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Old 05-18-2018, 09:03 AM   #1
Cam1968rsss
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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
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Old 05-18-2018, 09:51 AM   #2
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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?
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Old 05-18-2018, 09:59 AM   #3
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Re: What size Carb? 400 sbc

3.42 posi 12 bolt.
Stock torque converter.
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Old 05-18-2018, 10:01 AM   #4
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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
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Old 05-18-2018, 10:49 AM   #5
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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.

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Eddie
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Old 05-18-2018, 11:13 PM   #6
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Re: What size Carb? 400 sbc

Since both are double pumpers, I would go with the 650.
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Old 05-19-2018, 09:04 AM   #7
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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.
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Old 05-19-2018, 07:55 PM   #8
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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.
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Old 05-19-2018, 10:59 PM   #9
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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.
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Old 05-19-2018, 11:25 PM   #10
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Re: What size Carb? 400 sbc

You're gonna hate that stock converter...

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Old 05-25-2018, 02:43 PM   #11
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Re: What size Carb? 400 sbc

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Originally Posted by Cam1968rsss View Post
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.
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Old 05-26-2018, 11:19 PM   #12
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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?
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Old 05-27-2018, 08:40 AM   #13
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Re: What size Carb? 400 sbc

BIG difference in 6" stroke vs 6" rods....6" stroke is big for a big block.
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Old 05-27-2018, 08:55 AM   #14
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Re: What size Carb? 400 sbc

Like this.
http://www.hotrod.com/articles/1211s...-block-engine/
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Old 05-29-2018, 05:32 PM   #15
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Re: What size Carb? 400 sbc

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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?
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Old 05-29-2018, 06:00 PM   #16
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Re: What size Carb? 400 sbc

what size carb would he run on his 10.5L engine ?
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Old 05-29-2018, 06:34 PM   #17
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Re: What size Carb? 400 sbc

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Originally Posted by Cam1968rsss View Post
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.
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Old 05-29-2018, 07:10 PM   #18
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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
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Old 06-07-2018, 07:58 PM   #19
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Re: What size Carb? 400 sbc

Quote:
Originally Posted by Cam1968rsss View Post
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.
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Old 06-08-2018, 12:03 AM   #20
Captainfab
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Re: What size Carb? 400 sbc

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

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