Carburetor questions - The 1947 - Present Chevrolet & GMC Truck Message Board Network

byates2 · 12-07-2012, 06:52 PM

I have a recently rebuilt engine. It was bored to a 390 and is stroked out.

I have a edelbrock performer series manifold on it with a 600 cfm 1406 carb.

I want to go bigger then that. Would an edlebrock thunder series 800 cfm be ok or would that potentially flood the engine?

Any recomendations??

truckster · 12-07-2012, 07:27 PM

I don't know about the Edelbrock 800, but the Quadrajet might be a good option. One of the beautiful things about the Quadrajet is that the secondaries are vacuum operated, so they only open as far as the engine can use.

geezer#99 · 12-07-2012, 07:42 PM

Leave it alone. Your 600 is big enough!
As for the quadrajet. They're not vaccuum secondaries. Secondary air valve is controlled by spring pressure.
Here's a cfm calculator.
http://www.carburetion.com/calc.asp

byates2 · 12-07-2012, 08:04 PM

well i want to replace the carb anyway because its old and pretty worn and i want to get something a lil more performance. The thunder series doesnt seem to have 600, only 650 cfm. Would that make much difference

truckster · 12-07-2012, 10:02 PM

Quote:

Originally Posted by geezer#99

Leave it alone. Your 600 is big enough!
As for the quadrajet. They're not vaccuum secondaries. Secondary air valve is controlled by spring pressure.
Here's a cfm calculator.
http://www.carburetion.com/calc.asp

While it's true the Quadrajet secondaries aren't "pure" vacuum secondaries, the secondaries will only open as far as the vacuum pulls them open (the spring determines the amount of resistance).

PanelDeland · 12-07-2012, 10:11 PM

Th ething to remember is that in carbs bigger is not better,depending.If it's a street driven truck a 650 is plenty.Many claim you want a 750 but the vacuum signal from a 650 will give better response on the street for normal driving. A smaller carb is also less sensitive to tuning for normal street use.

hfd410 · 12-07-2012, 10:16 PM

I have the 650 thunder series on a performer intake. Its on a .040 over 350 with goodies. You have a few more inches but this set-up runs really good on mine...

piecesparts · 12-08-2012, 12:32 AM

I also have an Edelbrock 650 Thunder carb on an engine. Mine is a 385 stroker engine with a 700 R4 tranny and a 3.73 gear ratio. I will say the 650 is a good street carb, after you tune it to your driving. I will also say the carb is limited on what you can max out in performance. I had a 750 on my truck for a while and found it to not work well with my cam and what level of stall I had on my tranny. I changed the carb to the 650 and later changed the stall numbers on the converter and I could possibly go back to the 750 carb, now. The 750 gave me a higher set of RPMs that I could acheive from the engine, where the 650 just runs out of air at those speeds. I do not normally drive with the engine at RPMs above 3000 to 3500, but it is nice to know that the capability is there when you need it. My setup runs very well and the 650 will let me work the truck hard in normal driving and it handles very well. Unless you are going to the track and planning to run at very high RPMs or using the engine in a truck pull, you do not need a larger carb.

hfd410 · 12-08-2012, 12:36 AM

mine is a .040-350/ TH350 with shift kit, eagle red clutches, 2200 stall, and 3.73 gears

12-07-2012, 06:52 PM	#1
byates2 Registered User Join Date: Feb 2007 Location: Acton Posts: 158	Carburetor questions I have a recently rebuilt engine. It was bored to a 390 and is stroked out. I have a edelbrock performer series manifold on it with a 600 cfm 1406 carb. I want to go bigger then that. Would an edlebrock thunder series 800 cfm be ok or would that potentially flood the engine? Any recomendations?? __________________ 1967 C10 Long Bed, Soon to have a 350 1997 Chevy 2500 454 BB

12-07-2012, 07:27 PM	#2
truckster Registered User Join Date: Jan 2001 Location: Orem, Utah Posts: 7,982	Re: Carburetor questions I don't know about the Edelbrock 800, but the Quadrajet might be a good option. One of the beautiful things about the Quadrajet is that the secondaries are vacuum operated, so they only open as far as the engine can use.

12-07-2012, 07:42 PM	#3
geezer#99 Registered User Join Date: Aug 2009 Location: Bowser Posts: 13,738	Re: Carburetor questions Leave it alone. Your 600 is big enough! As for the quadrajet. They're not vaccuum secondaries. Secondary air valve is controlled by spring pressure. Here's a cfm calculator. http://www.carburetion.com/calc.asp Last edited by geezer#99; 12-07-2012 at 07:59 PM.

12-07-2012, 08:04 PM	#4
byates2 Registered User Join Date: Feb 2007 Location: Acton Posts: 158	Re: Carburetor questions well i want to replace the carb anyway because its old and pretty worn and i want to get something a lil more performance. The thunder series doesnt seem to have 600, only 650 cfm. Would that make much difference __________________ 1967 C10 Long Bed, Soon to have a 350 1997 Chevy 2500 454 BB

12-07-2012, 10:11 PM	#6
PanelDeland I am a Referee of life. Join Date: Jun 2000 Location: Greensboro N.C. Posts: 13,992	Re: Carburetor questions Th ething to remember is that in carbs bigger is not better,depending.If it's a street driven truck a 650 is plenty.Many claim you want a 750 but the vacuum signal from a 650 will give better response on the street for normal driving. A smaller carb is also less sensitive to tuning for normal street use. __________________ The 47-present Chevrolet and GMC Truck Message Board Network,it's owners,moderators,members,and associates of any type should not be held responsible for my opinion. You can't fix stupid,not even with duct tape. "My appearance is due to the fact that "GOD" does punish you for having too much fun!" Barrett-Jackson has perfected alchemy,they make rust into gold! "You can lead a horse to water but you can't saddle a duck" "Cleverly disguised as a 'Responsible Adult' "Sometimes your Knight in shining armor is just a retard in tinfoil"

12-07-2012, 10:16 PM	#7
hfd410 Registered User Join Date: Jul 2012 Location: Burleson Texas Posts: 570	Re: Carburetor questions I have the 650 thunder series on a performer intake. Its on a .040 over 350 with goodies. You have a few more inches but this set-up runs really good on mine...

12-08-2012, 12:32 AM	#8
piecesparts Parts and more parts Join Date: Nov 2003 Location: Lebo, Kansas (middle of nowhere Posts: 6,821	Re: Carburetor questions I also have an Edelbrock 650 Thunder carb on an engine. Mine is a 385 stroker engine with a 700 R4 tranny and a 3.73 gear ratio. I will say the 650 is a good street carb, after you tune it to your driving. I will also say the carb is limited on what you can max out in performance. I had a 750 on my truck for a while and found it to not work well with my cam and what level of stall I had on my tranny. I changed the carb to the 650 and later changed the stall numbers on the converter and I could possibly go back to the 750 carb, now. The 750 gave me a higher set of RPMs that I could acheive from the engine, where the 650 just runs out of air at those speeds. I do not normally drive with the engine at RPMs above 3000 to 3500, but it is nice to know that the capability is there when you need it. My setup runs very well and the 650 will let me work the truck hard in normal driving and it handles very well. Unless you are going to the track and planning to run at very high RPMs or using the engine in a truck pull, you do not need a larger carb. __________________ Frank

12-08-2012, 12:36 AM	#9
hfd410 Registered User Join Date: Jul 2012 Location: Burleson Texas Posts: 570	Re: Carburetor questions mine is a .040-350/ TH350 with shift kit, eagle red clutches, 2200 stall, and 3.73 gears



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