Broken inner Valve springs Dart Iron Eagle SS Heads on Chevy 383 Stroker - Hot Rod Forum : Hotrodders Bulletin Board
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Old 12-29-2012, 03:54 AM
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Broken inner Valve springs Dart Iron Eagle SS Heads on Chevy 383 Stroker

I have a 383 chevy stroker with Dart Iron Eagle SS heads in 64 chevy C10 pickup.

I discovered a couple of small metal particals when changing my valve cover gaskets. Turns out that the top part of some inner valve springs broke off..
These inner springs are quite thin.

I friend of my told me to just take them out and run the heads without inner springs. He was certain that I wouldn't notice any difference.

Is anybody familiar with this problem?

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Old 12-29-2012, 04:06 AM
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Are you refering to the spring damper inside the spring?
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Old 12-29-2012, 04:16 AM
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Click image for larger version

Name:	image.jpg
Views:	115
Size:	1.28 MB
ID:	70169If these are spring dampers then yes. They are very thin inner springs.

Last edited by Hotrod1979; 12-29-2012 at 04:34 AM.
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Old 12-29-2012, 06:28 AM
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If the heads are under warranty contact Dart Machine and or where you bought the heads.
Other wise repalce the whole set of 16 springs with new. Inspect the retainers for gouging damage ETC
replace if scored.
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Old 12-29-2012, 06:48 AM
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The heads came with the engine witch was allready in the car when I bought it. So no warrenty..

And sure I can remplace them, but 4 of them are broken and I lost my trust in the strengh of these springs.

That's why I wonderde if I could not just leave them out.
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Old 12-29-2012, 07:52 AM
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If you are gonna have the springs off why not just replace them with the correct spring that matches the cam? I think thats what caused the spring failure to start with, whoever built the motor didn't match the springs to the cam and just assumed, "well these are Dart heads so the springs will handle the cam". How much metal did you see? I would definately drain the oil and cut the filter and see what you have going thru your motor, put a magnetic plug back in. If you have a small but pretty strong magnet, as soon as you pull the drain plug, stick it over the hole and let the oil drain over it and see what you catch on the magnet. JMO. but I do wish you the best on whatever path you choose to take.
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Old 12-29-2012, 09:41 AM
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It appears that the spring pocket (seat) is too large O.D. for the valve springs. That allows the springs to dance on the seats. If you have a damper, dancing will cause the damper to fail first, then the valve springs themselves. It appears the spring seats may be machined 1.500" O.D. That needs to be verified before you order a new set of valve springs. The spring seat O.D. should be .030" to .060" larger than the valve spring O.D.

If the seats are 1.500" O.D., install a set of Comp Cams 995 dual valve springs with dampers that are 1.437" O.D. along with the appropriate retainers. The larger O.D. outer valve springs will allow .030" - .060" clearance for the damper and inner valve spring to valve guide boss. The ledge on the O.D. of the valve spring seat serves to stabilize the valve springs. Sometimes hardened spring locators can be used but they are difficult to fit with the correct inner and outer clearances with the correct spring height. In order to use dual springs (with or without a damper) , you must use a larger diameter outer valve spring.
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Old 12-29-2012, 02:36 PM
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Thank you for your reply. Looks like the Dart heads are stock. Are you sure this is why these springs failed?

I will take one spring out and do some measuring...

I am not sure what kind of cam I have got..

Last edited by Hotrod1979; 12-29-2012 at 02:46 PM.
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Old 12-29-2012, 04:08 PM
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You can see in the photo that the valve spring seats are too large for stock valve springs. A stock single valve spring with a damper is 1.265" O.D. to 1.300" O.D. and those valve spring seats are at least 0.200" larger in diameter.

A spring that dances around on the seat at high RPM due to spring seats that are too large will fail. That is probably the #2 reason why valve spring fail. The #1 cause is coil bind or inadequate assembled height for the valve lift your cam has.

You may have both problems if you do not know how much valve lift your camshaft has.
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Old 12-29-2012, 04:49 PM
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This is the kind of thing that makes you want to go back and beat the snot out of the guy who assembled the heads. He had no business putting his hands on them. Makes me wonder what else is wrong.
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Old 12-29-2012, 05:01 PM
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Since you don't know what your cam lift is you are going to verify that your spring you plan on installing are suited for your cam. If your lucky you might find the manufacture and grind # on the end of the cam. If this info is there it will be a simple manner of contacting the cam manfacture for the correct springs. You will still have to insure that they are intalled at the correct installed height and that you have no coil bind. The retainer to guide clearence should have been checked by the person that built the engine but since you're having problems I'd double check everything.
If you can't verify your cam you'll need a dial indictor and check your lobe lift and mutiplt this figure by the rocker arm ratio to get your vavle lift. By know this and the type of lifters you have ( hyd., flat, solid roller, hyd roller) then you can go shopping for springs.
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Old 12-30-2012, 01:53 AM
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Quote:
Originally Posted by Hotrod1979 View Post
Thank you for your reply. Looks like the Dart heads are stock. Are you sure this is why these springs failed?

I will take one spring out and do some measuring...

I am not sure what kind of cam I have got..
I'm not convinced that the spring seat size was the cause of the dampers breaking. Might be third or fourth on my list of probabilities.

Not knowing anything more than what you know at this stage (which is limited until you can dig further), I suspect floating or lofting the valves. This can happen even at lower than expected rpm if the springs aren't right for the application, or have a too-tall installed height, or are faulty from the factory, etc. Besides the pounding the springs take when that happens, this also sets up harmonics that can break dampers and springs (spring surge). That has been associated w/dampers breaking, and I have had this happen on engines w/insufficient valve spring pressure for the rpm/cam profile being used. 1.6 ratio rockers can magnify this.

In any event there's MANY things that could cause the damper to break, not just the spring seat size. Even a bad batch of spring dampers can cause it, like I went through with the K-Motion springs I was using a while back. They finally redesigned the damper (has a reverse coil from the old ones) and problem solved.

Spring locators:
I prefer to use an ID spring locator. But regardless of what you use (spring cup or an ID spring locator sized to the guide boss), the spring locator HAS to be a close fit to either the guide boss OD or the ID of the head's spring cup, else you're no better off than you were with no locator, period.

The MAIN thing is to have a spring that's spec'ed for the cam and rpm, and to not exceed the redline. If you can do that, you can leave the locators on the shelf.

See:

Valve spring installed height
Points to check
Geometry
Adjust lifters
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Old 12-30-2012, 06:57 AM
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Originally Posted by techinspector1 View Post
This is the kind of thing that makes you want to go back and beat the snot out of the guy who assembled the heads. He had no business putting his hands on them. Makes me wonder what else is wrong.

thats not really fair, most any thing you'll ever read, only says match the springs to the cam..
tons of guys will buy a cam/lift/springs out of summit, not knowing anybetter,, because nothing they've ever read, said anything about the spring seat.. most times it's coil bind/seal clearance/etc
not spring dia. to spring seat..
only one in the car mag world I ever see say anythign about it was jeff smith..
and face it 75% of the guys in the hobby, car mags are what they read for "tech"
then they do a cam swap.. and because the guy on the tech line at jegs/summit sent him "matching springs" he thinks it's all good..
not knowing anybetter..
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Old 12-30-2012, 12:39 PM
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Thanks everybody for the advice. I was lucky to discover the broken dampers on time... I will first try to find out what kind of Cam I have got.
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Old 12-30-2012, 04:45 PM
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I checked the heads. They are Dart Iron Eagle SS heads.

76 CC chamber and 165 CC runner.

Isn't this far too small for a 383 stroker??
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