nakamura_racing_sports
Aug 28th, 04, 9:00 PM
Any help on this is greatly appreciated:
I have a 750cfm 4150hp race carb on a 350 with BRE ported sportsman 2 heads, a port matched victor jr, a big cam(not sure but about 525 lift and probably 250 or so dur at .050). Thing is I ran this motor to a 13.2 sec best a little over a year ago. The heads were freshened about 6 months before that. The motor was kind of lazy till about 5000 rpm in first gear, but then ran good for the rest of the run. The mph was 106. But recently, it has been backfiring through the carb and the venturi is all black. Timing is locked out, at 38, but has been there since that 13.2 run. It never used to backfire like that. But now it does all the time. The carb is same as it was. but after it started backfiring, I changed the power valve to the 3.5. Vacuum at idle in gear is about 5 inches. I also noticed the vacuum gauge flutters a little. I was thinking maybe a valve or valve spring? Please help. THank you for all your support.
I have a 750cfm 4150hp race carb on a 350 with BRE ported sportsman 2 heads, a port matched victor jr, a big cam(not sure but about 525 lift and probably 250 or so dur at .050). Thing is I ran this motor to a 13.2 sec best a little over a year ago. The heads were freshened about 6 months before that. The motor was kind of lazy till about 5000 rpm in first gear, but then ran good for the rest of the run. The mph was 106. But recently, it has been backfiring through the carb and the venturi is all black. Timing is locked out, at 38, but has been there since that 13.2 run. It never used to backfire like that. But now it does all the time. The carb is same as it was. but after it started backfiring, I changed the power valve to the 3.5. Vacuum at idle in gear is about 5 inches. I also noticed the vacuum gauge flutters a little. I was thinking maybe a valve or valve spring? Please help. THank you for all your support.