327/300 carb CFM - Page 2

Mark Yacavone · 05-05-2013, 11:15 PM

4 GC is 245...
AFB is 260 in a 65 Chevelle ..

Might be fun with a T200 ..but it's a lot cheaper to find out on a dyno...in the long run.

Reed Granrt · 05-06-2013, 09:33 AM

Going in memory, the 327 with 250 hp had the 283 cylinder heads with a 1.75 int valve and a 1.5 exh ,small intake with a 4GC car and small exhaust pipe. The 300hp had the double hump heads with 1.94 intake valve with 1.5 exh with a larger intake manifold with the AFB with larger exhaust manifold. I started going thru some dyno sheets where I pulled the 250 intake and carb and installed a AFB and int. I think we picked up some hp but the heads were a restriction. Some of you guys will probably remember more than I do
reed

ss wannabee · 05-06-2013, 10:05 AM

Quote:

Originally Posted by Greg Reimer 7376

That carb wasn't the only difference between the 62-65 250 and 300 horse 327. A good question was brought up, but I'd like to know what the CFM rating of the 4 Jet carb that the 220 and 250 horse small blocks was. The intake difference was notable, and the 461 head as opposed to the 520 head was another factor. Is the factored horsepower really that great a difference?

Not sure on the AFB carb...but checked into the 4GC's cfm rating many years ago...

Think I found about 475 cfm for the smaller early carb..(circa '57-'60?)...

Thought that the later carb was about 525...on the 220 and 250 hp engines...

Think there's one other 4GC as well...but that doesn't apply here....

Talking Chevrolet ONLY here...other GM's might be different....

tony5022 · 05-06-2013, 10:51 AM

My Corvette is able to run both combinations and we found that the AFB is 2 tenths faster than our WCFB with the right tune up. No dyno time just track tested.
Tony Hernandez

FED 387 · 05-06-2013, 11:52 AM

Not sure of the carb specs that is being used with that particular combo but the smallest AFB is rated @400 CFM and they go up in size to 750 CFM while a WCFB is kinda rated @ 385 CFM for the smallest ones--- Found this a long time ago not sure how accurate it still is

AFB Carbs
CFM Venturi Diameter Bore Diameter
Primary Secondary Primary Secondary

400 1 1/8 1 1/4 1 7/16 1 7/16

500 1 3/16 1 1/4 1 7/16 1 11/16

575 1 1/4 1 9/16 1 9/16 1 11/16

625 1 3/16 1 9/16 1 7/16 1 11/16

750 1 7/16 1 9/16 1 11/16 1 11/16

ALL AVS CARBS

Primary & Secondary same size 750 CFM
Primary & Secondary different size 630 CFM

4GC CARBS

CFM Venturi Diameter Bore Diameter
Primary Secondary Primary Secondary

486 1 1/8 1 1/4 1 7/16 1 7/16

553 1 1/8 1 15/32 1 7/16 1 11/16

692 1 1/8 1 15/32 1 9/16 1 11/16

Dwight Southerland · 05-06-2013, 04:25 PM

Quote:

Originally Posted by Reed Granrt

Going in memory, the 327 with 250 hp had the 283 cylinder heads with a 1.75 int valve and a 1.5 exh ,small intake with a 4GC car and small exhaust pipe. The 300hp had the double hump heads with 1.94 intake valve with 1.5 exh with a larger intake manifold with the AFB with larger exhaust manifold.

Except '65; the 327-250 used the same heads as the 327-300 in 1965. Been that way as long as I remember.

Dan Fahey · 05-06-2013, 05:15 PM

Quote:

Originally Posted by Dwight Southerland

Except '65; the 327-250 used the same heads as the 327-300 in 1965. Been that way as long as I remember.

That is correct..
In 64 and 65 the 327 were both rated at 250hp.

D

Dan Lattimore · 05-11-2013, 08:58 AM

Quote:

Originally Posted by Mark Yacavone

Anybody know the CFM rating on that (AFB) carb ?

