Hey guys, I just swapped out my 600 Edelbrock Performer for a 750 Holley 3310, with vacuum secondaries. Now I definitely need to tune the carb, but I haven't done anything with a Holley before, and am relatively inexperienced with carbs in general, and I'm not exactly sure where to start. I swapped the carb after talking to a local, very reputable performance shop who recommended a 750.
The motor is a 355" small block, just under 10:1 compression, flat top hyper-eutectic pistons with 4 valve reliefs, World Product Sportsman heads (I know they're a little big for my motor), with 64 cc combustion chambers, Lunati Voodoo hydraulic FT cam, Performer intake with a 3310 Holley 750 carb with vacuum secondaries (72 jets). If it matters, the trans is a TH350, stock torque converter, with 3.73:1 rear gears. Timing is set at 18* initial and 37* total around 3600 rpm.
The carb had sat around for a little bit before I bought it, so I gave it a cleaning and now it has new gaskets because of a small leak. When I first fired up the motor, it smoked quite a bit of white smoke out of the exhaust when revving the motor, but that cleared up pretty quickly.
Now for the issue, the car is really temperamental at low rpms (i assume the tight converter is part of the cause), but then under light throttle the car performs well. But if I try any sort of hard throttle before 2500 rpms the car bogs pretty bad, and sputters and slight backfires from the exhaust. if I try it from above 3000 I can roll into the throttle pretty hard with no issues though. Also, from a stop, if I try anything more than half throttle the car pretty much has a panic attack on the line and bogs like crazy, then takes off like a freaking rocket!
Also, I noticed that when doing a rolling start (about 50 mph), when I rolled into the gas, giving it about 3/4 throttle, it pulls great, but after I let off the gas it backfires really bad out of the exhaust.
I'm not sure if timing might be an issue, but I know that the carb needs some tuning as well because the old carb didn't have any of these problems. I would guess that it is running rich, and the backfiring from the exhaust is unburned fuel reaching the hot muffler, but I'm not sure if that actually is the case, or where to start to fix it.
Where should I start? Thanks a lot,
Steve
The motor is a 355" small block, just under 10:1 compression, flat top hyper-eutectic pistons with 4 valve reliefs, World Product Sportsman heads (I know they're a little big for my motor), with 64 cc combustion chambers, Lunati Voodoo hydraulic FT cam, Performer intake with a 3310 Holley 750 carb with vacuum secondaries (72 jets). If it matters, the trans is a TH350, stock torque converter, with 3.73:1 rear gears. Timing is set at 18* initial and 37* total around 3600 rpm.
The carb had sat around for a little bit before I bought it, so I gave it a cleaning and now it has new gaskets because of a small leak. When I first fired up the motor, it smoked quite a bit of white smoke out of the exhaust when revving the motor, but that cleared up pretty quickly.
Now for the issue, the car is really temperamental at low rpms (i assume the tight converter is part of the cause), but then under light throttle the car performs well. But if I try any sort of hard throttle before 2500 rpms the car bogs pretty bad, and sputters and slight backfires from the exhaust. if I try it from above 3000 I can roll into the throttle pretty hard with no issues though. Also, from a stop, if I try anything more than half throttle the car pretty much has a panic attack on the line and bogs like crazy, then takes off like a freaking rocket!
Also, I noticed that when doing a rolling start (about 50 mph), when I rolled into the gas, giving it about 3/4 throttle, it pulls great, but after I let off the gas it backfires really bad out of the exhaust.
I'm not sure if timing might be an issue, but I know that the carb needs some tuning as well because the old carb didn't have any of these problems. I would guess that it is running rich, and the backfiring from the exhaust is unburned fuel reaching the hot muffler, but I'm not sure if that actually is the case, or where to start to fix it.
Where should I start? Thanks a lot,
Steve
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