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Old 04-18-2019, 12:53 AM   #19
Flathead Fever
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Join Date: May 2010
Location: Yucaipa, CA
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Default Re: spark at the plugs

Quote:
Originally Posted by 1934 View Post
On the right side the 2 middle cylinders are not firing, on the left side it's the first and last that are not firing. I think the plug wires are good because there is a strong spark when I short out the plugs.
Last fall I had the distributor out and put a NOS rotor in and new points. Maybe something got screwed up when I reinstalled it. But I don't know why the spark is good at the plugs if it is shorting somewhere? Guess I'll take the dist. off again and see if I can find anything.
Thanks.
Since there is a strong spark to those four cylinders if everything else in the cylinders are good the spark must not be arriving at the correct time. You have done exactly what I would have done testing this engine.

You do not have an ignition scope to verify the firing pattern so all you can do is kill the cylinders and see if each cylinder drops the rpm, which they did not. You sprayed carb spray in the intake. Very good idea, that is the second thing I would have done. Had the carb not been providing fuel to those four cylinders the addition of the carb spray would have straighten the engine out and the rpm would have come up. Its not a fuel delivery issue. You swapped the intake, that did not fix it. Its not an air delivery issue.

That leaves compression valve problems or the spark not arriving at the correct time. I hate to say this but is there anyway this is as simple as the firing order getting mixed up on those four cylinders? The cylinders are numbered like most V8s. On every single V8, if you look down at the top of the engine you will see that one head is further forward than the other. That furthest forward cylinder is always number #1. Except on a flathead V8. A lot of people make that mistake.

My dad replaced his flathead plug wires with the correct original lacquered, color coded, cloth wires. When he got done it would barely run. He swore to me that he replaced them one at a time and that was not the problem. I drove down there and he had them all screwed up? Sometimes you can mix a couple wires up and an engine can still run pretty decent, especially a V8. You would think it would be bucking ,coughing and shaking drastically but sometimes they just feel like they are down on power. It depends on which ones in the firing order got mixed up I would double check and then check them again to make sure they are correct. Remember that these new V8s can kill four cylinders at an idle to save fuel and you cannot tell that it is not running on all eight. I have one and its smooth as glass at an idle.
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