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ZZ4 valve train upgrade

 
fwb35
I love my Chevy Chevette!
Posts: 19
Joined: 12/09
Posted: 12/28/09 11:03 AM

I have a ZZ4 in a Busch road race car I race in the SCCA, we can upgrade the valve train, I was told if I upgrade to the 26918-16 Comp Cam valve springs with 1.6 full roller rockers that I have to change the cam due to the increased spring pressure. Is this true?  

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55Guy
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Posts: 1153
Joined: 07/06
Posted: 12/29/09 08:01 AM

Not really true. You just need to make sure you set the new springs up at the correct seat/open pressures for your cam.

Now, the thing is, you also have ot make sure that the new springs will take the extra lift form the 1.6 rockers.

I'd call the Comp Cams tech help line, give them your cam specs and see what they recommend for a spring. Also mention what you're doing with the car, and you'll be using 1.6 rocker arms.  

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55Guy
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Posts: 1153
Joined: 07/06
Posted: 12/29/09 08:05 AM

One other thing, increasing the lift with the 1.6 rocker arms, you need to check the valve length in your ZZ4 heads, I believe they're stock length valves so they won't take ove .525" of lift, unless you've already installed longer length valves?  

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fwb35
I love my Chevy Chevette!
Posts: 19
Joined: 12/09
Posted: 12/29/09 01:56 PM

I believe they wont take more lift then .525 because the springs will go into coil bind. I am changing the springs to the GM 12499224 that will handle up to .580 lift
and have less spring pressure then the comp cams 26818 springs that have 365lbs open, the 12499224 springs are 295lbs open and wont wipe my cam.  

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55Guy
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Posts: 1153
Joined: 07/06
Posted: 12/30/09 02:30 PM

Don't worry about wiping out the cam. 365 lbs of open pressure won't wipe the cam out. You want that extra open pressure for valvetrain stability and to avoid having spring surge/valve float problems through the RPM range of the cam. The GM springs tend to be a little soft.

To go past .525" of lift, you're going to need to install longer than stock valves in your heads, otherwise the bottom of the retainer will hit the top of the valve guide, and mechanical carnage will be the result.  

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fwb35
I love my Chevy Chevette!
Posts: 19
Joined: 12/09
Posted: 01/01/10 12:26 PM

The retainers will hit the guides? Even a engine guy told me I just needed new springs for my zz4 to use 1.6 rockers. You mean the retainers will hit the seals?
I have actually had more then one person tell me I just need higher lift springs.  

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fwb35
I love my Chevy Chevette!
Posts: 19
Joined: 12/09
Posted: 01/03/10 04:54 PM

Ok, since nobody knows, I went out and took it apart and measured it myself. My book states the installed height is 1.78, I came up with 1.74 on my valves, I checked 2 on each side. Then I checked for height when the retainer hits the valve seal, it was 1.175, that gives 0.565 of lift clearance. With the LT4 hot cam kit it states .525 lift intake and exhaust. My book states coil bind is at 1.21, if my math is correct that would give me .005 clearance. GM sells a bolt on kit that would do this? Wow.
Anybody want to buy a almost new ZZ4, I am leaving Obama motors and going back to Ford  

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