AFB Mods by ACR

[fugly]

This is a compilation of ACR's modifications according to white paper:
acr
Re: Posting Images of Work on AFB
« Reply #4 on: October 16, 2009, 11:18:42 PM »


The first photo below is what I saw when I removed the air horn, not a pretty sight. The venturi clusters & carb body were corroded & needed mild clean up with 240 grit, then 320 finger nail board.


The second photo shows the before & after work on the secondary venturi clusters, here I used a 320 grit board since
I didn't want to remove material, just clean up. I also used 320 grit paper for the underside of the cluster. Lot's of work
on the bottom side.


This photo shows the amount of corrosion, or poor casting that I cleaned up with a mildy worn 180 grit board, followed by 240 & 320. I had to be careful to keep the original lines & angles.


The next photos show the primary booster venturi with casting flash removed & 240/320 treatment top & bottom. I used Scotch Brite on the bottoms & insides that were hard to reach.


The last photo I need advice on. As you can see this cluster has a ridge at the top & side. Do I need to blend these in or..??


Fugly
Re: Posting Images
« Reply #5 on: October 17, 2009, 09:40:34 AM »

If you are talking about the one to the outside of the ring, it needs nothing as it has no bearing on flow


acr
Re: Posting Images
« Reply #6 on: October 17, 2009, 08:39:34 PM »

I mean the one at about 12:00 o'clock to 2:00 o'clock in the picture. It's right behind the nozzle of the booster venturi & is cast into the venturi cluster ring & sits up about .025". The 400 CFM are the only ones I've seen with this.


Fugly
Re: Posting Images
« Reply #7 on: October 17, 2009, 09:26:27 PM »

Blend the circled areas- the little nub on the bottom of the booster leg can be blended also if you want

Left side venturi cluster is a picture of the rough blended in work. Does it look OK or do I need to buy some A+B Epoxy?

Booster tube looks very nice-the back will work, but in the future simply file the ridge with a flat file to bring it down to the level of the rest of the ring. You don't want to disturb the shape of the entry any more than necessary- I have cutters I made to do this and still have to be careful....I would leave that one as is (no epoxy) and try filing the other one and lets see what you get


Fugly
Re: Posting Images
« Reply #11 on: October 21, 2009, 10:38:33 PM »

Very nice- you are going to have a nice carb


acr
Re: Posting Images
« Reply #12 on: October 22, 2009, 08:23:02 AM »

Thank you. One last question; What do you recommend for the choke horns (chokes are removed): 2-400 CFM AFB's, 18"x9"x3" air cleaner, Edelb. Air Gap 2x4 intake, mild plus build, 350 SBC., 2000 stall 700r4, 3.50 gear.

Leave stock height & radius?
Cut down to bottom of air filter?
Or other height?
I'll post pics of the air horn & carb when done.
Many thanks, Fred


Fugly
Re: Posting Images
« Reply #13 on: October 22, 2009, 10:27:42 AM »

what rpm range?


acr
Re: Posting Images
« Reply #14 on: October 22, 2009, 07:46:56 PM »

Mostly street driven, max apprx. 5800 RPM, shifts at 6000.

Fugly
Re: Posting Images
« Reply #15 on: October 22, 2009, 09:32:30 PM »

Cut the horn square. even with the air cleaner locating ring on the carb, deburr but don't rount the edges to any degree.

[fugly]

acr
Latest Images-Modified Air Horn, etc. Carter AFB.
« on: October 24, 2009, 04:24:37 PM »

Here are pics of the modified air horn & what the modified parts should look like when assembeled. The choke horn has been cut down, left square & cleaned up. The secondary area had been previously radiused. If more work is needed let me know. Many, many thanks for your suggestions.





Fugly
Re: Latest Images-Modified Air Horn, etc. Carter AFB.
« Reply #1 on: October 24, 2009, 10:07:09 PM »

Nice work- one suggestion, not necessary, but it's worth a little- look on the shot looking straight down- see how the main body is slightly smaller than the lid all the way arounf the primary area? (where the gasket sits). If you want , use a cartridge roll or some such and blend the mating area ( you have to take the boosters out to do it and screw the lid to the base), If you put the gasket in and tighten the lid while you do it, it will make a perfect blend, Primary side only and be careful to stay away from the venturies....

acr
Re: Latest Images-Modified Air Horn, etc. Carter AFB.
« Reply #2 on: October 26, 2009, 08:16:20 PM »

Damon, How do I outline certain parts of one of my images? Like you did in your reply to me regarding the areas to remove metal on the sec. boosters.
Thanks, Fred (acr)


Fugly
Re: Latest Images-Modified Air Horn, etc. Carter AFB.
« Reply #3 on: October 27, 2009, 09:24:13 AM »

I downloaded the picture and opened it in microsoft paint, did the outline and re uploaded it


acr
Re: Latest Images-Modified Air Horn, etc. Carter AFB.
« Reply #4 on: October 27, 2009, 09:56:43 PM »

Just to be sure. The areas inside the red lines are what needs to be blended & do I blend them at an angle or flat like the sec. clusters?

