Valvetrain Question

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Apr 23, 2006 | 08:52 AM

dmiz0420

Thread Starter

Racer

Joined: Dec 2005

Posts: 426

Likes: 0

From: Northern Virginia

Valvetrain Question

After searching the Forums, I still havn't been able to find GM's specs on a '97 C5 (lift, duration, and seperation) Can any one help me with a resource or the #'s? I want to calculate the change from an increased rocker ratio(so your help would be for a good cause).

Also I'm looking to upgrade the valve train when I replace a bad

lifter(s).
I need help deciding on Crane or Comp cams systems (lifters, springs, push rods and roller rockers w/ misc hardware).

The biggest difference seems to be in the roller rockers: Crane has cnc aluminum body 1.8 ratio, and Comp pro-magnum uses chrome moly steel body with a 1.85 ratio and costs a little less.

Any one have experience or know any other difference? Bearings? Noise? Durability? Performance?

Thanks guys

Last edited by dmiz0420; Apr 23, 2006 at 09:10 AM. Reason: wording

Apr 23, 2006 | 10:47 AM

vettenuts

Team Owner

Joined: Mar 1999

Posts: 22,025

Likes: 192

From: At the beach in little Rhody

I run the Cranes and am happy with them. Their lift pattern is different so you will be more valve timing.

According to my book, the 97 had:

I/E 199/207 .472/.479 LSA117

Apr 23, 2006 | 12:28 PM

dmiz0420

Thread Starter

Racer

Joined: Dec 2005

Posts: 426

Likes: 0

From: Northern Virginia

Thanks and more rocker info

Thanks looks like the stock cam could use some advance and the 1.8 ratio crane would get it to .499/.507.

I'm not sure I understand how the difference in design can make a difference. To me the 1.85 would just magnify the cam lobe that much more, greater lift and duration. But thats just taking the manufacturer at their #'s, and I just dont know the physics and theory of it... yet.

***I did find out that comp cams have clearance issues on early model ls1 engines (00&newer)and need $200 .5in valve cover spacers w/ bolts.

I looked at yella terra rolling rockers and they state nothing other than the stock hardware to be installed with no clearance issues. Any Ideas or experience?

Apr 23, 2006 | 12:31 PM

dmiz0420

Thread Starter

Racer

Joined: Dec 2005

Posts: 426

Likes: 0

From: Northern Virginia

Thanks and more on comp

Thanks looks like the stock cam could use some advance and the 1.8 ratio crane would get it to .499/.507.

I'm not sure I understand how the difference in design can make a difference. To me the 1.85 would just magnify the cam lobe that much more, greater lift and duration. But thats just taking the manufacturer at their #'s, and I just dont know the physics and theory of it... yet.

***I did find out that comp cams pro mognums have valve cover clearance issues on early model ls1 engines (00&newer)and need $200 .5in valve cover spacers w/ bolts.

I looked at yella terra rolling rockers and they state nothing other than the stock hardware to be installed with no clearance issues. Any Ideas or experience?

Apr 23, 2006 | 12:49 PM

0C_Williams@RPM

Former Vendor

Joined: May 2005

Posts: 3,749

Likes: 4

From: Valencia Ca

I know you didn't ask this - but you would be 10 times better off changing the cam and sticking with the stock rockers arms.

Apr 23, 2006 | 01:37 PM

dmiz0420

Thread Starter

Racer

Joined: Dec 2005

Posts: 426

Likes: 0

From: Northern Virginia

More info needed

I'm trying to fix a bad lifter and beef everything up before next weekend's track event, I figured untill I know more about what cam properties makes a good road race cam I woulfd hold off and change the cam in due time and the valvetrain would be ready.

That being said

Is it much more work to change the cam when changing the lifters?

Wouldn't the timing chain need to be changed as well?

Does any one offer a kit or package? A good road race track (scca) cam, lifters, push rods, rolling rockers and valve springs?

See Pandora's box, but I only want to open it once

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