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39 LZ backfires


nova6972

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i have a 39 lincoln zephyr with the flathead v-12 in my shop. it backfires out of the exhaust and what could be causing this and i was also wondering if there is a way to time the motor and if there is a way how to do it

thanks for any help you can give me

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We need a little more info. What work has been done on this engine prior to the backfiring and what things have you checked? Spark plug wiring/terminal plates, stuck valve etc. The timing is preset on these cars with the distributor off. This should be done on a special machine however you can get fairly close with some careful measurements. Give us some more info so the "brains" can go to work!

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it backfired when we got the car in the shop and the things that i have checked is the spark plugs which the gap was to small so i make the right gap and the backfire went away alittle but the one thing i did notice is that from idle to about 2000 rpm the right back has alot of spark but on the left bank there is little to no spark. i have tried to adjust the carb but that did not do anythink to help out if there is any more info you need please let me know also when we got the car we rebuilt the lower end in it because the there were no bearing left in it and when i put it back together i made sure that i lines up the cam and crank gear do you think this could have anything to do with it backfiring

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Guest imported_V12Bill

Nova, I think you have a couple of problems.

You say one bank of cylinders fires good but the other bank is weak. Keep in mind that the Zephyr ignition system is two separate systems. One bank fires from one half of the system and the other bank fires from the other half of the system. Since each bank of cylinders is connected by a common crankshaft, each half of the ignition sysstem must be syncronized to fire at the correct time. This must be done on a distributor machine to set the dwell of the points and syncronize their firing.

#2 Since one bank fires weak, I would suspect a condensor is bad. If you had the engine apart, maybe a spark plug wire was switched on a ternimal plate. The terminal plates have a tang that fits into a slot in the distributor. Maybe the tang is not in the slot and the rotor is not lined up with the terminals in the terminal plate. It is possible that half the coil has gone bad and is not firing one bank as strong as it should.

#3 I doubt that your problem is in the fuel system. I have to assume a valve is NOT hanging up. The correct timing of the engine is pre-set from the distributor when it is off the car. Unless the distributor is set up correctly you don't stand a snow balls chance of getting that V 12 to run smooth. Perhaps you need to send it to Jake Flemming in Texas to have it done right.

Bill

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Guest imported_V12Bill

Nova, The terminal plates are marked. There are two sets of numbers on each plate. One set is marked on the inside of the radius where the wires plug in and the other set is marked on the outside of the radius. The terminals are the same left and right, but are rightside up for the side that is being used. The tang on the plate is in the rear to fit the slot in the distributor. I know this sounds confusing, but when you remove a terminal plate you will see what I mean.

To check out a condensor, just reverse them on their mounts. If the weak bank becomes strong and the strong bank becomes weak, you have a bad condensor. The left side of the distributor controls the left bank and vice versa. Therefore if the left bank becomes weak it is caused by the condensor on the left and should be replaced. Actually if one condensor is weak, the other condensor is not far from failing so replace them as a pair to avoid this exercise all over again.

Bill

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Guest imported_V12Bill

Nova, This bolt holds on the cover for the adjustment to syncronize the two sets of points. DO NOT CHANGE THIS SETTING. You must have the distributor on the proper machine such as Jake Flemming uses to properly set this.

Bill

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are you able to check out the points by getting a dwell reading from one side to the other and if you can what would that dwell reading be and if you can check it do you have to have a dwell meter that reads a 12 cylinder or can you set the meter to 6 cylinder and check each side by it self?

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Guest imported_V12Bill

Nova, Yes you can get a dwell reading on the points and you would set the dwell meter for 6 cylinders. I believe a dwell of 28 would be equal to about a .015 or .016 gap. I think you would take the reading where the condensor screws into the yoke type mount on the coil. Each side would correspond to the points on that side. confused.gif Or try to take a reading where the wires attach from the resisters under the dash. I don't think I have tried this before, but it should work. tongue.gif

How is your backfire problem?

Bill

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ive checked the dwell and it about 55 on each side but i took the caps off and the gap on the points is about 14 to 15 thousands ive got most of the backfire out of the motor but it still does it when ever the motor is up to operating temp and under o slight load or sitting idleing for a period of time. and i was also wondering where i would be able to find two of them one for each side because bother of the caps are in pretty bad shape

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Guest imported_V12Bill

Nova, I assume you mean the terminal caps. These are available from Jerry Richman for about $125 per pair. His price was cut from $250. This is cheap as they are not available any where at any price. If your dwell was 55 degrees your gap is less than .014 by quite a bit. I would suggest you send the distributor to Jake Fleming and have it set up correctly.

Bill

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Guest imported_V12Bill

Nova,Jake Fleming Tele is 214 333 3l97 in Dallas Tex.

Gerry Richman Tele is 508 644 5825 in Mass.

Bill

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