[wswartzwel]

I recently replaced the stock carb. on my 81 CJ7 Laredo 258 6 cylinder with
an MC2100 (108 stamped in the carb body) I do very little off roading, and this is my daily driver. I was getting 15-17 mpg with the stock carb, but it ran like crap and was hard to start.... Perhaps I should have just rebuilt the original carb, but after seeing the rave reviews here on the MC2100 swap, I figured I would just go that route. I got a carb from a friend for free, rebuilt it, got the adapter plate, and did the swap. The jeep starts and runs great... Just bump the key and it starts and idles smoothly. My gas mileage has dropped to 13 mpg however.. The main jets in the carb were stamped # 57 if I remember correctly. Has anyone experimented with different jets? Is it possible to adjust the metering rods on this carb? How about lowering the float level?

Thanks so much,
Bill

[CJ5_Fan]

Originally Posted by wswartzwel

I recently replaced the stock carb. on my 81 CJ7 Laredo 258 6 cylinder with
an MC2100 (108 stamped in the carb body) I do very little off roading, and this is my daily driver. I was getting 15-17 mpg with the stock carb, but it ran like crap and was hard to start.... Perhaps I should have just rebuilt the original carb, but after seeing the rave reviews here on the MC2100 swap, I figured I would just go that route. I got a carb from a friend for free, rebuilt it, got the adapter plate, and did the swap. The jeep starts and runs great... Just bump the key and it starts and idles smoothly. My gas mileage has dropped to 13 mpg however.. The main jets in the carb were stamped # 57 if I remember correctly. Has anyone experimented with different jets? Is it possible to adjust the metering rods on this carb? How about lowering the float level?

Thanks so much,
Bill

I would verify the jets... for that size throat (108) you should be running 44 to 46 not 57s. Also, make sure the powervalve you have in your carb is matched to your current motor HG levels or your MPG will suffer because the enriichment circuit will be open by default all the time.

[motojoe]

Originally Posted by CJ5_Fan

powervalve you have in your carb is matched to your current motor HG levels

"HG level" ???

I get about 10 MPG with my MC2100(108) with my 258 I6 Auto.

[CJ5_Fan]

Originally Posted by motojoe

"HG level" ???

I get about 10 MPG with my MC2100(108) with my 258 I6 Auto.

The HG level is the vacuum measurement. Most vehicles have a consistent vacuum reading at idle, and another under load. The powervalve is rated in HG also. You want to ensure that whatever you constant load HG level is, the Powervalve is set 2 below. That way your dont have it in the open position until you step on the gas aggressivley and force a drop in vacuum that signals the enriment circuit (via the powervalve opening) to exponse its ports and therfore enrichen the mixture.

[wswartzwel]

I replaced the power valve with a new one when I rebuilt it.. I did not see any adjustment... Could you explain how to set it? I have Mercury guages so getting readings should not be a problem.

BTW Thanks so much for taking the time to respond.

[wm69]

You're running jets that are too big. You should check your vacuum at idle, divide that number by 2, then subtract 2 from that number.
My vacuum reading was 23, divide that by two and I get 11.5, subract two from that and I got a 9 holley power valve at the local oreillys. Then I discovered that I had a two stage power valve....

Anyhow, I'm in fayetteville and I'm running 47's and still running a bit rich, so if you're in conway and running 57's your jets are waaaay to big. Swap your jets to 46's or 47's, check your vacuum at idle, get a new power valve (they aren't adjustable, but they are only about $7 for a new one) and then you should see an improvement.

[wswartzwel]

Thanks So Much!

My Jeep sees Fayettville ocassionally, when visiting my daughter at U of A.

[wm69]

Originally Posted by wswartzwel

when visiting my daughter at U of A.

Is she hot?












Just kidding. I'm married with 2 and 4 year old girls. I DREAD my girls getting older, and can't even fathom then in college.
They've each already picked out one of the Jeeps that they think are theirs.
Anyhow, take a vacuum reading at idle to figure out what power valve you need, I'd try some 47's as far as jets go, and then you can fine tune with your mixture screws and that thing should run like a top.

[wswartzwel]

Where would you suggest I go to buy Jets??? I don't think local autoparts stores carry them.


Yes your little girls will grow up... She took my bronco... I told her sister that my jeep was off limits

[OldSailor]

You should be able to get jets at any decent auto parts store, like NAPA. If you don't have any local, you can order them from Summit or Jegs.