AFB rebuild question

[HP2]

I've got several of the newer Carterbrock style AFBs lying around. A few of these are gummed up so bad the linkages wouldn't move. Dunked one in carb cleaner for a week and it loosened it all up, so I tore it apart for a rebuild. Because of its condition, I removed the throttle blades and shafts. Now that it is going back together, I noticed two grooves on the primary throttle shaft, seemingly for some o-rings. I don't recall seeing any material on these during dis-assembly. There are no similar grooves in the secondary shaft. None of the books or diagrams I have show the carb di-assembled this far to give a view of what goes in these grooves. There also appears to be grooves in the main body primary shaft bore, but they don't necessarily appear to line up with the grooves in the shaft. Should there be an o-ring or seal of some sort on this shaft?

2nd thought, anyone ever run these style AFB without the air valve door in place? Are there any drawbacks/advantages to doing so?

[UKcuda]

Well I don't know about the Edelbrock ones but I've played with proper Carter AFBs quite a lot and I like them, but I don't remember ever seeing O rings on there 

I would say if you remove the secondary air valve it definitely won't work out unless you somehow rig it like a Holley double pumper and even then it's dubious - why bother?

[jimynick]

I'd recommend looking at the schematic that comes with the rebuild kit as well as the parts list in it to see if they list/include any O rings in the kit. You could remove the secondary air valve- that's why they call them AVS's, but unless you're running it on a race engine, it'll bog, badly. The air valve is controlled by the vacumn shown the carb and will open the door as the engine can take it. Best leave it on or you're back to the old AFB. 

[UKcuda]

............. You could remove the secondary air valve- that's why they call them AVS's, ..........

No offence, but the OP is asking about AFBs, he is not asking about about AVSs which  are a different design altogether.

And even if he was asking about AVSs, your statement makes no sense;  they are not called AVS because you can remove the secondary air valve, they are called AVS because it stands for "Air Valve Secondaries".

If it stood for "you could remove the secondary air valve" they would be called YCRTSAV.

[dodj]

If it stood for "you could remove the secondary air valve" they would be called YCRTSAV.

[jimynick]

None taken UK, but I guess you missed the hyphen between "you could remove"  and" the air valve...", maybe it's a grammatical, ESL thing. Since you appear to be expert on AFB's perhaps you could let us know which AFB had an air valve; all the ones I ever had/saw never did. The AVS was the follow-on carb design to the AFB for the reason I mentioned.

[UKcuda]

......... I guess you missed the hyphen between "you could remove"  and" the air valve...", maybe it's a grammatical, ESL thing.

Wha?  But you didn't put a hyphen between "you could remove"  and "the air valve...".  I just cut and pasted what you said, look I'll do it again:

"......You could remove the secondary air valve- that's why they call them AVS's......"

Since you appear to be expert on AFB's perhaps you could let us know which AFB had an air valve; all the ones I ever had/saw never did. The AVS was the follow-on carb design to the AFB for the reason I mentioned.

Well I would hesitate to say I was an expert, but I think I can see where you are coming from.

Since the OP stated his carbs were "Carterbrock" AFB design I was assuming he was referring to the valve on the AFB which sits below the boosters rather than the valve on the AVS which sits above the boosters.

A lot of people would say that all the AFBs have an air valve, but I think I can see your point, officially the AFBs don't have an air valve because the official name for the air valve in the AFB is the "velocity valve" whereas in the AVS Carter actually called the valve the "air valve". 

As Carter carbs the AVS replced the AFB as you say, but as Edelbrock creations (ie. Performer and Thunder series) the manufacture of both designs has been concurrent.

So if the OP was referring to a valve above the boosters then he has either Carter AVS or Edelbrock Thunder series and he shouldn't have said AFB, but if he was refering to a valve below the boosters then he was right to say AFB, but you can argue at a refined level of nomenclature that he was technically wrong to use the expression "air valve".

However, you are still wrong to say that removing the air valve on the AVS puts you back to the old AFB design, because the AFB would still have the valve below the boosters whereas the modified AVS would not.

[HP2]

Well, the exploded diagram I have calls it the air valve. I suppose you could call it the air door, but since I have AFBs, it is under the secondary venturies, not on top. http://www.edelbrock.com/automotive_new/mc/carbs_acc/pdf/carb_owners_manual.pdf  scroll down to page 26, part #42, air valve and weights. The removal was mostly a curiosity question. So the impression I get from this conversation so far is that without a secondary squirter, removing this valve/door/flapper can create a bad bog on a street application but may work out fine on a dedicated race engine that lives above 4500 rpm most the time. Yes?

Similarly, you'll note in the above referenced diagram, which is included in all the rebuild kits, they do not show the throttle shafts removed. I actually have one of the older SA Designs Carter books from way back before even the Weber days. No where in there do they show the throttle shafts removed and they actually go so far as to say do not remove them because the throttle blades screws are swedged to avoid them falling out and removing them overrides their ability to stay in place. Since this particular carb had the throttle shafts gunked shut and they would not move, I wanted to removed them and verify there were no issues in the bores. So it sounds like there are no rings or seals in these shafts to worry about.  I'll put them back together and make sure the baldes align tightly to the bores and call it good.

[UKcuda]

So the impression I get from this conversation so far is that without a secondary squirter, removing this valve/door/flapper can create a bad bog on a street application but may work out fine on a dedicated race engine that lives above 4500 rpm most the time. Yes?

Basically yes, if you boot it without the valve/door/flapper in place the fuel circuits won't be able to react fast enough to the sudden gulp of air that will go down it.

[jimynick]

HP, I suspect the grooves may just be old fashioned lubricant retainers if they don't take a o ring. Maybe a wee bit of graphite based lube and don't forget to re-stake the throttle blade screws! Sticky wicket, what! 

[HP2]

Graphite lube, thats a decent idea, thanks!

I used blue loctite on any screws in the air flow path, so all the throttle blades and choke components got it.