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  #1  
Old 07-04-2001, 02:58 PM
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cageman cageman is offline
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Question fire in the hole no more

I pulled a plug in # 8 and it looked like it had hardly fired and I did a compression test and it only had 30 pounds when the others had 160. What might have happened to this cylinder to lose that much compression in 7 nights of racing. I have never gotton this motor over 220 degrees and it allof a sudden started to sound different, that is why I checked the plugs. I Think at this point with only seven cylinders my old 318 would kick this 360's butt!
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  #2  
Old 07-06-2001, 11:05 AM
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I just had the exact same thing. Number 4 cylinder had a plug that looked like it wasn't firing. Checked compression and nothing. Pulled the valve cover off and the pushrod on the intake valve was broken in two. Looks like the hydraulic lifter came apart, causing a bad angle on the pushrod, which then broke. Something like that anyway.
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Old 07-06-2001, 12:57 PM
340king 340king is offline
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Default Bent on Improvement

Sorry for the corny title, but I couldn't resist. It would appear that you have a bent valve. From your other posts, it appears to be an intake valve, on the number 8 cyl. Now, the real question is what caused the bent valve. I would research this thouroughly prior to running this combo again. I would also pray to the God of broken engines, thanking him for sparing yours. Bent valves=broken engines.
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Old 07-08-2001, 03:26 PM
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Default pierced rocker

Well when I took the valve cover off it was apparent what the problem was. The pushrod went through the rocker on the intake on #8. The guts out of that lifter were missing to so now I pulled the intake to check the cam and it looks good. So now I will moly up a new lifter and I bought some NEW rocker arms. I will probe the drain hole in the pan with a magnet to find those lifter guts.
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Old 07-09-2001, 06:22 PM
340king 340king is offline
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Was the rocker arm holding the valve open? If not, then you still have a bent valve. If there isn't compression, then there is a hole somewhere in the combustion chamber. Either the valve is bent or the piston/rings aren't sealing at all. If the rocker arm was holding the valve open, then you might have a chance that the valve didn't get hit, but there is still a pretty good chance that it did. If it were mine, I would pull the head.
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Old 07-09-2001, 11:11 PM
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I had the exact same problem. I haven't completed the fix yet. Got the new pushrod and lifter, but haven't installed them yet. If the intake wasn't opening, would there necessarily be compression? If the intake valve doesn't open, there is nothing to compress, right? Now I'm wondering if I have to pull my head. I was thinking a new pushrod and lifter would be all. Hmmm. And what caused this to start with? Faulty lifter?
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Old 07-10-2001, 10:59 PM
340king 340king is offline
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Default Reversion Psychology

There should be compression anyway. That is because the air will come in the exhaust during overlap. It will be a little lower than the others, but it will have some compression. The reason I suspected that there was a bent valve on Cageman's engine is that he was complaining about not being able to rev up and there was a weird miss. I have had plug wires fall off and the car would still rev, albeit slower.

When you bend a valve, the entire intake tract is thrown for a loop. This causes a severe reaction and reduces power greatly and a wierd miss. Engines are kinda funny when it comes to desiring a steady rhythm of pulses. Upset that rhythm and the engine will stumble.

The technical term is called intake reversion. That is why most cams are cut with differing durations on the intake and exhaust. They are trying to maximize the cam tuning without suffering from intake reversion. Intake reversion is evidenced by staining of the intake port and even the intake itself. The depth or length of the staining indicates the seriousness of the reversion.

Even after fixing the problem, the engine may still stumble for a little while. I think it has to do with the manner in which the intake and cylinder head ports are wetted by the flow of the intake charge. I think it takes some time for the wetting to even out and not effect the mixture. This can be seen when running on a dyno. Sometimes it takes two pulls to get a true feeling for how a jetting change affected the engine.
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Old 07-12-2001, 10:50 AM
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Thumbs up Compression is back

I put the new lifter and new rocker arms in and it has 160 for compression.
Now my qustion is how can I find what my comp ratio is from this info on a 30 over 360 with 202 160 J heads.
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  #9  
Old 07-13-2001, 01:14 PM
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I also put in a new lifter and new pushrod. Cranked it up and practiced last night. Runs great, no bent valves. My compression guage shows 160 also. My engine builder built mine to 10.25:1 by cc'ing the heads and zero deck height. Good to have the motor back in peak form.
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