endofzworld Posted May 9, 2016 Share Posted May 9, 2016 got a 73 240z with the l24 and triple webers. changed the spark plugs last night and found that the number 6 spark plug was smashed in and also very wet. im still trying to get the carbs dialed in and the timing was done by ear. the car runs good at idle but sputters and backfires a lot when you get on it. Quote Link to comment Share on other sites More sharing options...
Pillar Posted May 9, 2016 Share Posted May 9, 2016 I would say that the plug being really wet when you pulled it is because the cylinder is not firing due to there not being sufficient gap on the plug. You said it runs good at idle. Is this after you changed the plug, or have you not run it with a new set of plugs? Were you the one that installed the last set of plugs? If you are, and you are sure they were gaped properly before putting them in, then there was obviously something inside the cylinder that hit and smashed the plug. Being as your plugs do not move at all, I would say there was either a foreign object in the cylinder, the plug was smashed before it got installed, or if that plug was somehow longer than the others (wrong plug maybe) then it protruded too far into the cylinder and the piston smashed it when it was at the top of its stroke. Quote Link to comment Share on other sites More sharing options...
endofzworld Posted May 9, 2016 Author Share Posted May 9, 2016 no it idled pretty well (surprisingly) with both sets of plugs and i made sure they were gaped right both times. after. changing the plugs and test driving it i pulled that same plug out and its wet with fuel. it doesnt sound like anything is wrong other than back firing and sputtering. no clunking or anything like that iv attached a photo of the old plug Quote Link to comment Share on other sites More sharing options...
Leon Posted May 9, 2016 Share Posted May 9, 2016 Is the new plug smashed in? The picture is blurry but it looks like you have a foreign object in #6. Quote Link to comment Share on other sites More sharing options...
Wizzurp Posted May 9, 2016 Share Posted May 9, 2016 Yep, definitely something in there if your plug is getting smacked. Quote Link to comment Share on other sites More sharing options...
endofzworld Posted May 10, 2016 Author Share Posted May 10, 2016 The new plug is not smashed. Just put a bore scope in there and didn't see anything. But Im still getting fuel on the end of plug so what's next valves? Quote Link to comment Share on other sites More sharing options...
Leon Posted May 10, 2016 Share Posted May 10, 2016 Compression and leakdown test. Take a good photo of your new plug and post it. Quote Link to comment Share on other sites More sharing options...
endofzworld Posted May 10, 2016 Author Share Posted May 10, 2016 will do do that tonight. maybe it could be a bad wire or something in the ignition? seeing as its only that one plug. i just hope nothing is bad internally. Quote Link to comment Share on other sites More sharing options...
TimZ Posted May 12, 2016 Share Posted May 12, 2016 maybe it could be a bad wire or something in the ignition? seeing as its only that one plug. i just hope nothing is bad internally. Nope - sorry. Damage like that is not likely caused by an ignition issue. Something made physical contact with the plug. Period. Could be that something got ingested into the engine and has subsequently left the engine, or something is wrong in that cylinder. I had similar damage when I had a valve seat become unseated - it was held captive by the valve and then popped back into the seat, so it was hard to figure out at first. Quote Link to comment Share on other sites More sharing options...
NewZed Posted May 12, 2016 Share Posted May 12, 2016 (edited) The new plug is not smashed. Just put a bore scope in there and didn't see anything. But Im still getting fuel on the end of plug so what's next valves? Are you sure it's fuel? Not oil? Or oil and fuel? If you have good rings, the cylinder should be getting the same amount of fuel as the others, it's blended at the carbs.. A wet plug could either be a misfire or it's not just fuel, it's oil and fuel, and the oil is causing some misfires. Fuel will dry off pretty quickly, oil won't. Edited May 12, 2016 by NewZed Quote Link to comment Share on other sites More sharing options...
endofzworld Posted May 14, 2016 Author Share Posted May 14, 2016 I know it's fuel and not oil. And I put a bore scope in there to check out whats in there and everything looks fine now so whatever was in there must be gone now. Because the new spark plug is getting covered in fuel I was hoping that was just an ignition problem but found no issues with that. I did a compression and number 6 had no compression soo yeah. Fun stuff Quote Link to comment Share on other sites More sharing options...
endofzworld Posted May 16, 2016 Author Share Posted May 16, 2016 (edited) Finally got around to doing a leak down test and survey says bad exhaust valve. Is there a good reference to removing the head? I'm no expert but I wanna try it myself. I have a Haynes manual but is there anything better? Edited May 16, 2016 by endofzworld Quote Link to comment Share on other sites More sharing options...
cgsheen Posted May 16, 2016 Share Posted May 16, 2016 http://www.nicoclub.com/datsun-service-manuals Quote Link to comment Share on other sites More sharing options...
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