Ok, so some of you may realize by now that I tinker too much.  I have a problem, I admit it!  A friend of mine who was giving me an old Autolite 4100 that he had laying around, also gave me a 625  Carter afb.  It needs a kit, & this is the one carb I have never toyed with.  I've  built dozens of all the others for fords, scrubs, smodges, etc.  Everything from 2bbl Rodchesters, q-jets, holleys, 2bbl carters, all autolites.  Looking into the afb, I love the on paper flexibility (as I am learning), of the different rods & associated springs to alter the fuel curve to fit engine & chassis combo.  I also love the fact that the carter 625 cfm has the exact same primary venturi & throttle plates as the carter 500 cfm.  With my f-100 with the ported heads & straight up e-4 cam, throttle response has been an issue with big carbs off the line. 

My question is for those of you who run The AFB style carb & who are familiar with the tuning of it, what combo of jets, meetering rods, & the meetering rod spring(?) did you end up with?  I haven't any Idea what this carb came off of, so chances are it will be way off & I'd like to see what worked for other y's. 

Does anyone run this carb??

Or should I ask, does anyone who does care enough to share their info?

Well I'll be glad to share my limited info.  The Carter AFB on my engine is their number #9635 which is for GM applications and rated at 625 cfm.  When I got it, the metering rods were missing along with some external linkage.  I bought another carb, a #9637 (Ford) core unit and took the metering rods out of it.  Anyway I've got it on my 312 and I really like it.  It had a hesitation at first when I hit the throttle, so I reduced the accelerator pump travel and the hesitation is gone.  Ted has written some of the advantages of the Carters and edelbrocks over the 4150/4160 Holleys, so I won't repeat all that.  I've run two Holleys on this engine, a 600 cfm and a 465.  The Carter can sit for a week or so, and then start right up without having to crank for 30 seconds or prime the carb before cranking.  I can floor the throttle at any rpm in any gear and it is smooth and ready to rev.  Mileage is also better than I got with the Holleys.  I haven't changed any springs or metering rods, although it is easy to do.

What is the model number on your carb, by the way?  Good luck with your Carter.  Nick Brann

Stake,

           Not sure it's indifference to your question, most likely nobody has altered one from stock. See if Edelbrock will tell you the original numbers for the carb and the recommend a combination for a 289. Should get you started.   

Frank/Rebop

Bristol, In ( by Elkhart) 

Nick- Thanks for the info.. I also have aquired the same carb. 9635.  Also looks to be an original gm app.  I was able to modify the throttle arm to allow my truck linkage to bolt on.  (thank god it fits!)

I've rebuilt it & test started it & ran it some & it sounds real crisp.  I do need to swap the pcv line to the front of the actual carb & put my modified 4 hole spacer back on & chuck the open one.  (was using an open one for the pcv fitting)  The carb doctor has some info posted that says to make sure & use the front large vac. fitting for pcv.  I'd guess since it is closer to the primary's it will ballance out the mixture changes as the pcv valve intermitently lets in extra air & won't cause a sudden lean condition, thereby dropping manifold vaccumm & affecting the power pistons & the meetering rods depth, thereby affecting the ovearl mixture... yada yada.

Thanks Frank.  Yeah, it doesn't look like anyone on this site plays with this carb too much.  I guess I'll have to pick up the tuning kit & start playing with rods & springs. 

I presume that the tuning kit comes with some sort of jet screwdriver that you might be able to change out the main jets without pulling the top??  Would be nice.  I don't enjoy standing on my head with one knee on the valve cover & the other up my..well, you get the picture!  I used to spend hours under the hood all contorted when I was 15.  All the old guys would say, " I wish I could still get up under the hood like that"; Now I feel like I understand!!

I see jet sizes batted around pretty freely without the specifics to the exact carb that’s being used.  A Carter 625 will not necessarily be the same jet/rod combination as an Edelbrock 625 and likewise, there are several models of the Carter 600 which all vary in their stock or as delivered baseline jetting.  Exact model numbers on carbs get important at this point as air bleed sizes and fuel circuitry within the same cfm rating will differ and in turn will dictate different jet sizes and hence different model numbers.  This is also true with the 600 cfm Holleys as there are a multitude of them with this cfm rating but different model numbers and subsequently different jet sizes to go with the different circuitries.  As a rule, always begin any tuning with the stock or as delivered jet sizes as a starting point as these jets are generally in the ballpark.

 

On my ’55 Customline with a mildly hopped up 272, I ran a 500 cfm Carter (Model #9503) and ultimately ended up with  0.073 X 0.060” metering rods and 0.092” jets in the primary side.  This gave good all around performance and decent fuel economy but this jet/rod pairing is for this particular application and likely will not work as well if at all with other size or model AFB carbs.  Like has been said, the AFB carbs are very flexible in their tuning capabilities and in certain areas, much more tuning friendly than the Holley carbs especially when it comes to everyday street driving.

 

When dealing with the Carter AFB carbs, it becomes important to know how to calculate the effective fuel surface areas at the jet when dealing with rod and jet combinations as the two typically have to be changed at the same time for fine tuning purposes.  Just changing the rod or the jet without consideration of the other can be a drastic fuel delivery change and can easily be too much or too little fuel.  But after saying this, the metering rods can be changed without removing the carb top which makes it quite easy to make some quick primary side jetting changes without any serious carb dissassembly but fine tuning typically requires both the jet and rod to be changed.  Power valve springs can also be changed quite easily without carb dissassembly as well as altering the fuel curve for the power enrichment circuit.  Changing the secondary jets still requires the top of the carb to be removed.  Many of the newer AFB’s will require Torx style screw drivers in which to access the metering rods, power valve springs, and to remove the carb top.

Lorena, Texas (South of Waco)