High performance jeep 258 six

What are the most desired performance characteristics for a Jeep engine? If we took a survey, the list would probably look something like this: 1. Instant throttle response and resistance to stalling. A usable rpm range from idle to 4, rpm, with loads of torque. Stock or better fuel economy. If the 4, rpm figure sounds low, conduct your own survey and count the number of times in a month you exceed 4, rpm.

If it's more than just a couple times a month, then you're either running a competition rig or are a dedicated lead-foot. The fact is, most off-pavement driving is done slowly, sedately, and under 3, rpm, unless you're in the mud, cinders, or sand. Spirited driving usually takes place on the street from stoplight to stoplight. Even then, 4, rpm is rarely exceeded. What launches your Jeep so nicely is torque, and if you tell the truth, it's that nice launch you want during those moments of leadfootedness.

A replacement cam is near the top of many Jeepers wish lists, but would you believe that most factory cams can equal aftermarket cams in dyno tests of torque up to about 2, rpms? The stock cam exhibits most of the desirable characteristics listed above.

Here's a reality check for you. Unless you need a new cam or plan a lot of other engine mods, the stock cam is a cost-effective choice. Making a Cam Choice Even simple nonengine factors can affect your cam choice. Gearing and tire size are two factors that immediately come to mind because they can change the operating rpm of your engine. Why is this important?

If you use your Jeep everyday, fuel economy is probably of some importance. An engine is most fuel efficient near the middle of its torque range. The ideal range is dictated by the cam profile.It continued to be used through in the Wrangler. It is basically a stroked engine.

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The great thing about this engine is it reliable, inexpensive, and has horse power and toque peaks at low RPM. The inline 6 I6 engine always came from the factory carbureted any many people complain about the Carter BBD carburetor and the maze of emmissions vacuum hoses.

There are a couple articles below that can help you sort through those hoses and tune the Carter BBD. For a carbureted engine, the with the Carter BBD performs very well off road.

The always came with a cast iron block and cylinder head, hydraulic lifters with non-adjustable rockersand 7 main bearings.

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It is very simlar to the used in ''86 CJs, but performance suffers due to emmission controls. The computer controls mixture based on an O2 sensor and other sensors.

how much HP can be pushed out of a 258?

The used in ''81 CJs, some used a 1bbl carb and some used a 2bbl carb. The used in ''78 CJs, J-series pickups, and Wagoneers, some used a 1bbl carb and lower compression than later s. Learning to Love Your : An easy fix for the most common idle problems with the 4. Leave a Comment: Name: Are you Human? Not a Spam Bot Comments:????

high performance jeep 258 six

Problem is the guy I bought the jeep from butchered all the emission stuff and allot of vacum lines have bolts or their just loose and open. The control module next to the battery was tested and they said it did not work right.Featuring the factory 4. The CJ -7 Limited was an upgraded package that added many unusual features to the standard CJ -7 of that time and only were built.

Some features included painted fender flares versus black fender flares, a chrome front bumper and chrome b. This is the Jeep Scrambler CJ you have been looking for. This CJ Scrambler is in great condition, ready to drive! It has been a garage toy all its life. This is a VERY nice driver that needs to be driven! Its part of a car collection on a farm. This is one nice ride. Call Gary. Jeep for sale. Great for riding around in woods. Big tires, newer front seats and newer back seat. Manual transmission.

LED lights on front bumper and side steps. Rebuilt with high performance parts including a Comp Cam, three speed transmission, transmission cooler, new radiator. Steel braided lines, magna flow exhaust. New LED headlights, new 33" mud tires. Soft Bikini Top, Soft doors and a windjammer.

Dana 44 axles, Dana 20 transfer case, CV drive shaft, slip yoke eliminator.Fully assembled 6cyl. Our 4. Engines are not painted. No more headaches with trying to get the factory plastic valve cover to seal!

high performance jeep 258 six

Shipping charges displayed when ordering will be incorrect. You will be notified of correct shipping charges before delivery. Rating Required Select Rating 1 star worst 2 stars 3 stars average 4 stars 5 stars best. Email Required. Review Subject Required. Comments Required. Year: Required Choose Options Please choose your year model pre Install Aluminum Valve Cover?

Current Stock:. Description Description Fully assembled 6cyl. Quick view. Our V-8 engines are completely rebuilt using quality parts, and come with On Sale. Choose Options. Shipping weights and dimensions: 2 x 30lbs 50x22x8 1 x 38lbs 35x26x Our 4 cyl.I have options, I have a 96 4. The i could just re-ring and drop a 4.

