1999 454 carb swap. best street carb, 600? 650? 750? CFM

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

Nasty-LSX

Nasty-LSX

TogetherforeverCovid19
Joined
Nov 22, 2014
Posts
1,395
Reaction score
1,737
Location
HOUSTON TX
First Name
Mi Hung Lo
Truck Year
85/86/87
Truck Model
c10/k10/k20
Engine Size
LSX
I have this carb now it it sucks really bad. Not even going to rebuild it.
You must be registered for see images attach


I'm not asking what carb I need I'm asking whats the best CFM for a stock hydraulic roller 454 with headers and full 2 1/2 in exhaust.
Came out of a 1999 2500 suburban. Vortec fuel injection converted to carb. Its not a race truck just a tow pig or commuter to where ever it goes lol. here is what it looks like in a video. I dont have pics. SQUARE BORE weiand intake.

xc_hide_links_from_guests_guests_error_hide_media
 
carfanatic63

carfanatic63

Full Access Member
Joined
Nov 24, 2014
Posts
56
Reaction score
148
Location
Houston
First Name
Austin
Truck Year
1976
Truck Model
C15 SWB
Engine Size
454
People might disagree but a good quadrajet is hard to beat.

Flows 750-800 cfm, great street manners, plentiful, etc..

Been running one on my 454 for 10 years (intake, headers, exhaust) and it's been fantastic. Starts below freezing, hot, never bogs, great power and throttle response.

It's got better throttle response than most efi systems on new cars in my opinion.

Negatives, they are old at this point so some used ones are missing parts and/or warped. They are also difficult to set up compared to a holley or edelbrock but once they are dialed in, they are fantastic.
 
Nasty-LSX

Nasty-LSX

TogetherforeverCovid19
Joined
Nov 22, 2014
Posts
1,395
Reaction score
1,737
Location
HOUSTON TX
First Name
Mi Hung Lo
Truck Year
85/86/87
Truck Model
c10/k10/k20
Engine Size
LSX
carfanatic63 said:
Negatives, they are old at this point so some used ones are missing parts and/or warped. but once they are dialed in, they are fantastic.
Click to expand...
I agree with everthing you said, but this is why i will not buy a used one. Just going to pic up a Eddy AVS II. :happy160:
 
ali_c20

ali_c20

Full Access Member
Joined
Sep 20, 2016
Posts
1,300
Reaction score
1,852
Location
Austria
First Name
Alexander
Truck Year
1974, 1979
Truck Model
C20, K5
Engine Size
350, 350
The AVS 2 has a great throttle response. I run a 500 cfm on my crate 350 in my K5. I calculated the cfm I need with a carb size calculator. I feared it would be to small but it runs better than ever before. Order a tuning kit with the carb.
 
75gmck25

75gmck25

Full Access Member
Joined
Oct 13, 2016
Posts
2,263
Reaction score
2,203
Location
Northern Virginia
First Name
Bruce
Truck Year
1975
Truck Model
K25 Camper Special TH350 NP203
Engine Size
5.7
The Edelbrock AVS2 seems to be a reliable solution that will probably only need some minor tweaking with springs and rods if you buy the 750 cfm version. A Quadrajet has the potential to be an even better solution, but it’s usually hard to find someone to set it up right.
 
R

Robert Bare

Full Access Member
Joined
Sep 13, 2020
Posts
107
Reaction score
166
Location
MT
First Name
Robert
Truck Year
1978
Truck Model
k20
Engine Size
5.7
What are your complaints? Anyway, best to stick with a square bore carb, adapters suck, generally. Bigest problems with slappin a carb on a FI engine is, they tend to run too rich, and re-calibration is necessary, lots of times. I used to be a wiz at Q-Jets, even set them up for racers, back in the day.
Personally, holly's are easiest to change jets and things in.
 
Nasty-LSX

Nasty-LSX

TogetherforeverCovid19
Joined
Nov 22, 2014
Posts
1,395
Reaction score
1,737
Location
HOUSTON TX
First Name
Mi Hung Lo
Truck Year
85/86/87
Truck Model
c10/k10/k20
Engine Size
LSX
bucket said:
I'd say it can be a happy engine with anything in the 650-850 range.
Click to expand...
Thanks Bucket. I dont want to over or under carb it, Thats why I ask. Just was not sure what a stock 454
should have.
 
