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Old 08-31-2009, 10:17 AM
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Installed spring height question

Greetings All,

I have an Olds 455 that I have installed an Comp extreme cam. The valve spring they recommend requires an installed height of 1.700 the factory installed height is 1.670.

How is the best way to get there? I have seen one recommendation to mill the spring seat down 0.030 and I have had another recommendation to mill the mill down the valve seat during a valve job thus increasing the valve stem height.

My concern with the second option is that it would screw up the rocker geometry. The machine shop I talked to said machining the valve seat down 0.030 had the potential to hit water jackets.

Anyone out there got any suggestion?

Thanks,
Rob

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Old 08-31-2009, 10:43 AM
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I recommend that you find out where you are by mocking up a valve, retainer and locks without the spring and measuring the distance from the bottom of the retainer to the seat. You're assuming that the Comp retainer has the same dimensions as the stock retainer and that may not be the case at all.

Even if they are the same and you actually do have 0.030" less installed height, multiply the spring rate times .030 and find the new seat pressure and open pressure. Example, 370 lbs per inch times .03 = 11 lbs. In my opinion, that wouldn't make or break the deal as long as you have no coil bind and the retainer misses the guide and seal at full lift. As far as coil bind, you want a minimum of 0.010" between each of the 5 coils. As far as retainer/seal clearance, you want 0.060"-0.120" at full lift.
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Old 08-31-2009, 10:50 AM
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If it came down to it I'd machine the spring pad before I'd sink the valve seat.
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Old 08-31-2009, 10:51 AM
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On top of what the Inspector said, NEVER sink a valve seat to get installed height, that is the absolute wrong way to do the job. Correct way is to cut the spring seat, use a different retainer, and/or you can get +.050" and -.050" installed height valve locks also.
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Old 08-31-2009, 10:57 AM
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Quote:
Originally Posted by ericnova72
On top of what the Inspector said, NEVER sink a valve seat to get installed height, that is the absolute wrong way to do the job. Correct way is to cut the spring seat, use a different retainer, and/or you can get +.050" and -.050" installed height valve locks also.
Thanks Eric, forgot about the lock fix.
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Old 08-31-2009, 10:58 AM
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Thanks for all the info guys. I thought working on the valve side sounded like a bad idea.
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Old 08-31-2009, 11:49 AM
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0.030" is close enough.
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Old 08-31-2009, 02:17 PM
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Quote:
Originally Posted by Rufus_2
Greetings All,

I have an Olds 455 that I have installed an Comp extreme cam. The valve spring they recommend requires an installed height of 1.700 the factory installed height is 1.670.

How is the best way to get there? I have seen one recommendation to mill the spring seat down 0.030 and I have had another recommendation to mill the mill down the valve seat during a valve job thus increasing the valve stem height.

My concern with the second option is that it would screw up the rocker geometry. The machine shop I talked to said machining the valve seat down 0.030 had the potential to hit water jackets.

Anyone out there got any suggestion?

Thanks,
Rob
I'm with 545C10 on this, .030 inch isn't worth sweating.

Bogie
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Old 09-01-2009, 08:39 AM
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Thanks for the mock-up suggestion. I bought the parts and mic'd the height. My install height was 1.820, which is 0.120 taller than needed. I was amazed at the thickness difference between the Comp Cams retainers and the factory retainers. It looks like I'm going to swap my retainer locks for -0.050 locks and add a 0.060 shim to make up for the distance. But atleast I don't have to machine anything. Thanks again for all the help.

Rob
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Old 09-01-2009, 10:34 AM
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I think I may have spoken too soon about machining. I forgot about my stem seal clearances. THe Comp Spring is a double spring. The stem seal I have is an umbrella that is to big for the inner spring ID. Comp recommends a positive stop Teflon which requires machining the stem guide.

Can I get away with a smaller OD umbrella?

Any other suggestions?

Thanks,
Rob
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Old 09-01-2009, 10:39 AM
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If you can find one with the correct stem diameter that is small enough to go inside the spring, you can do it. You are not likely to find one that will fit inside a dual spring, however.
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Old 09-01-2009, 11:14 AM
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I never have cared for umbrellas. There's a reason Teflon and Viton positive seals are available and umbrellas are probably part of the reason. I'll give you an alternative to having the machine shop do the guide cutting. Here's the 0.530" cutter and 11/32" arbor to do them yourself. 50 bucks. Use a low-speed 1/2" drill motor with plenty of cutting oil applied by an assistant and a way to drain the excess into a pan so you can keep recycling it. Here also are Manley Viton 0.530" seals. Many manufacturers make them in both Teflon and Viton. I just happened to copy the Manley units. Measure the I.D. of the inner spring to make sure there is plenty of clearance for these 0.674" O.D. seals. There are seals available from others that are slightly smaller on the O.D.

http://www.summitracing.com/parts/MAN-24045-8/
http://www.summitracing.com/parts/CCA-4732/
http://www.summitracing.com/parts/CCA-4726/

Watch this video all the way through and you'll see why you want a little extra clearance between the seal and the spring....
http://www.youtube.com/watch?v=_REQ1PUM0rY

Last edited by techinspector1; 09-01-2009 at 11:29 AM.
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Old 09-01-2009, 11:48 AM
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sinking the valves can have some bennefits if you match the chamber and cam to it properly
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Old 09-03-2009, 03:04 AM
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If I were to try the machining myself, how far down would I need to go?
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Old 09-03-2009, 05:02 AM
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heads

Quote:
Originally Posted by ap72
sinking the valves can have some bennefits if you match the chamber and cam to it properly

OH boy... DO-NOT do this to your heads....It will make zero difference in how the engine runs in your application.

Get the proper installed height with the correct locks, retainers, shims.

Do you know what the inside diameter of those springs are. I might be able to help out with a seal for you.

Keith
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