Assembled heads....

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Assembled heads....

Post  Straubtech on August 16th 2016, 1:01 pm

Assembled heads are for "street engines" up to moderate performance.  After that one should buy the heads and then ship them to someone that can prep the heads for the application.   If we have a customer that exceeds "street performance" we ship the assembly here unassembled.  The "Fox" then goes through the head and preps it for the application.  

One huge mistake people make is spring to cam clearance.  To much clearance is just as bad as not enough.  Just because your assembled heads come with .600" lift springs and you have a .520 lift cam doesn't mean your in good shape.  In some cases you may be worse.  With the use of Spintrons we have discovered spring surge.  This harmonic is the wave traveling on after max lift is seen.  Much like making a wave in the pool, once it hits the side of the pool the wave bounces and comes back toward you.  The greater the distance between coil bind and max cam lift the larger the harmonic is.   For years we thought .100" clearance was good.  Now we use .040 to .050".  Some professional teams run to .000" base on the testing equipment they have access too.

So if you think you have plenty of room with .200" before coil bind, your correct.  You got plenty of room for a harmonic tidal wave.

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Re: Assembled heads....

Post  rmcomprandy on August 16th 2016, 1:45 pm

Straubtech wrote:Assembled heads are for "street engines" up to moderate performance.  After that one should buy the heads and then ship them to someone that can prep the heads for the application.   If we have a customer that exceeds "street performance" we ship the assembly here unassembled.  The "Fox" then goes through the head and preps it for the application.  

One huge mistake people make is spring to cam clearance.  To much clearance is just as bad as not enough.  Just because your assembled heads come with .600" lift springs and you have a .520 lift cam doesn't mean your in good shape.  In some cases you may be worse.  With the use of Spintrons we have discovered spring surge.  This harmonic is the wave traveling on after max lift is seen.  Much like making a wave in the pool, once it hits the side of the pool the wave bounces and comes back toward you.  The greater the distance between coil bind and max cam lift the larger the harmonic is.   For years we thought .100" clearance was good.  Now we use .040 to .050".  Some professional teams run to .000" base on the testing equipment they have access too.

So if you think you have plenty of room with .200" before coil bind, your correct.  You got plenty of room for a harmonic tidal wave.

Through viewing many Spintron tests, The amplitude of that wave is mostly determined by what the nose profile of the cam is imparting on the valve.
A "slow over the nose" or most "dwell" type lobes will see much less of the returning wave and coil bind clearance is then not near as important however, a "quick" nose profile will see a much larger wave.
Knowing and treating the entire valve train is much needed and, as said earlier, getting "assembled" heads is not for any engine meant to be aggressive.

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Re: Assembled heads....

Post  JBR-3 on August 17th 2016, 1:02 am

Isn't the spring dampener supposed to control this coil surging ?

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Re: Assembled heads....

Post  Lem Evans on August 17th 2016, 1:36 am

No

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Re: Assembled heads....

Post  Lem Evans on August 17th 2016, 1:39 am

"With the use of Spintrons we have discovered spring surge." Put some context to this deal....it's like "Lem Evans discovered America"  Very Happy

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Re: Assembled heads....

Post  JBR-3 on August 17th 2016, 2:02 am

Then what does the spring dampener dampen ?

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Re: Assembled heads....

Post  rmcomprandy on August 17th 2016, 2:19 am

JBR-3 wrote:Then what does the spring dampener dampen ?

It diminishes vibratory and frequency osculations; it does not totally remove them ... "spring surge" is neither of those.

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Re: Assembled heads....

Post  BBFTorino on August 17th 2016, 3:49 am

Some of those slow motion videos of the valve spring at high speeds even shows the bottom of the spring bouncing off the seat.

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Re: Assembled heads....

Post  Scott Foxwell on August 17th 2016, 1:30 pm

BBFTorino wrote:Some of those slow motion videos of the valve spring at high speeds even shows the bottom of the spring bouncing off the seat.
If the spring is bouncing off the seat, imagine what the valve is doing. Remember, the spring controls the valve. This is the biggest danger with spring surge, is valve bounce. Several things happen with excessive valve bounce. 1) the valve isn't sealing and we're losing valuable cylinder pressure and power. 2) there is less seat time for heat transfer and a valve, especially an ex valve, can quickly overheat, and 3) it can eventually cause a valve to break. If nothing else, it's going to beat the piss out the valve job and guides.

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Re: Assembled heads....

Post  dfree383 on August 17th 2016, 2:56 pm

Frequency and resonance is important

Got to get it all right on a proper valvetrain.
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Re: Assembled heads....

Post  gt350hr on August 17th 2016, 6:12 pm

The scariest slo mo I've seen is the one that shows the valve locks fall off the stem and away from the retainer , and then snap back together.

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