Opinions needed. Broke a valve spring. Need a lil help. UPDATE 5/28/16

TomD

Member
Rebuilt my motor a while back. Ran great for about 3,000 miles and out of nowhere broke a valve spring. Babied it for the first thousand miles and things were looking fine and it was pulling hard. Was about to throw it on a dyno to really see what it could do but this happened before I had the chance. Well the valve seal and guide got chewed up pretty good so I pulled the head and the machine shop repaired it free of charge and replaced the spring. Upon inspection of the failed spring, they told me it broke because of excessive heat and asked if I had an oil cooler. The rest of my springs tested fine.

I did not replace the oil cooler when I did the rebuild and I'm sure it's been on there a very long time. I know some guys don't run one at all.

Springs are K motion hardened steel and should be fine for my application. Engine details are in my sig. If I can tell you anything else let me know.

So now I have my head back and ready to go but thought I'd get some more opinions on why this happened or how to avoid it in the future.

Thanks!

 
I think if you had that much "excessive heat" to break a spring you would have a host of other problems. My guess is that it was a manufacturing defect.
 
How many thousandths before coil bind is it set up for??

Was it set up tight with a 1.55 ratio and then you went with the 1.65 rockers?

What lift cam do you have and did the builder do all the work IE; cam, heads and assembly?

Those are just a few questions I have, and if heat was what broke the spring why did he not recommend changing all of them and not just one??

The damage looks like a coil bind issue. Or it could be a fluke bad spring but I would ask what the clearances are and see what he says. That will tell you whether or not he knows what he's doing or just assembling shit without measuring like he should.

Get some answers to these questions because heat didn't take out the spring. It was RPM and the wrong clearances in my opinion but with what little info you have provided this is just my best guess.
 
Thanks for your input. Yes they did the whole assembly. They strictly build engines. The 1.65 rockers should be set up correctly. The cam was custom from comp so I'll have to dig out the exact specs. I can ask them about the coil bind measurement. I just had a hard time believing it was heat as well because of the reasons you mentioned.

Really appreciate the input!
 
Usually when springs fail due to a mechanical reason it's because they were run too far from bind. Not too close. Chances are it's just a bad batch of springs.


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Rebuilt my motor a while back. Ran great for about 3,000 miles and out of nowhere broke a valve spring. Babied it for the first thousand miles and things were looking fine and it was pulling hard. Was about to throw it on a dyno to really see what it could do but this happened before I had the chance. Well the valve seal and guide got chewed up pretty good so I pulled the head and the machine shop repaired it free of charge and replaced the spring. Upon inspection of the failed spring, they told me it broke because of excessive heat and asked if I had an oil cooler. The rest of my springs tested fine.

I did not replace the oil cooler when I did the rebuild and I'm sure it's been on there a very long time. I know some guys don't run one at all.

Springs are K motion hardened steel and should be fine for my application. Engine details are in my sig. If I can tell you anything else let me know.

So now I have my head back and ready to go but thought I'd get some more opinions on why this happened or how to avoid it in the future.

Thanks!


Without seeing the valve , the spring, guide, seat, retainer in person .. nobody can tell you what the cause was
the machine shop probably saw heat indicators in another area on that cylinder valve train or the valve itself that we cant see in the 1 picture.

The spring can just as likely break from over heating due to EXCESSIVE coil bind clearance as it can from not enough clearance.

Just make sure to check the clearances and if all the other springs were checked for coil bind and pressure you shouldn't have an issue ...
 
Without seeing the valve , the spring, guide, seat, retainer in person .. nobody can tell you what the cause was
the machine shop probably saw heat indicators in another area on that cylinder valve train or the valve itself that we cant see in the 1 picture.

The spring can just as likely break from over heating due to EXCESSIVE coil bind clearance as it can from not enough clearance.

Just make sure to check the clearances and if all the other springs were checked for coil bind and pressure you shouldn't have an issue ...

Ok I hear you...

So I'll check with the shop on clearances and I think I'll spend the $250 for a new clean oil cooler. Anything else I should be looking into?
 
........Upon inspection of the failed spring, they told me it broke because of excessive heat and asked if I had an oil cooler. The rest of my springs tested fine.

I did not replace the oil cooler when I did the rebuild and I'm sure it's been on there a very long time. I know some guys don't run one at all.

Thanks!

My opinion is the shop excuse that it failed because of heat is total BS?

We have many GN's here in the brutal summer heat w/o an oil cooler, including one of my street cars, that do not break valve springs.

If anything was wrong, it would be the valve guide was too tight which melted the seal and also broke a new valve spring.
 
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I have had very good results with the bee hive springs from PAC. I'm not buying a heat related issue either
 
My opinion is the shop excuse that it failed because of heat is total BS?

We have many GN's here in the brutal summer heat w/o an oil cooler, including one of my street cars, that do not break valve springs.

If anything was wrong, it would be the valve guide was too tight which melted the seal and also broke a new valve spring.

Well now I have a new sleeve in the valve guide so if it was too tight because of their machining, hopefully its fixed and the others are fine. Wishful thinking i know. It always shifted right at 6000 RPM so i don't think I'm revving too high.

Coil bind clearance is set to a hundred thousandths per my latest conversation with the shop.

Here is my cam card. The format is a little hard to read and I'm not sure I fully understand all of it. Maybe someone could tell me if i went too extreme.

 
Well now I have a new sleeve in the valve guide so if it was too tight because of their machining, hopefully its fixed and the others are fine. Wishful thinking i know. It always shifted right at 6000 RPM so i don't think I'm revving too high.

Coil bind clearance is set to a hundred thousandths per my latest conversation with the shop.

Here is my cam card. The format is a little hard to read and I'm not sure I fully understand all of it. Maybe someone could tell me if i went too extreme.

.100" a little looser than I'd rec. .060"-.080" is typically what I aim for or I select another spring that will get me in that range with the pressures I want.
 
I just took a quick glance at the lobe catalog and I see your problem. You have two very aggressive lobes that need a lot of spring. There isn't even a spring available that will work properly with those lobes much past 6000rpm on stock heads and that's if you put the most aggressive spring you can get on there and use the lightest hardware you can get which is a project in itself. I would want at minimum 180 seat with those lobes and 520 open. 1.55 rocker ratio or all bets are off. You really need a different head with a taller valve to be able to get a set of springs that will work properly with those lobes.
If i was setting up heads for a customer if be looking for 200 on the seat


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Good to know, thanks.

If I'm reading my card correctly, my cam lift is 230/224.
No. Your lobe lift is .360/.354. Multiply times the rocker ratio for theoretical lift. There's only one a couple select lifters id use with those lobes also
 
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Lucky that spring has a damper and the valve didn't drop in the hole.

In that pic, I had air holding it open. It did drop in the hole and smack the top of the piston when this happened but it was very obvious something went wrong, I shut it down as soon as I heard it. Still took a bit of a beating though. More horror below.





 
I just took a quick glance at the lobe catalog and I see your problem. You have two very aggressive lobes that need a lot of spring. There isn't even a spring available that will work properly with those lobes much past 6000rpm on stock heads and that's if you put the most aggressive spring you can get on there and use the lightest hardware you can get which is a project in itself. I would want at minimum 180 seat with those lobes and 520 open. 1.55 rocker ratio or all bets are off. You really need a different head with a taller valve to be able to get a set of springs that will work properly with those lobes.
If i was setting up heads for a customer if be looking for 200 on the seat


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Ok so if I put this thing back together, it's just a matter of time before it self destructs again....
 
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