Posted by Dave in CA [172.68.46.32] on Thursday, September 13, 2018 at 11:24:59 :
In Reply to: Carburetor / Intake Manifold Options posted by Dan in Sebastopol [172.68.141.109] on Wednesday, September 12, 2018 at 19:46:31 :
Compatible TBI systems are available from just under $1000 to a little over $2000 from Holley, FAST, FiTech, Quick Fuel, and MSD. But, you can make a carbureted setup run at any angle and never vapor lock, if you know the tricks. Any carbureted intake you consider should be a dual plane, and not a single plane, if you need low rpm torque. All the new intake manifolds currently available for the LA small block have a generic port size that is supposed to fit the small 273/318 port, as well as the larger 340/360 port. In reality, the manifold port is in between the two port sizes, but if you do a little port match grinding, you can minimize this issue on a 340 or 360. One of the new Edelbrock Air Gap manifolds would be a good choice. Edelbrock used to make a small port intake for the 273/318, the LD4B, and a large port intake for the 340/360, the LD340. The LD340 will make more power than the OEM manifold, although with slightly longer runners, will move the torque curve up in rpm. For you, the OEM manifold used on the 68 to 70 340 engines would be an excellent choice. The 70 340 intake is part number 3462848. It has the correct port sizes you need and any of the square bore carbs are a direct bolt on. To avoid vapor lock, a phenolic spacer under the carb is a big help. I use a 3/8” thick spacer made by Trans-Dapt. I had to do some minor filing with a half round file on the center hole to make a perfect fit to the carb and intake. Another trick to avoiding vapor lock is to run a vapor separator filter and a return line to the tank. I run a 3/8” supply and a ¼” return line, using a filter mounted vertically, in front of the engine. For those line sizes, a Carquest part number 86041 filter works great. If you run a Carter or Edelbrock AFB/AVS four barrel, there are spring loaded needle valves available for off-road use. I’ve run Carter four barrels for decades and can tell you a lot more tricks for float settings, metering rod spring selection, metering and jetting, etc. You should already have my email address, since we exchanged email addresses when I sold you the rear shock mounts. Just drop me a line and I can tell you a lot more.