Fugly
Re: Latest Images-Modified Air Horn, etc. Carter AFB.
« Reply #5 on: October 27, 2009, 10:39:29 PM »

A slight angle is easiest- the point is to eliminate the sharp transition, and yes thos are the areas


acr
Re: Latest Images-Modified Air Horn, etc. Carter AFB.
« Reply #6 on: October 29, 2009, 04:50:04 PM »

This picture shows the straight & angle work to promote smoother air flow into the primaries. Looking at the top of the picture, on each side of the (missing) pump jet location, you'll see "before" (on the right side) & "after" on the left, angle blending of the carb body. The black line on the right side is from a felt pen. The other area done is the back side of the primaries,on each side the big hole for the threaded rod. That shows both sides cleaned up straight down to the venturis,compare these pics with the previous posts. You can really tell a difference in the slickness of the air entry areas when you run your finger or nails over the smoothed surfaces.

If you decide to do this be aware that the top lid, or air horn, that bolts to the body has some play in it & can be bolted down a few thousands or so "off" each time. You need to make sure it's tightened down in the same location each time you work on it. I'd also suggest using masking tape on areas you don't want scratched. I used a variety of small hand files & a Dremel cordless 10.8 volt tool for doing the early work, followed up with various grits of wet-dry or nail files. For me, the cordless/variable speed Dremel is MUCH easier to work with than corded models. Questions or suggestions are encouraged.
i798.photobucket.com/albums/yy266/acr3/PA280095.jpg[/img]

Fugly
Re: Latest Images-Modified Air Horn, etc. Carter AFB.
« Reply #7 on: October 29, 2009, 11:55:15 PM »

Nice work- on the angled side (top of picture), keep the angle as gradual as possible- imagine high speed water hitting what you are looking at and where it will go- the way you have it is just barely in the range of where you want to be- if you use the whole height between the lid and where the venturi starts, you can get an angle that is less steep.


acr
Re: Latest Images-Modified Air Horn, etc. Carter AFB.
« Reply #8 on: October 30, 2009, 01:12:03 PM »

Like this?


Fugly
Re: Latest Images-Modified Air Horn, etc. Carter AFB.
« Reply #9 on: October 30, 2009, 05:08:24 PM »

Perfect


acr
Re: Latest Images-Modified Air Horn, etc. Carter AFB.
« Reply #10 on: October 30, 2009, 10:28:06 PM »

Good news, I'll do the other side tommorrow, & maybe start on the other carb. next week. Will you "guesstimate"
about how many CFM I've gained in this 400 CFM carb? And thanks again for all the coaching.


Fugly
Re: Latest Images-Modified Air Horn, etc. Carter AFB.
« Reply #11 on: October 30, 2009, 11:03:33 PM »

typically 4-9% for these kind of mods so 16-36 CFM-going in the middle maybe 25,


acr
Re: Latest Images-Modified Air Horn, etc. Carter AFB.
« Reply #12 on: November 05, 2009, 08:04:58 PM »

I'm starting on the 2nd carb, the oxidation isn't quite as bad on this one, but still rough. Was the area OK where I smoothed the entrance to the throttle bores, just below the primary clusters, or does it need less work?
Thanks as usual, acr


Fugly
Re: Latest Images-Modified Air Horn, etc. Carter AFB.
« Reply #13 on: November 05, 2009, 10:20:32 PM »

What I can see looks real good- don't alter the venturi shape, just clean it up


Jwdrew22
Re: Latest Images-Modified Air Horn, etc. Carter AFB.
« Reply #14 on: March 02, 2010, 12:48:54 AM »
acr,

I'm glad I came across your photos of the AFB mods. Looks great!

I'm in the process of doing the same thing on my Edelbrock 1406 AFB. Still working on the primary venturi at the moment. So far I've been using the Dremel tool at first (grinding stones or sandpaper wheels), coming back with sandpaper (240 grit, then 600 grit) and finishing off with the buffing wheel attachments and polishing compound. The surfaces have been coming out with a mirror like finish.

Is yours a race application? Just wondering since the choke has been removed. Not sure I want to get rid of mine. It gets pretty cold here in Oklahoma during the winter months and I need it for easier start-ups.

[acr]

Mine is not a race application, it's a weekend cruiser. My carbs are hard to find 400 CFM Carter AFB's (that's why I didn't trash them). I'm putting them on a 2x4 set up. Since it's not a daily driver & I live in central Florida where cold weather isn't a big problem, I'm OK w/no choke.