Please read the whole post there is a lot of info here. I have a 1959 Chevy Viking crew cab on a 1973 Chevy C30 Ramptruck chassis with a 454, th400 3 speed transmission, Q-jet, headers, Edelbrock performer 2.0 intake. I will be hauling a 1958 Chevy Delray on the ramp and pulling a 1958 Chevy Impala on a trailer behind. That is 7000 pounds of cars by themselves. Here is my plan and I would like for you to respectably blow holes in it with either experience or past proven knowledge. Not just your opinion cause I have my own. The plan is to bore and stroke the 454 oval port to 496 and go for as much torque as possible. This is NOT a race truck so get that out of your head. It’s for low end torque only and not high performance. The 454 has headers and a Q-jet now. I was thinking of using a 3x1 manifold adapter on top of my Edelbrock performer manifold. I already have the 3 Rochester 2G carbs and the manifold adapter. The good thing is the carbs are the big 1 1/4” venturi ones and already set up for Tripower operation. These flow about 380cfm each which will get me about 1150cfm at full throttle. The cam I will use will probably be a Lunati Voodoo series BBC hydraulic roller tow grind with .575-.592 lift or thereabouts. Here’s my thoughts. 496ci, 3 speed TH400, 4.11 rear with possible future Gear Vendor add on Edelbrock Performer 2.0 for better flow and throttle response Tripower adapter to dual plane manifold with 1 1/4” venturi for mpg and more low end cylinder filling velocity and wow factor appeal plus 1150 cfm at WOT with progressive linkage Lots of hydraulic roller cam lift to get the fuel charge in without sacrificing the bottom end, ground for torque HEI or the like to fire it off Headers to get rid of the nasty Stock converter Most of this stuff I already have and I’m trying to utilize as much as possible What I’m after is just a towing piece of art that will get better than 3gpm, have wow factor and be able to take the 2 58s to car shows every once in a while without asking toooo much of it. Yes I have already heard the go diesel stuff. Don’t bother. I don’t have a diesel I have a 454. Looking forward to your knowledge and experience.
Forget the 3 carbs. Rebuild, rework the quad carb. Quad carb has small primaries just for cruise. With that many cubes you should be making gobs of torque so I'd definitely drop gears especially cruising the hiway with a standard turbo 400. I'd run nothing deeper than 3:73. I built a nice pontiac 455 .030 over, stock intake, my reworked quadrajet, decent cam, lots of detail work in a 80's 1ton chevy dually that pulled a trailer full of steel purlins all over this country with 3:73 gears it would light those duallies up from any stop light and leave the coolest set of black marks, surprised some hot rods back in the day. Point is with cubes\torque less gear is needed and with a little planning and blueprint work on assembly (gasket match ports etc) you can build a monster.
Yea you would theoretically have all those CFM's BUT they all have to crowd down to go through that tiny adapter. Not a good idea.
If you are not drag racing you will need all your usable HP and Torque at low RPM, I would have thought the single 4 barrel would be ample.
You're building a torque engine for sure! Having run BBCs with oval and square ports, I agree 100% with the heads & cam. Possibly consider a 2x4 setup for wow factor, much better fuel distribution than ''choking the chicken'' with all that carbureation into an adaptor. Those things are rarely flow tested. Most recent combo I had similatr to yours: 490 cube bbc stroker Flat tops, roller cam - more hairy than what you'll run Edelbrock street tunnel ram, pair of 500 cfm Thunder series Edelbrocks 4.11 gears NO stumbling, gobs of low end torque.The Gear Vendor O/D is cool. But they eat power. You could save the 3K$ and replace your gears with 3.55s. Let the engines' torque work for you. 500+ lb/ft is what you'll make, easy! '59 pulling a '58, thats classy.
I like your combination except for the carburetors. I feel it’s too much work and upkeep for not enough gain. If you are after low end torque, you don’t need all those CFM. What is your top RPM going to be? Honestly, how much time will you spend there? Remember, Chevy C-60 through C-80 hauled all that weight with a single four barrel. I’ve seen some tandem axle 427 grain trucks haul some ridiculous loads with only a five speed manual transmission behind them. I have no experience with the Gear Vendors overdrive, so I can’t comment on that. However, your rear axle ratio will depend on your cams RPM and your rear tire size more than anything else. If you are going to run a size to properly handle this kind of weight, I’m guessing a size like LT235/85-16? This is a tall (32-33”) tire and going to need some gear. For me, I would start at 4.10 and even go lower if using overdrive. Figure out your tire size you are going to use, then you can calculate your speeds vs RPM in top gear. Be honest with yourself, are you really going to haul this kind of load down the freeway at 100 mph? My guess is that 70 mph would be plenty. People drive 80 everyday, but don’t realize that hauling weight that fast is another matter entirely. Don’t forget about your brakes either. Remember, this is not a B model Cummins, you don’t want to lug the engine. Lastly, would you consider a manual transmission? An NV 4500 would give you an overdrive and four other ratios to play with. Sorry for the long post, but trucks are what I do for a living. I love your project and please keep us updated. Sent from my iPhone using The H.A.M.B. mobile app
Respectfully, as you requested: The Rochester 2G series with the 1 1/4 venturii are rated 381 CFM on the 2 barrel scale. Converting this figure to the 4 barrel scale results in 269 CFM each. Plus, multiple carburetor CFM is not an additive property, so you won't have 3 times 269 (807) CFM total. End of theory, now real world experience: My Dad had an OT motorhome with a 454 (this is mentioned because of the mass of the motorhome comparing to the mass of your setup pulling your trailer). Dad's motorhome had a 800 CFM (200/600) Q-Jet. The Q-Jet worked decently on more or less level ground, but the performance suffered in hilly terrain. Simply insufficient air to feed the mass under load, unless wide open throttle was used, which would downshift the transmission. Dad would try to stay in high to keep from shifting, but would often be in low gear before topping the hill. Dad was an unhappy camper (literally), and asked me what I would suggest. I suggested changing the Q-Jet to a 750 CFM Carter AFB (375/375), and replacing the original intake with an Offenhauser 4-barrel intake. Dad was less than thrilled because the Carter 750 AFB (4760s) had a manual choke. So I said, "what if I make it automatic choke"? He says "can you do that"? The answer is yes. So I "married" the 4760s (750 CFM) with parts from a donor 9635s, specifically the automatic choke, and the fast idle circuit. Then installed the manifold, carb, and while I was at it, installed a fresh air duct to the air cleaner. WHAT A DIFFERENCE!!!!!!! At the time, Dad was furnishing transportation for me (the motorhome) to swap meets. Time from our home in central Missouri to Hershey, PA before the change was 20 hours. After the change 18 hours. And Dad set the speed control exactly the same. The difference was in the performance of the motorhome in hilly terrain. And, we actually improved fuel economy by 6 percent overall (significant with a heavy vehicle). The Q-Jet, even the 800 CFM, has only 200 CFM on the primary side. The AFB had 375 CFM on the primary side. Study carburetion on many heavy duty trucks, and you will find they use large 2-barrel carbs. As an example, GMC used a large Stromberg 2-barrel on their 478 CID. Total CFM is less important on a truck than CFM on the primary side (if a four barrel). Jon.
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