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Old 03-02-2006, 08:06 PM
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Cleaning Carb Question

I've asked about the tuning of a Road Demon and I've used the suggestions to dail it in. I'm still trying to get it right. I'm still getting some backfire through one side of the carb. I thought, "okay, I've got it too lean on one side, now how did I do that". I pulled the plugs and sure enough I saw 4 of the 8, pretty clean looking and the other 4 were still gas fouled, with the 4 fouled feeding from one side of the carb and of course the 4 clean were coming from the other side. As I said the carb had been backfiring out of one side of the carb so I just knew that side was running lean. But when I pulled the carb, the side that was backfiring was the side were the plugs were fouled. Is that normal? I was thinking it would be the lean side, because from what I've read when it pops out the carb it indicates a lean condition. So now I'm confused, but I intend to tear the carb completely down and try and clean it out. As I started out it's a 625 Road Demon sitting on a 350 Chevy bored 40 over with Vortec heads, Crane Cam with 216 duration and 454 lift at 0.050. Is there anything special I need to do to clean this thing out? Any tricks I need to know? Thanks for taking the time to read this long post and I do appreciate any suggestions.
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Old 03-02-2006, 08:47 PM
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How did your motor run befor the carb change?
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Old 03-03-2006, 06:58 AM
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cleaning carb question

The engine is a new rebuild and this was the first time to run it. I bought the carb used and thought I had cleaned it out fairly well. But apparently I didn't. It was fouling all the plugs until I replaced the power valve, now it's only fouling 4 plugs, with the 4 plugs being feed from one side of the carb. I haven't started re-cleaning the carb yet, so I was wondering if there were any tricks I needed to know to make sure I have it clean.
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Old 03-03-2006, 07:33 AM
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Sounds like you could have an intake manifold leaking on the side that is running so lean.
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Old 03-03-2006, 08:34 AM
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cleaning carb question

At first I was thinking I was running lean on one side since it was backfiring out of one side of the carb. But after pulling the plugs, the side that was backfiring had the plugs that were fouled out due to a rich condition. So I'm thinking some air passages in the carb are closed off. My thread is pretty confusing, which reflects my confusion, but I was just wondering will fuel fouled plugs cause a backfire through the carb and what air passages do I need to pay close attention to during cleaning.

Thanks
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Old 03-03-2006, 09:43 AM
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Fouled out plugs could possible cause the backfire through the intake, but normally are more prone to an afterfire in the exhaust since they can burn all of the fuel.

From where you're at now, and not really knowing the exact history of the carburetor I'd take it apart. Clean out all of the holes in the main body, baseplate, and metering blocks with some good carburetor cleaner and compressed air. From there put here back together with fresh gaskets.
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Old 03-03-2006, 10:26 AM
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Cleaning Carb Question

Thanks BG

I should have done that from the start. I plan to the clean out this afternoon, if I can get away from work early. I hope this will clear up a few things in dialing in the carb.

Thanks for the help
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Old 03-03-2006, 10:31 AM
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No problem...
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Old 03-03-2006, 05:11 PM
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cleaning carb question

Okay now I'm really stumped. I just finished putting the carb back together with new gaskets, I took everything apart and sprayed carb cleaner into every hole I could find and blew everything out with compressed air. When I put the carb back on the engine and after it warmed up I readjusted the mixture screws to the highest vacuum reading and it seemed to be running pretty well. I had cleaned the plugs prior to cranking the engine. I let it idle for a while, so I thought I would take a look at the plugs. Sure enough the plugs on the side that had fouled before, fouled again and the plugs on the side that looked not fouled, were not fouled again. Now what do I do? The carb is used and this might be why the guy got rid of it. Any help is much appreciated.
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Old 03-03-2006, 05:32 PM
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i would try 4 new plugs, you will get a better reading, a foul plug may not clean up
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Old 03-03-2006, 08:40 PM
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"The engine is a new rebuild and this was the first time to run it."

I'm guessing that it's a stock rebuilt by a reputable company.


Well, if your running a stock or aftermarket dual plane intake, then the right side of the carb feeds cyl. 2,6,3 and 5 while the left side feeds 1,7, 2 and 4 (I think) At any rate one side does not feed the same side of cyl's. The only common denominator there is the intake gasket area.

Tell me/us more about the motor. Is it possible that there are Vortec and pre Vortec parts mixed?
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Old 03-03-2006, 09:15 PM
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cleaning carb question

I had the machine work done locally and I put the engine together, which I've done on all my other engines. I do have vortec heads along with the appropriate vortec intake and gaskets. I should have been more clear, the plugs that are fouled are two on each side, feed from the same side of the dual plan intake, which I take it means the carb is the common denominator. It's the driver side of the carb, which the intake feeds cylinders 1 & 7 on the drivers side and 4 & 6 on the passenger side, so I take this to mean that this is the side that's running rich, and which would mean to me that it's not getting enough air. I've adjusted the mixture screws using a vacuum gage to the highest vacuum reading. So I'm at a loss of what might be causing this. I did bead blast the plugs (just the tips) to clean them and I may get some new ones to try. I'm using AC R44LTS, I may go up in heat range to see if that makes any difference. I've used Edelbrocks on my other engines and I know them, but I wanted to try something different, but it's getting the best of me right now.
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Old 03-03-2006, 09:33 PM
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This may be a long shot but maybe just maybe the person that sold it to you was in there changing the IFR (Idle Fuel Restrictions) in the metering block.

That would explain the one sided fouling from excessive fuel.

Tmod
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Old 03-03-2006, 09:56 PM
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carb cleaning question

I didn't think of that, but as this is my first bout with a Demon, I wouldn't even know about that. If that was the case, do you think replacing the metering block might be the answer? Or what would the best way to measure the openings to see if one had been modified. When I was cleaning the carb, I didn't notice anything. I did notice one thing, the threads where the float bowls bolts screw into, looked like they had heli-coils inserted. I don't know if it came like that from the factory or not.

Thanks for the suggestion.
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Old 03-03-2006, 09:57 PM
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Quote:
Originally Posted by oldcarguy36
I had the machine work done locally and I put the engine together, which I've done on all my other engines. I do have vortec heads along with the appropriate vortec intake and gaskets. I should have been more clear, the plugs that are fouled are two on each side, feed from the same side of the dual plan intake, which I take it means the carb is the common denominator. It's the driver side of the carb, which the intake feeds cylinders 1 & 7 on the drivers side and 4 & 6 on the passenger side, so I take this to mean that this is the side that's running rich, and which would mean to me that it's not getting enough air. I've adjusted the mixture screws using a vacuum gage to the highest vacuum reading. So I'm at a loss of what might be causing this. I did bead blast the plugs (just the tips) to clean them and I may get some new ones to try. I'm using AC R44LTS, I may go up in heat range to see if that makes any difference. I've used Edelbrocks on my other engines and I know them, but I wanted to try something different, but it's getting the best of me right now.
Your a lot more on top of it than your first post lead me to believe. I wish I had some better answers for ya. Anyone around that you can bum a carb from just to get it running and then put it back on you wife's car. Just kidding................
Tmod has a good point, you don't know what the PO might have done.
Wish ya luck. You might be oldcarguy36, I'm just old.
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