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Old 03-30-2004, 12:59 AM
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Best Way to change valvesprings w/ heads installed?

I'm in the process of getting the parts together for a head & cam swap for my 454. I do have one quick question though. I plan on going with a solid flat-tappet cam, running dual valve springs. It is my understanding that the cam manufacturer recommends breaking in the cam with only the outer spring. What I am wondering is what is the best way to remove the springs so I can install the inner spring also. I know of two methods, but I am wondering what you have had the best experience with. I have the necessary tools (air compressor) for both methods, but have never tried either one.

#1: Using air compressor, rotate piston to BDC, leave all other spark plugs in, and fill the cylinder with air. I heard to rotate to BDC, so the air pressure will not try to turn the motor over. Also, how much pressure would be necessary to hold the valves against their seats? What worries me about this method, is what happens if I accidentaly push on a valve? Will there be enough pressure so that it won't open and lose the air in the cylinder?

#2: Use a nylon rope, and tie a knot in the end so if can't fall through the spark plug hole. Rotate piston almost all the way up, shove rope into cylinder, and then rotate piston the rest of the way up to push the rope against the valves to prevent them from falling into the cylinder. Install valve springs, then rotate crankshaft counter-clockwise to relieve pressure on rope, and withdraw rope from cylinder.

Do I understand both procedures correctly? I think I would feel more comfortable using method #2, but I have never personally tried either method. Thanks for any ideas.

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Old 03-30-2004, 01:45 AM
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I always use method 2. I always buy a new nylon rope and bring the piston up about halfway in the bore, fill the cylinder with rope then bring it up until the rope stops the piston. after I finish, I put the rope back in the bag in came in and place it away until the next time I need it.
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Old 03-30-2004, 04:35 AM
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I have used both methods. They both work well. The choice is yours.
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Old 03-30-2004, 07:57 AM
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Air is much quicker, used to change springs between rounds at the drags that way.
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Old 03-30-2004, 09:56 AM
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Thanks for all of your responses. It is really putting my mind at rest as this is the first time I have had to change the springs with the heads installed.

One more question though. When using the air compressor, how much air do you pump into the cylinder? Is there a certain psi range I'm looking for? And is it recommended to bring the piston to the bottom to keep the air from turning the motor over?

Thanks again.
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Old 03-30-2004, 10:02 AM
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Shoot for 100 psi+ or whatever your compressor line pressure is. Always put the piston down at BDC or the air pressure will take it there. NOW!
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