273 carb choice

-
jh66cuda

jh66cuda

Well-Known Member
Joined
Mar 17, 2013
Messages
47
Reaction score
15
Location
Ontario
I purchased a 66 273 Barracuda, the engine was rebuilt before I purchased it and the car runs great..It came with the orginal 4121s AFB carb and I can't find the CFM rating for it but I assume its in the low to mid 400's. The engine's dyno sheet shows 352hp @ 6000 rpm and was dynoed with a 660 CFM..The heads were ported, 10:1 comp ratio, .050 cam..it also has a Elderbrock performer intake, AL6 msd ing box, headers etc.. I don't want to over carb it so does anyone have any suggestions!!
 
jh66cuda said:
I purchased a 66 273 Barracuda, the engine was rebuilt before I purchased it and the car runs great..It came with the orginal 4121s AFB carb and I can't find the CFM rating for it but I assume its in the low to mid 400's. The engine's dyno sheet shows 352hp @ 6000 rpm and was dynoed with a 660 CFM..The heads were ported, 10:1 comp ratio, .050 cam..it also has a Elderbrock performer intake, AL6 msd ing box, headers etc.. I don't want to over carb it so does anyone have any suggestions!!
Click to expand...

The 4121 AFB is around 500cfm, and that would be a good carb choice for your engine.

".050" tells us nothing about your cam....that is merely a factor in measuring it.

Please...PLEASE...not Elderbrock...EDELBROCK!!!
 
Auto,600 Edelbrock, manual choke.4 spd,the smallest Edelbrock AVS. Are you sure,about that 352 h.p. post? If so,cam specs needed.
 
I can only go by the documents i was given. I have the intake off and for sure the heads were ported and everything looks fresh.

valve lift int .443 - duration 214
valve lift exh .456 - duration 224

cam lift int .295
cam lift ext .310
Duration SAE intake 288/ext 298

1.5:1 rockers

Also has 3000 stall 4;10 gears 904
 
I can only go by the documents i was given. I have the intake off and for sure the heads were ported and everything looks fresh.

valve lift int .443 - duration 214
valve lift exh .456 - duration 224

cam lift int .295
cam lift ext .310
Duration SAE intake 288/ext 298

1.5:1 rockers

Also has 3000 stall 4;10 gears 904
 
Cam,fairly decent. Any idea,on head porting? This cam,shouldn't need more than a 600,650 vacuum secondary. A AFB / Edelbrock will work. My choice if you can find it: 625 Carter Competition Serires AFB.
 
Carter #4121S AFB

1 7/16" Primary......(1.063" Venturi)
1 9/16" Secondary..(1.250" Venturi}

500 CFM (Factory Rated)

Though some will say that they can flow at 517 to 525 CFM
 
I have a 600 eddy on mine with Comp cams 20-246-4, 468 lift. solid. works great with a stock intake. I have a D4B which I have not tried yet.
 
i was looking at a 650 avs "eldelbrock" only because I don't see where they are available in a 600. from whats on thier web site they start at a 500 and jump to a 650..
 
Didn't know the AVS ,sizes. The 625,was dropped ,30 years ago by Carter .
 
I'd go with the AVS @ 650. Use a K&N extreme flow air cleaner with it.
 
The stocker is a 500 cfm like the guys said before. A 600 or 650 Edelbrock will work fine. I like the specs of that cam. Is it a hydraulic or solid. Do your specs say what brand it is? tmm
 
Summit/ Mellings/Crane,TMM .Most likely,old Crane. Same grind ,on Chev's.It does work,until past bowl ported heads.
 
jh66cuda said:
I can only go by the documents i was given. I have the intake off and for sure the heads were ported and everything looks fresh.

valve lift int .443 - duration 214
valve lift exh .456 - duration 224

cam lift int .295
cam lift ext .310
Duration SAE intake 288/ext 298
Click to expand...

Pretty mild....also known as "RV" or "jobber" cam"...lazy ramps....probably on a 112*/114* CL. Stock AFB or 500/600 Holley or Carter/Edelbrock carb will be fine.
 
Welcome jh. I agree with the others, 600/650 range carb.....

Might not be a popular comment among the 273 guys, but i have to say, that was a pretty friendly dyno that engine was run on.....
 
If you could find one,

The Carter #3447 AFB is rated at 600 CFM.

This Carburetor was used on the 1962 '413' Super Stock and
1963 '426' Super Stock (Stage 1)

Primary........1 7/16" (1.186" Venturi)
Secondary....1 11/16" (1.563 Venturi)

This AFB was all the rage back in the day for the 273 Commando.

I use one on our 273 Commando 'Magazine Test Car'.
 
I have a holley 570 street avanger carb if that is of intreset to you. It looks like a 750 but is 570 CFM so you get the best of both worlds. It has an electric choke and has very few hours on it. PM me if you are interested and we can talk.
 
The Commando 273 in '66 used a Carter 3855 S carburetor which was rated at 625 cfm. In the Competition Series 9607-9641 are also rated at 625. The differences among these are choke, metering rods, and secondary jets.

In general, the smaller carb (500 - 550 cfm) will yield better throttle response. A larger carb will produce better top end at the expense of low end bog. For a street ride, I'd go with something in the 600 to 650 cfm range using a vacuum operated secondary (like the Carter/Eddie carbs discussed above). IMHO avoid mechanical secondary carbs on a street driven, small displacement engine (like the 273 & 318 ) with an automatic transmission.

It may be worth noting that the 318 cop car engine used a Rochester Quadrajet on it. The smallest Quadrajet is rated at 750 cfm. My Demon uses a Carter Competition Series AFB 9635 with a mild cam. Throttle response is very good. These combinations work because they have vacuum operated secondaries.
 
2 Darts,,,,,,

Check those 'numbers' again.........

1965 '273 Commando'
#3853S
#3854S

1966 '273 Commando'
#4119S
#4120S

1967 '273 Commando'
#4294S
#4295S

All '273 Commando' Carter AFB's were Rated at 500 CFM by Carter.

Primary........1 7/16" (1.063" Venturi)
Secondary....1 9/16" (1.250" Venturi)
 
You must log in or register to reply here.
-

Back
Top