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Old 01-30-2019, 08:29 AM   #1
1934
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Default spark at the plugs

('37 FH motor)
When I short out the plugs with the motor at idle there are 4 cylinders that seem to be doing all the work and 4 that seem to be doing nothing. I.E. when I short out one of the 4 good ones the motor bogs down considerably and when I short one of the other 4 there is no difference in the idle. I thought it might be the plugs so I switched them up and no difference- always the same 4 cylinders not firing properly.
Does this sound like a timing issue or.... Any ideas appreciated.
Doug.

Sorry, just realized I meant to put this in the early V8 forum.

Last edited by 1934; 01-30-2019 at 08:32 AM. Reason: Wrong forum
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Old 01-30-2019, 09:33 AM   #2
Kurt in NJ
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Default Re: spark at the plugs

each side of carb does 4 cylinders, if idle passage on one barrel has a problem it can cause the problem you are describing
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Old 01-30-2019, 09:36 AM   #3
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Default Re: spark at the plugs

ditto what #2 said
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Old 01-30-2019, 10:00 AM   #4
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Default Re: spark at the plugs

I don't think it's a fuel issue because there's 2 on each side not firing correctly.
Thanks guys.
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Old 01-30-2019, 10:21 AM   #5
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Default Re: spark at the plugs

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Originally Posted by 1934 View Post
I don't think it's a fuel issue because there's 2 on each side not firing correctly.
Thanks guys.
IIRC, each barrel feeds 2 cylinders on each side, look closely at the intake manifold and you can see where the runners go.
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Old 01-30-2019, 10:41 AM   #6
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Default Re: spark at the plugs

According to my calculations you have too many cylinders, discard the four that are inactive and retain the four that are firing.
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Old 01-30-2019, 11:11 AM   #7
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Default Re: spark at the plugs

I agree with burner31.
You don't need more than 4 cylinders as 4 is enough. If it was good Enough for Henry Ford then its Good enough for Me!!!
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Old 01-30-2019, 11:27 AM   #8
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Default Re: spark at the plugs

HI 1934
How are your brakes and winshield wipers.If no good drop the pan.
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Old 01-30-2019, 11:30 AM   #9
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Default Re: spark at the plugs

Be sure to remove the pistons and rods on the four dead cylinders to reduce the drag . I'm only kidding!!!
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Old 01-30-2019, 12:51 PM   #10
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Default Re: spark at the plugs

Look for a plugged idle passage. One barrel of the carb feeds the middle two cylinders on one bank and the end two on the other bank while the other barrel feeds the remaining two end cylinders and two middle cylinders.
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Old 01-30-2019, 02:54 PM   #11
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Default Re: spark at the plugs

Some of you guys are a riot! Just imagine how much gas I'd save! LOL! Kidding aside, it sounds like a plugged idle passage as was suggested. On one bank it's the middle two cylinders and the other bank it's the two end cylinders not firing. Besides taking the intake off is there any other way to determine if that's really the problem?
Thanks for your help, (jokes and all), Doug.
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Old 01-30-2019, 03:08 PM   #12
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Default Re: spark at the plugs

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Originally Posted by 1934 View Post
Some of you guys are a riot! Just imagine how much gas I'd save! LOL! Kidding aside, it sounds like a plugged idle passage as was suggested. On one bank it's the middle two cylinders and the other bank it's the two end cylinders not firing. Besides taking the intake off is there any other way to determine if that's really the problem?
Thanks for your help, (jokes and all), Doug.
Don't mess with the intake manifold. Just take the carb off, open it up, spray carb cleaner through all the passages, shake the excess cleaner out, put it back together and reinstall. Test drive.

The plugged idle passage is in the carb, if that's the problem, not in the intake manifold.

.
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Old 01-31-2019, 07:31 AM   #13
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Default Re: spark at the plugs

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Originally Posted by Jim/TX/GA View Post
Don't mess with the intake manifold. Just take the carb off, open it up, spray carb cleaner through all the passages, shake the excess cleaner out, put it back together and reinstall. Test drive.

The plugged idle passage is in the carb, if that's the problem, not in the intake manifold.

.
Thanks for the advise. As soon as things warm up a bit here, (-3 F. in my unheated garage), I will try some carb cleaner.
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Old 04-13-2019, 08:18 AM   #14
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Default Re: spark at the plugs

I've posted an update on the early V8 forum just to keep things simple and not to have 2 threads going at the same time. I appreciate your help.
Doug.
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