| Hi Tony, Sorry for the late reply here – I have been in Minnesota on a trip to assemble Tyler Duschane’s engine and dyno tune it for him. I have had your situation on my mind the whole time and the time to think about all of this has been of benefit. One thing that has come to my attention in the past hour of reviewing the pictures you sent to me while discussing your issue with my local engine builder is that your cylinder heads do not have the plug bosses shaved off. In several of the images you sent to me of the damage to the valves you can see the plug bosses completely intact. In image “Damage 2008 3” where it shows the top of the piston, you can see an impression made on the outer lip of the piston crown which indicates mechanical binding with some foreign object. In image #4 you can see a large section of the exhaust valve is missing and in image #1 the valve head shows signs of mechanical damage (denting out at the valve edge in two places). The only aspect I have had in question in my mind was due to my assumption that your cylinder heads had the plug bosses removed. With the plug bosses removed, the extended plug tip of the 6B-11B plugs to be exposed. With them exposed directly to combustion they are going to operate at a higher temperature than if they had the plug bosses in place and the damage to the plugs led me to believe this was the case. However, your heads have the plug bosses in place which refutes that possibility – the plug body is entirely insulated by the plug boss. Here is a link to an image of what shaved plug bosses look like as well as what a PFR6B-11B plug and a PFR6B-11 (NA) plug look like when installed into the head. You can see in the image on the right chamber how the 11B plug tip extends into the chamber whereas the NA plug tip is flush with the combustion chamber crown. With the plug bosses intact, the 11B plug body is not exposed on both sides of its wall. [ http://ashspecz.com/Image%20Gallery/2004-Engine%20Build/images/H-HEADMACHINE-PLUG-16.jpg ] Even despite the un-insulated 11B plug in a head with the plug bosses removed, we have never seen a plug or valve burn up – and in engines making considerably more power than yours. According to your previous email, you noted that the fuel mixture at the track was spot-on to what we saw on the dyno. There isn’t any question in my mind at this point of the validity of the tune. The only other time I have seen an exhaust valve burn up was in a car running nitrous oxide – it takes a considerable amount of heat to melt inconel. In this one case, the valve only burned up a very small amount – very similar to what is seen in the damage2008-1 image you sent to me. The mechanical damage seen in the image of the piston and one of the valves could have been a result of the debris from the plug. I’m not sure what plugs in the image you sent to me where in which cylinder or which cylinder had the damaged piston. I can tell from the image that the valve missing a large chunk is cylinder #6. The dent in the top of the piston is of considerable size and I have spent a few moments here with both a plug and a piston to see if any of the plug parts could have created a dent that large in the piston crown. I am unable to see how any of the plug pieces could have created a dent that large. The smaller dent in the piston crown does look like it could have been created by a piece of the ceramic insulation or the electrode itself. The larger dent in that piston raises some questions though. What cylinder has the damaged piston (with the large dent in the top edge of the crown)? I find myself continuing to come back around to the fact that both the plugs and the valves burned up. It wasn’t just damage to the plugs so it is clear to me that those two cylinders ran lean enough to melt steel as well as inconel. You don’t have shaved plug bosses which provides ample insulation for the 11B’s projected tip so I no longer have any question about the choice of plugs used in your setup – the 6B-11Bs are plenty cool enough for the power level you are running at – the plugs were not the cause of the failure. The plugs simply burned up as well as the exhaust valves and general theory states that if it were the plugs weren’t cool enough, it would have only resulted in pre-ignition/detonation and you would be replacing a bottom end as the bearings would have been beat to a pulp. But the fact the exhaust valves burned up tells me so lely that those two cylinders ran lean enough to melt the valves – the plugs being made of steel is easy to understand that they would have been torched as well at temps high enough to melt inconel. The damage wasn’t dependent on the heat range of plug you were using – if it is hot enough to burn valves, the plugs will burn up too. There are only a few different theories to explain the exact sequence of events but it is of no question that those two cylinders ran lean enough to melt inconel. According to your feedback on the wideband information it is apparent that the tune is not the culprit for the lean condition so the lean condition was a result of something else…. And it isn’t because of the plugs – plugs don’t burn up valves, only high combustion temps can do that. Given that the car ran at the PINKS event without issue leads me to believe that something happened to the car on that third run, perhaps a vacuum hose blew off or the fuel pump starved of fuel under the hard acceleration, or perhaps some dynamic in the old DOOLZ intake caused the engine to lean out momentarily. It is very difficult to nail it down and it could have been a result of a combination of effects.&n bsp; But it is clear that those two cylinders ran lean – valves and plugs being burned up takes a ton of combustion temps to achieve , not to mention, the other four plugs didn’t burn up nor did their valves. The coloration of the other four plugs is spot-on to what I would expect to see with a proper air/fuel mixture. This is obviously a bad situation for the both of us. While it is clear you believe the plugs were the cause of the problem, that is too narrow a view for diagnosis given that you have plug bosses and the exhaust valves also burned up. We made 14 pulls with your car on the dyno and made several street runs without incident at full boost. The damage to the piston crown also raises questions about what caused that and even something as small as a washer accidentally dropped into the intake tract would result in the mechanical damage seen to the components. The valve with the large gaping hole in it also raises suspicions as to whether or not that hole was burned or if a piece of the valve actually broke off. At this point, knowing you have the plug bosses installed, I would still recommend you to use the PFR6B-11B plugs – they weren’ t the cause of failure in your engine and I only questioned that myself based on the inaccurate presumption that your plug bosses were shaved. The spark plugs simply cannot melt the valves – the combustion temps were too high which resulted in both the plugs and the valves being burned up. I am going to send a few emails to various individuals who competitively drag race their vehicles to further validate that the 6B-11B plugs being used in their cars haven’t caused problems for them. I’m not sure who all you have spoken with about the use of the 11B plugs being the cause of your issue but I would rather ask the folks who are running the 11B plugs to give some empirical feedback on this. I don’t know of anyone else who has experienced this kind of failure where the problem was corrected by running iridium plugs. Iridium plugs haven’t been used in these cars for very long – they are a new plug that only a few have been using and no one previous using the 6B-11Bs have experienced the problem you have…. And many of them are making more power than your car and running faster ETs. The fuel mixture you reported assures me that the tune is on par but something happened which made those two rear cylinders run lean. As I said previously, this is a bad situation and although nothing had been concluded at the time, I offered to fix the heads at no charge just to help out any way I can as I already have the parts and equipment on hand to do that – it would have only taken a couple hours of my time and cost virtually nothing. The main problem I think we have at the moment is over the issue with the plugs. I can only hope that you can understand the dynamics within these engines and see how the cause-effect relationships really work – the plugs weren’t the cause of the problem; the plugs suffered from the same problem that the exhaust valves did, which is a result of a combustion temperature high enough to melt the components.&n bsp; If the wideband had been installed into the car as I had strongly recommended you do, this issue may have been prevented, although it is still inconclusive whether something went through the motor or some other culprit is to blame. I haven’t written this off and I am completely open to any other evidence or theories which can provide an alternate explanation to this. I can’t say what I am willing to do at this point but I hope we can come to an agreement on a reasonable cause for this problem – I hope it is clear to you that the 6B-11B plugs aren’t the cause – their failure was due to the effects of a lean mixture, as well as the exhaust valves. I’ll be in touch soon once I hear back from some other folks about this.. -Ash
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