Thats a nicer pic! Im sure it will work great, cant wait to hear it run!
650 is a bit too much for a 273. Also, is it 4 speed? If not, get rid of the dbl pump.
ANY small fairly stock engine should have a vacuum secondary carb and not a DP or other mechanical secondary design. That's one reason the old venerable Holley "780" was so popular, the vacuum secondaries let you throw it onto about anything.
The AFBs and AVSs are also much more forgiving in that regard
I would think a 600 AFB would be about the top of the max
This is terrible advise.
First off you did no tuning on the eninge or carb so to blame it on the carb is just a scapegoat.
2nd a vac secondary carb is nothing but a mask for a problem(s) and thus creates one or them. Only run vac secondaries on a auto car? WTF? Learn how to tune an engine. If it doesn't work right with a mech sec carb you don't have it dialed in...period. I don't know any engine builders that recomend a vac sec carb. My engine builder doesn't even stock them. They are not a better carb they are more driver friendly as you control when the secondaries kick in.
Put the holley back on. Set the timing and then get your idle speed and idle mixture screws set. Get a vaccum reading. Now you are ready to begin digging deeper into the carb.
Eddy 600 all day long.
I've run a QJet off a 72 Chevelle 350 on a stock 273 Commando and it would take whatever cfm that is. I really like the factory AFB's also.
You seem to be outnumbered.....
Give me the proper Holley,every time. I prefer consistent response.....
I've run my share of Holleys like me everyone else has. Just that when I bought my first edlebrock a few years ago, thru it on adjusted the air/fuel and the car was running great within five minutes. Very little adjustment. Time will tell with shitty gas though. The 600 is a good carb for these motors.
Doesn't Holley still make a 600 dp? Anybody try one of those?
A Quadrajet is 750 cfm, Infinately adjustable secondary air valve, like an AVS or a TQ. Thermoquads are definately my favorite. I Dorked with Holleys for a while. They are fine for a race car, but an everyday driver at temps from -20 to 100 degrees, you can have them. I sold all of mine. I'm not a Racer, but I have friends who are. I the end, it comes down to tuning and keeping it in tune for the street. A factory AFB is tuned very well for a 273 Commando. There are 3 steps for enrichment, idle, midrange and WOT. It has an air valve tailored to the little Commando so it doesn't bog when you floor it, but opens when the 273 revs up. The OP asked about a stock Commando.
Any of you guys run a AVS on their Charger/Commando instead of a AFB? I have a 600 AFB on mine and it runs well. The AFB's do have a secondary air valve but it isn't adjustable. I have a 4 speed though and I'll bet the AVS would be better with a automatic. tmm
We had a 1403? 500 cfm on my son's 318 with a small cam and 273 Commando intake. It ran good but I found an original 4295s, rebuilt it and it runs much better. If I remember right, your original Carb, 4119s, was in bad shape? Some of the Carter 600 cfm carbs would not open the secondaries on the original manifold... I measured a 4294s and it only has 1 9/16 secondary blades. Did you check to see if your secondaries are opening after you installed it? Also the secondary air valve is heavy on the Edelbrock compared to stock Commando.