you've all seen the adapters that sit on top of 4-71 and 6-71's to run 3,4 and 6 carbs. what mods do you have to make to the carbs run in these applications? i would think at the very least, tight fitting throttle plates and heavy return springs. if you go to dyers website, they'll sell blower carbs that are darn near twice the price of a regular 4bbl. what makes them special? so four 97's atop a 4-71 or a 650cfm holley?
A lot depends on you, the look, and performance you want. Many favor the Stromberg over the Holley 94 when using 2 barrel carbs due to the Stromberg having a mechanical power valve. And in some cases physical size. The issue with any carb that uses a power valve is that when on top of a blower the carb base see vaccum all the time. A blower prepped carb has the signal for the power valve moved from the carb base to under the blower. Many say you don't need it and will remove and plug the power valve. In most cases the engine will run very rich at part throttle. In my opinion the Stromberg setup gets the right look. The 650 will be the easy one to tune.
I ran eight 97s on my blown hemi. The stock 97 throttle blades are round. They dont seal well. The more carbs the more air leaks by. It can be hard to control the idle speed. I used throttle blades made by dick Crawford. They had a 13 degree bevel cut on both sides of the blades. The blades were oval shaped and fit tight. I could close them enough to kill the engine. The other possible air leak is the throttle shafts. They need go be perfect or again the idle will be uncontrollable. The float bowls are very small. A blown engine can suck them dry fast. A good fuel delivery set up is a must. I ran a fuel log with 8 individual lines. I also increased the hole in the needle and seat assemble. Tight linkage is a must. Sloppy linkage ruins drivability. Good swivel heims threaded right and left screwed into hex shafts work good. I use a angle gauge to set up all the arms at the same angle. Make sure the linkage doesn't bind. Have a toe loop on the gas pedal just in case it does get stuck. Dont use springs that are bigger than needed for return springs. If you do the linkage will flex causing all kinds of problems. Having a air fuel gauge is the only way to get the jetting right. I used externally adjustable jets. That way everything doesn't need to come apart to make a adjustment. Carry a extra float in the car at all times. I have changed out floats several times on the side of the road.
stop it, you're scaring me. i'm talking four 97's on top of a 4-71 making 4-6 lbs of boost. @dickster27 @uncle max
I only have 3, I ran out of room and money. Built in England, Clive knew they were going on the blower. Progressive linkage, runs on the center till practically half throttle. Center is the only one choked for that reason. I tried running all three at once and it was way too much carb for my flatty. Uber low fuel pressure (2-3 Pounds) is the key I found out.
If I can find my notes, I tuned the 4 97's on my friends coupe years ago. He had a duel bowl Holley on it then swapped to the 97's. I have a 4-71 on my 283 with a 50 Caddy WCFB. My choice would be the 97's.
Hello, When we were teenagers, we decided to get into the Gas Coupe and Sedan Class. One of our best friends already had a big Olds motor in a 5 window coupe and was fairly successful in A/Gas. So, after being in the A/Stock class since 1957-58 with our 58 Impala, we were now being overpowered by 40-50 hp with the newer cars at Lions. Then, in 1959-60, after finding the 1940 Willys coupe, we went searching for a 283 SBC motor. We weren’t particular about whether the motor was complete or not, we had plans that could adapt to whatever we were able to find. A complete ready to run SBC at Reath Automotive was above our budget, so we looked around at other smaller local shops. Finally, we found a long block SBC with an Isky Cam and Jahns Pistons in a small, neighborhood speed shop. We wanted to drive it on the street, so running the Hilborn Injectors (our first choice) was not going to work. No one could make the adjustments to allow ordinary street driving, using the port injectors. (We originally wanted those cool long injector stacks, too.) The same small speed shop had a new set up with 6 Strombergs on a Edlebrock manifold sitting on the counter. We mentioned the Hilborn port injectors and the discussion started about street reliability for the long run. The Strombergs, if adjusted correctly, would give almost as much power as we needed. So, now, we had a SBC long block, Isky Cam, Jahns Pistons, Stromberg Carbs and an Eldlebrock manifold. All we needed was a pair of Chevy truck heads, ported and polished, assembly, and we were ready to drive. Dec 1959: similar, with Strombergs Jnaki The adjustments on the 6 Strombergs on the SBC were difficult, but eventually, we made them work well on the SBC motor. It fired up and ran well around the block. The weight of the 40 Willys Coupe plus the SBC motor made the specs for us to be in B/Gas. We thought it would be competitive for our first home made build. It was, for the first few runs, but then, the fastest guys in B/Gas were too far out in front, as far as times and speeds were concerned. So, there was little chance for us to have a winning car. https://www.jalopyjournal.com/forum...ght-a-used-motor.1116376/page-3#post-12716522 So, my brother had the great idea of putting added weight (steel plates) welded into the trunk . Not only would it be just added weight, but it would keep the empty trunk more secure with the weight over the rear axle. It was legal, as the plates were welded in, not bolted. The Lions Dragstrip tech inspectors deemed it part of the car. All of this extra weight would drop us into the C/Gas class. But, the motor was the same power. It ran well and the times were fine for the first time build. So, after a few months, we happened to get a new Isky/Gilmer 671 Blower Drive that just came out on the market and we had to stop to rebuild everything. It had to be a motor geared specifically for the 671 added on power. A very similar 671 and 6 Strombergs on an SBC motor. photo… B. Balogh Oct 1960 After rebuilding to a specific, blower safe, 292 cubic inches, a Joe Hunt Vertex Magneto, new speed parts, and a new racing rebuilt 671 blower, we did not have enough money for the two port, Hilborn Injectors for our 671. We had to put the 6 Strombergs back on a new flat Weiand manifold that was made for a 671. 1960 Lions The Stromberg carb adjustments had to be redone and finally, it fired up and ran well for us. The sound coming from those 6 Strombergs, were like a basket full of snakes… ssssssss. The final speed and times were very close to the national record for C/Gas. Now, we were competitive. Until… After sitting in the garage since August, 1960, in January 1961, it was sold to a buyer from the Midwest.
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