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Old 01-31-2011, 11:10 AM
v8hed's Avatar
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Question about shimming valve springs

I'm setting the installed height of my valve springs (Comp 987) and I'm wondering if I should account for the seating of the locks once the engine is running. Even though I'm checking the heights with plenty of lube on the locks and valve stem groove and yanking is hard as I can on the retainer to try and seat the locks as far as possible, I still can't help feeling once the engine is running, the locks will probably seat another .010 or so.

It is a good idea to shim, say, .015 on the tight side anticipating that the locks will seat more fully once the motor's running? I've got plenty of coil bind clearance and retainer to stem seal clearance to play with, so a .015 shim won't make any difference there.

PS. I'm using Comp 10* super locks with matching retainers.

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Old 01-31-2011, 04:59 PM
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10 locks can require some force for the retainer to fully seat. Are you using a spring height mic? Just twist your mic,loosen,twist again until it fully seats to maximum height and you should be good. Add,subtract shims(if needed)to obtain your desired height from there and check again.

Not necessary but another .015 should not hurt you as long as you still have at least .060 before coil bind.
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Old 01-31-2011, 05:05 PM
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Quote:
Originally Posted by GMC boogie
10 locks can require some force for the retainer to fully seat. Are you using a spring height mic? Just twist your mic,loosen,twist again until it fully seats to maximum height and you should be good. Add,subtract shims(if needed)to obtain your desired height from there and check again.

Not necessary but another .015 should not hurt you as long as you still have at least .060 before coil bind.

Yea, I'm using a spring height mic. I've done exactly what you describe, but then I found that if I tap the top of the valve stem with a hammer, I can find another .010". I was also thinking about the springs losing some temper after break-in.

Think I'll shim .015 tight on assembly then. Thanks.
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Old 02-01-2011, 08:08 AM
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In an video I have on building a hi-po 383 SBC, the guy taps the valve and adjusts the mic three times... meaning he sets the mic snug, taps on the valve tip with a plastic-headed hammer a couple of times, re-sets the mic, taps a couple more times, re-sets the mic and taps a couple more times, then re-sets the mic a final time. IIRC he picked up something like .020 between the first setting and the last. This was with standard keepers.
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Old 02-01-2011, 09:08 AM
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Quote:
Originally Posted by XNTRCI-T
In an video I have on building a hi-po 383 SBC, the guy taps the valve and adjusts the mic three times... meaning he sets the mic snug, taps on the valve tip with a plastic-headed hammer a couple of times, re-sets the mic, taps a couple more times, re-sets the mic and taps a couple more times, then re-sets the mic a final time. IIRC he picked up something like .020 between the first setting and the last. This was with standard keepers.
That's exactly what I've found too (with 10* locks).

I'm going to shim .010-.015 tight to allow for a little more seating once the engine is running. Also doesn't hurt to make up a little for the spring pressure slacking off once the springs have heat cycled a few times.
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