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| Dale1990 | Broken valve spring, again... Why? | ||
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Senior Guru
 
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I'm in the middle of buttoning up the 86 after installing an LT1 intake thanks to "project creep" after finding some bad injectors. While cleaning things up and poking around with a flashlight, I found a broken spring on #2-exhaust. I guess I found why she was running rough. In hindsight, I should have done a compression check.
Anyway, this is the second time I've had to replace a spring on this car. The last time was a few thousand miles ago on either #6 or #8. I replaced all 16 springs on that head at the time. The replacements were from LPE but they turned out to be Melling and probably stock (judging by what is on the '90). As far as I know, the setup is an LPE 219 cam, 1.6 roller rockers (unknown brand) all riding on ported '113 heads with what appears to be stock springs. Am I just this unlucky or something funny going on here? Are these the wrong kind of springs for this application or did I just get 2 bad batches? What should I be looking for? Thanks! |
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Posted on: 2010/4/10 18:45
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| PeteK | Re: Broken valve spring, again... Why? | ||
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2 Bad batches are unlikely. You need to remove an unbroken spring, and check the open and closed pressures at your installed heights. Then, you must compress the springs to max lift, and be sure you have a minimum of .060 between coils. Before doing the above, look very carefully at the coils where they would touch, if the spring was compressed solid. If you see slight shing marks, the spring was on coil bind. Also, look very close at the tip of the valve. If you see a sort of starburst pattern, you were floating the valves. |
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Posted on: 2010/4/10 19:51
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"It was really on a pass until it came apart." "Yeah. They always are." |
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| cuisinartvette | Re: Broken valve spring, again... Why? | ||
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Elite Guru
 
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Stock spring will never work with that cam..take Petes post to heart. Even with the right spring they need to be set up right to function properly.
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Posted on: 2010/4/11 0:25
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| Dale1990 | Re: Broken valve spring, again... Why? | ||
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Senior Guru
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Quote:
Thanks for the info. Removing the springs won't be a problem but how do I "check the open and closed pressures at your installed heights"? I assume there is some spiffy tool I'm going to have to buy for this. Is there a decent tutorial anywhere on how to do this? Thanks! Also, if this is a fairly well known thing that stock springs won't work in this setup I'm a little miffed that the "tuner" would have done this. |
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Posted on: 2010/4/11 19:15
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| Churchkey | Re: Broken valve spring, again... Why? | ||
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Guru
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You need to know the total valve lift with the 1.6 rockers.
You need to know the distance between the spring seat cup & the spring retainer. Check it with this tool: http://www.summitracing.com/parts/SUM-900032/ You need to know the spring height when coil bind occurs. If you have coil bind: You may be able to purchase spring seat cups that are thinner, get retainers that position the spring higher on the valve, get springs with a smaller wire diameter, remove the heads & have the spring seats machined or install 1.5 rockers. Also check the under side of the rockers for an interference wear mark. Some rockers will contact the retainer & the spring will bind on one side causing failure. You can clearance the rockers with a die grinder. |
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Posted on: 2010/4/11 19:46
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| PeteK | Re: Broken valve spring, again... Why? | ||
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You need a spring pressure tester to verify open and closed pressures.
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Posted on: 2010/4/11 21:27
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"It was really on a pass until it came apart." "Yeah. They always are." |
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| BillH | Re: Broken valve spring, again... Why? | ||
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The Stig Moderator
 
