what size is the stock 4bbl carb on an lg4
#3
In other words, well more than any 305 would likely ever require, and more than enough for all but the highest RPM 350s. These things used to feed 454s and 455s to 5,000+ RPM with no problems, and did it by the millions. If you want reassurance, just open the secondaries and look at the bore sizes. Then remember that NASCAR engines with restrictor plates have only four 7/8" bores to make 700HP.
#4
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Car: 1986 firebird trans am
Engine: 350
Transmission: 700r4
i guess this is one of those things that nobody knows isnt it ? and here i thought it was a simple question that atleast some one on here had to know
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Car: 1984 Z28 Hardtop
Engine: 383 Carb
Transmission: 4L60
Axle/Gears: 3.54 Dana 44
Actually it's one of those things that pretty much everyone knows.
The factory never "rated" OEM carbs for flow like the aftermarket manufacturers do. Even in the aftermarket there are variations in testing. Some manufacturers might test wet flow, some might test dry, some might vary the pressure differential, all of which lead to variations in flow.
The factory never "rated" OEM carbs for flow like the aftermarket manufacturers do. Even in the aftermarket there are variations in testing. Some manufacturers might test wet flow, some might test dry, some might vary the pressure differential, all of which lead to variations in flow.
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Car: 1986 firebird trans am
Engine: 350
Transmission: 700r4
Originally posted by Apeiron
Actually it's one of those things that pretty much everyone knows.
Actually it's one of those things that pretty much everyone knows.
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Car: 1986 firebird trans am
Engine: 350
Transmission: 700r4
because it just happens to be somthing that i want to know right now. and i figured that it would be a quick and simple question that would get a quick and simple and correct answer. but i guess i was hoping for a bit to much
#9
If you're arguing with your friends with the hoods up in the McDonald's parking lot, you can tell then "1,080 CFM". That should shut them up.
Beyond that, the total flow has little relevance. Using a "Holley-type" rating is just as insignificant, whether your friends understand that or not. Advertising numbers mean little. Results are king.
If you really want to throw numbers around, the typical post-1972 Rochester 4MV/E4ME (QuadraJet) has a peak primary flow of 161 SCFM @ 1.5" Hg PD, and 760 SCFM on the secondary side. At 3.0" Hg PD the primary flow peaks at 227 SCFM, and total flow with secondaries is 1,080 SCFM.
Comparatively, the ratings of a Holley 1850/4150/4160 are at 300/600 SCFM @ 1.5", and 424/848 SCFM @ 3.0" Hg PD.
Strictly by the numbers, a Holley is generally a big step backward. That, of course, is with no regard to the cool stickers you get with every Holley purchase, and the stigma that surrounds the name - Deserved or not. In primary fuel metering and transition, the step backwards is more along the order of 4-5 times worse than a proper Rochester 4MV.
Beyond that, the total flow has little relevance. Using a "Holley-type" rating is just as insignificant, whether your friends understand that or not. Advertising numbers mean little. Results are king.
If you really want to throw numbers around, the typical post-1972 Rochester 4MV/E4ME (QuadraJet) has a peak primary flow of 161 SCFM @ 1.5" Hg PD, and 760 SCFM on the secondary side. At 3.0" Hg PD the primary flow peaks at 227 SCFM, and total flow with secondaries is 1,080 SCFM.
Comparatively, the ratings of a Holley 1850/4150/4160 are at 300/600 SCFM @ 1.5", and 424/848 SCFM @ 3.0" Hg PD.
Strictly by the numbers, a Holley is generally a big step backward. That, of course, is with no regard to the cool stickers you get with every Holley purchase, and the stigma that surrounds the name - Deserved or not. In primary fuel metering and transition, the step backwards is more along the order of 4-5 times worse than a proper Rochester 4MV.
Last edited by Vader; 08-07-2005 at 11:06 AM.
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Originally posted by zeek
well if its one of those things that every one knows why cant i get a str8 answer ???
well if its one of those things that every one knows why cant i get a str8 answer ???
Perhaps is the words "straight", "can't", and "too" could be typed correctly, a "str8" answer would be forthcoming.
Strange, "isnt it ?"
