FrontEngineDragsters.Org Forum
Technical => Spud Miller's Cave => Topic started by: retroboy on September 30, 2016, 08:57:38 PM
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Howdy.
These plugs are NGK BP6ES from a small block mopar. It's an 10.5 :1 engine with factory iron heads. Has a 4" single butterfly injector on methanol. The plugs were gapped at.018" with an internal coil Vertex. It was a pig to start so I took the Mag out fitted a factory Magnetic dist and a MSD6A box with a conventional oil filled coil. Reset the plugs to .040". I have only run the car once previously (with the Vertex) and it was very rich, I did damage and have repaired changed the ignition and ready to go again. As well as changing the ignition I've leaned it out a heap. It is still hard to start but I ran it last week and after a few minutes it started to break down - can't call it missing it was way more complex than that. I pulled the plugs today to close the gaps to about .035 and this is what I found. Number 3 plug (second from the front on the left looking toward the front of the car, and numbers 2 and 4 ( the first and second plug on the right side facing the front of the car). Don't worry about how dirty and sooty they are that's becausse I've been messing around trying to start with a squirt bottle with petrol and meths (at different times of course.) I checked the manifold is tight in case it was as simple as an air leak but OK. I figure I'm not the only person to have seen this before so what is it? Have you had it.
Cheers
(http://i567.photobucket.com/albums/ss117/Retro-boy/2016-10-01_zpsohjtip7r.jpg) (http://s567.photobucket.com/user/Retro-boy/media/2016-10-01_zpsohjtip7r.jpg.html)
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I'm no expert but that looks like aluminum from detonation. I would say your to lean and/or your timing is way off. Like I said I'm no expert so lets see what the more knowledgeable peolpe on here have to say.
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Ok I have since found a check valve in the delivery line on top of the pump sticking and only opening a very small amount so good by to the spring so that combined with my leaning it right out maybe the problem. If I have time tomorrow I'll gap some plugs down a bit to .035" give it a little more fuel, and set the ignition at a conservative 34 degrees. And see how it goes. I thought detonation showed on the porcelain but happy to be corrected. I hope I haven't hurt it again.
Cheers
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I agree with Dr. AWAG's prognosis : ) All I would add is the strap heats up faster than the porcelain, so we see most of the debris stuck on the strap. This might be connected to the length of time the engine ran; running for a longer time, the debris would make its way to the porcelain, which is what most of us are more familiar seeing with detonation. Obvious answer, reduce ignition timing, or richen fuel mixture, or both which is what you wrote for a solution. Good find on the check valve.
p.s. I'm no expert either.
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fuel injection is a controlled leak thru the checks, If the poppet does not open or opens a small amount, the system goes rich not lean, if the poppet is stuck open at the time its supposed to be closed , then the system loses pressure at that point as is lean.
Looking at the plugs with specks, they are so lean that there is no heat in the cyl. but what is there is killing the piston. alc plugs are read by the amount of discolored threads by burning the cad off of them. No more than 3 threads should be gray (instead of gold/yellow) 4 threads and you are close to the edge and not gaining any performance value.
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The check valve is on top of the pump to function as a starting aid by keeping the delivery line full from the pump to the barrel valve/metering block.
I'm going do invest in a cheap bore scope and have a peep inside.
Cheers
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If only those two plugs look like that, you will want to take a look at the nozzles for those cylinders in particular. Also to watch for is if they are restricted or too small extra fuel will be forced through the remainder of the nozzles either making them rich or looking better than they might really be.
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Since we now know the “partially stuck open” check valve was placed inline on the fuel feed line to the BV, and not on a return fuel line, that partially stuck open check valve no doubt did restrict fuel flow to the BV and could cause your lean condition.
From looking at mechanical fuel injection schematics, you want your fuel feed line between the pump and BV clear, with perhaps only a filter such as this one in place.
http://www.fuelinjectionent.com/webstore/product_info.php?products_id=77
Anything else like a “check valve” to restrict fuel flow to the BV maybe problematic.
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I can honestly say that I have never seen a plug look like that ! That is an awful hot plug ! Try a set of 9's or 10's . What percent dose your barrel valve leak and how much timing did you have ?