Fuel System: R-1 Carburetor

[Flashback]

Anybody know where there is anything that really tells the CFM on a 63 R-1 Carb?

[bezhawk]

625 CFM it's in factory specs. and on Bob Johnstones' technical pages

[sals54]

I guess I have the same question, but has the carb indeed been flowed to get to that 625 ? or is it just stated as such in the literature. Reason I ask is that the R1 carb does not appear to be as large as the later Edlebrock 600 carbs. They look closer to the 500s. I'm just asking and observing.

[11SecAvanti]

I researched the R-2 AFB and based on the Johnstone tech info the 625 cfm rating is posted. However if you read the fine print on that report it states the test pressure was 2 inches of Hg. The flow standard for 4 barrel carbs is 1.5" Hg. That means the real cfm is lower and most likely in the 500 range. I recently rebuilt an AFB # 4331S off a 67 Buick 340 and based on the code number it flows 400 cfm @ 1.5" Hg. Very few Carter AFB's were factory flowed. One that has factory flow cfm is the 64-65 Corvette AFB #3721SB. The official flow rating on this carb from Carter is 575 cfm per internet research.

[Gunslinger]

The reason an original AFB doesn't look as large as current versions is due to the diameter of the air horn being 4 1/4", which was the norm back then. Outside of racing carbs, the current standard air horn diameter, regardless of whether it's Edelbrock, Holley or Demon is 5 1/8", regardless of its flow rating.

[sals54]

The reason an original AFB doesn't look as large as current versions is due to the diameter of the air horn being 4 1/4", which was the norm back then. Outside of racing carbs, the current standard air horn diameter, regardless of whether it's Edelbrock, Holley or Demon is 5 1/8", regardless of its flow rating.

[64V-K7]

That means the real cfm is lower and most likely in the 500 range.

Right on target... this data point was also published in a 1991 Turning Wheels in Jon Myers column. See http://www.studebaker-info.org/TW/tw...191p16left.jpg

[Chicken Hawk]

Several years ago I contacted Carter to ask about the cfm on the Stude R 2 carb. They told me to send them every part number on every part in the carb.

I sent them everything I could find and they told me they needed one more number to nail it down but said it was between 625 and 635. How accurate that is I don't know but assumed they would know as much as anyone.

Ted

[Flashback]

Thanks, everyone. I have seen the numbers Ted has here(625-635), and the Jon Meyer article in turning wheels article says 500 CFM. This is right where I started out. I guess there is nothing really in print, we can all look back on?

[bezhawk]

The stock CFM is too much for two....but I have my ways of correcting that!

[SN-60]

Too much carb Dept.!

[Flashback]

[ATTACH=CONFIG]30970[/ATTACH]The stock CFM is too much for two....but I have my ways of correcting that!

I bet you do. I would figure it out too, if I had that setup.

[bezhawk]

Here is how I cut down the CFM and rejetted, and modified the air bleeds on dual 4 setups. New CFM is approxamately 370 CFM Each. Much better throttle response. NO BOG ANY TIME EVER! Secondary air valve is also re weighted.

[SScopelli]

I researched the R-2 AFB and based on the Johnstone tech info the 625 cfm rating is posted. However if you read the fine print on that report it states the test pressure was 2 inches of Hg. The flow standard for 4 barrel carbs is 1.5" Hg. That means the real cfm is lower and most likely in the 500 range. I recently rebuilt an AFB # 4331S off a 67 Buick 340 and based on the code number it flows 400 cfm @ 1.5" Hg. Very few Carter AFB's were factory flowed. One that has factory flow cfm is the 64-65 Corvette AFB #3721SB. The official flow rating on this carb from Carter is 575 cfm per internet research.

The Chevy 3721 is the one I use for my clones.. I have to add the Timed Vacuum advance which is easy.

It also has a more aggressive initial fuel pump spray (CC wise) which helps in throttle response.



On the 3721/3720 the fuel inlet is in the front like original Stude AFBs.

If you do decide to go with this 372x and see one on eBay or swap meet.. Do NOT buy it unless it has the choke housing! They are unique to this carb and hard to find if missing.