Valve spring install, BDC.
Thread Starter
Melting Slicks
Joined: Oct 2004
Posts: 3,117
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From: St. Louis, MO
Valve spring install, BDC.
Ready to install rockers after replacing a spring. I used 80 lbs of compressed air, which should have put piston at BDC. Both valves should be closed at this point, allowing me to torque down rockers. Correct?
I know it should be at TDC, but this seems to make sense to me. Granted, I haven't cracked open a valve cover in about ten years.
I know it should be at TDC, but this seems to make sense to me. Granted, I haven't cracked open a valve cover in about ten years.
Tech Contributor
Joined: Jan 2007
Posts: 19,360
Likes: 1,127
From: Dyer, IN
No offense, but it doesn't make sense to me. Why would you want to use the air method with the piston at it's lowest point? That way you have to have more volume of air to do the same job. Additionally, with the piston at TDC, if the air fails in the process, the valves don't drop into the cylinder.
Race Director
Joined: Oct 2002
Posts: 16,477
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From: Gone
CI 6-7-8-9-10 Veteran
St. Jude Donor '03
No offense, but it doesn't make sense to me. Why would you want to use the air method with the piston at it's lowest point? That way you have to have more volume of air to do the same job. Additionally, with the piston at TDC, if the air fails in the process, the valves don't drop into the cylinder.
You can put the rockers on, even if it depresses a valve...just snug the bolts up, then if you find a valve is open...just rotate engine until you see both valves closed, then torque the rocker bolts.
Thread Starter
Melting Slicks
Joined: Oct 2004
Posts: 3,117
Likes: 0
From: St. Louis, MO
Sounds to me like he already changed the valvespring, and now wants the engine rotation at a point where both valves are closed for putting the rockers on.
You can put the rockers on, even if it depresses a valve...just snug the bolts up, then if you find a valve is open...just rotate engine until you see both valves closed, then torque the rocker bolts.
You can put the rockers on, even if it depresses a valve...just snug the bolts up, then if you find a valve is open...just rotate engine until you see both valves closed, then torque the rocker bolts.
Le Mans Master
Joined: Mar 2002
Posts: 5,955
Likes: 161
From: PNW
Yep, too much valve overlap at BDC (due to radical cam timing) so there would be major air leakage to keep the valves closed with springs removed unless you have one insane air compressor.
Last edited by ZeeOSix; Apr 14, 2009 at 08:49 PM.
