73 CJ5 304 with Holley 2 bbl

[gtocj5]

Just picked up a 73 CJ5 with the original AMC 304 with 75000 miles on it. It runs good but the first tank of gas I used I got just under 8 MPG. This was all in town easy driving. My 67 GTO 500 hp run hard gets better than this. Is this what I can expect or do I have a carb issue? Jeep has 33s on it , 4 speed. Anything I can do to get up around 12-15 in town?

 

[derf]

First thing to do is to make sure your speedometer (and hence, odometer) are reading correctly. Find a nice straight stretch of road and run exactly one mile on the road (using mile posts or GPS), checking to see how much your odometer has reported. If that's off, your mileage calculations will be off by the same percentage. It's possible to correct that by swapping out the speedometer drive gear in the Transfer Case .

Second thing to do is to give it a thorough tune up. Plugs, wires, cap, rotor, carb rebuild, check all your vacuum lines, vacuum tune the carburetor and distributor, etc. When I bought my J10 pickup, it was getting around 8 MPG. After I rebuilt the carburetor (including putting in a missing gasket on the power valve), fixed a lot of vacuum problems, etc. I was able to get it up to 12. And that's a heavier truck with a 360. There's no reason you can't get good mileage with the AMC 304 in a much lighter CJ.

 

[gtocj5]

Already checked that out. Speedometer etc is working fine. 1 mile equals 1 mile on odometer. Carb was rebuilt professionally appx 1 year ago. New plugs and wires, Has points dist but parts are fresh. Checked all of this thats why I am asking if 8 mpg is what I can expect from this rig. Would changing carbs help? I know a Holley 4bbl on my GTO sucks gas and actually runs no better. So I was thinking of getting rid of the holley carb what do you think?

 

[derf]

Already checked that out. Speedometer etc is working fine. 1 mile equals 1 mile on odometer. Carb was rebuilt professionally appx 1 year ago. New plugs and wires, Has points dist but parts are fresh. Checked all of this thats why I am asking if 8 mpg is what I can expect from this rig. Would changing carbs help? I know a Holley 4bbl on my GTO sucks gas and actually runs no better. So I was thinking of getting rid of the holley carb what do you think?

I found that a professionally rebuilt carburetor on my truck was missing the power valve gasket so that could still be an issue with yours.

I'd go through the tuning again. Make sure the idle is set right, both with the distributor timing and the idle settings on the carburetor. Being a Holley, you may want to check what power valve is in there and make sure it's right for your engine. You could be running too rich.

Honestly though, I'd consider a rebuilt Motorcraft 2100/2150 to replace that Holley. It's one of the better carburetors out there and runs very well with the AMC 304 . AMC picked that carburetor for a bunch of good reasons. There's really no reason to go with any other carburetor for that engine. The only reason to get rid of it is if you're swapping in fuel injection.

 

[gtocj5]

Thanks for your help. I was also thinking about switching to the 2100/2150 carb. Is a wrecking yard the best place to look and then do a rebuild?

 

[gtocj5]

Also will I run into linkage issues with a new carb, my jeep is also setup with a hand throttle on the shifter arm. Works great for crawlin when you need both feet on cluth and brake.

 

[derf]

Thanks for your help. I was also thinking about switching to the 2100/2150 carb. Is a wrecking yard the best place to look and then do a rebuild?

I haven't searched for a 2150 in a long time. I imagine a good wrecking yard would be able to get you something that you can rebuild. I wouldn't know what to look for other than a V8 CJ but I'm sure there are plenty out there.

It may be worth your time to just grab the first carburetor you find and use it as a core for a remanufactured unit. Then you know you've got the right carburetor with the right jetting and venturi size for your Jeep.

As far as linkage issues may go, that's hard to answer. It all depends on what the previous owner did to the linkage in the first place.

 

[gtocj5]

Thanks

I found a guy who rebuilds these and can set up to my specs. Looked at the linkage on the Holley and shouldnt be a problem to do the same or similar on another carb. Just do like I did on my GTO. Just read, learn, then just take it apart with notes and pictures, then rebuild or replace. Learn as I go.

 

[GoldenEagle36]

Thanks for your help. I was also thinking about switching to the 2100/2150 carb. Is a wrecking yard the best place to look and then do a rebuild?

i have an old motorcraft stock 2 bbl that came on my CJ7 AMC 304 , it does need rebuilt, PM me if you would be interested

 

[gtocj5]

I appreciate the offer but found one local.

 

[johnbilt]

Hmmm. My 73CJ with the AMC 304 2bbl got around 15 mpg. Not sure why yours would be so bad. Is your front axle unlocked? Good Luck

 

[gtocj5]

Yes it is unlocked, sure wish I could get 15 mpg in town.