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Old July 9th, 2012, 11:15 PM   #1
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Default removing valve springs without removing heads ?

Im changing valve springs on a 1979 for 400cid and am not pulling the heads off, i have a tool to compress the springs and to presurize the cylinder but am simply wondering how much psi to put in the cylinder? Thanks
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Old July 9th, 2012, 11:19 PM   #2
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why not do it the correct way and check the cross hatch on the cylinders and replace the gaskets. its not that expensive for a set of gaskets.
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Old July 9th, 2012, 11:19 PM   #3
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Put all the psi in.
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Old July 9th, 2012, 11:29 PM   #4
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Because the motor was a recent crate motor install, im just throwing in a cam, valve springs, double roller chain, hi volume oil pump, alum intake, 4bbl carb and header before the silver lake trip
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Old July 9th, 2012, 11:30 PM   #5
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Put all the psi in.
Lol i cant spell -- edit below --
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Old July 9th, 2012, 11:32 PM   #6
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Put all the psi in.
Thanks jaysusr
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Old July 9th, 2012, 11:35 PM   #7
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well since your already going to have the headers and intake off just pull a few more bolts and do it right.
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Old July 10th, 2012, 04:08 AM   #8
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There is nothing wrong with pulling the springs without pulling the heads. Pulling the heads to do it is not necessarily "doing it right".

Air pressure can be as low as about 75psi or so, but just leave it at whatever pressure you run your shop at (125 or so). Also be careful not to tap the valves with the springs removed. If it breaks the seal on the seat, the valve may drop, and you will be pulling the head then.
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Old July 10th, 2012, 04:31 AM   #9
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Quote:
Originally Posted by Yota Bill View Post
There is nothing wrong with pulling the springs without pulling the heads. Pulling the heads to do it is not necessarily "doing it right".

Air pressure can be as low as about 75psi or so, but just leave it at whatever pressure you run your shop at (125 or so). Also be careful not to tap the valves with the springs removed. If it breaks the seal on the seat, the valve may drop, and you will be pulling the head then.
Agreed.
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Old July 10th, 2012, 08:49 AM   #10
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well since your already going to have the headers and intake off just pull a few more bolts and do it right.
By doing it right you mean wasting time and money,along with lifting those heavy heads out of the truck?

Instead of using air you can also use a lenght of soft rope,feed it in through the plug hole and bring that piston to tdc.The rope will squish between the piston and valves,holding them in place.
This takes a little longer then air,but you dont need to worry about losing airpressure when your buddy walks in the shop and unhooks your air hose to fill his tire.
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Old July 10th, 2012, 08:52 AM   #11
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When you inject the air, sometimes it rotates the motor, don't have your breaker bar or rachet attached to the balancer bolt at that time .
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Old July 10th, 2012, 09:22 AM   #12
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I set each cylinder at tdc when doing it this way. That way if the valve drops you can still get at it.
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Old July 10th, 2012, 08:20 PM   #13
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i used shop air and it worked like a charm, my grandpa actually told me about the rope thing a while back but have never tried it
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Old July 10th, 2012, 09:10 PM   #14
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i used shop air and it worked like a charm, my grandpa actually told me about the rope thing a while back but have never tried it
I don't like rope. I did it that way a few times. Once the rope snagged on the spark plug ( I assume ) and caused a miss fire. Shop air has always worked flawlessly for me after that.
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Old July 10th, 2012, 09:39 PM   #15
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I don't like rope. I did it that way a few times. Once the rope snagged on the spark plug ( I assume ) and caused a miss fire. Shop air has always worked flawlessly for me after that.
How would it snag the plug if it was out? That said I always use air.
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Old July 11th, 2012, 06:35 AM   #16
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How would it snag the plug if it was out? That said I always use air.
good question. Maybe it was on a 4cly ranger with 8 plugs.
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Last edited by GREASYHANDS; July 11th, 2012 at 06:47 AM.
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Old July 11th, 2012, 10:02 AM   #17
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Or maybe this two plug hemi I'm doing right now.

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Old July 11th, 2012, 10:30 AM   #18
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Ive done air and rope. with air I was always nervous that the valve could drop, esp. when trying to get the spring and retainer lined up. with rope there is no worry. use a soft rope like cotton sash cord. stuff alot in and leave about a foot out
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Old July 17th, 2012, 11:46 PM   #19
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using shop air i used a very crudely built homemade tool to compress valve springs that had to be held down by hand the whole time and it would bind up against the valve and i didn't have one valve even seen to want to break seal ? maybe i got lucky this time
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Old July 17th, 2012, 11:50 PM   #20
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Quote:
Originally Posted by Yota Bill View Post
There is nothing wrong with pulling the springs without pulling the heads. Pulling the heads to do it is not necessarily "doing it right".

Air pressure can be as low as about 75psi or so, but just leave it at whatever pressure you run your shop at (125 or so). Also be careful not to tap the valves with the springs removed. If it breaks the seal on the seat, the valve may drop, and you will be pulling the head then.
you'd think so but i know a mechanic that knocked one in and the piston wasn't on tdc so by using 2 magnets, 1 through the valve hole and one through the spark plug hole (while the engine was still in the vehicle) he managed to get the valve back where it belonged lol
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