I have a 1973 modified 350 engine. It has original L-82 short block, aluminum angle plug heads, Torker II, Crane 70 LT-1 cam, Isky lifters, Moly rods, Comp Cams roller tip rocker arms,HEI ignition. It has the Muncie M-21 and 4:11 posi rear.

I was thinking of a Holley 650 DP or maybe the 750 DP but I'm thinking the 750 might be a little to big. This is not a daily driver but I want something with a choke. What are your suggestions?

 

I'm not a fan of the Torker II. You will do much better with a Performer RPM (pn #7104) which has the port sizes of the Performer RPM Air Gap, and is drilled for both a spread-bore or a square-bore carburetor.
Personally, I'd use the Quadrajet carb which has small primaries like a 600, but has overall flow of 750 or 800 cfm - Best of both worlds!

 

If its a toy and mileage isn't a concern get a Holley 750 mechanical secondary 4150 model carb. You have a manual trans and a steep gear so you would be better of with a mechanical secondary over vacuum. They offer a model with a choke but if this is going to be a nice day toy you don't really need it. My choke is disabled and it starts fine.

 

I have my Q jet and love it, its been tweeked a little for my zz4 by the best.....

 

I agree with the mechnical secondary. If the 750 won't be to big than I'll probally go with that. Yes this will be a nice day toy. How much of a difference would the MPG be between a 650 and 750 driving normal?

 

The difference would be very hard to detect if each carb is setup properly as the engine combo will determine the majority of how much fuel and air is sucked in. Go with the 750 as the WOT will be the big factor.

 

If you use the tried and true basic formula for carburetor selection (Cubic inches x max. RPM / 3456) and use 7000 RPM as your max RPM it works out to 708 cfm. If you use 6500 as a max RPM it works out to 658 cfm. My personal experience with Holleys on my vintage racer (Sorry, it's a Ford but the Holley didn't know!) was with a 750 double pumper on a +.040" over 302 (about 306 inches) with a .557" intake lift cam and 7000 RPM redline-that particular combination absolutely screamed at high RPM's but it would not respond to idle mixture adjustments, so I just bottomed out all four idle mixture screws and ran it that way at the track. I also had a 4.11 rear gear. The 750 also lacked real crisp low-end response, but again, where I was running it , at high RPM's, it ran beautifully. When I streetified the car with a 331 inch stroker and the same cam I went to a 650 cfm 4150 which then would respond nicely to idle mixture changes and was very snappy on the primaries but when I took it to Willow Springs for a track day was starving at upper RPM's. Switched back to the 750 and it was like a complete different car, blubbery bottom end and again screamed up top.
I think for your combination and for what it sounds like you want to do with the car your best bet is a 750 cfm 4150 double pumper. With 350 inches to start with and a healthy solid-lifter cam it should respond to changes in idle mixture OK and especially with the short rearend gears will give you the punch you want at higher RPM's. There are those of course who are devoted to Quadrajets (I have one on my unmodified, low hood clearance, cruiser C3) and they certainly do have their place but if you choose the right Holley for your application and tune it correctly you can have reasonably decent fuel economy (your gearing will be the biggest problem there) and the tunability of a Holley. QJets can be tuned and modified of course but it's a PITA even on a good day because they simply weren't designed for tuning and modification...my $1.380

 

Most people will buy a new double pumper 750, along the lines of the 4779, based on cost. So whats changed on it in 40 yrs, next to nothing. Yep it does now have some blow out protection for the fuel enrichment valve, some better gaskets this is pretty much it. same boosters, same poor very little adjustability, same cast aluminum parts. You put it on your street car with pretty good idle vacuum the idle circut in it is set up for lower idle vacuum pull of a race cam, now the idle is to rich.

Would you like much stronger annular boosters, four corner idle adjustment, the ability to change idle feed channel restriction,, simply change your idle and high speed air bleeds. better ( not cast ) billet aluminum throttle plate, billet mettering blocks. The electric choke you want. None of this stuff is on the 40 yr old tech 4779. Part # QFT-SS-750-AN. $100.00 extra to get past 40 yrs ago.The carb is already setup with being a street carb in mind.

The annular boosters on a street car just alone by themself would be worth the price of admission. Then you get all the adjustabilty.