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| Repeatedly Fouled Plugs https://slantsix.org/forum/viewtopic.php?t=23541 |
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| Author: | Greg Ondayko [ Sat Jun 09, 2007 12:26 pm ] |
| Post subject: | Repeatedly Fouled Plugs |
Hello, I have a plug fouling problem. Engine is a 77 440. It is pretty clost to stock - Different intake and has Headers - I believe cam is stock - I use it to tow with. Anyway I Am Repeatedly getting fouled plugs - I have Changed the plugs, The wires, Pickup in the Dist, coil, Cap, Rotor, - It is really noticable in low - rpm ramge say 1000 - 2500 when hot - the motor feels like it runs on 4 cylinders - My dad has suggested to cahnge th oil - I ran synthetic in there for a bit, So I listend to him and swiched it back to dino oil, And same problem. He suggested this due to the large amounts of Vacum a 440 pulls. The Engine Does not smoke - Not even at start up - So I am guessing the rings and Valve seals are in good shape - The depoists just look like chorcal crusty crap - not black or anything like that. I have ran both 87 and 93 gas with no change. Thansk for any and all help. Greg |
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| Author: | Jeffc [ Sun Jun 10, 2007 9:21 am ] |
| Post subject: | |
Any cold weather running problems? maybe carb is set way rich or sticky choke, plugged intake crossover exhaust passage, is engine running 'cold'........ |
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| Author: | Greg Ondayko [ Sun Jun 10, 2007 3:50 pm ] |
| Post subject: | |
Well, I dont really use it in the cold, but it does run fine cold Choke works fine hot or cold The carb is the stock thermoquad, So unless Someone before be messed with the curb idle screws, It sahould be good. - There is never any black smoke from the pipes. I am not sure if the Exhaust crossovers are Plugged or not, as it does have headers and no heat riser. I neve have had the intake off to check.. Engine Runs on the cold side of the normal operating range in the summer weather - It climbs to the middle of the temp gauge when things are extremly hot and I am towing in stop and go traffic. I just had the rad recored with slighty larger tubes due to the oveheating I had before - But I had the plug problem with the old plugged up rad too. Greg |
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| Author: | Sam Powell [ Sun Jun 10, 2007 4:29 pm ] |
| Post subject: | |
If you have headers, then you do not have a cross over under the carb. That means your carb is always running a little cooler than designed for. I wonder if there is a water heated base plate you could put in there. Sam |
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| Author: | volaredon [ Mon Jun 11, 2007 2:01 pm ] |
| Post subject: | |
"If you run headers then you don't have a crossover under the carb"... Headers are a form of an EXHAUST manifold, the heat crossover under the carb would be under the INTAKE manifold,,,, how would running headers eliminate that? |
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| Author: | Sam Powell [ Mon Jun 11, 2007 2:56 pm ] |
| Post subject: | |
I have never really thought about it, just have heard this is so. I have rebuilt several V-8's and cannot remember how the exhaust gets from one set of exhaust ports into the crossover. I just know that when the heat riser is closed, the heat is forced up over the engine through the intake manifold, and for the crossover to work at it's maximum, one exhaust manifold has to be shut off, which will not happen with the headers. I kept a set of v-8 exhaust manifolds around for years, and then finally pitched them out, or I would go look now. You might get some heat, with headers but it would not be forced over under the manifold the way it happens when the heat riser closes on a manifold setup. So maybe it is only when it is cold that the cross over would function differently with headers. This might just be enough to foul a set of plugs. But you would think they would then get cleaned when driven warm for awhile. It is something to think about though. Can anyone help us out here with v-8 exhaust crossover theory? Greg, have you tried running warmer plugs? Sam |
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| Author: | volaredon [ Mon Jun 11, 2007 6:32 pm ] |
| Post subject: | |
Yeah but even with a heat riser, most every Mopar V8 Ive ever seen a manifold off of, the heat crossover is clogged up. Would the lack of a heat riser (iron or tubular "manifold") keep this from happening; passage stay clear and although heat wont be held within the crossover passage, wouldnt the fact that can actually pass thru be better than one thats plugged up (and good for nothing anyway)? I can't see this being a contributor to fouled plugs unless the engine were run for short bursts that the choke never had a chance to fully open; the engine never had a chance to completely warm up. |