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Pete, did you end up with that tester and an arbor press or get the the complete rig? |
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Posted on: 2010/4/12 13:44
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Every man dies but not every man lives. |
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| PeteK | Re: Broken valve spring, again... Why? | ||
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Moderator
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My local Harbor Freight was out of the arbor every time I stopped, so I wound up buying the rig. Decent piece for the money. I checked it against my buddies recently calibrated Rimac, and it is right on the money.
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Posted on: 2010/4/12 13:51
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"It was really on a pass until it came apart." "Yeah. They always are." |
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| BillH | Re: Broken valve spring, again... Why? | ||
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The Stig Moderator
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It's probably the best for someone like you who will use it a lot. Dale, The least expensive spring pressure tester is about $65 and has to be used with a vice or press. http://www.summitracing.com/parts/PRO-66834/ Your vice will have to open far enough to accept the spring and the tester. The tester base is probably about 1 inch thick. Pete would know. |
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Posted on: 2010/4/12 13:57
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Every man dies but not every man lives. |
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| Dale1990 | Re: Broken valve spring, again... Why? | ||
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Senior Guru
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I don't know much about this stuff so please forgive the questions.
If I get the pressure tester, what is that going to tell me about why I'm breaking springs? I can see using the micrometer to get the installed height then subtracting the total lift and see if I still have >.060 left. How do I get the total lift? Do I hope the cam card the previous owner gave me is right and use the lift * 1.6? Would I be better off just rotating the engine and use a feeler gauge to check the clearance between the coils on an intake and exhaust spring? Sorry for the questions - I'm just trying to wrap my head around what I'm trying to do. |
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Posted on: 2010/4/12 15:09
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86 Coupe: SR 383 90 Convertible: Stock L98 06 Z06: Stock LS7 |
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| Churchkey | Re: Broken valve spring, again... Why? | ||
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Guru
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"If I get the pressure tester, what is that going to tell me about why I'm breaking springs? "
Nothing. The feeler gauge will work, I used that method at the track a few times. Just a reminder, check the underside of the rockers to insure that they are not contacting the retainers. Found some info on your cam .560" lift intake/exhaust with 1.6 rr's. If memory serves 113 heads will only allow about .540 lift however I think the area of interference is the guide to retainer. |
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Posted on: 2010/4/12 19:59
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| PeteK | Re: Broken valve spring, again... Why? | ||
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Moderator
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Based on the opening post, I am under the impression that you are concerned about springs having both quality, and being correct for your cams needs. If spring pressures are too high, or too low, bad shit can happen.
I did not recommend buying a spring tester, I recommended having your springs tested. A stop at the local machine shop can get this done. If you are going through the diagnostic process, you want to check all of the possibilities.99 times out of 100 the springs are not defective. |
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Posted on: 2010/4/12 21:08
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"It was really on a pass until it came apart." "Yeah. They always are." |
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| Dale1990 | Re: Broken valve spring, again... Why? | ||
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Senior Guru
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Thanks for the info guys! I'll see if I can get one of the good ones removed and give it to a machine shop for a pressure test (unless they charge more than the tool will cost). What info will they need to know - just the installed height and the max lift? That would basically be the closed pressure and open pressure, right? I guess I'll have to pick up the valve micrometer to get those values.
I'll take a good look (and pics) at the rocker and valve tip to see if anything is amiss there, too. Since I'll have to rotate the engine anyway, I'll try throwing a feeler in there and see if anything is obvious. For removing the springs, any recommendations/tips? I've done it with the pry-bar style (like this) and it went OK. Would one like this be easier? When I did this last time I had the head off the car and used the big c-clamp-looking thingy which was really easy. PeteK, you're impression is spot on. I'm just a little shaky on what I'm doing so I'm asking a lot of questions  EDIT: Churchkey, thanks for looking up the cam specs! I'm going to see if the cam sheet from the "tuner" is still around in the files and see if that matches - hopefully it does so we have some good numbers to work with. |
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Posted on: 2010/4/13 14:21
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| PeteK | Re: Broken valve spring, again... Why? | ||
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Dale,
Testing springs is a 10 minute procedure. If a local place gives you shit, or tries to gouge your wallet, mail me one or 2 and I will test them for you. My favorite spring compressor is compact, and has a star wheel attached to the top. I am 1100 miles from home, or I would snap a pic for you. |
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Posted on: 2010/4/13 22:58
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"It was really on a pass until it came apart." "Yeah. They always are." |
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