small carb on big motor - The 1947 - Present Chevrolet & GMC Truck Message Board Network

veltex · 05-12-2004, 08:15 AM

anyone running a 650 performer on a 454? Is it enough gas? I am changing out my 396 for a 454, 40 over, roller everything, 8.8 to 1, 049s, quite a bit of lift, low end power, all in by 5000rpm, should be a great truck motor just hoping I had enough carb, its new so I want to use it if I can. Any info helpful, thanks

stepside454 · 05-12-2004, 08:28 AM

Id say you need about 680 CFM for a 454 that goes to 5000 RPMs. Id use either a 670 Holley with a 1 inch open spacer or a demon 725CFM. John

junkyardjohn · 05-12-2004, 12:01 PM

650 CFM HAS PROVEN TO BE A LITTLE TOO SMALL FOR BIG BLOCKS IMO. EVEN STOCK 396s SEEM TO REQUIRE MORE FUEL THAN THAT. I LIKE TO USE EITHER THE 750 OR 800 CFM EDELBROCKS.

JOHN

shortymac83 · 05-12-2004, 02:31 PM

I've calculated that a stock olds 455 that goes to 5500 RPM's technically should only require 630 cfm, however practical experience will lead me to think that a motor that big really needs at least a 750 carb. I'd go with a quadrajet.

stepside454 · 05-12-2004, 06:15 PM

shorty, I calculate a 5500 RPM 455 needs 742 cfm, so a 750 would be a about perfect. But I do agree with the Qjet, hard to go wrong on a properly tuned Qjet.

72C203503ONTHETREE · 05-12-2004, 10:44 PM

The stock Q jet is either 750 or 800 cfm depending on the engine, so a 750 cfm Holley or Edelbrock will be fine.

Longhorn Man · 05-12-2004, 11:07 PM

Even though they are right that the engine could use more, and at 5000 RPM would need more...in all reality, the engine will run fine and rev to redline with no problems. This carb could even boost low end torque by keeping the intake charge velosity up.

veltex · 05-14-2004, 12:53 AM

thanks all, I will know soon enough, might have new motor on the road Sunday.

05-12-2004, 08:15 AM	#1
veltex Registered User Join Date: Oct 2003 Location: Idaho Posts: 257	small carb on big motor anyone running a 650 performer on a 454? Is it enough gas? I am changing out my 396 for a 454, 40 over, roller everything, 8.8 to 1, 049s, quite a bit of lift, low end power, all in by 5000rpm, should be a great truck motor just hoping I had enough carb, its new so I want to use it if I can. Any info helpful, thanks __________________ beater 65 gmc at the moment

05-12-2004, 08:28 AM	#2
stepside454 Registered User Join Date: Nov 2003 Location: st. louis area Posts: 1,551	Id say you need about 680 CFM for a 454 that goes to 5000 RPMs. Id use either a 670 Holley with a 1 inch open spacer or a demon 725CFM. John __________________ 75 GMC C-15 short/step factory 454, lowered

05-12-2004, 12:01 PM	#3
junkyardjohn Registered User Join Date: Aug 2001 Location: SOMERSET KY. Posts: 6,427	650 CFM HAS PROVEN TO BE A LITTLE TOO SMALL FOR BIG BLOCKS IMO. EVEN STOCK 396s SEEM TO REQUIRE MORE FUEL THAN THAT. I LIKE TO USE EITHER THE 750 OR 800 CFM EDELBROCKS. JOHN __________________ junkyardjohn 69 1 TON TOW TRUCK // 84 4WD CUCV BLAZER// 85 1 TON 4WD STAKE TRUCK// 86 M1031 5/4 TON 4WD CUCV// ALOT OF OLD TRUCKS FOR ONE OLD MAN TO DRIVE. THERES ROOM FOR ALL OF GODS CREATURES RIGHT NEXT TO MY MASHED POTATOES// LIFE MEMBER OF P.E.T.A (PEOPLE EATING TASTY ANIMALS) DON'T RENT U-HAUL ALWAYS TELL THE TRUTH IT WILL AMAZE PART OF THE PEOPLE & ASTONISH THE REST

05-12-2004, 02:31 PM	#4
shortymac83 hmm... Join Date: Jan 2004 Location: Culver, Indiana Posts: 1,631	I've calculated that a stock olds 455 that goes to 5500 RPM's technically should only require 630 cfm, however practical experience will lead me to think that a motor that big really needs at least a 750 carb. I'd go with a quadrajet. __________________ 1983 Oldsmobile Delta 88 1967 Chevy C-10 stripper www.fcrperformance.com - wanna go...faster? talk to FCR.

05-12-2004, 06:15 PM	#5
stepside454 Registered User Join Date: Nov 2003 Location: st. louis area Posts: 1,551	shorty, I calculate a 5500 RPM 455 needs 742 cfm, so a 750 would be a about perfect. But I do agree with the Qjet, hard to go wrong on a properly tuned Qjet. __________________ 75 GMC C-15 short/step factory 454, lowered

05-12-2004, 10:44 PM	#6
72C203503ONTHETREE Registered User Join Date: Apr 2004 Location: Grant, Alabama Posts: 504	The stock Q jet is either 750 or 800 cfm depending on the engine, so a 750 cfm Holley or Edelbrock will be fine. __________________ 72 Chevy C20, SOLD (Dang it.) 09 Challanger RT six speed in all black. 74 Datsun 710 wagon, all 1.8 liters of screaming Datsun power. 73 C10 long bed, 350/350 combo, nice shape.

05-12-2004, 11:07 PM	#7
Longhorn Man its all about the +6 inches Join Date: Jan 2001 Location: Hilliard Ohio Posts: 2,693	Even though they are right that the engine could use more, and at 5000 RPM would need more...in all reality, the engine will run fine and rev to redline with no problems. This carb could even boost low end torque by keeping the intake charge velosity up.

05-14-2004, 12:53 AM	#8
veltex Registered User Join Date: Oct 2003 Location: Idaho Posts: 257	thanks all, I will know soon enough, might have new motor on the road Sunday. __________________ beater 65 gmc at the moment



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