I have what appears to be stock 350 SBC with shorty headers, HEI distributor, 1405 Edelbrock carburetor. Not sure of the internals because I purchased the motor as is. I have it mated to a 350 trans and they are both sitting in a 1964 Impala SS HT.
While driving up a hill one day, I began to hear the engine backfire in rapid succession. I figured the carb was the cause so I inspected it and found nothing. I checked the time and made sure that it was where it needed to be and still nothing, engine kept back firing.
A friend if mine suggested that I check the rocker arms so I did. I found that the number 8 was extremely loose. Its the one closest to the back of the motor on the passenger side. I went ahead and tightened it up until it felt like the rest of the other ones and the backfiring stopped.
Thinking I fixed the issue, I drove the car like that for about 50 miles and it has started to do the same thing again. I popped the valve cover and the same rocker arm is now loose and backfiring again.
What do you gentlemen think is causing the rocker arm to come loose to the point where it is cause the 8 piston to backfire? All recommendations are welcome.
1964 Impala SS HT
2007 Tahoe LTZ
2006 Kawasaki ZX10
2003 Yamaha R1 (sold)
1995 Impala SS
1993 Tahoe GT (sold)
1978 Buick Regal (sold)