I originally had a Autolite 350 CFM on my 200 six. The problem with the Autolite was it would not always idle. I would set the air mixtures screws and idle screw and after driving it a few miles it would either idle too fast or the motor would die. I assumed the carb was just worn out. Yesterday I installed a new out of the box Holley 350 CFM with an electric choke and dash pot. The idle does not change now and it idles very nice at 750 RPM's. The problem I have now is that from idle to about 2500 RPM's it feels like it has a miss or stumbling. Once I hit 2500 RPM's it smooths out and has a lot of power. With the Autolite carb I had a lot of low end power. I could drive at 35 MPH in overdrive (1400 RPM's) and gradually accelerate. The instructions say that the Holley Carburator is calibrated at 70 degrees @ sea level and to decrease the jet size by one number for every 2000 ft. in altitude. Has any one else had this problem and what size jets are you running? My engine is a 1978 200, fresh rebuild with 40 overbore, modified log for 2 V carb, Isky 260 cam, Clifford dual out header with 2" dual exhaust, DS II Distributor and MSD box. Where I live is about 4500 ft. above sea level. Any help is appreciated. Thanks
Need help with my Holley 350 CFM Carb
- Thread starter PLP6400
- Start date
A stock Holley 350cfm uses #61 jets. Your build is much the same as mine only you have the better later model head. This weekend I tried different jet sizes while at the quarter mile track. I tried 64, 66, and 68s. I found the 64 and 66 the best. I did a plug check after one of the runs and they looked much better then with the 61 jets. Simply just trial and error testing.
.......Alex
.......Alex
Pat, at your altitude i would try a 59 jet & possabily a .029 accerator nozzle instead of the .031 nozzle. Just make sure your float level is correct & you have enough fuel pressure. Anytime i see someone riching up a holley which you can run up to 7 # of fuel pressure is a condition of fuel starvation. I maybe wrong but those carbs are jetted for a v8 engine & normally require de-jetting with a smaller engine.
for example a couple of years ago i keep riching up the jets & still running the same et & mph. I went back to my original jetting & redid the fuel system & immediately dropped 3 tenths & picked up 3 mph in the quarter mile. Never take for granted you have enough fuel supply.
All my vehicles run a holley red pump @ 7 # pressure with the 2300 or other holley carbs. I can't speak for the weber or the other holley series carbs which came as oem on earlier products. more pressure to you, william
for example a couple of years ago i keep riching up the jets & still running the same et & mph. I went back to my original jetting & redid the fuel system & immediately dropped 3 tenths & picked up 3 mph in the quarter mile. Never take for granted you have enough fuel supply.
All my vehicles run a holley red pump @ 7 # pressure with the 2300 or other holley carbs. I can't speak for the weber or the other holley series carbs which came as oem on earlier products. more pressure to you, william
