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James, I just put a 305 V/8 in my 1972 Nova. I'm having a lot of problems with this engine! It “pops” out the carburetor on right side, and pops out exhaust on left. I've disassembled this engine to the check timing chain. I've also ran a compression check all cylinders (all averaging about 122 to 125psi). Also pressure checked the intake valve and exhaust valves while heads are still on the car. I also checked to see if cylinder head gaskets were leaking from one cylinder to next. I checked the cam, lifters, push rods, rocker arms, valve springs. I have put 2 different distributors, new distributor cap, rotor button, wires, and spark plugs. I have replaced all components in distributor and the voltage to the distributor is (14.5 volts when running) I have even put 4 different carburetors on this car and still the same problem! I even installed a new intake manifold; every thing is new or has been changed. When I advance the timing it almost stops popping and runs good. When I do this the starter wants to drag when I try to start it up. I have noticed the exhaust smells like it is running rich. The battery is located in the trunk. Could this have a lot to do with my starter drag? The only thing I didn't do is check the cylinder heads for cracks. Can you help think of any thing I might have forgotten?

Boy, you sound like you have a lot of problems that may be very simple fixes. So let us address each area of concern and see if we can come up with an answer. To address the back fire through the right side of carburetor and the left side of the exhaust: I know you looked at the timing chain and it is lined up properly. What you didn’t possibly check is the pin that holds the cam gear to the cam! I have seen this slip before and cause similar problems you have described. The pin may be sheared or not properly positioned. The only way it can “pop” through the right side of the carburetor is the intake valve is open when the sparkplug “fires”. The same problem will cause it to “pop” on the left side of the exhaust manifold. So this does sound like a mechanical timing problem. If the cam shaft lobes are rounded off that could cause similar problems. (You said you looked at the cam and it was okay) So remove the timing cover and look real close at cam gear pin going into the camshaft. The pin may be missing or bent or the hole may be elongated causing the cam gear to shift. The starter dragging problem may be related to the above problem. To verify if the starter DOES NOT have a voltage drop, you will need a digital multi meter or DMM. (I am assuming the starter is the right one for this engine.) Place one lead of the DMM on the positive battery cable and the other lead on the positive stud on the starter. Crank the car while watching the DMM. If you have more than .5 volt drop, clean and re-tighten all your connections. You need to do the same test on the negative side of the battery to check for proper grounds. Take one lead of your DMM and attach to negative side of the battery. Take the other lead and attach to the starter housing. Crank the car, if you have less than .5 of voltage drop, the ground circuit is okay. If anymore than that, clean and tighten the cables. (I would suggest that you remove the starter to make sure that the starter is getting a good ground through the engine if you have a higher amount of voltage drop. (Freshly painted parts can cause a big voltage drop on the starting circuit.) Speaking of fresh paint make sure that your distributor has a good ground as well. I have seen a lot of driveabilty problems from freshly painted engines causing similar problems. The prettiest painted engines can give you the biggest headaches by having the poorest grounds! Now to your distributor, is it electronic type or point’s type? If it is a point type distributor, 14 volts is way too much voltage. A “ballast resistor” will be needed to cut the voltage down to 9 volts when the car it is running. If it is an electronic type ignition distributor, then battery/alternator voltage is okay. I think I have touched on every area of concern except the running rich problem. If you address these areas of concern I have written about, the running rich problem will go away! And if all else fails seek professional help from a Certified Master Auto Technician with L-1 certification. They will put it on a scope, and a 5 gas analyzer to see what the problem might be. Plus most Master Auto Technicians have years of experience to help solve the problems your having. There is no “shame” in not being able to fix a car. If it was so easy everyone could do it, and I’d be out of a job!

 

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