistic about the actual use of your jeep ( only driven to the trails? 90% highway?) will help in the decision. But I'll bet that the axle gears will play a greater role in highway performance than the cam. Although I obviously haven't seen them all I am unaware of an AMC V8 RV cam that won't still allow you more RPM's than the realistic upper end of a stock AMC 258 i6 / 4.2l .

I am unfamiliar with the CJ's I4 engines so if you are asking about a cam change for you factory '84 ihave no info to offer.

 

[1986cj7]

Installing the classic "rv" cams generally requires no valvetrain mods. Obviously upgrading stock components to aftermarket may optimize performance but that is true with the stock cam, too. The higher lift coupled with the extended duration of the higher rpm cams are generally what leads to the binding an misalignment issues in the valvetrain.

Modifying jeeps, like any vehicle, is a series of compromises. Being realistic about the actual use of your jeep ( only driven to the trails? 90% highway?) will help in the decision. But I'll bet that the axle gears will play a greater role in highway performance than the cam. Although I obviously haven't seen them all I am unaware of an AMC V8 RV cam that won't still allow you more RPM's than the realistic upper end of a stock 258.

Not to high jack this thread Incommando and others, I have a thead titled differance between AMC 258 i6 / 4.2l and AMC 304 if you would like to discuse gearing in my jeep. Unless the original poster would be intersted in this discussion also?

 

[1986cj7]

I have 4.10 gears in my axles and 33 tires. I drive about 50/50 highway and trail in my jeep. What is the difference in hp and tq #' and rpms between an rv cam and a mild mod cam? Also I'm looking at the AMC 304 not a 360 because I already have a AMC 304 in the barn. What are the differences in torque and hp that can be made between the AMC 258 i6 / 4.2l and the AMC 304 . Since there is only 46 ci difference between the two. And the oiling issues in the AMC 304 .

 

[Incommando]

The AMC V8 is said to have an issue getting the oil from the front of the engine to the rear when rebuilt to high RPM levels. This is not an issue with the stock or stock-ish engines as hundreds of thousands of them lasted just as long as any V8 of that era with no oiling issues.

If you are rebuilding an AMC V8 and having machine work done it may be worthwhile to do some of the upgrades such as drilling new and larger oil passages and running oil lines from the front to the back of the motor but many many rebuilds have been done without such mods and no issues with oiling. Running 6,000 plus under full load at the track all day? You might have oiling issues. Using it as 99% of people do on the street and/or off-road? No oiling issues.

 

[poppatello]

Installing the classic "rv" cams generally requires no valvetrain mods. Obviously upgrading stock components to aftermarket may optimize performance but that is true with the stock cam, too. The higher lift coupled with the extended duration of the higher rpm cams are generally what leads to the binding an misalignment issues in the valvetrain.

Modifying jeeps, like any vehicle, is a series of compromises. Being realistic about the actual use of your jeep ( only driven to the trails? 90% highway?) will help in the decision. But I'll bet that the axle gears will play a greater role in highway performance than the cam. Although I obviously haven't seen them all I am unaware of an AMC V8 RV cam that won't still allow you more RPM's than the realistic upper end of a stock 258.

I am unfamiliar with the CJ's I4 engines so if you are asking about a cam change for you factory '84 ihave no info to offer.

I wasn't asking about rebuilding or putting a cam in my AMC 150 . I have thought about it though after I talked to a well know engine shop in my area. He said he could make the AMC 150 an incredible motor. I just don't have the funds to do so @ the moment and I came across this rebuilt AMC 304 cheap.

Problem is I just don't know what's in it. Not sure if it's been bored, upgraded cam or what. Lifters are stock. You can see the internal engine in my thread here. http://www.jeep-cj.com/forums/f2/well-getting-304-a-14349/index2.html

I'm now thinking I should take the motor to the engine shop and have them look it over. If it has a stock cam I'm thinking of upgrading the cam for low end torque.

This is what I plan to do with my Cj. I want to be able to pretty much go anywhere I point it and hit the gas. I want to swim through mud and water. I want to scale tall mountains. I take it surf fishing. I also drive it on the HWY to and from the outing. I want to be able to hit 72 mph without the motor screaming like my AMC 150 does now. I don't want to kill the mpg to much but I can install my 20 gal tank if I must. Rock crawling is last on my list but I want to do just fine on that as well if I decide someday to try it.

Most of the trails around me are mud (clay, swamp, and rut), water, and woods.

I'm running 35" tires and I will NEVER go over that. I didn't even want to go 35's but I couldn't turn down the price. I was looking for 34's and they were out of stock. The 35's were cheaper then 33's and 34's! So I got them.

I already have the Aussie Auto locker up front. When I do the AMC 304 swap I already have the Ford T-18 that I am going to rebuild. I plan to do the adapter kit to the Dana 300 which is already twin sticked. I have already trussed my AMC20 and plan to install 4.56 gears and one piece axles. When I do the rear I plan to install my spool.

That is pretty much all I plan to do with my drive line lol. So with all this said what I'm looking for out of my AMC 304 is to be able to get out of any rut I get myself into without using my 8274. I also want to keep up in traffic on the HWY and run up to around 70 72 mph if I choose. Do you think I need a mild low end torque cam or should I be happy with the stock AMC 304 ? Should I have the engine shop check over the motor to see if they can tell me what I have as far as pistons, cams and lifters. Lifters look stock...

 

[1986cj7]

Now the $64,000 dollar question. What is the price difference in building a 4.7 stroker, and building a nicely mod AMC 304 . I don't have a 4.0 block but I have a complete AMC 258 i6 / 4.2l and complete AMC 304 . I know a lot of people on here have built both and would like best estimates. I would like to get the biggest bang for my buck. And a big thank you to every one for all there opinions and links. Hopefully this will help others out there that are also trying to make a decision on the stroker or AMC 304 build.