Tonimus

Tonimus

Full Access Member
Joined
Sep 17, 2024
Posts
63
Reaction score
108
Location
Phoenix
First Name
Tony
Truck Year
1978
Truck Model
C10 Suburban
Engine Size
454
I've got a QFT SS 850 on my 383. Excellent carb. Was also on a 427 and a 350. Ran great on the 427, just a little big for the 350.
 
JD Miller

JD Miller

Full Access Member
Joined
Sep 30, 2024
Posts
185
Reaction score
389
Location
Goober Idaho
First Name
JD
Truck Year
1981
Truck Model
K20 silverado
Engine Size
350
Get a Quadrajet. Its the Best Carb

I have 3 , 800 Q-jets .

My '81 k20 350 factory original is a 800 q-jet

Built Motor has Hi-perf. heads, perf. Cam, headers, edelbrock perf. intake etc. running a 800 Q-jet with rebuild parts from Cliff Ruggles
https://cliffshighperformance.com/

(Typo, 800 cfm not 850)
 
Last edited:
SquareRoot

SquareRoot

Full Access Member
Joined
Mar 18, 2017
Posts
4,192
Reaction score
8,030
Location
Arizona
First Name
Mike
Truck Year
85
Truck Model
K20
Engine Size
350
carfanatic63 said:
It's got better throttle response than most efi systems on new cars in my opinion.
Click to expand...

Assuming both are properly tuned it's impossible. A dry flow system (EFI) will have better throttle response than a wet flow system 100% of the time. Law of physics. Just saying.
 
bucket

bucket

Super Moderator
Staff member
Super Moderator
Joined
Aug 3, 2010
Posts
30,438
Reaction score
28,342
Location
Usually not in Ohio
First Name
Andy
Truck Year
'77, '78, '79, '84, '88
Truck Model
K5 thru K30
Engine Size
350-454
SquareRoot said:
Assuming both are properly tuned it's impossible. A dry flow system (EFI) will have better throttle response than a wet flow system 100% of the time. Law of physics. Just saying.
Click to expand...

I'm not arguing, but can you explain this further?
 
J

Jimmyperf400

Junior Member
Joined
Mar 29, 2022
Posts
15
Reaction score
13
Location
06606
First Name
Peter
Truck Year
1990
Truck Model
Full size gmc jimmy
Engine Size
Sbc 400
The stock carburetor from gm would of been a 800cfm Quadrajet with electric choke.
 
J

Jimmyperf400

Junior Member
Joined
Mar 29, 2022
Posts
15
Reaction score
13
Location
06606
First Name
Peter
Truck Year
1990
Truck Model
Full size gmc jimmy
Engine Size
Sbc 400
The Q-jet carb is only 800 cfms if you open up all 4 barrels if just driving moderately the front two barrels on a Q-jet are 600 cfms. Everyone bad mouths the q-jet but one of the best street carbs ever made no power valves to blow out and cause a fire. If you want a little extra power as a big block would want at higher rpms the two larger barrels are there to do the job.
 
You must log in or register to reply here.

Similar threads

Nasty-LSX
1986 c10 with 1999 vortec 454 carb swap. degree Timing??? Help
Replies
2
Views
967
Ricko1966
R
C
1973 k20 tranny swap
Replies
2
Views
455
chevykid71
C
68dhayes
Building a new motor for my 79 C10 - would love some advice!
Replies
14
Views
1K
75BEASTK20
75BEASTK20
Urbanburban22
The Overlander: Gen3 LS, 6L90, MP1125 AND BODY SWAP
Replies
3
Views
400
Urbanburban22
Urbanburban22
squaredeal91
1995 454 has 2 timing tabs?
Replies
3
Views
1K
bucket
bucket

Latest posts

Forum statistics

Threads
44,157
Posts
950,595
Members
36,272
Latest member
armchair
Top