Drag season is over for me, so I performed a leak down check on my motor.I found 8-10% on the good cylinders,45% on a couple cylinders. The bad ones are leaking through the exhaust valves. I'm pretty sure that they are sooted up from not having nearly enough timing in the motor on my last pass. (Lost my mag, then while running late for the round miss timed it 14 degrees off)The question is, do I have to tear the heads off and grind the valves, or will this problem correct it self with a proper tune up?
If you are sure the valve is not bent or burnt and think it is sooted up you can "stake them"
With air pressure in the cylinder pop the valve tip with a soft mallet.
You can even spray carb cleaner on the valve when it is open.
No help? valve job.
[ October 14, 2003, 06:57 PM: Message edited by: Infomaniac ]
Thanks for the tip Infomaniac. Thats easy and cheap. I'll try that this weekend.I'm pretty sure they are sooted, I did the same thing earlier this year. I tried to slow my boat down by adding fuel and taking timing out.That was the first time I've ever been frusturated by going "TOO FAST"
Late Timing + Blown Alcohol = Valve job. That's the math. Exhaust temperature high due to burn in the pipe. Exhaust seats out of round.
Thanks Fiat, at least you are not afraid to spell it out for a guy. I always thought that late timing made a motor run cold due to less burn time. Less burn time causes havoc on the exhaust seats...hmm
I had late timing as the probable cause in my reply. I edited it out for some reason.
Trying to be positive I guess.
Hows this for spelling out: Dude you screwed up big time when you backed off the timing. Now your exhaust valves or seats are seriously jacked up.
Only kidding dude.
Yep, I would say valve job but maybe you lucked out and all you need to do is lap the valves!..
I wasn't trying to be harsh. Just been there, done that. We used to try to slow the drag car down my taking a little timing out sometimes. Whenever we got later than 30 degrees, we'd knock the seats out of round on the exhaust. Happens if you run too fat also. I've seen 2500 degree exhaust temps, and knock the seats out of round big time, just because the motor was way fat.
But like Info said, sometimes you can warm the motor up and rap the exhaust valves and get em back.
Alcohol a very funny critter. Hauls ass if it's even close to the tune up, but hurts stuff in a sneaky way. Might not melt a plug when lean, but will take a 2nd ring land instead. Fat can hurt too. I know, I got hurt one recently. Blower rise came a little quicker than the fuel curve.
It's a humbling fuel though. 'Bout the time you think you really got a handle on it, you get hit up side the head!
[ October 15, 2003, 09:50 PM: Message edited by: Fiat48 ]
I didn't think you were being harsh at all. In fact, you don't know how much I appreciate the info I get from guys like you on the forum.Our local dragstrip won't even allow a blown alky car for insurance reasons.This means lessons in tuning my motor come from the computer or the "school of hard knocks" at the boat drags.
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