Back firing question

Robert Luland
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Re: Back firing question

#31

Post by Robert Luland » Sat Nov 20, 2010 3:48 pm

Back in the eighties, I was having starting problems with my mag. Called Morris and the second question he asked me was which plugs I was running. I said Champions, he said throw them in the garbage can. He went on to tell me that the Champion electrode is two pieces and to use Motorcraft. Thinking this guy was pulling my leg; I went out to the shop floor and pulverized a Champion plug. He wasn’t bullshitting me, It is two pieces. By the early nineties I to had switched over to Bosch Platinum’s to. I call them foul proof. Bob L



jdpan
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Re: Back firing question

#32

Post by jdpan » Sat Nov 20, 2010 9:27 pm

Is WR8DC4 the correct numper fpr early Pans? Been using Accel but I might give the Bosch P's a try.

Robert Luland
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Re: Back firing question

#33

Post by Robert Luland » Sat Nov 20, 2010 11:05 pm

I don't know. I have STD heads and use Shovel plugs. Bob L

panbagger
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Re: Back firing question

#34

Post by panbagger » Sun Nov 21, 2010 12:37 am

I posted the number back on page two for Bosch plugs from Auto zone it is #4036. that's the number they need to find the plugs. On the plug itself the # is WR9FP. I have used these plugs for 6 years and they are the best plugs I ever used. Just my opinion. Scott

Bigincher
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Re: Back firing question

#35

Post by Bigincher » Sun Nov 21, 2010 3:04 am

I might've gotten a bad plug, but I had a Bosch Platinum go bad on me one time-- the ceramic insulator broke and slipped down over the electrode.

doc308
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Re: Back firing question

#36

Post by doc308 » Tue Nov 30, 2010 2:26 am

Follow-up: I found a leak in the rear exhaust pipie. Fixed it and the backfiring has stopped.

Re: the idea that I have an air leak in the front cylinder--I don't think so. As I noted, the plug is burning perfectly ( tan color) and I'm getting no symptoms of an air leak. However, I think I found a problem with my rear head. As I mentioned, the sparkplug is very black and , for the first time since the rebuild, I noticed some oil burning out of the rear exhaust pipe ( I have only about 150 miles on the rebuild--so I think that something is wrong inside). I'll be starting a new post for this problem soon.

Cotten
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Re: Back firing question

#37

Post by Cotten » Tue Nov 30, 2010 2:41 am

Doc!

If your plugs are burning different, it sounds like Evil Manifold Leak to me.
Your rear is rich because the front wont run with the carb otherwise.

Bubbles won't lie,

....Cotten

doc308
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Re: Back firing question

#38

Post by doc308 » Tue Nov 30, 2010 3:01 am

I hear ya , Cotten and maybe your right. However, here's what I've begun to experience that makes me believe that something else is going on: I noticed that the idle was a bit off lately, with the rear exhaust sounding less steady.
I checked the lifters--perfect adjustment.
I switched the plugs--no difference.
Replaced the plugs--no difference
I switched the leads from the coil--no difference.
When I pull the lead off of the front plug, the engine continues to idle steadily on the front cylinder alone. When I pull the coil wire off of the rear plug, the engine stumbles and will shortly die. So, I'm left with the Q of something going on inside the head. As I mentioned in the previous reply, I noticed smoke steadily coming out of my rear exhaust pipe today--I can't tell whether it's pure white or bluish white--but it's steady with each stroke. The rebuild only has about 100--150 miles on it.

Q--the engine was running perfectly until a couple of days ago. Can this have something to do with the rings or valves seating , given the recent rebuild, or is this clearly asymptom of somthing going wrong inside?

I started another post ( "'48 rear head leak") wherein I just noticed for the first time a slight leak coming from a plug ( not the sparkplug) in the rear of the rear head. Could this be related. ( I provided pictures in that post).

Panacea
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Re: Back firing question

#39

Post by Panacea » Tue Nov 30, 2010 4:06 am

Wait a second, you pulled the front plug wire and it kept running on the rear? If thats the case I'd suspect the front ...

doc308
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Re: Back firing question

#40

Post by doc308 » Tue Nov 30, 2010 1:49 pm

No--when running on the rear cylinder, it sputters and stalls out in lees than a minute. It runs fine on the front cylinder.

Cotten
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Re: Back firing question

#41

Post by Cotten » Tue Nov 30, 2010 3:04 pm

doc308 wrote:No--when running on the rear cylinder, it sputters and stalls out in lees than a minute. It runs fine on the front cylinder.
Doc!

Just for clarity:
My suspicion is that you have the carb adjusted for the front cylinder, which has a leak.
The rear is too fat, because there is no leak (or not as much!)

There may be other issues of course.

....Cotten

doc308
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Re: Back firing question

#42

Post by doc308 » Fri Dec 03, 2010 2:51 pm

Cotton--will the bubble test detect leaks in areas of the head other than the intake area? If so, do I set the valves at different positions to investigate other areas? The article you referred me to do said to be sure that the intake valve is closed in investigating intake leaks. What about looking into leaks in the exhaust port area?

The reason I ask is because I have a small crack somewhere in the front of my front head between the valve cover gasket and head gasket near the exhaust port. I posted this earlier in the year and temporarily fixed it with JB Weld. However, I just noticed some oil in that area again, as the JB Weld is beginning to flake off. I presume that , if oil leaks out, air is likely being sucked in on the downstroke (?) Would such a leak in that area cause the symptoms I'm deaking with or are they specific to intake leaks only?

I'll be conducting the bubble test soonto look for any leaks anywhere and plan on removing the head over the winter for aproper fix.

Cotten
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Re: Back firing question

#43

Post by Cotten » Fri Dec 03, 2010 3:20 pm

Doc!

You can test just about anything with bubbles, and yes, you may well find leaks in places unimagineable, such as casting porosities, micro cracks, perforated pan cover screws, while just testing the manifold assembly alone.
I soap everything, even the finnage over each intake port.

The combustion chamber can be tested at much higher pressures, usually applied at the sparkplug hole, and un-seen blown headgaskets or leaky sparkplug inserts can be discovered. Just listening at the intake, exhaust, and timing plug hole will give you clues as to leaky valves or ring blow-by.

But I never considered an exhaust port leak, as I really don't imagine that an invisible one would be as critical as an intake,... but it cannot be a good thing.

Cork it up, and if it blows bubbles with air applied anywhere, including the pushrod holes if you can (two #2 rubber stoppers, one perforated for a hose barb), then we will certainly learn something about Panheads!

Be careful not to blow out the pancover gasket, though.

Good luck!

....Cotten

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