Avs three barrel mod

Posted By: dannysbee

Avs three barrel mod - 11/08/13 04:47 PM

I was reading an old carter tuning guide that I have and it showed pictures of an old nascar afb that was a three barrel. Said they were quite rare. Wonder if any one had modified a four barrel afb or avs to 3 barrel for fast.

Posted By: dannysbee

Re: Avs three barrel mod - 11/08/13 06:17 PM

It was rated over 900 cfm

Posted By: lewtot184

Re: Avs three barrel mod - 11/08/13 07:15 PM

interesting. i don't remember anything like that back in the day, but somebody could've got creative. got any pics?

Posted By: burdar

Re: Avs three barrel mod - 11/08/13 07:35 PM

Years ago there was a Hot Rod magazine with a yellow Mustang on the cover that was air born over a hill. I remember that car had a three barrel on it. That's the first time I'd ever heard of such a thing.

Posted By: 340SHORTY

Re: Avs three barrel mod - 11/08/13 07:45 PM

I remember Holley having a 3 bbl carb back in the 70s..

Posted By: Hemi_Joel

Re: Avs three barrel mod - 11/08/13 08:40 PM

Quote:

I remember Holley having a 3 bbl carb back in the 70s..

Same here. I Have had a couple Holley 3 barreles, but I have never even heard of a Carter 3 bbl.

Posted By: MoparforLife

Re: Avs three barrel mod - 11/08/13 09:03 PM

Think he is looking at the air door.

Posted By: 62maxwgn

Re: Avs three barrel mod - 11/08/13 09:52 PM

Nope,three-barrel 3636s used on the Pontiac NASCAR 421 super duty engines.

Attached picture 7916828-Carter3bbl.jpg

Posted By: 62maxwgn

Re: Avs three barrel mod - 11/08/13 09:54 PM

Top.

Attached picture 7916831-$(KGrHqV,!lsFGnHHwfU+BRtT4P!!H!~~60_1.JPG

Posted By: ScottSmith_Harms

Re: Avs three barrel mod - 11/08/13 09:56 PM

And that is a VERY rare carburetor!

Posted By: lewtot184

Re: Avs three barrel mod - 11/08/13 10:01 PM

Quote:

Nope,three-barrel 3636s used on the Pontiac NASCAR 421 super duty engines.

cool! i bet that would be a fun little gadget.

Posted By: cjbill

Re: Avs three barrel mod - 11/08/13 10:15 PM

Never could understand why that didn't "catch on" but instead the 4500 series came about...

Looks like it would be great for a hot 440, although all the ones I've seen (Holleys) have no choke.

Posted By: 383man

Re: Avs three barrel mod - 11/08/13 10:18 PM

Wow I have been around muscle cars since the late 60's and have never heard of the Carter 3 barrel only the Holley 3 barrel. Learn something every day.

Ron

Posted By: ScottSmith_Harms

Re: Avs three barrel mod - 11/08/13 10:33 PM

Look at the new Demon Thermo-Quad, they use a similar setup, they call the single butterfly a "goggle" valve because it's shaped like a pair of goggles

Posted By: dannysbee

Re: Avs three barrel mod - 11/08/13 11:24 PM

Looks like it would be cool to do an AVS for FAST. Or two AFB/ eddys for a big inch NSS. Wonder if a four barrel could modified and made to work.

Posted By: 62maxwgn

Re: Avs three barrel mod - 11/08/13 11:49 PM

Quote:

Looks like it would be cool to do an AVS for FAST. Or two AFB/ eddys for a big inch NSS. Wonder if a four barrel could modified and made to work.

Might just give it a shot,what I don't have I can probably make,nothing to lose.

Posted By: dannysbee

Re: Avs three barrel mod - 11/09/13 12:02 AM

I figured if anyone could make it work it would be you Bill. The originals were 1 to 1 on the linkage. Both ends opened at the same. Might be ok on a nascar but I believe progressive would be better. The avs would be easier as there would be no air valve to deal with. Keep us posted on how you are coming.

Posted By: ademon

Re: Avs three barrel mod - 11/09/13 01:15 AM

Those old LD 340 intakes and others of the time had the little notch in the divider for these carbs I think

Posted By: BSB67

Re: Avs three barrel mod - 11/09/13 02:06 PM

So, is it an AVS or AFB? it looks like it uses the full circular Venturi, unlike the Holley. how does it transition from the two Venturi to the single throttle bore?

that is very very cool.

Posted By: U code RR

Re: Avs three barrel mod - 11/09/13 03:18 PM

Very interesting carb. Do you have a pic of the top of the carb? Was it an AFB or an AVS? The top pic that is posted is a different carb from the bottom pic. Mounting holes are different.

Posted By: 383man

Re: Avs three barrel mod - 11/09/13 06:29 PM

Looks like an AFB to me. I dont think the AVS was out yet in the early 60's when Pontiac raced the 421 eng in Nascar? Ron

Posted By: 62maxwgn

Re: Avs three barrel mod - 11/09/13 11:03 PM

Quote:

Very interesting carb. Do you have a pic of the top of the carb? Was it an AFB or an AVS? The top pic that is posted is a different carb from the bottom pic. Mounting holes are different.

The top one had the additional holes drilled,it is similar to the 3705 Max wedge carb,fuel inlet on driver side and manual choke.

Posted By: dannysbee

Re: Avs three barrel mod - 11/10/13 03:07 AM

Yes it was an AFB. I think an Avs would be easier to con vert to the three barrel configuration.

Posted By: lewtot184

Re: Avs three barrel mod - 11/10/13 03:29 AM

when holley made their 3bbl they moved the venturi boosters closer together vs the 4160/4150 style carb to get the discharge nozzles more centrally located. it looks like carter took a different approach and move the bore area further out to keep the discharge nozzles in the "stock" location but keep them centrally located in the bore/venturi. if modifying a square bore without this change i'd bet there'd be some distribution issues. i have a pic of 3916 holley; see if you can see the relocation.

Attached picture 7918339-100_0318.jpg

Posted By: GO_Fish

Re: Avs three barrel mod - 11/10/13 03:34 AM

Quote:

Those old LD 340 intakes and others of the time had the little notch in the divider for these carbs I think

That is correct, LD340 secondary divider was notched for the 3 bbl carbs. IIRC, these were earlier LD340's. Later versions had the secondary divider almost completely removed as DirectConnection testing showed power gains with that modification.

Posted By: 62maxwgn

Re: Avs three barrel mod - 11/10/13 04:12 AM

The CH4B was also notched for the Holley 3 barrel.Here is one of each,#3916,950 CFM on left,# 4604,1050 CFM on right.Also,the discharge nozzles on the 950 CFM 3916 are different than the one Lew posted and they have never been modified,I bought in new in the mid 60's.
1

Attached picture 7918385-PB090615.JPG

Posted By: cjbill

Re: Avs three barrel mod - 11/10/13 07:20 PM

Very cool.