carburetor options, help me decide

[elwood blues]

Here's what I've got; a 1978 with a mildly built (cam) AMC 258 i6 / 4.2l . Stock it came with a single barrel Carter YF. The stock single barrel intake has been replaced with a stock 2 barrel intake off of a '79.

Currently I'm running a Barry Grant DEMON 350cfm 2 barrel on the 2 barrel intake. It's running way too rich, and has a stumble at low RPMs. Now, this could be a fairly simple tune job, but I'm a little concerned that this is not the correct carb for me.

I also have an Autolite 2100 1.14 sitting on the shelf, I was running this carb until I started the engine tear down, I believe it either needs rebuilt, or sent in somewhere to be remanufactured.

Also sitting on the shelf is a Holley 390cfm 4 barrel. Unknown mileage or condition, I traded a guy at work for it for two dozen of my wife's homemade chocolate chip cookies.

I also have a Clifford aluminum 4 barrel intake manifold, no not on the shelf, it's on the floor

So, if it was yours to do, which way would you go? I'm really on the fence and would like you all's advice, thanks

 

[tjmons]

I had the same problem with mine running rich. The PO installed a Weber. After researching this site , I found that the Weber needs 3.5 psi fuel pressure. The stock fuel pump puts out 7 to 10. I added a fuel pressure regulator and all the issues are gone. The CJ never ran any better. Not sure if this is your same problem.

 

[IOPort51]

MC2100 hands down. cheep. easy to build and tune. simple.

what needs re manufacture??

the 4 bbl is interesting though. Do you think you can keep your foot out of it??

 

[elwood blues]

I had the same problem with mine running rich. The PO installed a Weber. After researching this site , I found that the Weber needs 3.5 psi fuel pressure. The stock fuel pump puts out 7 to 10. I added a fuel pressure regulator and all the issues are gone. The CJ never ran any better. Not sure if this is your same problem.

Interesting, I never thought about fuel pressure, I just assumed it needed tuned to my engine, I'll do a little digging on that.

Thanks.

 

[elwood blues]

MC2100 hands down. cheep. easy to build and tune. simple.

what needs re manufacture??

I think it was leaking internally somewhere, if I shut it off and trying to start it within 15 mins or less it would act like it was flooded.

the 4 bbl is interesting though. Do you think you can keep your foot out of it??

Most of the time, yes, I think I can

 

[tjmons]

Thats exactly what mine would do. I could smell gas and would have to hold the pedal to the floor. It was also leaking from the base of the carb. All issues are gone now

 

[rr41mag]

If I were you I would mail that old nasty clifford 4bbl intake to me. I personally lie the stock carb.

 

[1979cj71ton]

I ran a clifford intake with a 390 holley and a long tube header and never had any problems with it hot or cold. It worked really well even in the woods on rough trails.

 

[gert]

well you just cant beat FOMOCO carb since you can find a rebuild kit in every single town in USA and they are easy to work on, i have no experience with the Demons, the Holley you can rebuild pretty quick almost anywhere but not quite as easy as the 2100, is the ethanol giving you fits yet? My old Quadrabog would foul up and idle crappy from junk clogging it up, didnt do that prior to the ethanol craze, might be whats wrong with your MC, just junk gas

 

[thiswontbetooexpensive]

Ethanol has been the downfall of many a good vehicle these days. Total lack of power and poor performance. I had a 2009 Chevy truck that would die for no good reason on occasion. I had to do some premature cleaning out of the fuel system and that might be the case here as well.

Good observation!

 

[elwood blues]

If I were you I would mail that old nasty clifford 4bbl intake to me. I personally lie the stock carb.

rr41mag, maybe... Give a couple more months, I might sell it too you for a steal.

I ran a clifford intake with a 390 holley and a long tube header and never had any problems with it hot or cold. It worked really well even in the woods on rough trails.

1979CJ71ton, I have a couple of questions for you. Did you have power brakes or power steering? That's the two big things I can't figure out, other than tapping the Clifford manifold for the vacuum that the power brake booster needs. Also, with the Clifford intake manifold there is nowhere to bolt up the power steering pump, any help is appreciated.

 

[elwood blues]

Quick update to this; like I just posted in the previous post, the Clifford as awesome as it could be, has some very big downfalls. There is no port for the vacuum port for the power brake booster. Also, there are no molded bolt holes for the power steering brackets. The vacuum port could be as easy as drilling and tapping. It is aluminium after all. But, the lack of power steering pump bracketry could be a killer. Also, I'm still running a stock exhaust manifold (except the internal baffle which I removed and plugged) the Clifford manifold has no provisions to bolt to the exhaust manifold, not that big of a deal, I've got a friend fabricating a 1/4" cover plate for the exhaust manifold. Just something else to deal with.

Looking at the Offenhauser 5999DP, it has all of the ports and bolt holes built in to the casting, it looks looks like it would work really well. #1 HUGE problem, the PO cutting it up so it would fit with a header. That creates a problem, same as the Clifford, stock exhaust manifold...

So, here's where I'm at, I pulled the DEMON carb off and put the Holley on. Wow, what a difference, my engine really likes that carb, now, if I could get it tuned properly... it has a really bad hesitation at low RPMs under load, adjusting the float helped some, it still needs dialed in. Yeah, I'm running a 4 barrel Holley 390cfm on a stock 2 barrel intake manifold. I think I'm going to post the Clifford and Offenhauser manifolds up for sale, and take the proceeds and buy a brand new Offenhauser, I think.

 

[1979cj71ton]

Elwood,i ran power steering and manual brakes. I used some aluminum flat stock and had it welded to the intake,then i just had to drill holes to mount the power steering pump to it. I sold that jeep before i bought this CJ7 ,as far as i know he's still driving it the way it was when he bought it from me. The hesitation could be the accelerator pump adjustment or the squirter nozzle is to small.The 390 came with a 25 cc squirter stock,so you might have to go to a 28 or 30 to get rid of the bog.

 

[elwood blues]

1979cj71ton;

Thanks for the info, both about the Clifford manifold and the Holley carb

 

[elwood blues]

Double checking for vacuum leaks, I realized that I missed a vacuum port, the manifold vacuum port under the float bowl

This one



So, I capped it off, fired it up, and took it for a ride. It ran pretty well at speed and any RPM above 1000. Low idle it was still sluggish, but manageable. But, when I brought it home and pulled in the garage it would not stay running at idle. For the life of me I have no ideas. It would stall, I'd pump the gas, turn the ignition and she would fire. It would idle for a couple of seconds, then it would stutter, the idle would drop down to 500 or so, then it would die. I checked vacuum lines, fuel lines, filter, I had no idea.

I pulled the negative terminal off of the battery and and walked out of the garage, I leave on Saturday for the next month for training, I'm not screwing with it any more before I leave, I'll deal with it when I get home.

 

[1979cj71ton]

How is your distributor hooked up to vacuum ? If you had it hooked to manifold vacuum or no vacuum,your base timing and the advance could be off.That might be why it stalls at idle. Just a thought...