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Old December 23rd, 2005, 02:50 PM   #1
The Nuge
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Default Carb is done, now engine problem it looks like...

We just put another working carb on the 258 now, and we started it up today and it sounded perfect, high rpms and all. Then we started driving and shit started f***in up again. Cant acclelerate, or still cant get the rpms high now that we started drivin. It sounds like maybe a piston isn't firing, we described it to a local mechanic and he said maybe a ring or a piston is fried. Any advice? do you think that is somthing BMF and I can tackle? thanks
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Old December 23rd, 2005, 03:55 PM   #2
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sounds like what I had on my SBC.

Run it to a high RPM for a minute or so, immediately shut it off and pull the plugs. Look for unburnt fuel or oil on the plugs. Unburnt fuel means no spark, oil means blowby (in which case that cylinder won't fire)
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Old December 23rd, 2005, 04:02 PM   #3
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lets work on senarios

1. runs fine revs up, can't drive and make speed? could be a plugged cat. converter. its flow could be very restricted and it get worse the longer it runs. I had one that blew up an engine and the thing started with the new engine , but I couldn't drive it out the bay door...plugged soild almost.
drop the pipe at the manifold and let it leak if it drives fine then you found the problem.

#2 could a fuel problem, are you sucking air? if so it will cause the fuel to "foam" in the carb. the fuel will make it run bad. the float won't float in faom and it makes you think the carbs bad.

#3 the timing chain, is it in good working order? the chain controls the cam timing and distributor and has the ability to bounce with in its links if severly worn, the chain won't nessarily break, but it won't run very good.

#4 head gasket & head is it leaking? if you have running issues of any kind I advise checking your plugs, but pull them out when the engine is hot to warm, and if you have a radiator presure tester then pump up the sytem while the plugs are out of the head and the holes are free of debries. if by chance you see steam coming out of one of the holes see if it will light. if so its just fuel that was hanging around and if the steam puts out the flame of the lighter them you have water leak into the sytem somewhere.
I have lots of stuff to help you in diagnosing this, but I need very good discriptions of the problems. so take notes and between me and the rest of the guys here will sort it out.
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Old December 23rd, 2005, 06:13 PM   #4
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If you suspect piston issues, I'd run a basic compression test at least, just to see. (Leakdown test is better.)

Can spray water on the exhaust runners to see if each is hot..


If you had a carb probelm already, any dumped fuel into the exhaust can melt your cat into a block that kills your exhaust as Yetti said. (Thats why misfires make your check engine light blink meaning 'Shut off engine NOW!')

Fuel flow ok? Filter and lines are good?
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Old December 23rd, 2005, 08:47 PM   #5
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Alright fellas, The carb is in working order and we dont think it is the problem, the CJ does not have a cat, its straight pipe right now but after xmas will have a flo pro muffler. When we check out the plugs after it was run and is warm, the front cylinder plug is black and fouled from oil I am almost postive and the gap in the plug is full of black crud, I can post pictures of the plug after xmas.
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Old December 23rd, 2005, 08:55 PM   #6
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well thats good, if you have something in your hand to show you a path to follow. I would start with a compression check and then if its ok, I would change out the plugs and posiblly the wires, it sounds like its been acting up for a while
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Old December 23rd, 2005, 09:01 PM   #7
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by the way, if you suspect the wires run the engine and use a 2 liter pop bottle full of water and drill or poke a hole in the cap and squirt the contents on the wires while its running, if you see lots of sparks your wires are bad, they should not have any jumping spark when they're wet. replace as needed
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Old December 23rd, 2005, 11:04 PM   #8
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Thanks Yetti, we will give it a shot after christmas and report back with some photos and maybe Video if CC will host or something
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Old December 30th, 2005, 11:33 PM   #9
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Here are some pics of the front spark plug, This plug was brand new and ran for about 3 minutes, started up fine, revved great, then when we put the beast in gear it started to spit and pop and miss fire I believe, I am sure if we ran it longer the plug would look like the last one and the gap would be completley full of black wet/oily looking gunk



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Old December 31st, 2005, 07:19 AM   #10
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so now you have at least one plug thats showing debries and is fouled in a short period of time. I have a couple of things to consider. the plug could have fouled by left over fuel in the intake runners that had pooled from the carb pryer to rebuild, second the fouling could be from lack of compression witch would meen you have to do a compression test dry and wet to see if you have ring damage. the other thing and its a regular thing that people miss..valve seals. if the sludge in the valve train is deep enough to pool oil it can over come seals around valve stems. if this is the case it will suck oil past the stems faster then you can change plugs. I have seen lots of engines with this condition and it was just a matter of cleaning the top of the head under the valve cover and making sure the oil return holes were clear. I have done many repairs to valve trains and the design of the L style engines lets oil and debries build up faster then V style engines.
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Old December 31st, 2005, 09:31 PM   #11
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Choke? Do you have that stupid heat coil choke setup still? If so, scrap it, go to Murrays and pick up a "help" choke manual cable for $5 and install it.

You could also check the idle screw settings.
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