Anybody have any good ideas/ways to keep the valve from accidentally falling down into the chamber when changing springs?

 

Two most common methods I've seen discussed here (which a should have revealed) are stuffing rope into the spark plug hole and bringing the piston up against it and the valves, and air pressure applied to the spark plug hole (the method I've used many, many times).

 

Yep. rope or air. Use air if at all possible. believe me.

 

Does it matter how much air pressure?

 

the more the better, but 70~80 pounds is plenty.

 

You typically need to wack the retainer with a socket/extension/hammer to break the keepers from the retainer. You can then compress the spring against the air pressure holding the valve closed.

Without the wack, the pressure typically isn't enough to be able to compress the spring and have the valve stay seated.

 

I like the rope method. Virtually no chance of the valve dropping then. Use rope like lawn mower starter rope not that yellow stuff that sheds fibers. The rope might take a little longer but it is safer imho.

 

While the springs are off, check the valve seals. Positive types being the prefered if not already installed. Might as well save the future labor if they aren't.

 

My shop teacher, who was a foreman at a GM dealership for 10 years, told me to use air connected directly to the shop's air tool lines instead of rope. I really didnt want to do it that way but he said to, so I tried it and believe me, at (what, 125 PSI?), it'll take a LOT to get them to drop. Think about it. 125 PSI x at least 1 sq. inch, you'd really need to reef on 'er before she would let go.

 

I use my leakdown tester at like 40-50 psi and go to town.

Just work semi carefully and no bone headed stunts and you should be fine.

I think air makes it a little quicker than rope, but if u have one and not the other , go for it.

I second giving everything a whack before you dissassemble, if anything looks particularly grungy, hit it with some penetrating oil.

later
Jeremy

 

I remember in high school mechanics class, my friend and I were demolishing an old Ford 302 that had so much sludge in it it would make yout head spin, and we discovered that if you hit the top of the valve just right, the keepers would fly out and shoot the spring into the roof.

 

Problem with air is, it tries to rotate the piston to BDC; and if that happens, and you then accidentally let go of a valve, you may have a problem on your hands.

To be honest, I usually don't do ANYTHING at all. I just put the piston to TDC for the cyl in question and go to town. The valve can only drop a half inch or so before it lands on the piston, and you can just grab it and slide it back up. Quicker and easier than fooling around with any of the methods of holding the valve closed.

 

Doesnt that make it a lot harder to get the spring back on?

 

Not really....

But maybe that depends on the tool you're using.

 

It also depends upon your engine's compression. High compression/tight clearance engines will be a lot easier to handle just by bringing the piston up to TDC. But, you'd better either hold it there or have it exactly on TDC, or you run just as much risk of the engine turning when the spring is compressed.

I probably don't have the most sophisticated on-head valve spring compressing tool out there, because I just don't do it that often (probably 10 times in the last 15 years). But, I found that I needed every bit of valve length available to be able to get the keepers off & on. Probably has a lot to do with the engines I've worked on having stock or nearly-stock parts as well. I only tried the TDC method once, gave up after one cylinder (and didn't even finish that cylinder) and went out to get an adapter for the air hose.

Take your pick which method you want to try. One may work better for the experienced mechanic that often does the job, while another might work better for those who will only do the job once.

 

i have done it both ways too.
i used the TDC way once when i didn't have an air compressor available, for me its much easier to do with air.

like Stekman said, replace the valve seals while your there, they are cheap & it will save you from having to mess with again it later down the road

 

I bought a $99.00 air compressor for tires at Home Depot(loke lows only not as good and it provided just enough pressure to hold the valve and not turn over the motor(aprox. 80psi @1.5gph) I use the compressor now for filling up my tires and it works fairly well. The adapter I made out of a quick disconnect from my air tools and an old spark plug hollowed out and internally threaded.. worked good even on a 100,000+ mile motor.

If all else fails .......Light the match and run!

J

 

Use cotton rope / string

fibers from it will burn away easy