backfiring in right exhaust

[Highbanked Hauler]

 OK, first I am  NOT  an engine person.. I  fired  up my "questionable" 12-1 comp. 440 yesterday and had to use two batteries and other than having to retard the timing to get it to start it lit and after warming up it idled at about 1000 rpm.  It is intermittently  backfiring down the right side exhaust like a rifle shot loud (headers with a muffler attached )  I did move the timing back and forth  to find the sweet spot. My thought is I have an exhaust valve not seating right for what ever the reason.  I am figuring to do a compression check to see what I have first, and depending on what it is,  pull the head off and go from there.
    Does this sound like a reasonable approach ?  Hind site being 20-20 I  probably shouldn't have bought the motor but since I did I will follow it through, I finish what I start.

[don duick]

my guess is a fouled plug

[Highbanked Hauler]

 That was my first thought and I put in a new set. The backfiring picks up with the  speed of the motor.

[Bronzedodge]

Next suspect is a bad valve.  Compression test or a leakdown test is in order.

[Highbanked Hauler]

Next suspect is a bad valve.  Compression test or a leakdown test is in order.

   I am not familiar with a leak down test but I am going to do a comp check. This thing has Crane 1.6 roller rockers and adjustable push rods in it.

[BLK 68 R/T]

That was my first thought and I put in a new set. The backfiring picks up with the  speed of the motor.

Was it verified that the plug is actually firing after replacement? Could be a bad spark plug wire.

[303 Mopar]

Start with the basics and double check your wires are not crossed.

[Bob]

Next suspect is a bad valve.  Compression test or a leakdown test is in order.

Exactly what my problem was. Started out as a miss but was a bad valve.

[Highbanked Hauler]

Next suspect is a bad valve.  Compression test or a leakdown test is in order.

Exactly what my problem was. Started out as a miss but was a bad valve.

   This thing has adjustable push rods  in it and I am wondering if one could have moved so the valve wont close. First thing is a comp check.

     I have the plug wires tagged with numbers.

[don duick]

if it increases with engine speed could be the secondaries are too lean or a weak ignition

[Highbanked Hauler]

if it increases with engine speed could be the secondaries are too lean or a weak ignition

   The carb is a 750 cfm Carter and the distributor is an ACCEL dual point.  Both of witch were off of the running motor in my 500 when I  upgraded it to a 650 carb and electronic ignition.

[firefighter3931]

If the backfire is isolated to the right side the logical assumption is a leaky/burnt ex valve that isn't sealing (right bank) or it could be a valve sticking in the guides. A compression test will confirm this.

Assuming that the compression test is good then it's more than likely ignition related. Could be a bad cap that is cracked causing a misfire or ignition wires spark leaking ?

You'll have to dig in and do some diagnostic investigation 



Ron