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| Author: | AndyZ [ Mon Jun 11, 2007 7:13 pm ] |
| Post subject: | |
Are all of the plugs fouling the same? |
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| Author: | Jeffc [ Mon Jun 11, 2007 7:32 pm ] |
| Post subject: | |
most above is correct to some degree. Heat crossovers in v8 engine will be open even with headers (passage starts in the head). However, they will not get the full affect of the heating since the exhaust valve on the one side to force the hot gas to cross the intake when the engine is cold is not there. Some heat will rise and crossover none the less as a v8 warms up. A plugged crossover in the intake will cause the carb to not fully warm up, headders or not, this will cause the carb to be cold enough that it will 'ice' the carb even in mild temps, esp if ran wide open or close to wide open- such as pulling up a long hill (just like a slant with headers and a unheated carb intake). This will cause a 'rich' burn and can foul the plugs given enough time (sometimes not so much time, depending on air temp). The more vacuum pulled- the worse it can be. My 2 cents here is a vote for a plugged crossover and the fact that he has a TQ which does not pass heat as fast as a fully metal carb 'might' play a part (TQ's are great carbs when set up right and that may also be part of this "being set up right'). But I am just making a guess...... |
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| Author: | Greg Ondayko [ Mon Jun 11, 2007 8:50 pm ] |
| Post subject: | |
Well, I thgink What i Will Do is Pull the intake and Check the cross over Passages - Chances are they are Plugged. I know the engine takes a while to kick off fast idle due to the fact that there is no heat riser to force the Hot air under the carb. 440's are nice because they are a dry intake - no coolant or oil mess to clean when they are pulled off. - Sam - I have already Gone 1 step warmer than stock with the same problem. - The Book reccommends NGk xr5's and I installed xr4's with the same results. - Not all the plugs fouls the same - Some are Worse than others - But I havent logged any data to keep track of which ones foul the worst. Thanks, Greg |
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| Author: | Sam Powell [ Tue Jun 12, 2007 4:35 am ] |
| Post subject: | |
If you haven't burned up the plugs with one step warmer, what is to prevent you from going another step warmer yet? I would try it before pulling things apart. Just keep tabs on them for a couple hundred miles. How long does it take for them to get fouled? Sam |
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| Author: | Greg Ondayko [ Tue Jun 12, 2007 11:07 am ] |
| Post subject: | |
It Usually will happen in less than 20 miles - However it was a bit longer with the Warmer plugs Greg |
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| Author: | Charrlie_S [ Tue Jun 12, 2007 1:28 pm ] |
| Post subject: | |
Quote: The carb is the stock thermoquad, Greg TQ carbs had a problem with the "wells" in the bottom of the float bowl. They would leak and make the carb run rich. There was a "fix" using epoxy, but I do not remember the details, as I never did it. Someone here should be able to help you with this, or maybe on one of the V-8 Mopar boards. |
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| Author: | Dart270 [ Tue Jun 12, 2007 2:47 pm ] |
| Post subject: | |
Yep, I have seen warped TQ bowls, especially if they're rebuilt, and they pee gas down at idle to make it rich. There are people around who do very nice rebuilds, and james longhurst knows one. Lou |
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| Author: | Sam Powell [ Tue Jun 12, 2007 4:29 pm ] |
| Post subject: | |
All Thermo Quad's are not equal. They were evolved over the years, and some design changes worked and others didn't. You will need to talk to an expert about this, but I got the lowdown when I built my 360, and put a "good" one on which I rebuilt myself. I never had a moment's problems with it. One of the spotting features is whether is has a bowl vent or not, and I can't remember which one is trouble prone. What Lou was refering to is a plug in the bottom of the fuel resevoir which is prone to leaking. I know I did the prefered repair to mine, and never had any problems with it. It ran for ten years for me, and is still on it in the hands of the current owner. |
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