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#1 |
Registered User
![]() Join Date: Nov 2006
Location: KINGSPORT,TN.
Posts: 3,035
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quadrajet size question
anybody know what CFM the stock Q-JET carb is for a 350 chevy ? and how big same carb is for a 396-402 bbc.
thanks bob
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I BELIEVE IN JOHN 3:16 |
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#2 |
Old Skool Club
![]() Join Date: Jun 2001
Location: Benton, AR "The Heart of Arkansas"
Posts: 10,880
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Re: quadrajet size question
Good question. I'm running an Edelbrock Q-Jet on my truck, which has a 350. The carb is rated 750CFM. It ran great out of the box and still does after 6 years. I think it would be more than adequate on your big block. Based on the computation, what I have is too big for the engine. But it runs great, hasn't flooded or bogged. Always starts. Keeps me braggin'. What else could a man ask for?
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Member Nr. 2770 '96 GMC Sportside; 4.3/SLT - Daily driven....constantly needs washed. '69 C-10 SWB; 350/TH400 - in limbo The older I get, the better I was. |
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#3 |
Registered User
Join Date: Dec 1999
Location: Old Mission, MI, USA
Posts: 2,510
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Re: quadrajet size question
They are all basically the same carb, rated at 750 cfm max. Because of the design of the Q-Jet, it will only flow the air that the engine requires. Big block and small block versions of the carb will have different primary jets and metering rods, and different secondary metering rods.
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Tim |
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#4 |
Account Suspended
Join Date: Sep 2005
Location: Monroe, WA
Posts: 3,815
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Re: quadrajet size question
My understanding is that the Q-Jet will flow 780 CFM unmodified. As noted, it acts like a vacuum secondary carb although it isn't in a pure sense.
Hoping to avoid the "yes it is <-> no it isn't" on the vacuum secondary comment ![]() |
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#5 |
Registered User
Join Date: Feb 2002
Location: Vacaville, CA
Posts: 2,746
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Re: quadrajet size question
There were some Qjets, mostly on BOPC cars the were rated @ 795CFM. You can tell the difference by looking down the primaries:
http://dyeager535.topcities.com/qjetidentify.html
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![]() ![]() 99 Pontiac S/C GTP, SLP Ram Air hood, GMPP Konis & springs 95 Neon ACR, MP PCM, AFX UDP, 3.0 CAI |
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#6 |
Registered User
Join Date: Dec 2006
Location: Trinidad, Colorado
Posts: 642
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Re: quadrajet size question
Blazer1970 is right.......BUT, almost all truck carbs after 1976 were 800CFM, and the Edelbrock carb Model 1906 I believe was an 850!! I do have Cliff Ruggles book if you need technical advice.
![]() That's what's so cool about Q-Jets...they work from 500 cube caddies to 305 smoggers! A.......
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69' 3/4 4X4 470ci BBC 700 HP.... ![]() D60/14bolt 205/465 http://profile.myspace.com/index.cfm...ndid=127691959 |
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#7 |
Registered User
Join Date: Jul 2006
Location: Fair Oaks, CA
Posts: 475
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Re: quadrajet size question
795 cfm I agree with neonlarry, but Im not sure of trucks after 76 being higher could be but Ive never heard of it
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1968 Short Fleet 350/700r4 http://67-72chevytrucks.com/vboard/s...d.php?t=249435 1997 Bagged XtdCab Vortec350/4L60e http://67-72chevytrucks.com/vboard/s...44#post2286144 1993 XtdCab Longbed 4x4 6.5Turbo/NV4500 "Daily Driver" 1985 Toyota XtdCab 4x4 22re/W-56/Dual T-cases, Doug Thorley Header, Homebrew front and rear spring packs, Tons of Mods to suspension and drivetrain, 35" boggers, coming soon ARB's and 5.29's, Possible 4.3/700r4 swap |
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#8 |
Registered User
Join Date: Dec 2006
Location: Rhode Island
Posts: 602
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Re: quadrajet size question
Yeah. 200 CFM through the primaries and 600 CFM through the secondaries.
That's largely why they are so driveable and fuel efficient around town/cruising and yet still yield the "Big Gulp" when smashing the throttle. Really a pretty decent design for a street carb, IMO.
