What size Carb? 400 sbc - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**Cam1968rsss** · 05-18-2018, 09:03 AM

Hi all, have 408 ci sbc (bored 40 over 6 inch stroke crank) have a Comp Cams 490 lift hydraulic cam 487 irons heads. Have two different Holley DP carbs, 650 and 700. Was wondering if anyone had an idea which would work better. Truck will have Turbo 350 trans, power brakes and power steering.

Thanks
Cam1968rsss

geezer#99 · 05-18-2018, 09:51 AM

Bigger is always better!
Actually either will work.
You gonna make enough vacuum to use your power brakes?
What stall?
What rear gears?

**Cam1968rsss** · 05-18-2018, 09:59 AM

3.42 posi 12 bolt.
Stock torque converter.

b454rat · 05-18-2018, 10:01 AM

Either will work if tuned. I had a 400 with a similar cam, had a Holley 600 on it, worked pretty good. I put a stock 3310 750 on it, ran like ****. Put that carb on a 350, and worked great. Who knows....also think you meant 6” rods, don’t think that stroke would fit in a small block lol

**Cam1968rsss** · 05-18-2018, 10:49 AM

Yes this 400 has a stroked 6 inch crank and rods in it instead of a 5.7. Came from Skip White Performance out of Kingsport Tennessee. Am told this will be a torque monster once I get it broken in. Just wondering about which carb would be best.

Thanks
Eddie

**Captainfab** · 05-18-2018, 11:13 PM

Since both are double pumpers, I would go with the 650.

cadillac_al · 05-19-2018, 09:04 AM

I would try them both. I would run the 650 for a few weeks and then try the 700 to see how much difference it makes.

Dead Parrot · 05-19-2018, 07:55 PM

Found this: https://www.summitracing.com/experta...cfm-calculator

Shows for your size motor @ 5000rpm a street cfm of about 500 and a racing cfm of about 650.

ProStreet68SB · 05-19-2018, 10:59 PM

I think you'll find the throttle response and idle quality better with the 650, so that would be my choice.

GASoline71 · 05-19-2018, 11:25 PM

You're gonna hate that stock converter...

Gary

Tom · 05-25-2018, 02:43 PM

Quote:

Originally Posted by Cam1968rsss

Yes this 400 has a stroked 6 inch crank and rods in it instead of a 5.7.

You do not have a 6" stroker crank. You might have a stroker crank of some size along with 6" rods vs stock 350's 5.7" rods, but why you brought that up since a 400 uses 5.56" rods is confusing.

**Cam1968rsss** · 05-26-2018, 11:19 PM

I do have a set up that has a 6 inch rod. With crank and pistons that came in the same kit. What is so confusing about that?

b454rat · 05-27-2018, 08:40 AM

BIG difference in 6" stroke vs 6" rods....6" stroke is big for a big block.

geezer#99 · 05-27-2018, 08:55 AM

Like this.
http://www.hotrod.com/articles/1211s...-block-engine/

Tom · 05-29-2018, 05:32 PM

Quote:

Originally Posted by Cam1968rsss

I do have a set up that has a 6 inch rod. With crank and pistons that came in the same kit. What is so confusing about that?

Because you said 6" stroke. A 4.125 bore with a 6" stroke would be a 641cid engine, or 10.5L
You also said it was done instead of 5.7", but those didn't come in the engine from the factory.
Do you see where the confusion comes from yet?

*YoungPup1977* · 05-29-2018, 06:00 PM

what size carb would he run on his 10.5L engine ?

DieselSJ · 05-29-2018, 06:34 PM

Quote:

Originally Posted by Cam1968rsss

Hi all, have 408 ci sbc (bored 40 over 6 inch stroke crank) have a Comp Cams 490 lift hydraulic cam 487 irons heads. Have two different Holley DP carbs, 650 and 700. Was wondering if anyone had an idea which would work better. Truck will have Turbo 350 trans, power brakes and power steering.

Thanks
Cam1968rsss

What is the duration on the cam? That makes more of a difference than the lift.

But from what you have told us so far, go with the 650.

*YoungPup1977* · 05-29-2018, 07:10 PM

Comp Cam's has a 12-326 cam that yields a .490 lift with .286 duration with a power range from 2200 to 6200....with the two carbs of choice, most likely will not be the issue here.... degree the camshaft correctly and upgrade to 2500 rpm stall converter, just my 2 cents

swissarmychainsaw · 06-07-2018, 07:58 PM

Quote:

Originally Posted by Cam1968rsss

Hi all, have 408 ci sbc (bored 40 over 6 inch stroke crank) have a Comp Cams 490 lift hydraulic cam 487 irons heads. Have two different Holley DP carbs, 650 and 700. Was wondering if anyone had an idea which would work better. Truck will have Turbo 350 trans, power brakes and power steering.

Thanks
Cam1968rsss

I would contact Holley directly, they'll give you sound advice.

