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Discussion Starter #1
Well, I finally ordered new valve springs late last week to resolve that "valve float" I get sometimes at the track over 5,500 rpm.

Car ran pretty well on Sunday, air was very good. Best pass was an 11.904 very hard on the brakes down to 103.97mph. This was the best pass of the 3 and I ran out by nearly a tenth. Hitting the brakes shed 10-11 mph from other passes at about this ET and I'm guessing .05 to .10 in ET. Car ran well, no apparent issues for the ride back and forth or the passes.

Anyway, I figured I'd start the teardown and at least get the first set or two of springs out. I knew I'd need to see if the new springs would match the old retainers.

I pulled the #1 plug and inserted the air chuck adapter and then installed the spring compresser on #1 Exhaust stud.

When I attached the air line, I heard a hissing sound.

I hadn't used this setup in 5 or 6 years but I didn't remember that happening the last time.

I removed and re-installed the air chuck, hissing sound still there. Since the cyl isn't hold pressure, it will not hold the valve up the the spring compresser.

I am not positive of the full status yet but my guess is I've bent a stem by dancing the valve off the the top of the piston and now the valve isn't seating anymore.

I've not had the time to check any others yet. Hopefully, I'll only have to remove one head and hopefully the piston or guide is not damaged, but why would my luck change now?

Am I right in saying that the point of closest possible contact is exhaust valve closing?
 

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Am I right in saying that the point of closest possible contact is exhaust valve closing?
Depends on the cam--I had a little problem on the dyno a few years ago--smacked a few intakes; repaired the damage, go back to dyno with cam in different spot...hit some exhaust valves!! [email protected]#%&*!!:mad:
 

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You should be able to tell where the hissing is coming from...See if it's coming from the intake, exhaust or the pan. Where the sound is coming from should tell you where the problem lies...


pops
 

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Before ripping into the motor, hook the air back up to it and squirt some soapy water on the valve stem to see if it is coming up from the valves. It could be seeping through your rings. This will help you narrow it down whether its the valves or something else. You will get some hissing from a small amount of air passing through you rings but if it dosnt hold the valve you could be getting to much! Hope this helpd and good luck.
 

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Discussion Starter #5
It is coming from the exhaust valve.
 

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Discussion Starter #6
Situation not looking good.
Still have not completed a compression test.
Have tried a few cylinders and none have held compression yet.
And this thing was running good!
Clipped several 11 second passes just last Sunday.

Wow, what can it do if it isn't injured?
 

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shoving straight compressor air to hold the valves up when taking off the springs you're gonna hear hissing. It's air escaping past the rings. You can't totally seal off 150 psi of compressor air. Do a compression test and leakdown, remember on leak down you have to have both valves closed and the piston at TDC.

OR....

just rip the heads off and get the valves checked out and install your new springs.:D
 

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If you can't seal off 150 psi of compressor air how do you expect 1,000 psi of combustion pressure to seal?
Air loss is an indication of a problem.

Listen for the sound of air leakage at the following locations:

Intake/Carb = Intake valve leaking
Exhaust pipe = Exhaust valve
Breather = rings

The piston should be held at TDC compression and you'll need a breaker bar on the crank bolt to hold it up. If you don't hold the crank, the piston will be pushed to BDC, the ring seal is poor and the exhaust valve may begin to open.
 

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With all due respect paul if there is no leaks...? but you can still hear the air? I just did a comp/leakdown on a 400 with 2% leakage in all cyls and had 195 psi and when I loaded the cylinder with air you can hear it. No leaks nowhere. then what is it? Are you sayin it will be totally silent?

FYI I was going to check the springs on this engine and I could change the sound of the air by opening and closing the valves. Again no leaks anywhere. So what is the air noise then? I'm talking as loud as a leaking air fitting.

how do you expect to seal 1,000 psi? how long does it have to? with parts moving at 6,000RPMs?
 

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Discussion Starter #10
OK, I think I am guilty of fearing the worst and getting carried away with that.

I have now completed a compression test on all cyliniders which all have returned results of 180 to 190 PSI. There appear to be no issues that I can tell. I couldn't believe that the car seemed to run as good as it did if it was really injured.

Anyway, I was not able to change the springs so she is back together just like she was b/4. I'll hold off a little longer b/4 going after the spring install, like mabe with a head swap or something. She fired right up and funs fine.