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69 C-10 SWB Fleetside 454/TH400 (For Sale) http://67-72chevytrucks.com/vboard/c...ct=1299&cat=12 70 El Camino 454 TH700 29 Model A 4-DR Sedan Deluxe |
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#9 |
Well, Whoop-dee-do!
![]() Join Date: Mar 2003
Location: Easton, Mo. pop.- me & scarcely a few others
Posts: 2,302
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Re: quadrajet size question
Buick was the first to use the larger Qjet, on the 455 in 1971, and they quit using the small Qjet on all 455's from then on. I think it was due to the fact that the B-455 loves air, and you would have to "tip into" the secondaries too easily on hills/etc. It also gives you a higher cruising speed on the primarys. Chevys seem to be a hit/ miss as to which one they have.
I had a warmed- up '71 Buick 455 with 2.73 gears & a TH400, the big Qjet- it would run 115 mph without touching the secondaries ![]()
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'68 GMC shortbox 4x4 350/SM465/T221- bought it in '83 SOLD ![]() '72 K20 500 Cad/TH400/NP205 SOLD ![]() '92 Chevy 2500 6.5 mech TD 4L80E crusty daily driver '72 Monte Carlo... sweet low mile toy '11 Dodge Challenger IE 392 6spd... midlife car ![]() |
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#10 |
Registered User
Join Date: Dec 2006
Location: Trinidad, Colorado
Posts: 642
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Re: quadrajet size question
Click the link under my signature and watch a Q-Jet on 500 horses do its work...Straight out of JEGS!!! Yes, this same carb will work on a 305 with very minor jet changes.
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69' 3/4 4X4 470ci BBC 700 HP.... ![]() D60/14bolt 205/465 http://profile.myspace.com/index.cfm...ndid=127691959 |
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#11 | |
Sierra Grande Club
Join Date: Jan 2007
Location: New Mexico USA
Posts: 2,433
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Re: quadrajet size question
Quote:
NICE! ![]()
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1971 GMC Sierra Grande, 1/2 ton short wide, original 4 bolt 010 020 block & heads. (matching #'s). 383 stroker, SMI q jet 750 cfm, Lunati Voodoo 60102 cam, Scorpion roller rockers, Spin Tech pro street mufflers with X pipe. ![]() |
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#12 |
Registered User
Join Date: Jul 2006
Location: Fair Oaks, CA
Posts: 475
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Re: quadrajet size question
Q jets are probably the best drivability and performance carbs out there hands down and you cant argue that, Ive seen people throw on a holley thinking they have a race car and get there doors blown off by a guy with a q jet I had one on my 79 malibu I had when I was 16 and we replaced the 305 with a 450hp 350 my pops rebuilt the carb and changed jets for me and that thing screemed, They work very well and can be very economical under easy driving
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1968 Short Fleet 350/700r4 http://67-72chevytrucks.com/vboard/s...d.php?t=249435 1997 Bagged XtdCab Vortec350/4L60e http://67-72chevytrucks.com/vboard/s...44#post2286144 1993 XtdCab Longbed 4x4 6.5Turbo/NV4500 "Daily Driver" 1985 Toyota XtdCab 4x4 22re/W-56/Dual T-cases, Doug Thorley Header, Homebrew front and rear spring packs, Tons of Mods to suspension and drivetrain, 35" boggers, coming soon ARB's and 5.29's, Possible 4.3/700r4 swap |
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#13 | |
Junior Member
Join Date: May 2006
Location: W-S, NC
Posts: 211
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Re: quadrajet size question
Quote:
Q-jets were installed on the '85 and '86 C10's with the 4.3 liter ( 262 c.i. ) before the tbi system. Seems to work quite well on my '86. ![]()
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Have fun, Don |
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#14 |
blood type; Retumbo
Join Date: Jan 2004
Location: next to my reloading bench
Posts: 10,269
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Re: quadrajet size question
keep in ind they changed more than jets and rods from one engine to another. each calibration has different air bleeds, aeration tubes, etc.
getting all these to match is like listening to a symphony compared to a simple jet/rod change being a grunge band. there are books out there which cover this in detail. "how to build horsepower, volume II" is a good starting point. |
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#15 | |
Junior Member
Join Date: May 2006
Location: W-S, NC
Posts: 211
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Re: quadrajet size question
Quote:
Using emission control equipment ( EGR, vacuum delay, hot air intake, ETC. ) or not has an effect as well.
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