Best size carb for a 402 at 5500' elevation? - The 1947 - Present Chevrolet & GMC Truck Message Board Network

glock35ipsc · 05-02-2007, 10:07 AM

I'm going to put a new Performer manifold and carb on Dad's 72 this weekend. Would the 600 or the 750 be the best choice? The engine is a semi-fresh (<1000 miles) all stock rebuild. It's just a driver, no hot rod. At this altitude, I'm torn between the 600 being too small and the 750 being too much.........

Lemield · 05-02-2007, 10:11 AM

Hey Bob...what's up? I had the same problem....put a 750 CFM on my 454 and it seemed too big. Sold it and put a spare 600 CFM on it....now seems too small. Need something in the middle.....700 CFM? Just my thoughts.

Been seeing your progress on the truck....looking good.

glock35ipsc · 05-02-2007, 10:26 AM

Thanks Larry! Hmmm, that's what I was wondering... Edelbrock makes a 600, 650, and 750. Although, most all of the BB Q-Jets were 750 I think. I still have an old Edelbrock jet kit I bought when I built the 454 in my dually. I guess I will just have to play with it.

I got almost all the body work done! Just need to finish the dash and the firewall. Hope to get it in primer in the next few weeks if my back will cooperate!

Ironhead · 05-02-2007, 08:10 PM

I'm not sure if a Holley 600 is the "best size" or not but I have had good luck and decent performance on my mostly stock 71 402/oval port in my 68 3/4T panel. I am getting ready to sit a Holley 670 Street Avenger/Performer manifold on and try it on for size.

1968SWBBigBlock · 05-02-2007, 09:02 PM

600 should be fine on a stock rebuild per holley. You may change to a bigger size squirter and or jet for the backs to help with FOT.

glock35ipsc · 05-02-2007, 09:11 PM

Thanks for the ideas guys, but I'm going with the Edelbrock. They are only available in 600, 650, and 750.

05-02-2007, 10:07 AM	#1
glock35ipsc Next project: 1970 K10 Join Date: Feb 2004 Location: Fort Collins, Colo 80524 Posts: 6,684	Best size carb for a 402 at 5500' elevation? I'm going to put a new Performer manifold and carb on Dad's 72 this weekend. Would the 600 or the 750 be the best choice? The engine is a semi-fresh (<1000 miles) all stock rebuild. It's just a driver, no hot rod. At this altitude, I'm torn between the 600 being too small and the 750 being too much......... __________________ *Bob* 1970 Chevy K10 LWB "Goldie" 350/TH350 *next project!!* 1981 Chevy C10 LWB 355/TH350 - My son's truck LS SWAP FORUM! Tons of LS swap info here! PLEASE CLICK HERE TO SUPPORT THE GREATEST BOARD ON THE NET! CLICK HERE FOR THE FAQ INDEX by KRUE Last edited by glock35ipsc; 05-02-2007 at 10:08 AM.

05-02-2007, 10:11 AM	#2
Lemield Registered User Join Date: Dec 2004 Location: Arvada Colorado Posts: 1,321	Re: Best size carb for a 402 at 5500' elevation? Hey Bob...what's up? I had the same problem....put a 750 CFM on my 454 and it seemed too big. Sold it and put a spare 600 CFM on it....now seems too small. Need something in the middle.....700 CFM? Just my thoughts. Been seeing your progress on the truck....looking good. __________________ Larry 1949 Willys CJ2A, Kubota Turbo Diesel engine, Warn Overdrive, 11 inch brakes, 12volt, Warn M8000 Winch "Little Green" 1970 Rustoleum Roller Red C20 Custom Camper 454 TH400 "Big Red" 1971 K20 6.2 Turbo Diesel 4x4 4spd Ranger Overdrive "Pumpkin Wagon" 2005 VW Beetle Diesel 44+ MPG "Silver Bullet"

05-02-2007, 10:26 AM	#3
glock35ipsc Next project: 1970 K10 Join Date: Feb 2004 Location: Fort Collins, Colo 80524 Posts: 6,684	Re: Best size carb for a 402 at 5500' elevation? Thanks Larry! Hmmm, that's what I was wondering... Edelbrock makes a 600, 650, and 750. Although, most all of the BB Q-Jets were 750 I think. I still have an old Edelbrock jet kit I bought when I built the 454 in my dually. I guess I will just have to play with it. I got almost all the body work done! Just need to finish the dash and the firewall. Hope to get it in primer in the next few weeks if my back will cooperate! __________________ *Bob* 1970 Chevy K10 LWB "Goldie" 350/TH350 *next project!!* 1981 Chevy C10 LWB 355/TH350 - My son's truck LS SWAP FORUM! Tons of LS swap info here! PLEASE CLICK HERE TO SUPPORT THE GREATEST BOARD ON THE NET! CLICK HERE FOR THE FAQ INDEX by KRUE

05-02-2007, 08:10 PM	#4
Ironhead Registered User Join Date: Feb 2007 Location: Westfield, Tioga County) Pennsylvania Posts: 113	Re: Best size carb for a 402 at 5500' elevation? I'm not sure if a Holley 600 is the "best size" or not but I have had good luck and decent performance on my mostly stock 71 402/oval port in my 68 3/4T panel. I am getting ready to sit a Holley 670 Street Avenger/Performer manifold on and try it on for size. __________________ Ironhead Mike '68 Panel 402BB '84 Shortbox 4X4 '85 Blazer '97 Silverado Ext. Cab

05-02-2007, 09:02 PM	#5
1968SWBBigBlock Active Member Join Date: Oct 2006 Location: Ohio Posts: 1,643	Re: Best size carb for a 402 at 5500' elevation? 600 should be fine on a stock rebuild per holley. You may change to a bigger size squirter and or jet for the backs to help with FOT. __________________ 1968 SWB 454 + .040, 490HP x 540 FT pounds of Torque 10-1 Kb Forged pistons, recon rods w/ ARP wave loc bolts 781 heads Ported with 2.19/1.88 SSTvalves Lunati 60204 cam, Micro Trol lifters, Ported Edelbrock Performer Rpm manifold armor coated, Pertronix Triple Strike Ignition Holley 770 Street Avenger carb,Headers armor coated Built by Watson Ruppel Performance in Sarahsville Ohio. Hardshift Tranny Built Turbo 350,TSI 10" 3000 stall 12 Bolt Eaton Posi 4.10 Richmond Gears moser axles 18.5" x 31" Hoosier Pro Street Radials ET Classic 5 Wheels - polished Power Steering, Power Brakes,Disc Brakes,Tach & Gauge Dash, Tilt,Factory Air (gone) Custom Paint & Body Work Special thanks to my wife, my son and my money tree

05-02-2007, 09:11 PM	#6
glock35ipsc Next project: 1970 K10 Join Date: Feb 2004 Location: Fort Collins, Colo 80524 Posts: 6,684	Re: Best size carb for a 402 at 5500' elevation? Thanks for the ideas guys, but I'm going with the Edelbrock. They are only available in 600, 650, and 750. __________________ *Bob* 1970 Chevy K10 LWB "Goldie" 350/TH350 *next project!!* 1981 Chevy C10 LWB 355/TH350 - My son's truck LS SWAP FORUM! Tons of LS swap info here! PLEASE CLICK HERE TO SUPPORT THE GREATEST BOARD ON THE NET! CLICK HERE FOR THE FAQ INDEX by KRUE



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