I have heard of using a piece of rope in through the sparkplug hole with the piston at TDC used to hold the valve in place to change springs. Trying to pressurize the cylinder would not hold the valve up against the spring compressor, though I did change springs like this on my previous engine. The valve lock simply would not release.

At least she is ready to go back to the track when I get back from my San Diego vacation.
 

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With all due respect paul if there is no leaks...? but you can still hear the air? I just did a comp/leakdown on a 400 with 2% leakage in all cyls and had 195 psi and when I loaded the cylinder with air you can hear it. No leaks nowhere. then what is it? Are you sayin it will be totally silent?

FYI I was going to check the springs on this engine and I could change the sound of the air by opening and closing the valves. Again no leaks anywhere. So what is the air noise then? I'm talking as loud as a leaking air fitting.

how do you expect to seal 1,000 psi? how long does it have to? with parts moving at 6,000RPMs?
i agree. if you have a ring gap you have passage for air to travel through thuss getting a hissing sound from the RINGS. oh ya and im prety sure i stated this earlier!!!!!^^^^^^^^^^^^
 

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The only time I tried to use air pressure to hold the valves up I could hear air leaking out. There is a a gap in the rings and clearance around the pistons. I would think it would leak a little bit of air.
After that time I just started using a piece of nylon rope pushed through the sparkplug hole. It worked really well and I didn't have to listen to the compressor run.
 

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I was going to suggest the nylon rope as well, My "uncle" gave me a big roll of 550 cord during my last stretch in the ARMY works really good for this and a lot of other things.
 

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I agree that there will always be some audible leakage but the initial post said the cylinder wasn't holding pressure. I assumed that the sound was louder because of a significant leak.

Those little compressors don't have enough CFM or pressure for this kind of operation.
I use a regulated nitrogen bottle for leak-down because it's a steady source of pressure and it's dry gas so it won't rust the cylinders. It's also useful for on-head spring removal because I can up the pressure to compensate for stronger springs. Sometimes you have to wack the retainer to free up the lock first. I use a homemade aluminum tool instead of a steel socket to keep from nicking the retainer. The 550 cord would work but I'd always worry about bending the stem on some race setups with small diameter stems and big springs.
 

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Tapping the retainer with a plastic mallet will do a lot to help get the retainer "unseated" from the keys. Put some tension on it with the compressor, and tap it a bit with the air in the cylinder.
 

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Discussion Starter #17
I am finally getting back to this after several weeks, my vacation, my daughter's wedding, my mother-in-laws funeral, and a lot of miles.

The thought didn't occur to me at the time but when I first put the air chuck in the cylinder, I failed to crank the engine over to TDC, consequently the exhaust valve was still open and hence the air leakage. Fearing the worst I jumped to the conclusion that I had injured the engine.

The compression test suggests maybe not.

After getting back into town Saturday night, I managed to get to Edgewater's Muscle Car Sunday. The wagon qualified #25 in the Street Tire Quick 32 race with an 11.96 ET. Obviously not a very fast field. Unfortunately, I red lighted in the first round. Oh Well.

I just found out that if I correct my quickest observed Et with this pass corrected, this was actually a better run.

The last time I changed the valve springs using the chuck in the sparkplug hole I had a smaller compressor than I do now.
 

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Dan, I used a spare spark plug wire. With a little wd40 on it, it goes in and out really easily and works perfectly. I have a solid flat tappet so I broke my engine in without the inner springs. Afterwords I had them all apart and back together in about 45 minutes. It's a piece of cake.

Of course since you're changing springs, you'll have to check heights and mess with getting that all correct. What springs are you going from/too. I don't remember what camshaft you have. Is it a hydraulic roller?

I think the air in the cylinder sounds like more work and you have to worry about it leaking down if you get distracted while you have it apart.


Oh yea, the rubber mallet trick works great. One tap and they'll let go.

Hope this helps. -Mike
 

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Discussion Starter #19
Hey that sounds pretty good.
With my new headers it takes more than 45 minutes just to remove the spark plugs though.

I'll give it a shot and see how it works.
Dan
 

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I performed this same task not long ago. To ease the procedure I loosened all of the rocker arms, and removed all of the plugs (all valves closed). For each cylinder I rotated the motor till piston was up, charged cylinder with compressor air then began spring removal.

There should be no appreciable external forces acting on the valve other than the spring trying to keep it seated, when the spring is removed, 150psi of compressor air should be adequate to counter act any gravitational forces acting on the valve itself.


Just a thought.

James
 
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