2x4 tunnel ram

[Rickuda]

What are the best carbs to run on a dual 4bbl tunnel ram for the strip on a 400 hp 383 magnum?

 

[6PKRTSE]

I would say dual 650's would suffice. Holley offers a dual carb specific pair of carbs in different cfm's. I run dual 1050 Dominators, on the street even.

 

[NoCar340]

I've got a friend with a super-low-mile 1968 Coronet sedan--yes, a 4-door--with a 318 and bolt-action (column-shifted) A230. The engine is stone stock, right down to the OEM single exhaust... except for the dual quad intake. You have to know his sense of humor. Anyhow, when he was doing the swap I told him he was insane, it would never work, blah blah blah. So he installed two 340 AVS carbs on a progressive linkage and promptly proved me wrong. No hesitation, bogs, sags, runs, hits or errors--the thing responds right now and makes a lot less black smoke than you'd expect. I doubt the secondaries even open... but therein lies the beauty: It can't over-carburete itself beyond what happens with the four primaries open, because the secondaries only open as far as demand requires, if there's any demand a'tall. Turns out old age and treachery really do win over (relative) youth and negativity. Obviously the car's no rocket, but it's quicker than you'd expect.

I'm not necessarily suggesting you run AVS carbs, but vacuum secondaries might work better in your application. I realize you really want to do the tunnel-ram thing where, depending on max RPM, a single 750-850 carb could do the job, and I understand that desire. I'd think a pair of good ol' 1850 Holleys (600 vacuum) would work nicely, after being converted to metering blocks for the secondaries and dual-inlet float bowls... I mean, you've gotta look the part, right? Plus, metering blocks are much cheaper and easier to tune. Speaking of cheap, 1850s can be picked up for a handshake and some magic beans at some of the swap meets I attend. It'll eat only what it wants, and leave the rest on the table.

Oh, and my friend isn't completely goofy... his other two '68 Coronets are both 4-speed R/Ts, respectively a 440 convertible he's owned since 1973, and a Hemi hardtop he bought in 2017. The ragtop is a numbers car, but the Hemi was born with a 440. The sedan? That just makes him giggle a lot.

 

[Chryco Psycho]

I would run a pair of reasonable sized Holley type carbs depending on the rest of the combination , the Holley types are far more tunable , I far prefer Proform carbs with adjustable air bleeds & they tend to be more reasonably priced

 

[NoCar340]

I would run a pair of reasonable sized Holley type carbs depending on the rest of the combination , the Holley types are far more tunable , I far prefer Proform carbs with adjustable air bleeds & they tend to be more reasonably priced

There's an excellent 18-page thread on Yellowbullet about air bleeds (idle and main), tuning, jetting, and the idiocy of trendy billet metering blocks with mutliple emulsion jets and high IFRs. The two main advisors, jmarkaudio and yeti, clearly know their stuff and not only tell others what works, but why it works better that way. It has some of the best information I've seen on how Holleys really work (i.e. the idle circuit is almost always active, not just at idle). There's much talk on how to reach the target A:F ratio for whatever situation, and very little of it involves actual main jets. It's great because guys keep reporting back after taking their advice, saying how much better their cars run with '60s-era IAB, MAB, and "emulsion" calibrations rather than what their engine builder, Holley, or whomever set the carb up with in the first place. It takes a couple of read-throughs but it's well worth the time. My 750 Race Demon got flung in favor of an old-school 4780, which ran much better. The car runs better yet with a 9381 (830 annular DP) tuned using their calibration advice. The eye-watering idle is gone, and I've much cleaner transitions and good cruise characteristics... better in every way than the 4780 and light-years better than the BG design--with the cheapest DP metering blocks AED sells, unmodified.

Any Holley can have tunable air bleeds. Pull the old ones, tap the holes, and install brass socket-head set screws drilled for your chosen orifice size. I bought pin gauges, wire-size drill bits, and brass set screws (fifty of the latter costing around $6). I can make any swap-meet Holley as tunable as any variant, and I'll never have to pay for a pre-drilled air bleed or emulsion jet again... but the penny-pincher AED blocks have nearly perfect emulsion ports right out of the box. I didn't touch mine.