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View Full Version : OD of inner spring is tight to ID of outer spring



gtemkin
06-09-2011, 11:01 PM
I have a non-EGR, wide spaced intake port head with dual valve springs. On disassembly I noticed the inner springs were "stuck" into the outer springs. I can't press the inner spring out of the outer spring by firm finger force. That doesn't seem right. Shouldn't they be clearanced from one another and easily separable? They are wound in different directions, one clockwise and the other counter-clockwise (anti-clockwise?), which makes sense. The inner spring is shorter in its free state.

According to a service manual I have, the difference between the OD of the inner spring and the ID of the outer spring should be .065". That should make the springs fall apart.

Is it possible someone put a set of incorrect springs in this head or are they normally this way? The head has definitely been worked on in the past with some porting and polishing evident.
Thanks,
Gregg

TR3driver
06-09-2011, 11:49 PM
Very likely that is an aftermarket set of springs. The interference is deliberate, as the friction provides extra dampening against resonance (which is the main reason for using two springs instead of one).

70herald
06-09-2011, 11:57 PM
Not being able to disassemble by light finger force does NOT sound good. Two different springs are used (if they are used) because they will have different natural frequencies. Any friction between them should be limited to an amount which allows them to move relative to each other.

If they as tight as you say, they are not acting as two springs, they are acting as one very stiff spring.

TR3driver
06-10-2011, 12:55 AM
Any friction between them should be limited to an amount which allows them to move relative to each other.
That's true, but there is a lot of difference between how much force you can apply with your fingers, and how much force the springs see in operation. Just try doing a valve job with your fingers!

I have a similar set, and you can see from the shiny spots that they do move in operation. But I had to use the bench vise to assemble them.