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Old 05-09-2008, 08:39 PM
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Spring Height????

Crew - How critical or how close does spring height need to be? I am installing a comp cams Magnum kit with the lifters, timing, springs, etc. They say 105 lbs @ 1.7 and If I'm measuring correctly, I get 1.78". The way I'm measuring is from the bottom seat where the spring sits to the very "flattened" end of the spring, not including the retainer. This with the valve closed and the little retainer clips in.

ANy help? I'm wondering if that's ok or I really need to do valve shims? Its an otherwise stock crate 350.

Thanks for the advice!!!!

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Old 05-09-2008, 10:24 PM
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Quote:
Originally Posted by dhunt00c
Crew - How critical or how close does spring height need to be? I am installing a comp cams Magnum kit with the lifters, timing, springs, etc. They say 105 lbs @ 1.7 and If I'm measuring correctly, I get 1.78". The way I'm measuring is from the bottom seat where the spring sits to the very "flattened" end of the spring, not including the retainer. This with the valve closed and the little retainer clips in.

ANy help? I'm wondering if that's ok or I really need to do valve shims? Its an otherwise stock crate 350.

Thanks for the advice!!!!
Your measuring correctly. The spring's force is related directly to installed height. It appears you'll need .08 inch worth of shims.

Are these aluminum heads? They are made for a hard seat under the spring and usually takes more to adjustment to get to proper height. Another consideration is stem length, and or how deep the valves set in their seats. Shooting seats and regrinding valves sinks them into the head which makes the stem look longer when measured back to the spring seat. Some of these are also sized for positive rotators and or oil shields that fit under the retainers which reduces spring length when they are used.

You need to watch the location of the bottom of the spring, if you shim it too high it will need a cup to keep it located under the retainer, most auto machine shops have this stuff if it's needed. Cups come as innies and outties, if your outside cups are easier and necessary if your running triple springs. Inners tend to orbit the the guide boss unless they and the boss are machined for a tight fit.

Bogie
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Old 05-09-2008, 11:00 PM
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Thanks.. no, these are GM stock iron heads.. likely smoggers since its a crate motor circa 77-79 years.

Whats odd, is that I've changed 2 more valves, and they are measuring spot on... just that first one seemed to have a taller height.

Do i really need to shim or you think I'll be ok?
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Old 05-09-2008, 11:15 PM
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Quote:
Originally Posted by dhunt00c
Thanks.. no, these are GM stock iron heads.. likely smoggers since its a crate motor circa 77-79 years.

Whats odd, is that I've changed 2 more valves, and they are measuring spot on... just that first one seemed to have a taller height.

Do i really need to shim or you think I'll be ok?
I rather think, from 2000 miles away, that what you say on that first valve is an example of a seat that had to be cut deep to get a good surface and or a refaced valve that took a big cut, this would set the valve into the valve/port pocket which will make the stem appear longer, or you've got and odd ball stem, they're out there.

I'd advise you shim where necessary, it isn't all that unusual, though .08 is getting kind of thick. They're, shims that is, usually found in .015, .030, and .060 inch thicknesses. You can run multiples if you want; example would be .060 plus a .015 making .075 which is only .005 off perfect.

Bogie
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Old 05-10-2008, 12:25 PM
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New info...

Well, I've caught on to a trend. The intake valves are spot on around 1.70". The exhaust valves seem to consistently be 1.78" or 1.79". I think this is because these stock GM heads have the "rotater" retainers on the exhaust valves that allowed them to rotate. They are thicker than the stock intake valve spring retainers.

That said, looking like I'm going to have to use some shims on the exhaust valve side; however none of the parts stores locally have them.

Can I shim about .05 or .06 without having a bowl type thing under the spring to keep things in place?
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Old 05-10-2008, 01:09 PM
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Quote:
Originally Posted by dhunt00c
Well, I've caught on to a trend. The intake valves are spot on around 1.70". The exhaust valves seem to consistently be 1.78" or 1.79". I think this is because these stock GM heads have the "rotater" retainers on the exhaust valves that allowed them to rotate. They are thicker than the stock intake valve spring retainers.

That said, looking like I'm going to have to use some shims on the exhaust valve side; however none of the parts stores locally have them.

Can I shim about .05 or .06 without having a bowl type thing under the spring to keep things in place?
Yes the stock GM heads used a rotator so if you're not, that distance should be made up with a shim.

I'm surprised that they are not available locally as any automotive machine shop will require them. But here's a few choices for you to pick from, mail without putting Fed Ex on the trail is usually about 2 days even here at the far end of the country.

http://store.summitracing.com/egnsea...1&autoview=sku

http://www.jegs.com/webapp/wcs/store...11305_-1_11071

http://www.gmpartsdirect.com/perform...CATID=734.html

http://www.compperformancegroupstore...Code=VALVESHIM

Bogie
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Old 05-10-2008, 07:18 PM
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You can also use -.050 locks along with a .030 shim under the spring.

Sometimes stacking .080 of shim under the spring leaves nothing to keep the spring from walking.
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