a lot of extra power from a 258CI inline six CJ7

Ditch the K&N -they pass a lot of dirt. I can't see you getting 250 hp without changing the cam and pistons to much higher compression ones. The

4.0 litre head is meant to be good for another 40 hp so I have read. Most interested to see your results.

Dave Milne, Scotland '91 Grand Wagoneer, '99 TJ

Good luck, be interesting to see the results

Well............

I am running an 86 with an Accel SuperCoil for hot spark, the timing advance 'ported', the stock Weber-Carter BBD carb unplugged and manually set up, the 'Nutter Bypass' or no emissions computer working, stock manifold with a straight 2" pipe back to a Dynomax 'Super turbo' high flow muffler, 3.31 gears turning 33" mud tires. In Canada it is a Utility vehicle and don't require a Cat.

I get a sweet 23 US mpg running at 65 mpg and passed the last emissions with 15 ppm HC and 0.16% CO.

1st gear will light up my 33's way too easy when turning onto a 40 mph road so I have to watch the pedal, 2nd pulls 'fast' up to 50 mph turning 4400 rpm, 3rd is the power gear and hauls hard up to 75 mph or so, 4th buries the needle easy and no freakin' way do I want to find out how fast 5th goes.

My speedometer is exact according to many checks with a GPS.

My total cost was about $45.00 for the Accel coil. The Nutter which puts the computer to sleep cost a couple bucks for wire, solder and heat shrink and gave me a sweet 25% seat of the pants power and mileage boost with at least a 10 mph increase in each gear and the ability to actually get the rpm up to the top at 4500 for the 'red line'.

I think the biggest boost anyone gets from 'any' mod to the engine is because the computer has to be put out of it's misery for 'any' mods.

New carb = kill computer = instant 25% power boost.

New Fuel injection = kill computer = instant 25% power boost.

MSD Ignition = kill computer = instant 25% power boost.

Or you can just stay stock and kill the computer = instant 25% power boost!

I wish you luck and will look forward to reading about the improvements you hope for.

If or when I modify anything I will pay close attention to performance increases. I think my 2" exhaust could use a set of headers and a 390, but my manifold isn't broke and my carb purrs so I have no urge to upgrade it. It runs pretty sweet for me now..... :-)

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

CJ7 Casey wrote:

"and a 390" what do you mean?

an AMC 390 v8 ? If I remember Bill 3 correctly, they came in the AMC Rebel or was it the Javelin ? They also did a 401 in the J series FSJs.

Dave Milne, Scotland '91 Grand Wagoneer, '99 TJ

appreciated.

The Holly 390 referred to in the original post. The larger exhaust with headers is a waste and can lower torque sometimes if you don't have a matching intake upgrade. A 390 is borderline too big for the 258 I think but is the best match if you don't like the BBD's.

Mike

Pi-eyed Piper wrote:

No no, I 'like' my 258, it hauls butt nice and gets decent mileage and when I had a choice during the frame up rebuild, I stayed with one.

The 390 is the Holly the OP was talking about that goes with the larger exhaust is what I was referring to.

Mike

Dave Milne wrote:

Someday I might want a Jeep 'toy' like that, but mine is still my daily driver. I 'like' the power and mileage I get from the 258.

Mike

"L.W.(ßill) Hughes III" wrote:

so with a 2.25" header and a new carb (sans pollution crap) am I going to be over exhausted?? or will the carb keep up

improvements

That setup is supposed to behave well although some Holly's have issues on inclines I think I read here. Some folks opt for a Weber.

I don't feel over exhausted with 2" and I did have stock to compare, got a boost I think, so I don't think the 2.25 would be overkill.

Mike

Pi-eyed Piper wrote:

that engines so clean...nothing like my leak box

Bill, I still get really good performance from the old thing so I really have no urge to upgrade it. It is super easy to toss a $20.00 carb kit in it every couple years and it goes like a scalded cat still with 23 mpg.....

It is easy to set the mix and passes emissions set up manually as is so why screw with it eh?

Mike

"L.W.(ßill) Hughes III" wrote:

I have an aluminum cover.changed the gasket, didn't leak for a couple months.

It's not leaks! It is "external oiling" :-).

Carl

I guess...it burns no oil but I swear there's a freakin gallon under the hood,