OK, so the motor is a 388 with an F1 on it. I am just trying to get the thing to run. It is already tunned and I drove it home from the dyno shop but when I got home it let off a massive, MASSIVE backfire. Made my ears ring. While it was at the shop, the battery cable came loose and touched the exhaust frying all the fuses. I then thought maybe I had hurt the MSD boxes. I decided to send the BTM box in for a checkup and they say it is fine. So I next bought a new cap and rotor just to make sure everything is in optimal shape.

I tried running the car with the Digital 6 Plus box to see if this would work and it turned on, but instantly started letting off these little, what I think sounded like, small backfires over and over. Not equally spaced but all sounding the same, no matter how much I reved the motor. (I never went over 1500 RPM.) The more RPM, the less it would pop. The pops did not sound violent at all, just constant popping, randomly.

I called C&S to see if they think I blew my power valves when it backfired and they said no. I will be replacing them anyways. (they must be replaced once a year). C&S also said that when MSD tests something it can at times still have issues. They also said that maybe the popping is coming from a bad intake gasket, a bad rocker or valve.


The big question is what the hell is that popping! I have no idea. This weekend I will spend all Saturday trying to figure it out so if you guys can help me formulate some kind of plan of attack that would really help me out.

So far I have this:
1. Check springs, make sure none are cracked or anything.
2. Turn motor over and make sure eveything is rotating correctly. No valves moving around funny.
3. Check spark plugs for anything funny.
4. Turn on motor and see if POP is coming from tailpipe, right bank, left bank or center of motor.
5. I have no idea, freak out and go insane. Maybe rip all ignition parts out and them them all to MSD.

 

It doesn't make any sense that a battery cable shorting would fry the fuses. The short has to be downstream of the fuses, and the battery cable is upstream.

Where are you hearing the popping, in the intake system, or exhaust? Have you done a compression test?

 

I have seen popping from the intake caused by restricted exhaust or exhaust valves not opening sufficiently. Popping in the exhaust is generally caused by one or more misfiring cylinders releasing unburned fuel into the hot exhaust. Too lean fuel mixture can cause a lean misfire and may lead to popping from the exhaust. Of course ignition timing is certainly something to look at. Is this a flat tappet motor? You may have peeled cam lobes.

 

Can you post a video of it running and backfiring?

 

So far I have not done anything. Car is just sitting there. Cam is a hydriolic roller. I have no idea where the pop is coming from yet, I am always alone working on the car and can't get it to stay on long enough to find out. Looks like the girlfriend will have to help out, haha. Once I check some easy stuff,I will post a video for sure. With everything practically new, I would be very surprised if any components failed.

 

Think maybe the plugs are bad. I will swap them out and try a colder plug perhaps.

 

Just curious what is your timing set to?