3361/3362 Cfm?

[jboatno4]

Anyone know the answer (I don't).

[JimKwiatkowski]

I belive there 600CFM

[Mr Goodwrench]

hmmmmmm I was thinking 450??? total of 900 ??

[walkerheaders]

i always thought they are 625 cfm each.

OZ......................................?

[CDNpontiac409guy]

It would seem that the actual CFM capability was just over 575. As a result of my persistant nagging, NHRA / IHRA recently accepted the Edelbrock 600 CFM carbs as suitable replacements in Stock and Super Stock. :deal

[CDNpontiac409guy]

OZ......................................?

I'm sorry, Bob... I didn't see that "invite" :doh ...

OZ ?
Let me get my **** together again :takethat ;)

my late brother used to call me "BOZO" :cuss :p

[ROYALOAK62]

The Chevrolet by the numbers book shows them as 500 cfm rating each. With a 4.5 inch diameter air cleaner base.
The 5.0 inch diameter air cleaner base type to be approximately 600 cfm.
As to what the true cfm is someone would have to test them.

Dave

[jim_ss409]

I always thought they were in the 450-500cfm range but after comparing them to a set of 500cfm Edelbrocks I think the stock carbs are bigger. I think my stock carbs were 1964 425HP models but I don't have the tag here. The numbers stamped into the housing are F7B-3361S (front) and A8-3804 (rear) I don't have callipers here but I can see that the primary bores are bigger on the old carbs. The secondaries look to be the same size. Also the booster is fatter and more restrictive on the Edelbrocks. So I'm guessing that the factory carbs are about 600cfm. :dunno I posted pictures but it's a little hard to see the difference. By the way I got the new carbs through Phill Reed and Tony Shaffer. At the convention I had a leaking float on one of the old carbs. So I talked to Phil and he got Tony to set up a pair of carbs with the same jetting as the ones he used on the 574HP engine he built for the convention. I'm only now getting around to installing them. I'm pretty sure they'll be really close to perfect right off the bat. I'll let you know when I get them installed.

[Fran Preve]

With the 4 and a 1/2 inch neck 450-500 cfm seems the most likely. I too always thought that's what they were. The were smaller than the single AFB on the 400hp.

PS: seeing as how rare they are it's no surprise the NHRA would accept a later, and larger AFB. Also, Carter offered a 500 cfm carb up until just recently. Nonetheless, it's the 4 and a 1/2 inch neck that limited the stock carbs.

[jboatno4]

I got the following response today from a carburetor guy I found on the 'net:

"Carter did not publish the CFM rating of O.E. (original equipment)
carburetors until the mid 1970's, including these. However the
internal venturii sizes of these units are the same as a
carburetor with published CFM rating of 625."

[Fran Preve]

Not with a 4 and a 1/2 inch neck.

[CDNpontiac409guy]

Fran... I'm looking at these two carbs... the original style 3361 / 3362 / 3804 / 3461 / 3720 / 3721... All virtually identical except for jetting, all with a 4 5/16" air cleaner opening. The "newer" style 5 1/8" opening has more obstructions than could be considered reasonable. Chunks and barriers and irregularities which NO DOUBT impede air flow. Nope. Not imprerssed. These original carbs TRULY look like a better unit. Big opening doesn't mean a d**n thing, if it's all blocked off after.
Have a look at that picture above.... it's obvious.

[jim_ss409]

I read an article in Hotrod Magazine where they tested the K&N Stub Stack. The carbs flowed more but I don't know if that would nesesarily mean more power. :dunno http://www.knfilters.com/Racing/stubstacks.htm

[Skip FIx]

I posted the question to one of the Pontiac guys who restores lots of dual wuad 'and tripower carbs. I'l leet you all know if he doesn't post it here himself.

[fatride]

The only way to really know is to put them on a flow bench. Some protuberances that you think would impede flow actually enhance the same! :?

[jim_ss409]

I installed the carbs I got from Phil & Tony. They worked great. :beerbang The weather wasn't very good so I only went around the block but everything seems right on, Good throttle responce and lots of power. :cheers

[JimKwiatkowski]

Jim,did you get that new 12 Bolt installed :D

[jim_ss409]

Jim,did you get that new 12 Bolt installed :D

Not yet, no time and we're just moving into a new shop. But I'll have it in by the time I get to Norwalk. I've also got a new 5 speed tranny that needs to get installed. I better hurry up!

[JimKwiatkowski]

Jim,what gears and tires are you using?What kind of times do you think your going to get?Do you know your weight of your 62 and HP of your 09?I have a Moroso Speed Calculator and I can figure within 2/10 tenths.I'll guess a 12.50 :D

[JimKwiatkowski]

Jim,in between installing tailpipes on the 57,watching TV and talking with friends.I found some time to play with my Moroso Speed Calculator :D Here's some possible ET'S,firgued on vehicle weight 62 convertible 8cly-3,560lbs + driver 200lbs( I'm guessing your weight) = 3,700lbs.
400 HP @ 3,700lb vehicle = 12.66 et
450 HP @ 3,700lb vehicle = 12.20 et
500 HP @ 3,700lb vehicle = 11.90 et
Jim,these are just guess's + or - 2/10 tenth's :dunno I'f you want to know more of a refined ET I have a freind that has a computer program he run a check :) If your interested send me a PM.

Befour my 482 stroker exploded,the 57 ran 11.60's :D

[jim_ss409]

I got 4.11 gears in the rear end. I think 4.30's would have been quicker but I wanted it to be good on the highway. With the .64 overdrive the 4.11's would give me a final drive ratio of 2.63 which adds up to 2,000rpm at 60mph. I'll be happy if I can get into the high 12's. My best time at the convention was 13.82 @ 104.99 so the MPH indicates that there is enough power to run about a second quicker. I'm also hoping to have a set of DOT legal slicks at Norwalk, trying to get that boat moving with the 17" street tires was pretty hard. I did have a carb float that was full of gas causing it to run badly and foul the plugs, at least that's the excuse I've been using. :D I'm going to bring a video camera to Norwalk so I can get some footage of the cars at the track and I know a guy that'll make up some video clips. :cheers

[Skip FIx]

Here you go guys
"Carter did not publish the CFM rating of the 409 dual quad carburetors; however comparing design and sizes (primary venturi, secondary venturi, booster venturi, throttle bore, and airhorn inlet) to those with published CFM suggests they are 625 CFM each.

We have a pair on ebay right now for sale.

Jon.

Good carburetion is fuelish hot air.

Owner of The Carburetor Shop, LLC (of Missouri). "

[Dond409]

How about a link to your auction.

[Skip FIx]

I posted this on the Pontiac board and copied Jon's answer here. I'm not sure of his E bay auction. He's always helpful with carb setups on the Pontiac boards.

[jboatno4]

Thanks for all the discussion - I've learned a lot!

Jack

[Skip FIx]

E bay auction 4539879861.

[Dond409]

This is what a link is to your auction.


http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=4539879861