Acertain chevy 350 engine in one of our old project trucks started having issues that seemed to be pointing to the carburetor as a culprit. On cold start-ups the truck would idle high like it should but then it wouldn't return to a normal idle no matter what we tried. It would also hesitate when trying to quickly accelerate and occasionally sputter and die when off-road in off-camber situations. Vacuum leaks were searched for and different adjustments were attempted but nothing seemed to help. While it is possible that the old Quadrajet carb could have been revived, we decided to simply upgrade it hoping for better drivability, performance and reliability. 1. The engine in this '74 chevy appeared to have most of the original equipment still intact. It had been rebuilt (or so we were told by the last owner) and an HEI distributor was installed in place of the older points-style ignition. We figured with some mild mods this motor could provide us with decent power while not breaking the bank.1. The engine in this '74 chevy appeared to have most of the original equipment still inta Due to the type of engine, and the fact that the truck was a '74 with little emissions requirements, there was a huge selection of carbs to choose from. We decided to call the crew at Holley, with their great reputation, and see what type they recommended for our application. It turns out the choice was quite easy. Holley makes a line dubbed Off-Road Truck Avenger Carburetors, which are made especially for off-road conditions. These carbs offer a slew of features that make adjustability and reliability paramount even in harsh environments. To complement the carb, we also chose an aluminum Weiand Street Warrior Intake Manifold. The dual-plane design has a power band from idle to 5500 rpm and will help our old 350 breathe easier. 2. Since we were changing the manifold the distributor needed to be removed. After removing the cap we took some pictures of where the rotor was pointing and the relation of the housing to the rotor. If we reinstall the rotor as our pictures show the timing should be close to where it was originally.2. Since we were changing the manifold the distributor needed to be removed. After removin 3. After removing the old manifold and carburetor an old towel was placed in the valley to keep debris from falling in. Then we carefully cleaned off the old gaskets and sealant to prepare for installation of the new parts. Holley lists, in its detailed directions, the recommended gaskets and supplies you should have on hand to perform this installation successfully.3. After removing the old manifold and carburetor an old towel was placed in the valley to 4. The new Street Warrior manifold was placed on the engine to check for proper fit. Once we were convinced everything would work we removed the manifold and placed the new gaskets and RTV sealant in the needed locations.4. The new Street Warrior manifold was placed on the engine to check for proper fit. Once 5. The old manifold bolts were replaced with these black oxide alloy steel allen head bolts and hardened washers that exceeded the strength of the original Grade 5 mounting hardware. The old bolts could have been reused but we happened to have these already and liked the clean touch they added to the appearance. Thread sealant was applied to all the bolts before being installed and properly torqued.5. The old manifold bolts were replaced with these black oxide alloy steel allen head bolt 6. Three sizes of the Off-Road Truck Avenger Carburetor are available depending on your application: 470, 670, and 770 CFM. We opted for the 670 CFM model, which is good on our engine in stock form and up to about 400hp. Notice the unique vent tube that forms an upside down U with 10 small holes in it. This is designed so that fuel does not spill over when going up or down very steep hills. Supposedly this carb will function properly when driving up a 40-degree incline. Sounds like fun.6. Three sizes of the Off-Road Truck Avenger Carburetor are available depending on your ap 7. An adjustable vacuum secondary is controlled by a spring and diaphragm inside the black housing on the left. The setting from the factory worked well for us but could be changed by swapping out the spring with a softer one that is supplied. The other black housing with electrical leads is for the choke that also is easily adjustable for length of operation and idle speed.7. An adjustable vacuum secondary is controlled by a spring and diaphragm inside the black 8. All that is left is to torque down the carb and hook up the spark plug wires, throttle and tranny kickdown lines, vacuum lines, and coolant hoses. Overall the install went smoothly. It took us about half a day to complete, including a run to the parts store. This is less time than we had spent trouble shooting the old equipment with no results.8. All that is left is to torque down the carb and hook up the spark plug wires, throttle 9. Thermostats only cost a few dollars, so it's silly not to replace our old one with a brand new one. We also managed to get a new fuel filter and fuel line in between the metal fuel line and the carburetor.9. Thermostats only cost a few dollars, so it's silly not to replace our old one with a br 10. We still have to hook up the throttle and transmission cables, but we were able to fire the engine over at this point and make sure everything was running correctly. The biggest hassle of this install was, without question, trying to get the distributor to line back up. If you are trying this at home, we highly suggest turning your engine to TDC (top dead center) before starting the removal of the original carb and manifold.10. We still have to hook up the throttle and transmission cables, but we were able to fir Holley insists in its installation instructions that the carburetor is wet-flowed and preset at the factory to fit most applications without any adjustment. We were pleased to find that Holley was right in our case. After a few cranks to get fuel into the new carburetors bowls, the truck started right up. Then, after a short drive, the choke turned off and the idle dropped down to where it should. Throttle response was much improved at lower rpm's in addition. It is possible that we could see even better performance with some fine tuning but for now we will continue to use the carb as it came out of the box. Sources Holley Performance Products 1801 Russellville Rd P.O. Box 10360 Bowling Green KY 42102 270-782-2900 www.holley.com By Jon Acuff Enjoyed this Post? Subscribe to our RSS Feed, or use your favorite social media to recommend us to friends and colleagues!
