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Old 07-24-2002, 07:00 PM
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Red face Need timing advice real bad

I have been fighting a timing problem on a pretty much stock 1967 327 SBC with 350 trans. It has the stock iron intake maifold with an Edelbrock carb with adaptor plate.

The car simply wont start unless I set timing to 40deg BTDC. If I try to run with 40deg of timing I get a lot of pinging and detonation under load. It runs good when at speed, butif you jump on it or take off from a stop light normally it pings terribly. Once its started, I've tried lowering the timing down but at about 20 deg BTDC it just stalls out. If I try at 30deg BTDC it will sometimes start, but when I try to give it a test drive I sometimes get a stalling condition when it goes into gear or a carb back fire.

I have verified TDC by using a piston stop, marking two points, and then taking the center. The timing mark on the balancer is right on. I have also verified that the distributors rotor is pointing directly at the #1 post when the motor is at TDC. I made sure the distributor was installed on the compression stroke by holding my finger over the spark plug hole while bumping the motor. I replaced the distributors pickup coil, wire harness, cap, rotor, checked the resistance of the coil, the mechanical wieghts and springs were all disassembled and lubed up. I've disconnected the vacuum advance and have verified what looks like a very stable and repeatable mechanical advance curve. I know I have reliable spark on all cylinders. As the car is running I've removed one plug wire at a time and can definately notice the rough idle each time.
I also did a compression check and all cylinders are about 170psi and are within 5psi of each other.

Should I just richen up the fuel mixture and just run it at 40deg? Is 40deg unreasonable? Do I need octane booster?

With 360 degress of rotation and 8 cylinders you get 45 degrees between plugs on the distibutor. If I'm at 40 degrees arn't I darn near firing the number 8 cylinder?

I'm ready and willing to try anything.
HELP ME PLEASE.



Thanks,
Jim

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Old 07-24-2002, 07:28 PM
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it sounds to me like you have the basics covered. im by no means an expert at this point but maybe theres something else wrong that your overlooking, you mentioned the mixture could there be a carb problem? forget about the timing for now and go over everything else maybe you'll see something else good luck.
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Old 07-25-2002, 07:49 AM
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Let me ask did this start after adding the carb ? if so are you sure the vacuum advance hose is on the correct port on the carb. The original may have been above the throttle plate ( no vacuum till you throttle it ) and it may be on a circuit now that is below the throttle plate ( has vacuum all the time and it only drops when you first throttle it ). Just a guess but I would say to look in that general direction. Oh is the 40 degrees with the vacuum connected to the advance or with it disconnected and plugged ? Vacuum leak's have caused me more trouble that about any other thing I can think of.

There is one other thing that comes to mind but I don't think you want to hear this , valve timing ( timing chain slipped a tooth ) . It has been sometime now since I worked on a older SBC so if I am off here someone speak up
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Old 07-25-2002, 09:45 AM
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I hope Slyfox is wrong for your sake, however I have changed more than a few timing chains on the old SBC. They used a nylon covered timing gear that will chip off and allow the chain to jump a notch. You might try changing the oil, and looking for tiny bits of nylon gear in the oil. That would be easier than pulling the water pump, bottom pulley and timing chain cover. Is this a new re-build or a "seasoned" motor? If it is a high mileage stocker it may well be the chain.
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Old 07-25-2002, 07:09 PM
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There is a way you can check to see if you have excesive slack in the timing chain without taking it apart. Take the distributor cap off, so you can see the rotor. Put a socket on the crankshaft nut and turn to the right. Keep your eyes on the rotor and turn it back to the left. If you turn the crankshaft and the rotor remains stationary you have a stretched timing chain. Try it the cost is nothing.
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