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Discussion Starter · #1 ·
I have a set of 781s with comp cams springs on them ( 930 part #). The engine was built at the end of 2004 and I started racing it in 2005 but I dont go to the track that often ( 20 passes since 2005). The valve sizes are 2.300 and 1.880. I guess I have two questions, 1 has anyone used these springs and 2 how did they work and how long did they last. The cam is a custom solid flat tappet and I try to shift at 6200 but have been on the rev-limiter many many times at 6600. Also I put about 3000-4000 street miles on it.

Thanks Pete
 

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Depends on the cam.

With some cams, those springs would break (or would break something else) the first time you started the engine.

With some other cams, they will last hundreds of thousands of miles.

Also depends on how they're set up. If they are installed at the "ideal" height, they'll last ALOT longer than if they're set up too tight or too loose.

In other words, there's way too many variables that can affect spring life besides just their part # and shift RPMs and valve head diameters, to be able to make any kind of meaningful WAG at it.
 

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Discussion Starter · #3 ·
Depends on the cam.

With some cams, those springs would break (or would break something else) the first time you started the engine.

With some other cams, they will last hundreds of thousands of miles.

Also depends on how they're set up. If they are installed at the "ideal" height, they'll last ALOT longer than if they're set up too tight or too loose.

In other words, there's way too many variables that can affect spring life besides just their part # and shift RPMs and valve head diameters, to be able to make any kind of meaningful WAG at it.

I have a comp cams camshaft and those springs are matched to that cam. The springs were installed at the "ideal" height. I thought maybe someone has used these springs and had an opinnion on them. The reason I listed RPM and valve diameters is becuse of the weight on the spring will be greater at high rpms shortning the life of the spring.

Pete
 

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comp cams camshaft
They make literally thousands of different ones.

What cam?

About 50% of the answer to your question is in the details of the cam; about 40% is in the details and numbers of how the springs are set up, in relation to that cam; ALL OTHER FACTORS, including the things you posted like the valve head diameters, are trivial by comparison, and account for the other 10% AT MOST.

Without the details, it is not possible to even come up with a credible WAG, let alone any kind of reliable "estimate".
 

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Valve spring life is a function of how many cycles they have been through, coupled with how far they have been compressed. If the springs are being operated anywhere even remotely close to coil bind, then their life expectancy is reduced significantly. A spring that is held is a compressed state will loose some value as well. This is why it is a good idea to back off the rockers if an engine is going to be stored for an extended period of time (like between racing seasons).
The only way to positively tell if a valve spring is going away is to check it on a spring tester . . . . .
 
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