Pretty strait forward. Or; Take the crank and rods from the block and put them in the 4. With this one i would keep the 4. Im thinking the second one is a bit of a gamble on the balancing but i've put lighter pistons in small block chevs before and never had to rebalance, so ive been there done that. I'd like to see others' comments here My opinion leans toward the 4.

The stock 4. What's your expectation here? I'm intrigued about the block being tolerant of a 4. Was the only year this was the case?

high performance jeep 258 six

Not complicated, either way, and you do wind up with more displacement at a minimal expense. I would target 8. Of course, you do have the Holy Grail crankshaft, and that sweetens the whole idea of a 4. Are you planning on EFI?

If so, either displacement with MPI would be a strong performer. A with a 4. Even TBI is not the same as MPI, as the long plenum runners to the outer cylinders of an inline six create fuel delivery imbalance. Each will work, depending upon parts availability and budget.

As for balancing, I would talk to the machine shop. Presumably, you're also using the flywheel and damper. There's a distinction between weight matching and balancing reciprocal parts. Piston weight differences between and 4. The machine shop can confirm this. My understanding what ive read around the net is blocks are cast similar to 4.

The Chevy is easy compared to this motor as there is a ton of info where the AMC is bits and pieces here and there not always correct. I think im gonna do the head swap and the 4.The Jalopy Journal.

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Register now to get rid of these ads! The H. Anyone have or know anyone that has High performance parts for a AMC 6 banger, Working on a stock car with a inline 6 cylinder I know there must be some aftermarket goodies out here Thanks racinman Rick.

Rusty O'TooleMay 9, Thanks guys We are building a rambler into a dirt track race car Clifford is there, but pricey. What are the rules? The internal parts are good for rpm, but you're better off to capitalize on the low end grunt rather than rev the hell out of it. Isky makes a few. If you can use a later model head get a casting head. The has very clean cast ports, the ports need a lot of pocket porting work.

With the 4. ANY 4. You MUST use the 4. What about carbs and intakes? For street and wheelin' I always recommend the Offy Dual Plane. Keeps charge velocity up during low rpm operation.

AMC straight-6 engine

You might benefit from that on the dirt track, at least during take-off. But an open plenum intake will probably work just as well, maybe better.

Jeep 258 4.2L with Fitech fuel injection and Clifford Performance

I'd use a cfm Holley or a cfm 4V carb. For street I recommend a cfm carb the little Holley for gas mileage and a bit of power. Anything over cfm is usually a waste, but for all out racing some of the guys have had good luck with cfm carbs, and they are much cheaper than smaller ones.

It all depends on how you build. The smaller ones work better at low rpm, the works better for high rpm There is a harmonic vibration in all six cylinders at some point. The longer the stroke the lower the rpm. For the AMC sixes it's somewhere in the rpm range.

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You can run right up to that point and even through it, just don't run AT it. The point is only like rpm "wide". If you start getting engine vibration at say rpm, it will be gone if you just get up to Run between and for long and you'll beat out the bearings and possibly break a crank. The exact point varies with engine stroke and balance. No need to balance the six cranks -- they are inherently balanced by design one good of the good things about the I-6 design!So what do you do when you want to get some more power from a used six-cylinder without breaking the bank?

That is exactly what we aim to find out with this Jeep hop up. The chassis this particular 4. To find out just where we stood, the first item on the agenda was to run some chassis dyno baseline tests. In order to keep drivetrain stress to minimum during dyno tests we tested it in rear-wheel-drive mode using Third gear in Hi-Range. This minimizes tire and driveline speeds. However, keep in mind that power assessment is most accurate with the transmission in gear. Why so little power? The answer lies mostly in the heavy-duty drivetrain and large tires.

Basically, heavy-duty translates to less efficient in terms of drivetrain power losses. However, a more efficient drivetrain will not hold up to the extreme environment of rock crawling and 4x4 abuse, so that is the tradeoff. After the dyno baseline tests a cylinder leakdown test revealed the valves were in poor shape. So what does every hot-rodder do now? Well, the typical approach is to overhaul the tired cylinder head and slide a new performance camshaft in place of the old one.

Of course opting for hand porting the intake and exhaust ports of the cylinder head will yield even more potential power increase. So we went ahead and did just that. Build It Up For easier access we removed the engine from the engine bay. The cylinder head was then pulled and inspected for wear.

We found the kind of typical valve seat and stem wear that the leakdown test suggested. Other than that the head was in usable shape, and even the valveguides checked out OK. Next, the original cam was removed and inspected.


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