Been Trying to get my old 239 Flattie tweaked and runnung prime and eliminate weak links. AS you may know,some of the areas I have updated or repaired on the fuel side are,.. new SS tank, new lines, in line filter, the carb was rebuilt by PO and I checked the powervalve seating,I also repaired a hole found in VAC line between carb and dizzy. Ignition side we got new points,condensor, dizzy cap, wires, plugs, and rotor. I got a pretty toasty original Dizzy in it,...old,and tired. Its a 6 V poss ground system.
Up to this point its running 95% good. It was running like crap before these updates and now it will,... once in a while, spit under load, if pressed in 3rd gear up hills.
I got a much cleaner dizzy to put in but I also picked up a real clean, rebuilt carb on ebay. ( D carpenter, and Macs were out ) and the seller has great rating and tons of sales.
I put the new carb on , adjusted idle screws and idle but it bogged down as soon as its given gas,...it would recover but bogged down ever time its given juice. I checked the timing and it was out of wack. I am guessing here but I am thinking this new , totally clean carb unit has a whole diifferent vacuum pull, and it set the vac advance on the dizzy off????. I set the timing up, and the bogg lightened up but it dont run strong like it did with the old carb on it and its sputtrtin more under lighter load.
ANYWHO, I am thinkin,...put the old carb back on so it runs half way decent for you , and then put on the updated dizzy. ANY IDEAS OUT THERE.
Is there and expectation that a new/rebuilt carb will need to have adjustment done to it other than Idle issues? I assumed rebuilt meant trouble free and I didnt think I would need to pull this rebuilt carb apart . Should I just leave well enough alone and just deal with the kind of rare load sputter?. The old dizzy really needs to go. What do you guys think? John

 

Hi John,

Well, a couple of over all answers. First, vacuum is generated by the engine and it is constant (provided you don't damage or change something in the engine) irregardless of what periferals you change (unless of course one of them has a leak).

It is possible though that the old carb may have had some gunk in the vacuum portion especially considering that you vacuum line was rusted trough - that stuff went somewhere. So it is possible that now you have a less plugged line and it changed the advance.

When you put a rebuilt carb on, the mixture has to be adjusted because that is specific to your engine and the amount of vacuum it produces/fuel it requires. But never assume for a moment that any new or rebuilt part you buy is good. On that carb, the floats should be correctly adjusted and it should be clean. But that's about it, and I'd question that if it's been sitting in the box on the shelf for awhile if perhaps it hasn't dried up a dash. I always rebuild my own and highly scrutinize the needle valve tips.

Your engine is an "interlocked" machine with all the fuel and ignition item balanced to one another. So any time you change one you need to readjust them all. You'll have to do that when you replace the dizzy too (you ought to be able to adjust all this stuff in your sleep at this point -tee hee).

I like the idea of putting the old carb back on and getting it back up to speed then doing the distributor. You don't want to have two areas where you have possible problems due to changes in two areas. With the old carb, you will know that any adjustments you need to make when replacing the dizzy have come from that replacement, and not the possibility of a troubled carb as well.

Maybe just for giggles and grins, you could rebuild the old carb later yourself and reinstall it just as a comparison. Some carbs are just plain shot and will not rebuild...hopefully you didn't get one of them. And of course this guy may have tried to rebuild it himself and totally hosed it up. You never know until try it on the car, but I have to wonder why the seller was selling it at such a good price (I know, I'm such a skeptic)

And just one more word of advice. You are getting to the point where you have replaced a lot of stuff and the truck is running well. You are going to have to drive it a bit, get it hot, burn out the gunk. Don't replace stuff just because it's old.."if it's not broke, don't fix it."

Do you have a vacuum gauge? If so, read through the types of tests and indications it will give you. If not, it's time to get one. They are generally aroud $25 for a basic gauge and a very good investment at that!

Julie!

 

Are thier other adjustments on/in the carb, other than the idle screws,I need to consider? If so were are these adjustments made and how? The new carb does have a more vacuum air sound to it than the old one.
I am with you Julie on puttin the old carb back on, do the Dizzy and then go from there. Yea ,...I do assume that these parts are automatically perfect from the get go.

 

Is there a tag on the new carb with specific ID? There were different calibrations for different models the carbs were used on, but they aren't that different. I suspect tho that the rebuilder doesn't change the jets that come in on the core. If the carb was used on a multi-carb system, it may be jetted wrong for single carb use. You should have at least #50 jets, more likely 51 or 52. Fuel level in the bowl should be per specs. No good way to check where it actually is when running, but if you relieve pressure in the fuel line going to the carb, take the hose off at the carb, then remove the upper air horn assembly, it's gonna be close enough. It sounds like you're running lean, or getting no advance out of the dizzy.

If it runs but is a dog, it's likely fuel related.
If it sputters ocassionally but otherwise is peppy, look at the ignition. Check your points gap and your advance. 6v condensers are notoriously crappy these days, right out of the box. That's why I went 12v (one reason anyway). Some folks get a big Radio Shack condenser rated for 600v and the correct capacitance and mount it at the coil.

 

john, like julie said, change only ONE item at a time! this way you know what worked well and what did not. ross is very correct on condensors!! if it's made in argentina---THROW IT OUT!!!!!!!!! usa made only!! the foreign made items will break down very fast, at different loads. usually, if condensor is weak, it will burn points.

 

do i have to change my condensor if i converted to 12 volt and if what do i use thanks elliot

 

parts plus, local supplier, had part # bor-G97, usa made

 

I put the old carb on this morning, set the timing and went for a 40 mile ride. It ran real decent. I got half a mind to leave the old dizzy in it, but its has seen better days. I guess I can put it in and see what happens like with the carb swaps.