racing last weekend i encounterd poping in third gear. i pulled the spark plugs and found this in cylinder #7 i ran a compression test and that cylinder is down %10 from the others. i just stuck a borascope in the cylinder and didnt see anything alarming. next im going to do a leak down test to see if my valves and rings are good or bad. i discovered that my timing retard was not pulling any timing out when the nitrous was on. looks like the only retard that was functioning was the one behind the wheel.
It's kind of sad that with on cylinder pretty much out you still killed me down the track. I hear Vique yelling SloMo . . . be quiet vique!
Ouch must have been pinging pretty good. Not that you can hear it running down the track. Hope you didnt burn anything up. Good luck.
What do you think caused it to melt? Lean on #7 only? I have seen, on rare ocasions, that the spark plug electrode is messed up and thin right out of the box. What's with the oil on the plugs threads?
I put a dab of oil the threads to keep them from seizing in the head. If the leak down test doesn't find anything wrong I'm going put in some colder plugs and try again.
just did the leakdown test. its the intake valve. that beter than it being the rings. so now im going to pull the head and get a new valve put in. sucks that its on the drivers side. i have to deal with that header. maybe ill be able to slip the head out with out totaly removing the header.
wouldn't this be the puuuurfect time for new heads? (evil laugh in the background) . . . I saw some AFR heads laying around your shop . . .
you know. the person whos afrs those are probly wouldnt be able to tell the difference if i paint my heads with alum. paint and take a sharpie and right afr on the end of them. hmmm that sounds like a plan.
That plug did not melt. It died of detonation. How much timing are you running? What is your compression? Are you using power adders of any kind?
I just had to remove my heads and I had to remove the headers. I have studs in the block though. I pulled the long studs out, then was able to lift the head over the others. Good luck.
first post says that i was runnig nitrous and the timeing retard was not working. my compression is around 12-1 i was running 34 degrees i run two fuel systems one for the 150hp nitrous system it has c12 race gas in it. the carb has 91 pump gas with lucas octane booster in it. the spark plug was a autolite 45. its to hot of a plug to run with nitrous. with out the retard working i didnt have a chance of not having a problem. next time it will all be right and ill run an 11 sec time.
Brian, Soory about forgetting to review the first post - it does get me sometimes. How can you run 12:1 compression on 91 octane??? most folks start having problems with it at just over 10:1 compression. The other plugs in your picture don't look like they are too hot for your setup. There may be something peculiar to that one cylinder that is causing detonation. did you polish all the sharp edges off the chamber and pistons? Best of luck with it in the future. If you are really running 12:1 compression I would think that 45s would be way too hot a plug but like I said the other plugs in your picture didn't look like they were running hot just the one that melted/ broke.
i dont know my compression exactly. i have domed pistons and big chamber heads to clear the pistons. im going to measure the head chambers and try to figure out the size of the dome on the pistons while i have the head off this time. the guy who dynod my motor said that the heads do flow enough to allow the compression to be an issue. that is as much as i know as how i can run pump gas on this motor.
ok so mo and i pulled the suspect head off the motor this morning. as soon as we got it off we could see that all the valves had problems. there are 2.02 1.60 valves in the heads so they are really close to each other. they were all beat up around the edges. we put a light in the port and could see it around the valve seat. we took the head to the machine shop that built the. they pulled the valves and found that the guides were all wallowed out allowing the valves to hit each other. so we went an pulled the other head. it was perfect. it looks like the valves that were messed up may have kissed the pistons. im not sure. going to have the guys at the machine shop look at the pistons. if thats the case we will need to figure out why it only happened on one side. so that were im at right now. mo took lots of pics and im sure he will post them.
