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43 popping too

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bob maxwell

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"OK my newly rebuilt 4.3 pops

"OK my newly rebuilt 4.3 pops after running for seven minuts - removing the fuel cap doesent help - rebuilding the carb, changing the coil and distributor as well as a complete removal of the t-bolt iv and replacing it with a conventional centrifrugal advance didnt help - so Valves or air leak? but I am at a loss as to how to do a vacum test I borrowed a gauge and hoses and foung the section in the mercruiser manual regarding what the values should be but how do I hook it up?"
 
"Bob:

Look on the intake ma

"Bob:

Look on the intake manifold riser behind the carb. There should be a plug there; remove it and install a brass nipple. Get a rubber cap for it so you can leave it installed. If it has been in there a long time, it can be removed but it takes a little effort. I had to take a 1/2" drive short extension and grind it down to fit tightly into the square hole. I then used a breaker bar to loosen it. DO NOT USE A TORCH."
 
"Bob:

Timing is 8 deg. BT

"Bob:

Timing is 8 deg. BTDC. If you don't hold the timing light directly overhead of the timing marks, you may set the timing off a few degrees.

You might try turning the mixture screw 1/2 turn richer. Carb may be leaning out too much when the choke opens all the way.

Are your plug wires new and routed to prevent them from cross firing which would cause backfiring."
 
"How's your point gap look

"How's your point gap look? I was having a similar problem with mine, and new points, and setting dwell, gap, and timing fixed it right up!"
 
"When you say the motor begins

"When you say the motor begins popping, do you mean backfiring? If so, check your voltmeter when it begins this and see if it is overcharging, ie V higher than 14.5. If the VR is bad and the voltage goes higher, say 7 mins after replacing the energy used to start?, that could be the problem. Overvoltage will cause sparks to be sent to multiple plug wires and result in backfiring.
Good luck. JW in Dixie"
 
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