Mark, Cupp has answers to all those questions. Dyno comparisons, on track back to back, every trans. and rear gear combination you can think of. We have MIR again on Monday and he will be beating the tar out of the green bean again. ------ I'm going to quit parking beside him----------Danny

Greg Reimer 7376 · 05-11-2013, 10:31 PM

Seems to me that the 409 340 horse engine of 1963-65 had a BIG 4 jet on it. 394 Olds motors and the big Buicks got it as well. Heard of a fellow putting one on a 283-220 horse and getting a BIG quantum jump in horsepower with it. I had a 65 Impala SS convertible with a 409 340 horse and a 4 speed, but I ran an AFB on it,since they were easier to maintain. That car was a real road monster with the 3.31 gears, and it would tow about anything. Nothing like torque.

05-05-2013, 11:15 PM	#11
Mark Yacavone Veteran Member Join Date: Mar 2002 Location: Miles From Nowhere Posts: 7,809 Likes: 2,900 Liked 5,114 Times in 1,948 Posts	Re: 327/300 carb CFM 4 GC is 245... AFB is 260 in a 65 Chevelle .. Might be fun with a T200 ..but it's a lot cheaper to find out on a dyno...in the long run. __________________ "We are lucky we don't get as much Government as we pay for." Will Rogers

05-06-2013, 09:33 AM	#12
Reed Granrt Member Join Date: Jul 2011 Location: Murfreesboro, Tn Posts: 149 Likes: 0 Liked 1 Time in 1 Post	Re: 327/300 carb CFM Going in memory, the 327 with 250 hp had the 283 cylinder heads with a 1.75 int valve and a 1.5 exh ,small intake with a 4GC car and small exhaust pipe. The 300hp had the double hump heads with 1.94 intake valve with 1.5 exh with a larger intake manifold with the AFB with larger exhaust manifold. I started going thru some dyno sheets where I pulled the 250 intake and carb and installed a AFB and int. I think we picked up some hp but the heads were a restriction. Some of you guys will probably remember more than I do reed

05-06-2013, 10:51 AM	#14
tony5022 Junior Member Join Date: Dec 2005 Posts: 29 Likes: 8 Liked 10 Times in 2 Posts	Re: 327/300 carb CFM My Corvette is able to run both combinations and we found that the AFB is 2 tenths faster than our WCFB with the right tune up. No dyno time just track tested. Tony Hernandez

05-06-2013, 11:52 AM	#15
FED 387 VIP Member Join Date: Jun 2006 Posts: 3,416 Likes: 522 Liked 330 Times in 178 Posts	Re: 327/300 carb CFM Not sure of the carb specs that is being used with that particular combo but the smallest AFB is rated @400 CFM and they go up in size to 750 CFM while a WCFB is kinda rated @ 385 CFM for the smallest ones--- Found this a long time ago not sure how accurate it still is AFB Carbs CFM Venturi Diameter Bore Diameter Primary Secondary Primary Secondary 400 1 1/8 1 1/4 1 7/16 1 7/16 500 1 3/16 1 1/4 1 7/16 1 11/16 575 1 1/4 1 9/16 1 9/16 1 11/16 625 1 3/16 1 9/16 1 7/16 1 11/16 750 1 7/16 1 9/16 1 11/16 1 11/16 ALL AVS CARBS Primary & Secondary same size 750 CFM Primary & Secondary different size 630 CFM 4GC CARBS CFM Venturi Diameter Bore Diameter Primary Secondary Primary Secondary 486 1 1/8 1 1/4 1 7/16 1 7/16 553 1 1/8 1 15/32 1 7/16 1 11/16 692 1 1/8 1 15/32 1 9/16 1 11/16

05-11-2013, 10:31 PM	#19
Greg Reimer 7376 VIP Member Join Date: Nov 2008 Location: Glendora,Calif. Posts: 1,135 Likes: 172 Liked 704 Times in 218 Posts	Re: 327/300 carb CFM Seems to me that the 409 340 horse engine of 1963-65 had a BIG 4 jet on it. 394 Olds motors and the big Buicks got it as well. Heard of a fellow putting one on a 283-220 horse and getting a BIG quantum jump in horsepower with it. I had a 65 Impala SS convertible with a 409 340 horse and a 4 speed, but I ran an AFB on it,since they were easier to maintain. That car was a real road monster with the 3.31 gears, and it would tow about anything. Nothing like torque.