There's a cool and helpful web address called "Google". The "web?" - You know, that thing Al Gore invented. You can find all sorts of trivial information there, like this:
http://www.mergetel.com/~fraso/RasoE...arburetion.htm
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Car: 1993 Nissan 240sx
Engine: Turbo KA24DE
Transmission: 5 spd
Axle/Gears: 4.08 VLSD
Originally posted by Merlin
And I thought that "every one" knew about Google...
Perhaps is the words "straight", "can't", and "too" could be typed correctly, a "str8" answer would be forthcoming.
Strange, "isnt it ?"
There's a cool and helpful web address called "Google". The "web?" - You know, that thing Al Gore invented. You can find all sorts of trivial information there, like this:
http://www.mergetel.com/~fraso/RasoE...arburetion.htm
And I thought that "every one" knew about Google...
Perhaps is the words "straight", "can't", and "too" could be typed correctly, a "str8" answer would be forthcoming.
Strange, "isnt it ?"
There's a cool and helpful web address called "Google". The "web?" - You know, that thing Al Gore invented. You can find all sorts of trivial information there, like this:
http://www.mergetel.com/~fraso/RasoE...arburetion.htm
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Car: 1982 Trans-Am
Engine: 355 w/ ported 416s
Transmission: T10, hurst shifter
Axle/Gears: 10 bolt, true-trac, 3.73
Is this some kind of joke? good ***, the first reply had the answer:
750-800CFM
Did you miss that or something? Most were "rated" at 750, with a handful out there with slightly larger secondaries putting them at 800CFM....
They're a damn good carb.
750-800CFM
Did you miss that or something? Most were "rated" at 750, with a handful out there with slightly larger secondaries putting them at 800CFM....
They're a damn good carb.
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Car: 1984 Z28 Camaro
Engine: H.O. 355 NOS
Transmission: 700R4
Well, the stock Q-Jet on my L69 had a tab on the sec. air valves that restricted their opening thus reducing the air flow (CFM) through the sec's. Wouldn't that reduce the CFM rating of this carb say to around 600 cfm?
Auggie
Auggie
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Car: 1984 Z28 Hardtop
Engine: 383 Carb
Transmission: 4L60
Axle/Gears: 3.54 Dana 44
Something like that, but it's nothing that can't be removed in a few seconds. That's why in my reply I said they can be made to flow 750 CFM.
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Car: 1984 Z28 Camaro
Engine: H.O. 355 NOS
Transmission: 700R4
Exately! We do that when we run a Q-Jet on the dyno and drill and tap a hole just above that removed tab and install an allen head screw. This screw will allow us to be able to adjust the open angle of the sec. air valves.
Auggie
Auggie
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Car: 1982 Trans-Am
Engine: 355 w/ ported 416s
Transmission: T10, hurst shifter
Axle/Gears: 10 bolt, true-trac, 3.73
Auggie (or anyone else), suppose you have a picture of that tab removal / set screw placement?
I'm just not able to picture it, are we talking about removing the vertical "plate" thats in the secondary air valves (a simple pull and remove), or a tab on the secondary air valve shaft on the outside of the carb? I remember reading about this on the main page, but it was lacking the necessary 1000word picture....
Thanks
I'm just not able to picture it, are we talking about removing the vertical "plate" thats in the secondary air valves (a simple pull and remove), or a tab on the secondary air valve shaft on the outside of the carb? I remember reading about this on the main page, but it was lacking the necessary 1000word picture....
Thanks
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Car: 1984 Z28 Camaro
Engine: H.O. 355 NOS
Transmission: 700R4
Sonix, it is the tab on the sec. air valve shaft on the outside of the carb. You will see that that tab prevents the air valves from opening to their 90* max. This limited the 750 cfm Q-Jet to a guess of around 550 to 600 cfm. I use a cut off tool to remove the tab and then locate the allen head set screw just above it so you can make air valve angle adj. I do not have any air valve spring tenision (see pic) because the dash pot controls the opening rate of the sec. air valves which is slow by the way. I have a dash pot from the Carb Shop that opens instantly but that is another story.
Auggie
Auggie
Last edited by Auggie; 05-04-2006 at 11:03 AM.
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