Carb suggestions

[H2Ogbodies]

There's a lot more to consider when it comes to a carb than just the engine specs. I tune my customers carbs for maximum all around performance. If your car is a stick, stay away from vacuum secondaries if you have a 5 or 6 speed and very low gears (4.10's or steeper) because often, the first two gears combined with steep gears create a situation where the slight hesitation where the secondary circuit is trying to dump more fuel can start to bog too much and you get unstable fuel delivery as you are grabbing for gears...and wiht a fairly heavy car, you may need to swap out the secondary spring for a lighter one so the secondaries come on quicker. Generally speaking, a heavier car requires lighter springs and vice versa. Then, if you have a very broad torque curve, you need to pick out an accelerator pump cam that more closely supports your power curve. So now, if you plan to be able to deliver more fuel, you need to swap out to a 50cc pump kit, increase your squirter nozzle size and go up in jet sizes. Stick with the 90 degree dog leg boosters because they offer much better throttle response on the street. To illustrate a real world scenario, I will explain how I went through a Holley 3310 vac. secondaries to be able to wake the motor up when the RPM climbed past 6000. I had a 78 Monte that pulled great up to around 5500 and then just kinda flattened out-still pulled strong but no real grunt behind it. I suspected it was due to lack of fuel, not spark or valvetrain flutter. Again, this is just to show you the ways in which you can really knock a problem completely out of the park and even surprise yourself. My Monte had a 355 with 461 iron heads which I ported (about 10.4:1 comp.), 3310 vac. sec. Holley, 282 cam with .466 lift, Performer manifold, TH400 with 3.73 limited slip rear with 275/60/15's. I raced against my friends 406 70 Camaro which had 4.10 rears and I launched hard and got the jump on him-he had to run me down but blew totally past me when he caught me. I knew he'd get me but I figured it would take him longer-my car just seemed to run out of steam upstairs and I decided to get into the carb a bit. To start with, it was an out-of-the-box bolt on carb with nothing done to it. I'm willing to bet most people do little as to swapping most or all of the internals in the search of the perfect combination but hey, I was willing to experiment. So here's what I did-I first swapped to a secondary metering block just so I could now change rear jets. Then, I decided to swap out the stock 30cc pump for a 50cc one. Then, I swapped from the stock front jets from 66 to 74. Rear jets I went with 82's. I experimented with various secondary springs but found the stock one (plain, no color banding) was the most responsive in this situation. I changed out the main accelaerator pump cam to the second from the largest progressive ramp style (dark red one I believe)-I visualized the longer, larger pump ramp as extending the RPM fuel delivery as well as allowing for a larger volume of fuel, so with larger jets, bigger pump cam and more fuel volume, I obviously need to increase the squirter size-I went from the stock .031 to an .041. The power valve I left it at 6.5, and knowing I now have the ability to empty the fuel bowls faster, a higher volume mech. pump was next so I installed an Edelbrock 6-valve pump regulated at 6.5 psi. So the next time out on a flog run, not only was the car much quicker off the line, it pulled like crazy well past 6500! Now the car had to off-idle bog which it did have before, mid range was very strong, and top end was very strong too. No doubt that my friends Camaro did still catch me, but it would now take him the entire length of the 1/4 to do it-and just barely by then. His 406 was a beast, but my 355 was much better tuned for my car than his was for his. This is just an example of basic Holley carb tuning which can vary from one car to another. There is no one carb for any engine combo. You have to experiment to get the most out of it. Even if you think it runs great now, making a few well reasoned changes can really wake it up!