**Captainfab** · 06-08-2018, 12:03 AM

You can always use Holley's online carb size selector.

https://www.holley.com/products/fuel...s/carburetors/

05-18-2018, 09:03 AM	#1
Cam1968rsss Senior Member Join Date: Oct 2010 Location: Montgomery TX Posts: 408	What size Carb? 400 sbc Hi all, have 408 ci sbc (bored 40 over 6 inch stroke crank) have a Comp Cams 490 lift hydraulic cam 487 irons heads. Have two different Holley DP carbs, 650 and 700. Was wondering if anyone had an idea which would work better. Truck will have Turbo 350 trans, power brakes and power steering. Thanks Cam1968rsss

05-18-2018, 09:51 AM	#2
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,508	Re: What size Carb? 400 sbc Bigger is always better! Actually either will work. You gonna make enough vacuum to use your power brakes? What stall? What rear gears?

05-18-2018, 09:59 AM	#3
Cam1968rsss Senior Member Join Date: Oct 2010 Location: Montgomery TX Posts: 408	Re: What size Carb? 400 sbc 3.42 posi 12 bolt. Stock torque converter.

05-18-2018, 10:01 AM	#4
b454rat Senior Member Join Date: May 2004 Location: Binghamton, NY Posts: 3,453	Re: What size Carb? 400 sbc Either will work if tuned. I had a 400 with a similar cam, had a Holley 600 on it, worked pretty good. I put a stock 3310 750 on it, ran like ****. Put that carb on a 350, and worked great. Who knows....also think you meant 6” rods, don’t think that stroke would fit in a small block lol

05-18-2018, 10:49 AM	#5
Cam1968rsss Senior Member Join Date: Oct 2010 Location: Montgomery TX Posts: 408	Re: What size Carb? 400 sbc Yes this 400 has a stroked 6 inch crank and rods in it instead of a 5.7. Came from Skip White Performance out of Kingsport Tennessee. Am told this will be a torque monster once I get it broken in. Just wondering about which carb would be best. Thanks Eddie

05-18-2018, 11:13 PM	#6
Captainfab 60-66 Nut Join Date: Mar 2007 Location: Coeur d'Alene, Idaho Posts: 23,246	Re: What size Carb? 400 sbc Since both are double pumpers, I would go with the 650. __________________ Power Steering Box Adapter Plates For Sale HERE Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE Hydroboost Mounting Plates HERE

05-19-2018, 09:04 AM	#7
cadillac_al Registered User Join Date: Oct 2013 Location: Maine Posts: 2,331	Re: What size Carb? 400 sbc I would try them both. I would run the 650 for a few weeks and then try the 700 to see how much difference it makes. __________________ 76 Chevy K20 76 GMC K15 77 Chevy C10 77 Chevy K10

05-19-2018, 07:55 PM	#8
Dead Parrot Registered User Join Date: Aug 2012 Location: Oklahoma City, OK Posts: 2,472	Re: What size Carb? 400 sbc Found this: https://www.summitracing.com/experta...cfm-calculator Shows for your size motor @ 5000rpm a street cfm of about 500 and a racing cfm of about 650.

05-19-2018, 10:59 PM	#9
ProStreet68SB The Engine Whisperer Join Date: Sep 2006 Location: Ohio Posts: 770	Re: What size Carb? 400 sbc I think you'll find the throttle response and idle quality better with the 650, so that would be my choice. __________________ -Automatics win races, 6-speeds impress high school kids -Save a tree, support your local dragstrip. -"Failure - The Secret To Success, the idea is that you can fail 100 times as long as you can succeed once" -Takeo Fukui columbuscarsandcoffee.net and on Facebook

05-26-2018, 11:19 PM	#12
Cam1968rsss Senior Member Join Date: Oct 2010 Location: Montgomery TX Posts: 408	Re: What size Carb? 400 sbc I do have a set up that has a 6 inch rod. With crank and pistons that came in the same kit. What is so confusing about that?

05-27-2018, 08:40 AM	#13
b454rat Senior Member Join Date: May 2004 Location: Binghamton, NY Posts: 3,453	Re: What size Carb? 400 sbc BIG difference in 6" stroke vs 6" rods....6" stroke is big for a big block.

05-27-2018, 08:55 AM	#14
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,508	Re: What size Carb? 400 sbc Like this. http://www.hotrod.com/articles/1211s...-block-engine/

05-29-2018, 06:00 PM	#16
YoungPup1977 Account Suspended Join Date: Jun 2015 Location: No longer here Posts: 1,000	Re: What size Carb? 400 sbc what size carb would he run on his 10.5L engine ?

05-29-2018, 07:10 PM	#18
YoungPup1977 Account Suspended Join Date: Jun 2015 Location: No longer here Posts: 1,000	Re: What size Carb? 400 sbc Comp Cam's has a 12-326 cam that yields a .490 lift with .286 duration with a power range from 2200 to 6200....with the two carbs of choice, most likely will not be the issue here.... degree the camshaft correctly and upgrade to 2500 rpm stall converter, just my 2 cents

06-08-2018, 12:03 AM	#20
Captainfab 60-66 Nut Join Date: Mar 2007 Location: Coeur d'Alene, Idaho Posts: 23,246	Re: What size Carb? 400 sbc You can always use Holley's online carb size selector. https://www.holley.com/products/fuel...s/carburetors/ __________________ Power Steering Box Adapter Plates For Sale HERE Power Brake Booster Adapter Brackets For Sale '63-'66 HERE and '67-'72 HERE and '60-'62 HERE and "60-'62 with clutch HERE Rear Disc Brake Brackets For Sale. Impala SS calipers HERE Camaro Calipers HERE D52 Calipers HERE 6 Lug HERE Hydroboost Mounting Plates HERE



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